Microbiology Lecture 1 PDF

Microbiology Ass.Prof.Dr Ibtihal Alshamarti Molecular Genetics –UK  Introduction in microbiology Microbiology, the study of microscopic organisms, derived its name from three Greek words: mikros (“small”), bios (“life”), and logos (“science”). Taken together they mean the study of microorganisms...

Microbiology Ass.Prof.Dr Ibtihal Alshamarti Molecular Genetics –UK  Introduction in microbiology Microbiology, the study of microscopic organisms, derived its name from three Greek words: mikros (“small”), bios (“life”), and logos (“science”). Taken together they mean the study of microorganisms which are very small and cannot be seen by naked eye. If an object has a diameter 0.1 mm or less, eye cannot see it and very little details can be seen in an object having diameter 1 mm. So roughly speaking organisms having diameter 1 mm or less are called microorganisms and are studied in Microbiology. The existence of microorganisms was unknown until the discovery of Microscope that is an optical instrument which can magnify small objects which cannot be seen by naked eye. Microscopes were invented in the beginning of 17th century. Early Microscopes were of two types; Simple Microscope, with a single lens of very short focal length and Compound Microscope, with two double convex lens system including ocular and objective lens with higher magnifying power. The Branches of microbiology Bacteriologists - study bacteria, there are medical, agricultural, biotechnological Protozoologists, study small “animal - like” single celled organisms such as amoeba, and various disease causing parasites. Parasitologists- a term generally used to describe those who study small animals as agents of disease (like some microscopic worms for instance) but also used to describe those who study protozoan pathogens. Mycologists - study fungi, there are medical, agricultural, biotechnological specializations Phycologists study algae AND Immunology -is often taught and researched in microbiology  Main characteristics of microorganisms 1. Their size is very small. 2. There is no cellular differentiation. they are unicellular and one cell is capable of performing all the functions. some microorganisms are multicellular with little or no cellular differentiation. 3. Microorganisms are present everywhere on the bodies of animals and humans, on plant surfaces, in the air, water, dust, soil, and even inside the intestinal canal of all insects, birds, animals and human beings. Historical Developments in Microbiology Robert Hooke (1635 - 1703) ,he made many scientific discoveries in the 17th century, including making one of the first microscopes and also using a copy of one of Leeuwenhoek’s microscopes to see and draw details of the structure of plant cells and some microbes. Antony van Leeuwenhoek (1632-1723) made the first useful microscopes in the 19th century, they were fiendishly difficult to make and use, they were essentially a lens held in a metal clip, the lens was made from a tiny drop of molten glass, and he used such a microscope to see the first microscopic cells. After the discovery of microorganisms, scientists began to study the origin of these small organisms from the point of view of the two schools of thought; One believed in the Theory of spontaneous generation i.e. living animalcules are formed spontaneously from nonliving matter, while the other supported the theory of biogenesis i.e. they are formed from the ‘seeds’ or ‘germs’ of these animalcules which are always present in the air. Louis Pasteur (1822-1895) was born in France , he emerged as one of the greatest biologists of the 19th century. His contributions are the most significant in the history of science and industry and his work with germs and microorganisms opened new areas of scientific studies. He was demonstrated through a series of definitive experiments that air contains microscopically observable ‘organized bodies’. 1857 – Lactic acid fermentation is due to a microorganism 1860 – Yeasts are involved in alcoholic fermentation 1861 – Disproved the theory of spontaneous generation 1861 – Introduction of the terms aerobic and anaerobic for yeasts. Production of more alcohol in the absence of oxygen during sugar fermentation- The Pasteur Effect 1862 – Proposed germ theory of disease 1867 – Pasteur devised the process of destroying bacteria known as pasteurization. 1881 – Development of anthrax vaccine. 1885 – Development of a special vaccine for rabies (the Pasteur treatment)  Robert Koch (1843-1910) confirmed Pasteur's germ theory and took it several steps further. He was put of four basic principles or postulates of bacteriology known as Koch’s postulates and they are: 1. Microorganism must be present in every case of the disease. 2. Microorganism must be isolated from the diseased host and grown in pure culture. 3. The specific disease must be reproduced when a pure culture of microorganism is injected into healthy susceptible host. 4. Microorganism must be recovered once again from experimentally inoculated host. EUKARYOTIC CELLS AND PROKARYOTIC CELLS CELL THEORY All living organisms include two types of cells that are prokaryotes (pro = before; karyon– nucleus),and eukaryotes (eu = true). Bacteria and archaea belong to prokaryotes. While fungi, plant and animal cells belong to Eukaryotes Eukaryotes A animals, plants and fungi are called eukaryotic cells. They contain membrane bound organelles such as a nucleus and mitochondria. Eukaryotic cells tend to be 10 to 100 times the size of prokaryotic cells.  Animal cells have a basic structure. As shows in table below Cell structure function A jelly-like material that contains dissolved nutrients, salts Cytoplasm and structures called organelles. It is where many of the chemical reactions happen. Contains genetic material which the instructions that cells use Nucleus to make proteins. Controls the cell's activities. Its structure is permeable to some substances but not to Cell membrane others. It therefore controls the movement of substances in and out of the cell. Organelles that contain the enzymes required for aerobic Mitochondria respiration and where most energy is released in respiration. Prokaryotes Bacteria are amongst the simplest of organisms - they are made of single cells. Their cell structure is simpler than the cells of eukaryotes and cells are smaller, most are 0.2 μm - 2.0 μm. These cells do not contain membrane bound organelles such as a nucleus and mitochondria. Essential Structures  Capsule polysaccharides Protect against phagocytosis Pili glycoproteins Attachment to cell surface flagellum proteins motility spore Keratinelike coat Resistance to Dehydration, heat, and Dipicolinc acid chemicals Plasmid DNA Contains variety of genes for antibiotic resistance, enzymes and toxins Granules Glycogen, lipid, Storage sites of foods polyphosphates Cell division ?  Bacteria Dr Ibtihal Alshamarti Molecule Genetics [email protected] Bacteria Cell wall Structures BACTERIAL CELL WALL  It is a rigid, multilayered structures make up of Peptidoglycan (unique to bacterial cell with no analogs in mammalians cells).  15% dry weight. Peptidoglycan is polymer (N-acetylemuramic acid (NAM) plus N-acetyle glucosamine( NAG) cross-bridge with penta peptide by Transpeptidase enzyme( penicillin- binding proteins).  Penicillin prevents formation of this Interpeptide bond Lysozyme breaks this glycoside bond between NAM and NAG Figure showing the sites of action of the antibiotic such penicillins and the lysozyme enzyme Gram positive and gram negative bacteria are the two types of bacteria, differentiated by the gram staining technique. Gram staining was developed by Cristian Gram in 1884. The stain used during the technique is crystal violet. Gram positive bacteria are more susceptible to antibiotics due to the lack of an outer membrane like staphylococcus spp. While gram negative bacteria contain an outer membrane, OR cell envelope they are less susceptible to antibiotics. Therefore, gram negative bacteria are more pathogenic compared to gram positive bacteria. The main difference between gram positive and gram negative bacteria is that gram positive bacteria contain a thick peptidoglycan cell wall along with teichoic acid, allowing the bacteria to stain in purple during gram staining whereas gram negative bacteria contain a thin peptidoglycan cell wall with no teichoic acid, allowing the cell wall to stain in pink during counter staining.  Teichoic Acids: Teichoic acids are polyol phosphate polymers bearing a strong negative charge. They are covalently linked to the peptidoglycan in some Gram-positive bacteria. They are strongly antigenic, but are generally absent in Gram-negative bacteria. Escherichia coli is gram negative and is used as the model organism in most bacterial studies. Gram negative bacteria are more pathogenic due to their less susceptibility to antibiotics. Antibiotic resistance of the gram negative bacteria is given by the outer membrane present in these bacteria.  GENERALLY; CELL-WALL FUNCTIONS? G-&G+? 1. Morphology:-cocci, bacilli, spiral, filamentous. 2. Protect bacteria against high internal osmotic pressure. 3. Role in cell-division. 4. Safe bacteria from external stress of host and environment. 5. Highly inflammatory, chemotactic, endotoxicity. 6. Passage of metabolites, necessary elements outside to inside. 7. Sites of major antigenic determinants of the cell surface. 8. Resistance to antibiotics. 9. It is target site of some antibiotics …penicillin and lysozyme enzyme hydrolyze it. VS Specialized Structures Outside the Cell Wall  Bacteria may or may not possess surface appendages that provide the organism with the ability to be motile, mediate attachment, resist host cell and to transfer genetic material that increase virulence includes; 1. Capsule 2. Pili 3. Flagella 4. Spore Capsule:  The capsule is a gelatinous layer covering the entire bacterium.  It is composed of polysaccharide except in the anthrax bacillus which composed of D-glutamic acid.  It is a determinant of virulence of many bacteria since it resist phagocytosis and attachment of host tissues. Pili (Fimbria)  Hair-like short filamentous not for motility, are numerous extend from cell surface.  Consist of protein mainly found in Gram- negative. Flagella  Function: Motility……. Almost all motile bacteria are motile by means of flagella.  Structure: Filament composed of the protein flagellin, antigenic (H-Ag). Salmonella typhi ( typhoid fever).  E coli Proteus H pylori Spores  Permit the organism to survive during conditions of desiccation, nutrient depletion, and waste buildup.  Have low-water content with incorporation of Ca-dipicolinic acid.  Highly resistant to disinfectants, antibiotics, radiations, boiling….etc  Requires heating to 120°C for 15-20 min Spore structure  The exosporium is composed principally of protein (43–52% of dry weight), but also contains lipids (15–18% of dry weight) and carbohydrates (20–22% of dry weight), as well as a minor (around 4%) component, which contained both calcium and magnesium as well as some undetermined components. The function in the spore is unknown. It has been suggested that the adherent, hydrophobic properties of the exosporium may be involved in the pathogenicity of some spores The spore coat has also been identified as a critical resistance mechanism against many chemicals, especially oxidizing agents such as hydrogen peroxide , ozone and hypochlorite. All of which kill spores more rapidly when the coat layer is absent. Bacterial Genetics  Bacterial Genome  Genes are carried on:  1. Bacterial chromosome  2.Plasmid  3.Transposon  Genome: an organism’s genetic material  Gene: a discrete units of hereditary information located on the chromosomes and consisting of DNA.  Genotype: The genetic makeup of an organism  Phenotype: the physical expressed traits of an organism  Nucleic acid: Biological molecules(RNA and DNA) that allow organisms to reproduce;  Nucleus = library  Chromosomes = bookshelves  Genes = books