Grade 12 Biology Unit 2 Short Notes PDF

Grade 12 Biology UNIT 2 Microorganisms Prepared by: Mr. Simon Solomon 20/2/2017 prepared by: Mr. simon solomon  By the end of this section you should be able to: ✓ Categorize microorganisms based on their morphology, mode of nutrition, molecular and bioch...

Grade 12 Biology UNIT 2 Microorganisms Prepared by: Mr. Simon Solomon 20/2/2017 prepared by: Mr. simon solomon  By the end of this section you should be able to: ✓ Categorize microorganisms based on their morphology, mode of nutrition, molecular and biochemical analysis, ✓ Explain the ways of transmission and prevention of pathogenic microorganisms, ✓ Explain the significances of Koch`s postulates for the advancement of microbiological techniques ✓ Apply the principle of microbiological technique ✓ Discuss the economic importance of microorganisms 20/2/2017 prepared by: Mr. simon solomon  Unit 2 Microorganism 2.1. What is micro organism? ❑ Microorganisms (also called microbes) are life forms that are too small to be seen with the naked eye can only be seen with the aid of a microscope. ❑ Most micro-organisms are unicellular (single-celled organisms), but some can form complex structures that contain more than one cell (multicellular). ❑ Microorganisms typically live in complex microbial communities and their activities are regulated by interactions with one another, with their environments, and with other organisms. ❑ Microbiology: - the study of microbes. ❑ The science of microbiology is all about microorganisms: what they are, how they work, and what they do. 20/2/2017 prepared by: Mr. simon solomon  2.2. Types of microorganisms ❑ Based on evolutionary lines, organisms are grouped into three domains: these are: 1. Bacteria 2. Archaea 3. Eukarya prepared by: Mr. simon solomon 20/2/2017  2.1. Eubacteria By the end of this section you should be able to: Describe the general features of bacteria. Describe the mode of nutrition in bacteria. Explain the mechanism of categorize bacteria based on their shapes. Distinguish Gram’s positive and Gram's negative bacteria. 20/2/2017 prepared by: Mr. simon solomon  2.2.1. Eubacteria ❑ Literally means “true bacteria” ❑ Bacteria are relatively simple in structure. ❑ They are prokaryotic unicellular organisms with NO nuclear membrane, mitochondria, Golgi bodies, or endoplasmic reticulum that reproduce by asexual division. General characteristics ❖ They are omnipresent; i.e. present in the soil, air & water. ❖ They are unicellular, ❖ They have thick rigid cell wall (peptidoglycan). ❖ The mode of nutrition; May autotrophic and heterotrophic. ❑ Heterotrophs may be parasite, saprophyte or symbiotic ❖ They lack true chlorophyll but few photosynthetic bacteria have a special type of chlorophyll called bacteriochlorophyll. ❖ They lack true nucleus, mitochondria, Golgi apparatus, plastid and EPR. ❖ DNA & RNA are present in bacterial cell 20/2/2017 prepared by: Mr. simon solomon 20/2/2017 prepared by: Mr. simon solomon  Structure of Bacterial Cell The general structural plan of a prokaryotic cell can be represented with this Flowchart: 20/2/2017 prepared by: Mr. simon solomon  Eukaryotic microbes Are an extraordinary diverse group, including species with a wide range of life cycles, morphological specializations, and nutritional needs. Are responsible for some disease of great public health importance. Have a variety of complex membranous organelles, genetic material. A cytoskeleton composed of microtubules, microfilaments, and intermediate filaments. Give cells shape; is also involved in cell movements, intracellular transport, and reproduction. When they reproduce, genetic material is disrupted between cells by the processes called mitosis and meiosis 20/2/2017 prepared by: Mr. simon solomon  Prokaryotes vs Eukaryotes Prokaryotes Eukaryotes mostly single-celled (unicellular) organism that lacks nuclear cells have a nucleus enclosed within a nuclear envelope membrane-enclosed nucleus No membrane bounded organelles membrane-bound nucleus DNA is found in a central part of the cell in continuous loops: the Linear DNA nucleoid Most prokaryotes have a peptidoglycan cell wall and many have a more complex structure than prokaryotic cells polysaccharide capsule Some prokaryotes have flagella, pili, or fimbriae numerous membrane-bound organelles such as the Flagella are used for locomotion. endoplasmic reticulum, Golgi apparatus, chloroplasts, Pili are used to exchange genetic material during a type of mitochondria, and others reproduction called conjugation. Fimbriae are used by bacteria to attach to a host cell Absent mitochondria and chloroplast Organelles allow different functions to be compartmentalized in different areas of the cell 20/2/2017 prepared by: Mr. simon solomon  2.1.1. Bacterial Shapes In fact, morphologically bacteria are classified based on numerous features. Such as: ❑ cell shape nature of multi cell aggregates, ❑ Motility ❑ formation of spores, and ❑ reaction to the gram stain Bacterial cells can be grouped into the following three main shapes: ❑Cocci (singular, coccus): spherical bacteria ❑Bacilli (singular, bacillus):-rod-shaped bacteria ❑Spirochaetes:-spiral or corkscrew-shaped bacteria ❑Comma -Vibrio cholera 20/2/2017 prepared by: Mr. simon solomon  Bacterial cell wall Besides their shape bacteria can be classified based on their cell wall composition. One of these ways is whether they are retaining dyes during Gram’s stain. ❑ Gram’s staining: a test for distinguishing bacteria (named after Hans Christian Gram, who developed the technique in 1884) ❑ Differential staining: is a staining procedure that distinguishes organisms based on their staining properties In this case, bacteria can be categorized into two: A. Gram-positive – Gram-positive bacteria have a distinctive purple appearance when observed under a light microscope following Gram staining. This is due to retention of the purple crystal violet stain in the thick peptidoglycan layer of the cell wall. Examples of Gram-positive bacteria include all staphylococci, all streptococci and some listeria species. 20/2/2017 prepared by: Mr. simon solomon B. Gram-negative – Gram-negative bacteria lose the crystal violet stain (and take the color of the red counterstain) in Gram's method of staining. This is characteristic of bacteria that have a cell wall composed of a thin layer of a particular substance (called peptidoglycan). Examples of Gram-negative bacteria include salmonella typhi, E.coli and other ❑ Peptidoglycan: The rigid layer of the cell walls of Bacteria, a thin sheet composed of N- acetylglucosamine, N-acetylmuramic acid, and a few amino acids. ❑ Endotoxin: The lipopolysaccharide portion of the cell envelope of certain gram-negative bacteria, which is toxin to human when solubilized. 20/2/2017 prepared by: Mr. simon solomon 20/2/2017 prepared by: Mr. simon solomon  Gram staining process The Gram staining process includes four basic steps, including: (1)Heat fix/attach the bacteria to the slide, (2).Applying a primary stain(crystal violet), (3).Adding a mordant (Gram's iodine), (4).Rapid decolorization with ethanol, acetone or a mixture of both,& (5).Counterstaining with safranin. Then observe the color change at each levels. 20/2/2017 prepared by: Mr. simon solomon 20/2/2017 prepared by: Mr. simon solomon  2.1.2. Nutritional types of bacteria Bacteria have evolved many mechanisms to acquire the energy and nutrients they need for growth and reproduction. ❑ Many are autotrophs – obtained their carbon from CO2. i. Photoautotrophs- obtained their energy from sun light ii. Chemoautotrophs- harvest energy from inorganic chemicals. ❑ Other bacteria are heterotrophs, organisms that obtain at least some of their carbon from organic molecules like glucose. i. Photo heterotrophs- obtain their energy from sun light ii. Chemo heterotrophs- harvest energy from organic molecules Sources of energy includes: ❖ Phototrophs use light as their energy source ❖ Chemotrophs obtain energy from the oxidation of chemical compounds(either organic or inorganic). 20/2/2017 prepared by: Mr. simon solomon ❑ Bacteria also have only two sources for electrons. I. Lithotrophs ("rock-eaters”)use reduced inorganic substances as their electron source II. Organotrophs extract electrons from reduced organic compounds. Based on their primary sources of carbon, energy and electrons, most bacteria may be placed in one of five nutritional classes. The majority of bacteria are either photolithoautotrophic or chemoorganoheterotrophic. 1. Photolithoautotrophic Often called simply photoautotrophs Use light energy and have CO2 as their carbon source. Photosynthetic bacteria and cyanobacteria employ water as the electron donor and release oxygen. Others, such as the purple and green sulfur bacteria, extract electrons from inorganic donors such as hydrogen, hydrogen sulfide, and elemental sulfur. 20/2/2017 prepared by: Mr. simon solomon 2. Chemoorganoheterotrophs Sometimes called chemohetrotrophs or chemoorganohetrotrophs Use the organic cpds as a source of energy, hydrogen, electrons and carbon. Nearly all pathogenic microorganisms are chemoorganoheterotrophs. Are photosynthetic bacteria (purple and green bacteria) Use organic matter as their electron donor and carbon source. 3. Photoorganoheterotrophs Are common inhabitants of polluted lakes and streams. Some of these bacteria also can grow as photolithoautotrophs with molecular hydrogen(inorganic) as an electron donor. 4. Chemolithoautotrophs Oxidize reduced inorganic compound such as iron, nitrogen, or sulfur molecules to derive both energy and electrons for biosynthesis. Carbon dioxide is the carbon source. 20/2/2017 prepared by: Mr. simon solomon 5. Chemolithoheterotrophs Use reduced inorganic molecules as their energy and e- source but derive their carbon from organic sources. Contribute greatly to the chemical transformation of elements( e.g., the conversion of ammonia to nitrate or sulfur to sulfate)that continually occur in ecosystems. Major Nutritional Types of Microorganisms 20/2/2017 prepared by: Mr. simon solomon 2.1.3. Reproduction of bacteria 2.1.3.1. Asexual reproduction Most reproduce by an asexual process called binary fusion. 1. The chromosome (DNA) replicates and the two DNA molecules separate 2. Cell fusion at mid cell involves the synthesis of a partition, or septum, that separates the mother cell into two genetically identical daughter cells 20/2/2017 prepared by: Mr. simon solomon 2.1.3.2. Sexual reproduction in bacteria In conjugation, two cells of d/t mating types come together, and genetic material is transferred from one to the other. Donor cells, F+ Cells (F-fertility),& recipient cells- F- F factor a DNA sequence in F+ cells Is necessary for a bacterium to serve as a donor Consists of about 20 genes, Can be in the form of a plasmid or it can be part of the DNA in the bacterial chromosomes. Genes encoded enzymes essential for transferring DNA. Certain F genes encode sex pili, long, hair like extensions hat project from the cell surface. The sex pilus recognizes and binds to surface of an F+ cell, forming a cytoplasmic conjugation bridge between the two cells. The F plasmid replicate itself, and DNA is transferred from donor to recipient bacterium through the conjugation bridge F plasmids may also have other types of genes, including those that determine resistance to antibiotics. 20/2/2017 prepared by: Mr. simon solomon  The F-plasmid genes encode both the proteins composing the F pilus and those involved in rolling circle replication of the plasmid. Cells containing the F plasmid, capable of forming an F pilus, are called F+ cells or donor cells, and those lacking an F plasmid are called F− cells or recipient cells. Figure 2.18. Bacterial reproduction by Conjugation 20/2/2017 prepared by: Mr. simon solomon  2.2. Archaea By the end of this section you should be able to: ✓ Give definition of archaea. ✓ Describe the general features archaea. ✓ Categorize archaea based on physiological characteristics. ✓ Explain the beneficial aspects of archaea 20/2/2017 prepared by: Mr. simon solomon  2.2. Archaea ❑ Similar to bacteria b/c these are also prokaryotes ❑ Archaeans are unicellular, microscopic organisms that live as producers or decomposers. Characteristics of archaea They are prokaryotic. Are single celled organisms. Lack membrane bound nucleus and membrane bounded organelles. Lack true peptidoglycan in their cell walls. Their cell membrane lipids have branched hydrocarbon chains. Many are found in extreme environments. Generally three major groups of archaea are recognized: 1. methanogens (they generate methane) 2. extreme halophiles, and 3. extreme thermophiles 20/2/2017 prepared by: Mr. simon solomon 1. The methanogens ✓ Are strictly anaerobic organisms ✓ Are found in anaerobic environment such as water logged soils, lake sediments, marshes, marine sediments and the gastrointestinal tracts of animals, including humans. ✓ Degrade organic molecules to methane. 2. Extreme halophiles ✓ Grow in highly saline environments such as the Great Salt Lake, the Dead Sea, salt evaporation ponds, and the surface of salt preserved foods. ✓ Are generally obligate aerobes 3. Extreme thermophiles (hypothermophiles) ✓ Are found near volcanic vents and fissures that release sulfurous gases and other hot vapors. ✓ With optimum temperatures usually in excess of 800C ✓ May be either obligate aerobes, facultative aerobes, or obligate anaerobes 20/2/2017 prepared by: Mr. simon solomon 4. Thermophilic extreme acidophiles ✓ Grow in extremely acidic, hot environment. ✓ Are members of two genera, Thermoplasm & picrophilus ✓ The tree, based on sequences of 16S ribosomal RNA genes, reveals a major evolutionary split of archaea in two phyla, the Crenarchaeota and the Euryarchaeota. ✓ Scientists originally identified archaea as a distinct type of prokaryotes on the bases of unique rRNA sequences. 20/2/2017 Figure 2.9:.Phylogenetic tree of archaea ❑ Archaea also share other common features that distinguish them from bacteria: ✓ Archaea lack true peptidoglycan in their cell walls. ✓ Their cell membrane lipids have branched hydrocarbon chains. ✓ The initial amino acid in their polypeptide chains, coded by the AUG start codon, is methionine (as in eukaryotes and in contrast to the N- fomylmethionine used by bacteria). ✓ Archaea multiply by binary fission, budding, fragmentation or other mechanisms. ✓ Nutritionally they are either aerobic, chemolithoautotroph to organotrophs. 2.2.1. Beneficial Aspects of Archaea i. Source of enzymes that are usually added to detergents ▪ In order to help it maintain its activity even at higher temp. and PH. ▪ Proteases and lipases derived from alkaliphilic bacteria are being used as detergent addictive to increase their stain removal ability ii. Some also bear the potential for bioremediation or help in cleaning contaminated sites. iii. The thermos aquaticus (thermophilic),is an essential part of the development of molecular biology as a science. ❑ Achaeans has become the source of the enzyme harnessed as the basis for the amplification of the DNA in a technique called PCR. 20/2/2017 prepared by: Mr. simon solomon 2.2.2. Physical Factors That Affects Microbial Growths ❑ The major physical factors which affect microbial growth are solutes and water activity, PH, Temperature, oxygen level, pressure and radiation. 20/2/2017 prepared by: Mr. simon solomon  2.3. Fungi By the end of this section you should be able to: ✓ describe the features of fungi. ✓ label the structures a typical fungus. ✓ explain the mode of reproduction in fungi. ✓ explain how fungi obtain nutrients. ✓ explain the economic importance of fungi. ✓ describe the major divisions of fungi. ✓ justify why yeasts are useful to humans. ✓ explain the mode of transmission of fungal diseases of humans 20/2/2017 prepared by: Mr. simon solomon  2.3. Fungi ❑ Mycologist:- scientists who study fungi ❑ Mycology:- the scientific discipline devoted to fungi ❑ Mycotoxicology:- the study of fungal toxins and their effects ❑ Mycoses (s., mycosis):- the diseases caused by fungi in animals. 20/2/2017 prepared by: Mr. simon solomon 2.3.1. General characteristics of true fungi ✓ All are eukaryotic= possess membrane- bound nuclei(containing chrs) and a range of membrane bound cytoplasmic organelles (e.g. mitochondria, vacuoles, EPR) ✓ Most are filamentous= composed of individual microscopic filaments called hyphae, network of hyphae called a mycelium ✓ Some are Unicellular:- e.g. yeasts ✓ Protoplasm of a hyphae or cell is surrounded by a rigid wall – composed primarily of chitin and Glucans, although the wall of some spp. Contain cellulose. ✓ Reproduce sexually and asexually ✓ Their nuclei are typically haploid- although the Oomycota and some yeast possess diploid nuclei. ✓ All are achlorophllous- lack chlorophyll and are incapable of photosynthesis. ✓ All are chemoheterotrophic (chemoorganotrophic) ✓ Possess characteristic range of storage compounds- e.g. trehalose, glycogen, sugar alcohols and lipids. ✓ Nutritionally categorized into three(saprophytic, parasitic and symbiotic) 20/2/2017 prepared by: Mr. simon solomon 2.3.2. Ecology of Fungi ❑ Are frequently found I cool, dark, moist places with a supply of decaying material. ❑ Fungi are saprobes that decompose organic matter. ❑ Lichens are a symbiotic relation ship between a fungus and a photosynthetic organism, usually an algae or cyanobacteria. ❑ the photosynthetic organism provides energy derived from light and carbohydrates, while the fungus supplies minerals and protection. 2.3.3. Classification of fungi ❑ The current classification of fungi includes:- 1. Ascomycota: - ascospore producing fungi. E.g. saccharomyces sereviciae 2. Basidomycota:- basidia forming fungi. E.g. rusts, smuts, and mushroom 3. Chytridomycota:- zoospore producing fungi e.g. allomyces & water molds 4. Glomeromycota:- e.g. mycorrhizal fungi. 5. Zygomycota:- sporangial fungi, e.g. rhizopus and mucor. 20/2/2017 prepared by: Mr. simon solomon 2.3.4. Reproduction in fungi ❑ Sporulation:- is the process of spore formation. A) Asexual Reproduction Asexual reproductive structures develop at the ends of specialized hyphae. As a result of mitotic divisions, thousands of spores are produced, all genetically identical. Many asexual spores develop within sacs or vessels called sporangia (sing sporangium; angio=’’vessel’’) Other fungi produces spores on supportive structures called conidiophores. These unprotected, dust-like spores are known as conidia (sing, conidium= dust) In yet other fungi, spores may form simply by fragmentation of the hyphae yielding arthropores (arthro=’’joint’’). The fungi that cause athlete`s foot multiply by this manner. Many yeasts reproduce asexually by budding. In this process, the cell become swollen at one edge, and a new cell called a blastospore, (blasto=’’bud’’) develops (buds) from the parent cell. 20/2/2017 prepared by: Mr. simon solomon B. Sexual reproduction Many fungi also reproduce spores by sexual reproduction. Opposite mating types come together and fuse. 2.3.5. Economic importance of fungi ❑ Fungi have both beneficial and harmful aspects. i. Beneficial aspects of fungi 1. Breakdown complex organic substrates (recycling of carbon and other elements in the cycle of life). 2. Food sources. E.g. basidiomycetes 3. In many industry processes involving fermentation 4. Preparation of some cheeses, soy sauce, and sufu, enjera, tej, tela… 5. Molds (such as Aspergillus spp. )are used in the production of citric, oxalic, gluconic and itaconic acid 6. Manufacturing of many antibiotics & immunosuppressive drug the cyclosporine. 7. For studying complex eukaryotic events, such as cancer and aging within a simple cell. 20/2/2017 prepared by: Mr. simon solomon 20/2/2017 prepared by: Mr. simon solomon ii. Harmful aspects of fungi 1. Are major causes of plant, animal human diseases. ❑ Plants are particularly vulnerable to fungal diseases b/c fungi can invade leaves through their stomata. 2. Molds can cause deterioration of fabrics, leather, electrical insulation and other manufactured goods. 3. Spoil the agricultural produce 4. Mycotoxicosis (ingestion of toxins off fungal origin) and Mycetismus (mushroom poisoning through ingestion of fungal elements). A. Aflatoxis: are mycotoxins produced by Aspergillus flavus and A. parasiticus. The molds are found primarily in warm, humid climates, where they contaminate agricultural products such as peanuts, cereals, sweet potatoes, corn, rice, and animal feeds. ❑ Are thought to be carcinogenic, especially in the liver 20/2/2017 prepared by: Mr. simon solomon B. Ergotism:- is caused a powerful toxin by from Claviceps purpurea, an ascomycetes fungus ▪ Grows as hyphae on kernels of rye, wheat, and barley. ▪ Gradually consume the substance of the grain and ▪ The dense tissue hardens into a purple body>> sclerotium. ▪ Sclerotium produce alkaloids (a group of peptide derivatives) ▪ deposited in the grain as a substance called ergot. ▪ Products such as bread made from rye grain may cause ergot rye disease, or ergotism. C. Mushroom poisoning, or mycetism:- Occurs from mushrooms that produce mycotoxins that affect the human body. 5. Superficial fungal infections ✓ Infections of the outermost areas of the human body: hair, finger nails, toe nails, and the epidermis (the dead outer most layer of the skin). ✓ Caused by any of several spp. Of filamentous fungi in the genera Trichophyton, epidermophyton, and microsporum. ✓ The various forms of dermatophytosis are referred to as tineas or ‘ringworm’ 20/2/2017 prepared by: Mr. simon solomon The tineas are classified according to the anatomic site or structure affected: 1. Tinea corporis(ringworm): Microsporum canis and Trichophyton mentagrophytes. Affects hairless skin. 2. Tinea pedis (athlete's foot):T.rubrum, T. mentagrophytes, and Epidermophytonfloccosum. Affects mainly the lower legs. 3. Tinea capitis:T.tonsurans and M.canis. The scalp, eyebrows, and eyelashes 4. Tinea barbae: T.rubrum and T.mentagrophytes. Beard ringworm. 5.Tinea unguium (also known as onychomycosis):T.rubrum, T. mentagrophytes, and E.floccosum. Affect the nails Figure 2.18. Fungal disease affecting human and plants 20/2/2017 prepared by: Mr. simon solomon Mode of transmission ❑ Superficial mycoses (Dermatomycoses) ✓ transmitted directly by human contact, animal-human contact or indirectly on inanimate objects (clothes, carpets, moisture, and dust in showers, swimming pools, wardrobes, gyms). ✓ The localization of the primary foci corresponds to the contact site. Thus feet, uncovered skin(hair, head, facial skin)are affected most frequently. Prevention ❑ Regular disinfection of showers and wardrobes can contribute to prevention of athlete's foot, a very frequent infection 20/2/2017 prepared by: Mr. simon solomon 20/2/2017 prepared by: Mr. simon solomon  2.2.4. Protozoa By the end of this section you should be able to: ✓ describe the general features of protozoa. ✓ describe the structures of amoeba, euglena, paramecium. ✓ explain how protozoans get nutrition. ✓ describe the modes of reproduction in protozoa. ✓ describe the process of conjugation in protozoa. ✓ list the common diseases caused by protozoans. ✓ explain the ways of transmission of protozoan diseases. ✓ explain the economic importance of on human protozoans. ✓ analyze the health impacts of different protozoan diseases. 20/2/2017 prepared by: Mr. simon solomon  2.2.4. Protozoa ❑ The term ‘’ protozoa’’ (sing. Protozoan; Greek ‘protos,’ First, and Zoon, animal ❑ Protozoology: generally refers to the study of protozoa. Characteristics of protozoa ✓ Unicellular organisms ✓ Lacks cell wall ✓ They are freeing living or parasitic and Aerobic/ ✓ They have true nucleus. ✓ They are eukaryotic. ✓ Mostly microscopic, although some are large enough to be seen with an aided eye Locomotion by pseudopodia, flagella, cilia, and direct cell movement; some sessile. ✓ Nutrition; autotrophs, heterotrophs, saprozoic (using nutrients dissolved in the surrounding medium) ✓ Aquatic or terrestrial habitat; free living or symbiotic mode of life ✓ Reproduction asexually by binary fusion, budding and cysts and sexually by conjugation or by syngamy (union of male and female gametes to form a zygote). 20/2/2017 prepared by: Mr. simon solomon 20/2/2017 prepared by: Mr. simon solomon Nutrition in protozoa ❑ Heterotrophic: receive nutrients by breaking down organic matter ❑ Can grow in both aerobic and anaerobic environments. ❑ Some protists, such as euglena, receive nutrients from organic matter and through photosynthesis b/c they contain chlorophyll. ❑ These protists are considered as both algae and protozoa. ❑ Protists obtain food in one of three ways: 1. Absorption: food is absorbed across the protists plasma membrane. 2. Ingestion: - cilia create a wave-like motion to move food into a mouth like opening called a cytosome. 3. Engulf: - pseudopods engulf food, and then pull it into the cell using a process called phagocytosis. E.g. amoeba. ❑ Food is digested in the vacuole inside the cell. Waste products are excreted using a process called exocytosis. 20/2/2017 prepared by: Mr. simon solomon  Reproduction in protozoa Most protozoa are asexual and reproduce in one of three ways. These are: ❑ Fission: Fission occurs when a cell divides evenly to form two new cells. ❑ Budding: Budding occurs when a cell divides unevenly. ❑ Multiple fission (schizogony): Multiple fission is when the nucleus of the cell divides multiple times before the rest of the cell divides. Forms around each nucleus when the nucleus divides then each nuclei separates into a daughter cell 20/2/2017 prepared by: Mr. simon solomon  Sexual reproduction also occurs during the life cycle of most protozoa. A distinctive feature of ciliates is the presence of two types of nuclei: ❑ tiny micronuclei and ❑ large macronuclei. Genetic variation results from conjugation, a sexual process in which two individuals exchange haploid micronuclei but do not reproduce. Ciliates generally reproduce asexually by binary fission, during which the existing macronucleus disintegrates and a new one is formed from the cell's micronuclei. Each macronucleus typically contains multiple copies of the ciliate's genome. Genes in the macronucleus control the everyday functions of the cell, such as ✓ Feeding ✓ waste removal and ✓ maintaining water balance. 20/2/2017 prepared by: Mr. simon solomon ❑ Some of the human diseases caused by protozoans include Malaria, giardiasis, African trypanosomiasis, amoebiasis, chagas disease, leishmaniosis, toxoplasmosis, crytosporidiosis 20/2/2017 prepared by: Mr. simon solomon  2.4.1.Common diseases caused by protozoa 20/2/2017 prepared by: Mr. simon solomon 20/2/2017 prepared by: Mr. simon solomon  2.3. Viruses By the end of this section you should be able to: ✓ describe the structures of a virus ✓ explain the characteristics of viruses. ✓ label the structures of viruses. ✓ classify viruses as RNA viruses and DNA viruses. ✓ explain the mechanism of replication viruses. ✓ Distinguish between lytic and lysogenic cycle of a virus. ✓ Mention the common viral diseases in Ethiopia. ✓ Describe the ways of transmission and prevention of HIV/AIDS, Hepatitis B. 20/2/2017 prepared by: Mr. simon solomon  2.5. Viruses Is very small, non –cellular parasite of cells. Genome (DNA or RNA) is enclosed in a capsid Have no cellular organelles and so cannot carry out any metabolic processes; i. e. lack the chemical machinery for genetic energy and synthesizing large molecules. They must all enter other cells to reproduce(obligate, intracellular particles). Most can be seen only with the electron microscope Characteristics of virus Have an inner core of nucleic acid surrounded by protein coat called envelope. Cannot be grown on artificial cell free media (however, grow in animals, eggs or tissue culture). Do not have a cellular organization. –do not have cell wall or cell membrane or cellular organelles including ribosomes. ❑ Do not occur free in nature but act as obligate intracellular parasite of bacteria, protozoa, fungi, algae, plants, and animals. 20/2/2017 prepared by: Mr. simon solomon  Lack the enzymes necessary for protein and nucleic acid synthesis and are dependent for replication on the synthetic machinery of host cells. Once it infects a susceptible cell, however, a virus can direct the host cell machinery to produce more viruses. Are unaffected by antibacterial antibiotics. And they are inert (i.e. metabolically inactive) nucleoprotein. Occupy a space b/n living and non- living, b/c they are crystallizable and non-living outside thee, body of the host- active only inside the host cells. Ultramicroscopic size, ranging from 20nm- 450nm (diameter) Nucleic acid can be double stranded /single stranded DNA or single/double stranded RNA. Molecules on virus surface impart high specificity for attachment to host cell Multiply by taking control of host cell’s genetic material and regulating the synthesis and assembly of new viruses ❑ Viruses infect all cellular life forms: eukaryotes (vertebrate animals, invertebrate animals, plants, fungi) and prokaryotes(bacteria and archaea). ❑ The viruses that infect prokaryotes are often referred to as bacteriophages, or phages for short. 20/2/2017 prepared by: Mr. simon solomon Structure of viruses ❑ Basic structures of virus i. Genome:- central core of nucleic acid either DNA or RNA but not both ii. Capsid:- protein coat iii. Lipoprotein layer:- in some virus, an envelope made up of glycoprotein and phospholipid bilayer is present inside the capsid. Nucleocapsid- the combined formed by the core and capsid Capsomeres- are identical repeating subunits that build up capsids. ❑ Some viruses contain enzymes which play central role during infection processes. E. g. ❖ Lysozyme – in some bacteriophage- makes small hole in bacterial cell ❖ Nucleic acid polymerase- in some virus transcribe the viral genome into mRNA ❖ Reverse transcriptase- in retrovirus-transcribe DNA from RNA 20/2/2017 prepared by: Mr. simon solomon 20/2/2017 prepared by: Mr. simon solomon  2.5.2.Viral symmetry 1. Helical symmetry Consists of identical protein subunits or protomers which assembled in a helical structure around the genome This protein subunits generally forms nucleocapsid. The helical structure provides flexibility to the filaments. E.g. tobacco mosaic &sendai virus 2. Icosahedral symmetry Refers to a type of polyhedron with 20 equilateral triangular faces and 12 vertices. The rigid structure provides protection to the genome. E.g. papovavirus, picorna virus, toga virus etc. 3. Complex symmetry Consists of complex structural components which made it different from other two groups. E.g. pox virus 20/2/2017 prepared by: Mr. simon solomon  Figure 2.25. Viral classification based on their structures 20/2/2017 prepared by: Mr. simon solomon  DNA Vs RNA Viruses DNA Virus RNA Virus DNA as their genetic material RNA as their genetic material double-stranded single-stranded DNA viruses replicate in the nucleus RNA viruses takes place in the cytoplasm DNA viruses are stable RNA viruses are unstable Contain large genome Contain a small genome Newly synthesized DNA is packed in a pre- Newly synthesized DNA is not packed in a pre- formed capsid called procapsid formed a procapsid mutation rate is lesser than the RNA mutation rate is higher than the DNA E.g. Herpes, Adeno, Pox , Hepatitis and E.g. Covid-19, polio, yellow fever, dengue, Papilloma hepatitis C, Measles, Rabies, Influenza & Ebola 20/2/2017 prepared by: Mr. simon solomon Bacteriophage/phage ❑ Bacteriophages are bacterial virus. ❑ They are the virus that infect bacteria ❑ They are obligate intracellular parasites that multiply inside by making use of some or all of the host biosynthesis machinery. ❑ They are also called phages 20/2/2017 prepared by: Mr. simon solomon  Retroviruses ❑ Retroviruses also contain RNA, but replicate in a different way. When they infect cells, they release into the cells their RNA and an enzyme that causes it to be ‘reverse-transcribed’ into DNA. ❑ Retrovirus an RNA virus that converts its genetic information from RNA into DNA after it has infected a host. Example: HIV, human T-lymphotropic virus type 1 & 2 Viruses infect all cellular life forms: eukaryotes (vertebrate animals, invertebrate animals, plants, fungi) prokaryotes (bacteria and archaea). The viruses that infect prokaryotes are often referred to as bacteriophages, or phages for short. HIV (human immunodeficiency virus) is a virus that attacks the body's immune system. If HIV is not treated, it can lead to AIDS (acquired immunodeficiency syndrome). 20/2/2017 prepared by: Mr. simon solomon 2.5.3.Classification of Viruses ❑The primary criteria for delineating the main viral taxa are: 1. The type and character of the viral genome 2. The strategy of viral replication and 3. The types of organisms they infect Viral replication ❑ A virus hijack the metabolism of the cell to produce copies of it self, and destroy the host cell when new virions are released. ❑ In general, viruses go through the following five steps in their replication cycles to produce more virions: 1. Adsorption:- the attachment of viruses to host cell. 2. Penetration:- the entry of virions(or their genome) in to host cells. 3. Synthesis:- the synthesis of new nucleic acid molecules, capsid proteins, and other viral components 4. Maturation:- the assembly of newly synthesized viral components in to complete virions. 5. Release:-the departure of new virions from host cells. Release generally, but not always, kills(lysis) host cells. 20/2/2017 prepared by: Mr. simon solomon 20/2/2017 prepared by: Mr. simon solomon  Bacteriophage Life cycle 1. Lytic cycle ❑ lytic cycle also known as virulent cycle. In this cycle, intracellular multiplication of the phage results in the lysis of host bacteria, resulting in release of progeny virions. ❑ The enzyme lysozyme, which is coded for by a phage gene, breaks down the cell wall, allowing viruses to escape. ❑ In the process the bacterial l host cell is lysed. Thus, phages such as T4 are called virulent (lytic)phages because they lyse and destroy the bacteria they infect. ❑ The released phages can now infect more susceptible bacteria, starting the infection process all over again. Such infections by virulent phages represent a lytic cycle of infection. ❑ Lytic cycle of bacteriophage (Replication of a virulent bacteriophage). ❑ A virulent phage undergoes a lytic cycle to produce new phage particles within a bacterial cell. ❑ Cell lysis releases new phage particles that can infect more bacteria). 20/2/2017 prepared by: Mr. simon solomon 20/2/2017 prepared by: Mr. simon solomon 2. Lysogenic cycle ❑ Infection with every phage does not result in lysis of the host cells. ❑ Unlike virulent phages, which cause lysis of the host cell, some phages(such as temperate phages)integrate into the genome of the bacterial chromosome without causing any lysis of the bacteria. ❑ The integrated phage nucleic acid is known as the prophage. The prophage behaves like a segment of the host chromosome and multiplies synchronously with it. This phenomenon is known as lysogeny. ❑ The bacterium that carries a prophage within its genome is called lysogenic bacterium and such phages are called lysogenic or temperate phages. 20/2/2017 prepared by: Mr. simon solomon 20/2/2017 prepared by: Mr. simon solomon  Lytic cycle Vs Lysogenic Cycle Lytic cycle Lysogenic Cycle The DNA of the virus doesn’t integrate into The DNA of the virus integrates into the host the host DNA DNA Host DNA hydrolyzed Host DNA not hydrolyzed Absence of Prophage stage Presence of Prophage stage DNA replication of virus takes place DNA replication of virus takes place along independently from the host DNA replication with the host DNA replication Occurs within short period of time Take time Symptoms of viral replication are evident Symptoms of viral replication not evident Genetic recombination in the host bacterium Genetic recombination in the host bacterium not allowed allowed The cellular mechanism of the host cell is The cellular mechanism of the host cell is totally undertaken by the viral genome somewhat disturbed by the viral genome 20/2/2017 prepared by: Mr. simon solomon 2.6. Normal microbiota By the end of this section you should be able to: Define the normal microbiota. Distinguish between resident and transient microbiota Mention three protective roles of the normal microbiota. Explain how the composition of the normal microbiota can change over time. · Describe germ theory of disease State at least three postulates formulated by Koch. Justify how the Koch's experimental procedure contributed to the advancement microbiological techniques 20/2/2017 prepared by: Mr. simon solomon Normal microbiota ❑ The normal microbiota is the population of microorganisms routinely found growing on the body of healthy individuals. ❑ Microbes that typically inhabit body sites for extended periods are resident microbiota, whereas temporary occupants are transient microbiota. ❑ There are many reasons to acquire knowledge of the normal human microbiota. Three specific examples include: a) An understanding of the different microorganisms at particular locations provides greater insight into the possible infections that might result from injury to these body sites. b) A knowledge of the normal microbiota helps the physician investigator understand the causes and consequences of colonization and growth by microorganisms normally absent at a specific body site. c) An increased awareness of the role that these normal microbiota play in stimulating the host immune response can be gained. This awareness is important because the immune system provides protection against potential pathogens. 20/2/2017 prepared by: Mr. simon solomon ❑ The normal human microbiota have protective role from diseases causing microorganisms. ❑ One of the most significant contributions of the normal microbiota to health is protection against pathogens. ❑ The normal microbiota excludes pathogens by; ✓ covering binding sites that might otherwise be used for attachment, ✓ consuming available nutrients, ✓ producing compounds toxic to other bacteria, ✓ to stimulate the adaptive immune system. ❑ When members of the normal microbiota are killed or their growth suppressed, as can happen during antibiotic treatment, pathogens may colonize and cause disease. For example: Oral antibiotics can also inhibit members of the normal intestinal microbiota, allowing the overgrowth of toxin-producing strains of Clostridium difficile that cause antibiotic-associated diarrhea and colitis. 20/2/2017 prepared by: Mr. simon solomon  The Germ Theory of Disease and Koch's Postulates ❑ Koch’s postulates state the following: 1. The disease-causing organism must always be present in animals suffering from the disease but not in healthy animals. 2. The organism must be cultivated in a pure culture away from the animal body. 3. The isolated organism must cause the disease when inoculated into healthy susceptible animals 4. The organism must be isolated from the newly infected animals and cultured again in the laboratory, after which it should be seen to be the same as the original organism. 20/2/2017 prepared by: Mr. simon solomon  2.5.1. Common disease-causing microorganisms The normal microbiota or flora not only do us no harm, but also in some cases can actually benefit us. For example, some normal microbiota protect us against diseases by preventing the overgrowth of harmful microbes, and others produce useful substances such as vitamin K and some B vitamins. Unfortunately, under some circumstances e.g., when some normal microbiota leave their habitat, they can cause diseases. The thousands of species of viruses, bacteria, fungi, and parasites, only a tiny portion are involved in diseases of any kind. The theory that disease can be caused by microorganisms is called the germ theory. Organisms that cause disease are called pathogens. A disease that is caused by a microorganism infecting the body is an infectious disease. 20/2/2017 prepared by: Mr. simon solomon  2.7. Modes of disease transmission Microorganisms are transmitted in health care settings by four main routes: A. Contact B. Common vehicle C. Airborne D. Droplet 20/2/2017 prepared by: Mr. simon solomon 20/2/2017 prepared by: Mr. simon solomon 20/2/2017 prepared by: Mr. simon solomon  2.8. Use of microorganisms A. Agriculture Microorganisms play an important role in agriculture. The microorganisms include bacteria, fungi, algae, protozoa, viruses. Microorganisms help in organic matter decomposition, humus formation. The important role of microorganisms includes Nitrogen fixation Phosphate solubilization potassium mobilization antagonism towards pathogens, pests. Microorganisms are primarily responsible for converting essential elements into forms that plants and animals can use. Microorganisms, especially bacteria and fungi, return carbon dioxide to the atmosphere when they decompose organic wastes and dead plants and animals. Nitrogen is abundant in the atmosphere but in a form not usable by plants and animals. Only bacteria can naturally convert atmospheric nitrogen to a form available to plants and animals (nitrate). 20/2/2017 prepared by: Mr. simon solomon  B. Sewage treatment Anaerobic bacteria are used in wastewater treatment on a normal basis. The main role of these bacteria in sewage treatment is to reduce the volume of sludge and produce methane gas from it. Methane gas can be used as an alternative energy source. This is a huge benefit considering the already high wastewater treatment energy consumption levels. Phosphorus removal from wastewater is another benefit of anaerobic microbes used in sewage treatment. 20/2/2017 prepared by: Mr. simon solomon  C. Bioremediation Bioremediation is a natural process that relies on microorganisms and plants and/or their derivatives (enzymes or spent biomass) to degrade Or alter environmental contaminants as these organisms carry out their normal life functions. Applied bioremediation methods therefore focus on tapping the naturally occurring microbial catabolic capabilities to degrade, transform or accumulate most of the synthetic compounds such as hydrocarbons(e.g. Oil), polychlorinated biphenyls polyaromatic hydrocarbons radionuclides and metals. The (PCBs), (PAHs), Natural existence of a large diversity of microbial species expands the variety of chemical pollutants that are degraded or detoxified. Bioremediation is a natural process, it takes a little time, as an acceptable waste treatment process for contaminated material such as soil. Microbes able to degrade the contaminant and increase in numbers when the contaminant is present. When the contaminant is degraded, the biodegradative population declines. The residues for the treatment are usually harmless products including water, carbon dioxide and cell biomass. 20/2/2017 prepared by: Mr. simon solomon D. Food production and processing The tart taste of yogurt, pickles, sharp cheeses, and some sausages is due to the production of lactic acid by one or more members of a group of bacteria known as the lactic acid bacteria. These bacteria -including species of Lactobacillus, Lactococcus, Streptococcus: Leuconostoc and Pediococcus are obligate fermenters that characteristically produce lactic acid as an end product of their metabolism. Some also produce flavorful and aromatic compounds that contribute to the overall quality of fermented foods. 20/2/2017 prepared by: Mr. simon solomon E. Biotechnology Biotechnology is one field which has made use of microorganisms most. By using the techniques of biotechnology, scientists have succeeded in developing human insulin, growth hormones and other useful components of the body. Biotechnological processes use microorganisms for the drug delivery in the form of vectors and plasmids. Microorganisms have provided many beneficial things to agriculture as they are responsible for increasing the fertility of the soil. Due to this, the production of the plants increases and economy becomes strong. Generally, microorganisms (MOS)have big role in, suppression of soil-borne pathogens, recycling and increased availability of plant nutrients, degradation of toxicants including pesticides, Production of antibiotics and other bioactive compounds, Production of simple organic molecules for plant uptake. In addition, MOS are essential in alleviating complexation of heavy metals to limit plant uptake, solubilization of insoluble nutrient sources, and Production of polysaccharides to improve soil aggregation 20/2/2017 prepared by: Mr. simon solomon The carbon cycle All organisms are composed of organic molecules such as proteins, lipids & carbohydrates. The carbon travels through the food chain as primary producers are eaten by primary consumers, which are then eaten by secondary consumers. Decomposers then use the remains of primary producers and consumers. Without primary producers, no other organisms, including humans, could exist. When heterotrophs consume organic material, they break it down using respiration and/or fermentation to release the energy, which is captured to make ATP. The processes usually make CO₂. A wide variety of organisms use sugars, amino acids, and proteins as energy sources, but rapidly multiplying bacteria often the O₂ supply has a strong influence on the carbon cycle. Not only does O₂ allow degradation of certain compounds such as lignin. It also helps determine the types of carbon-containing gases produced. When organic matter is degraded aerobically, a great deal of CO₂ is produced. When the O₂ level is low, however, as is the case in marshes, swamps, and manure piles, the degradation is incomplete, generating some CO₂ and a variety of other products. 20/2/2017 prepared by: Mr. simon solomon 20/2/2017 prepared by: Mr. simon solomon  Methanogenesis and Methane Oxidation In anaerobic environments, CO2 is used by methanogens. These archaea obtain energy by oxidizing hydrogen gas, using CO2 as a terminal electron acceptor, generating methane(CH₄). Methane that enters the atmosphere is oxidized by ultraviolet light and chemical ions, forming carbon monoxide (CO)and CO₂. A group of microorganisms called methylotrophs can use methane as an energy source, oxidizing it to produce CO₂. 20/2/2017 prepared by: Mr. simon solomon  The Nitrogen cycle Root nodules are found on the roots of plants, primarily legumes, which form a symbiosis with nitrogen-fixing bacteria. Nitrogen fixation in the nodule is very oxygen sensitive. Under nitrogen-limiting conditions, capable plants form a symbiotic relationship with a host- specific strain of bacteria known as rhizobia. 20/2/2017 prepared by: Mr. simon solomon  The sulfur cycle Sulfur is found in fewer types of organic molecules than nitrogen, but it is found in many proteins. The bacteria involved in the sulfur cycle and the roles they play. 20/2/2017 prepared by: Mr. simon solomon  The phosphorus cycle Phosphorus (P) occurs in soils as both organic and inorganic forms. Phosphorus can be found dissolved in the soil solution in very low amounts or associated with soil minerals or organic materials. The relative amounts of each form of phosphorus vary greatly among soils, with the total amount of P in a clayey-textured soil being up to ten times greater than in a sandy soil. A large number of compounds make up the organic P in soils, with the majority being of microbial origin. Organic P is held very tightly and is generally not available for plant uptake until the organic materials are decomposed and the phosphorus released via the mineralization process. Mineralization is carried out by microbes, and as with nitrogen, the rate of P release is affected by factors such as soil moisture, composition of the organic material, oxygen concentration and PH. Inorganic P in soils. The concentration of inorganic P (orthophosphates) in the soil solution at any given time is very small, amounting to less than 1Ib./A. Phosphorus in the inorganic form occurs mostly as aluminum, iron or calcium compounds. 20/2/2017 prepared by: Mr. simon solomon  Figure 2.30. The phosphorus cycle 20/2/2017 prepared by: Mr. simon solomon 2.9. Controlling microorganisms ❑ Sterilization is defined as a process by which an article, surface, or medium is freed of all living microorganisms either in the vegetative or in the spore state. ❑ Any material that has been subjected to this process is said to be sterile. These terms should be used only in the absolute sense. ❑ An object cannot be slightly sterile or almost sterile; it is either sterile or not sterile. ❑ Most sterilization is performed with a physical agent, such as heat, a few chemicals called sterilant can be classified as sterilizing agents because of their ability to destroy spores. ❑ A germicide, also called a microbicide, is any chemical agent that kills pathogenic microorganisms. ❑ A germicide can be used on inanimate (nonliving)materials or on living tissue, but it ordinarily cannot kill resistant microbial cells. ❑ Any physical or chemical agent that kills “germs” is said to have germicidal properties. 20/2/2017 prepared by: Mr. simon solomon ❑ Disinfection refers to the use of a chemical agent that destroys or removes all pathogenic organisms or organisms capable of giving rise to infection. This process destroys vegetative pathogen but not bacteria endospores. ❑It is important to note that disinfectants are normally used only on inanimate objects because they can be toxic to human and other animal tissue, when used in higher concentrations. ❑Disinfection processes also remove the harmful products of microorganisms (toxins) from materials. Examples of disinfection include bleach and alcohol solution ❑ Antiseptics: are a chemical agents that slow or stop the growth of microorganisms on external body surface (e.g. skin and mucous membranes),wounds, and surgical incisions to destroy or inhibit vegetative pathogens. Examples of antisepsis include: A. Preparing the skin before surgical incisions with iodine compounds, B. Swabbing an open root canal with hydrogen peroxide, and C. Ordinary hand washing with a germicidal soap. 20/2/2017 prepared by: Mr. simon solomon ❑ Sanitization is any cleansing technique that mechanically removes microorganisms (along with food debris) to reduce the level of contaminants. ❑ A sanitizer is a compound (e.g. soap or detergent)that is used to perform this task. ❑ Cooking utensils, dishes, bottles, cans, and used clothing that have been washed and dried may not be completely free of microbes, but they are safe for normal use. ❑ Air sanitization with ultraviolet lamps reduces airborne microbes in hospital rooms, veterinary clinics and laboratory installations. ❑ Preservation is a general term for measures taken to prevent microbe caused spoilage of susceptible products (pharmaceuticals, foods) ❑ Decontamination is the removal or count reduction of microorganisms contaminating an object. ❑ The objective of aseptic measures and techniques is to prevent microbial contamination of materials or wounds. ❑ In antiseptic measures, chemical agents are used to fight pathogens in or on living tissue, for example in a wound. 20/2/2017 prepared by: Mr. simon solomon Physical Methods of Sterilization and Disinfection ❑ Heat: The application of heat is a simple, cheap and effective method of killing pathogens. ❑ Methods of heat application vary according to the specific application. ❑ Pasteurization is the antimicrobial treatment used for foods in liquid form (milk) ❑ Low-temperature 61.5 ℃ ,30 minutes; 71℃, 15seconds. ❑ High-temperature pasteurization: brief of exposure to 80-85°℃ in continuous operation. ❑ Uperization (Ultra-pasteurization): heating to 150℃ for 2.5 seconds in a pressurized container using steam injection. ❑ Dry heat sterilization : sterilization by dry heat includes sterilization by a. Flaming: Sterilization of inoculating loop or wire, the tip of forceps, searing spatulas,etc. ▪ It is carried out by holding them in the flame of the Bunsen burner till they become red hot. b. Incineration: Incineration is an excellent method for safely destroying infective materials by burning them to ashes. ▪ Incinerators are used to carry out this process and are regularly employed in hospitals and research labs to destroy hospital and laboratory wastes. 20/2/2017 prepared by: Mr. simon solomon ❑ The method is used for complete destruction and disposal of infectious material, such as syringes, needles, culture material, dressings, bandages, bedding, animal carcasses, and pathology samples. ❑ This method is fast and effective for most hospital wastes, but not for metals and heat resistant glass materials. ❑ Hot air oven: Sterilization by hot-air oven requires exposure to 160-180°℃ for 2 hours and 30 minutes, which ensures thorough heating of the objects and destruction of spores. ❑ Autoclaves charged with saturated, pressurized steam are used for this purpose 121℃,15 minutes, one atmosphere of pressure (total: 202kPa). ❑ 134℃,three minutes, two atmospheres of pressure (total:303 kPa). Intermittent Sterilization ❑ Certain heat-labile substances(e.g. serum, sugar, egg etc.) that cannot with stand the high temperature of the autoclave can be sterilized by a process of intermittent sterilization, known as tyndalization. ❑ Tyndallization is carried out over a period of 3 days and requires a chamber to hold the materials and a reservoir for boiling water. 20/2/2017 prepared by: Mr. simon solomon ❑ Items to be sterilized are kept in the chamber and are exposed to free-flowing steam at 100°℃ for 20 minutes, for each of the three consecutive days. Bacterial Isolation techniques ❑ Microorganisms(bacteria or fungi)can be isolated from food, soil, water or from other materials. ❑ For bacterial/fungal isolation, the soil(food)samples are collected from the desired sites. Are separated on artificial media by serial dilution method. ❑ Each of the isolates are purified on new media and experimented for the morphological characteristic like shape, gram nature and arrangement of cells, motility etc. ❑ Enzymatic activities were tested by biochemical characterization. Finally, molecular techniques are used for further identifications. 20/2/2017 prepared by: Mr. simon solomon 20/2/2017 prepared by: Mr. simon solomon