MCB221 Lecture Progress PDF

MCB 221 (GENERAL MICROBIOLOGY) Dr. Sunday Omeike  All living things are composed of cells The average human person’s body is composed of around a hundred trillion cells (100,000,000,000,000). But there are even MORE cells than that living in you! You have trillions...

MCB 221 (GENERAL MICROBIOLOGY) Dr. Sunday Omeike  All living things are composed of cells The average human person’s body is composed of around a hundred trillion cells (100,000,000,000,000). But there are even MORE cells than that living in you! You have trillions and trillions of bacteria living in you too! (Even more bacteria than number of cells your body is made of). Some organisms are composed of just one cell (like these bacteria you can see on this slide) Other organisms (like plants, animals, and humans) are composed of trillions of cells. ⦿ Introduction: There are several classes of living organisms Based on the organization of their cellular structures, all living cells can be divided into two groups: eukaryotic and prokaryotic – Eukaryotic cell types - Animals, plants, fungi, protozoa, and algae – Prokaryotic cell types - bacteria & blue green algae Prokaryotic Cells Vs. Eukaryotic Cells What is the first thing that we need to know about cells?  Allcells fall into one of the two major classifications of either prokaryotic or eukaryotic.  What’s the difference between prokaryotes and eukaryotes?  Prokaryotic cells were here first and for billions of years were the only form of life on Earth. All prokaryotic organisms are unicellular  Eukaryotic cells appeared on earth long after prokaryotic cells but they are much more advanced. Eukaryotic organisms unlike prokaryotic can be unicellular or multicellular.  Vibrio fischeri  Glow in the dark bacteria  Helps it survive in the ocean  Lives in fish and other marine life  Characteristics of Prokaryotes  Prokaryotes are the simplest type of cell.  Oldest type of cell appeared about four billion years ago.  Prokaryotes are the largest group of organisms  Prokaryotes unicellular organisms that are found in all environments.  Prokaryotes do not have a nuclear membrane. Their circular shaped genetic material dispersed throughout cytoplasm.  Prokaryotes do not have membrane-bound organelles  Prokaryotes have a simple internal structure.  Prokaryotes are smaller in size when compared to Eukaryotes. What do prokaryotic cell look like?  characteristics of eukaryotes  Eukaryotic cells appeared approximately one billion years ago  Eukaryotes are generally more advanced than prokaryotes  Nuclear membrane surrounds linear genetic material (DNA)  Unlike prokaryotes, eukaryotes have several different parts.  Prokaryote’s organelles have coverings known as membranes.  Eukaryotes have a complex internal structure.  Eukaryotes are larger than prokaryotes in size  What do eukaryotic cells look Mitochondria like? Nucleus Cytoplasm Golgi Endoplasmic Complex Reticulum Cell Membrane  Prokaryotes vs Eukaryotes: Differences Prokaryotes Eukaryotes  Organelles lack a  Organelles covered by a membrane membrane  Ribosomes are the only  Multiple organelles organelles including ribosomes  Genetic material floats in  Membrane covered the cytoplasm (DNA and Genetic material RNA)  Circular DNA  Linear DNA  Unicellular  May be multicellular or unicellular  Cells are larger in size  Cells are smaller in size  Has smaller number of  Has larger number of organisms organisms How do the similarities line up? Lets See!!!  Both types of cells have cell membranes (outer covering of the cell)  Both types of cells have ribosomes  Both types of cells have DNA  Both types of cells have a liquid environment known as the cytoplasm ⦿ Microbiology: the study of organisms too small to be seen without magnification. ⦿ Micro - too small to be seen with the naked eye ⦿ Bio - life ⦿ logy - study of ◾ Microorganisms are ubiquitous. ◾ Microorganisms include:  bacteria  viruses  fungi  Parasite {protozoa &helminthes (worms) }  algae  Diversity of Microorganisms Protozoa (Sing. Protozoan)  Eucaryotes: “True nucleus”  DNA is surrounded by nuclear membrane.  Cells have membrane bound organelles and are larger than those of procaryotes.  Unicellular  Kingdom Protista  Sexual or asexual reproduction  Classified based on locomotion:  Pseudopods: “False feet”. Cytoplasmic extensions.  Example: Amoeba  Diversity of Microorganisms Protozoa (Sing. Protozoan)  Classified based on locomotion:  Flagella: Long whip like appendages.  Example: Trichomonas vaginalis, causes trichominiasis, a sexually transmitted disease.  Cilia: Small hair like appendages  Nonmotile: Do not move in their mature forms.  Example: Plasmodium spp., causative agent of malaria. Protozoa Belong to Kingdom Protista: Eucaryotic Unicellular or Simple Multicellular Organisms  Diversity of Microorganisms Algae (Sing. Alga)  Eucaryotes: “True nucleus”  Photosynthetic: Important part of food chain because produce oxygen and carbohydrates used by animals.  Unicellular or multicellular  Kingdom Protista  Sexual or asexual reproduction  Cell walls composed of cellulose  Found in aquatic environments (oceans, lakes, rivers), soil, and in association with plants. INTRODUCTION TO FUNGI  The Characteristics of Fungi Body form * unicellular * filamentous (tube-like strands called hypha (singular) or hyphae (plural) * mycelium = aggregate of hyphae * sclerotium = hardened mass of mycelium that generally serves as an overwintering stage. * multicellular, such as mycelial cords, rhizomorphs, and fruit bodies (mushrooms) fruiting bodies both are composed of hyphae mycelium  Tubular Hard wall of chitin Crosswalls may form compartments (± cells) Multinucleate Grow at tips  The Characteristics of Fungi Fungus is often hidden from view. It grows through its food source (substratum), excretes extracellular digestive enzymes, and absorbs dissolved food. Indeterminate clonal growth. Vegetative phase of fungus is generally sedentary. Cell wall present, composed of cellulose and/or chitin. Food storage - generally in the form of lipids and glycogen. Eukaryotes - true nucleus and other organelles present. All fungi require water and oxygen (no obligate anaerobes). Fungi grow in almost every habitat imaginable, as long as there is some type of organic matter present and the environment is not too extreme. Diverse group, number of described species is somewhere between 69,000 to 100,000 (estimated 1.5 million species total).  Properties of Fungi Heterotrophy - 'other food' * Saprophytes or saprobes - feed on dead tissues or organic waste (decomposers) * Symbionts - mutually beneficial relationship between a fungus and another organism * Parasites - feeding on living tissue of a host. Parasites that cause disease are called pathogens. Fungi as Saprobes and Decomposers Fungi as Symbionts (Mutualism)  Mycorrhizae “Fungus roots” Mutualism between: * Fungus (nutrient & water uptake for plant) * Plant (carbohydrate for fungus) Several kinds * Zygomycota – hyphae invade root cells * Ascomycota & Basidiomycota – hyphae invade root but don’t penetrate cells Extremely important ecological role of fungi “Ecto”mycorrhizae Russula mushroom mycorrhizas on Western Hemlock root Mycorrhiza cross sections Fungal hyphae around root and between cells  Lichens “Mutualism” between * Fungus – structure * Alga or cyanobacterium – provides food Three main types of lichens: * Crustose lichens form flat crusty plates. * Foliose lichens are leafy in appearance, although lobed or branched structures are not true leaves. * Fruticose lichens are even more finely branched and may hang down like beards from branches or grow up from the ground like tiny shrubs. Fungi as Parasites & Pathogens  Fungi are Spore Spores - asexual (product of mitosis) or sexual (product of meiosis) in origin. Purpose of Spores * Allows the fungus to move to new food source. * Resistant stage - allows fungus to survive periods of adversity. * Means of introducing new genetic combinations into a population  Reproduce by spores Spores are reproductive cells * Sexual (meiotic in origin) * Asexual (mitotic in origin) Formed: * Directly on hyphae * Inside sporangia * Fruiting bodies Penicillium hyphae with conidia Pilobolus sporangia Amanita fruiting body CHARACTERISTICS OF VIRUS  Viruses regarded as e i t h e r complex aggregations of nonliving chemicals or exceptionally simple living microbes Viruses contain a single type of nucleic acid a protein coat, sometimes enclosed by an envelope Viruses are obligatory intracellular parasites Host range host specific Host range is determined by the specific attachment site on the host cells’ surface Size Viral size is measured by electron microscopy range from 20 nm to 300 nm in length  Viral Structure Nucleic acid either DNA or RNA can be single stranded or double stranded nucleic acid can be linear or circular Capsid and Envelope HISTORY OF MICROBIOLOGY  History of Microbiology Early Studies Before 17th century, study of microbiology was hampered by the lack of appropriate tools to observe microbes. Robert Hooke: In 1665 built a compound light microscope and used it to observe thin slices of cork. Coined the word cell. Anton van Leeuwenhoeck: In 1673 was the first person to observe live microorganisms which he called “animalcules” (bacteria, protozoa), using single-lens microscopes that he designed.  History of Microbiology Spontaneous Generation vs Biogenesis Before 1860s many scientists believed in Spontaneous generation, i.e.: That living organisms could arise spontaneously from nonliving matter:  Mice come from rags in a basket.  Maggots come from rotting meat.  Ants come from honey.  Microbes come from spoiled broth.  History of Microbiology Spontaneous Generation vs Biogenesis Theory of Biogenesis: Belief that living cells can only arise from other living cells. Francesco Redi: In 1668 proved that maggots do not arise spontaneously from decaying meat. Lazaro Spallanzani: In 1765 found that nutrient broth that had been heated in a sealed flask would not become contaminated with microbes.  Some proponents of spontaneous generation argued that boiling had destroyed the “life force” of air in flask.  Others argued that microbes were different from other life forms.  History of Microbiology Spontaneous Generation vs Biogenesis Debate was finally settled by Pasteur. Louis Pasteur: In 1861 finally disproved spontaneous generation when he demonstrated that microorganisms in the environment were responsible for microbial growth in nutrient broth.  Designed swan neck flasks that allowed air in, but trapped microbes in neck.  Developed aseptic technique: Practices that prevent contamination by unwanted microorganisms.  History of Microbiology Golden Age: 1857-1914 Rapid advances led to the development of microbiology as a science. Pasteur’s Contributions to Microbiology: Fermentation: Pasteur found that yeasts were responsible for converting sugar into alcohol in the absence of air.  Souring and spoilage were caused by bacterial contamination of beverages.  History of Microbiology Golden Age: 1857-1914 Pasteur’s Contributions: Pasteurization: Developed a process in which liquids are heated (at 65oC) to kill most bacteria responsible for spoilage. Disease Causes: Identified three different microbes that caused silkworm diseases. Vaccine: Developed a vaccine for rabies from dried spinal cords of infected rabbits.  Directed Pasteur Institute until his death in 1895.  History of Microbiology Golden Age: 1857-1914 Germ Theory of Disease: Belief that microbes cause diseases. Before, most people believed diseases were caused by divine punishment, poisonous vapors, curses, witchcraft, etc. Agostino Bassi (1835): Found that a fungus was responsible for a silkworm disease. Ignaz Semmelweis (1840s): Demonstrated that childbirth fever was transmitted from one patient to another, by physicians who didn’t disinfect their hands. He was ostracized by colleagues.  History of Microbiology Golden Age: 1857-1914 Germ Theory of Disease: Joseph Lister (1860): Used disinfectant to treat surgical wounds, greatly reducing infection rates. Considered the father of antiseptic surgery. Robert Koch (1876): First person to conclusively prove that a specific bacterium caused a disease.  Germ Theory: One microbe causes one specific disease.  Proved that Bacillus anthracis causes anthrax in cattle.  Later identified bacterium that causes tuberculosis.  History of Microbiology Modern Microbiology: After 1914 Chemotherapy: Treatment of a disease by using a chemical substance. Chemical must be more poisonous to microbe than host. Quinine: First known chemical to treat a disease (malaria). Used by Spanish conquistadors. Synthetic Drugs: Made in the laboratory. Antibiotics: Produced naturally by fungi and bacteria.  History of Microbiology Modern Microbiology: After 1914 Paul Ehrlich (1910): Search for “magic bullet”.  Discovered salvarsan, an arsenic derivative, was effective against syphilis. Alexander Fleming (1928): Discovered that penicillin produced by the mold Penicillium notatum was able to prevent microbial growth.  Penicillin was not mass produced until the 1940s. Rene Dubos (1939): Discovered two antibiotics (gramidin and tyrocidine) produced by bacterium (Bacillus brevis).  History of Microbiology Modern Microbiology: After 1914 Problems with Chemotherapy: Toxicity Drug resistant microbes  Diversity of Microorganisms I. Bacteria (Sing. Bacterium) Small, single-celled (unicellular) organisms. Procaryotes: “Before nucleus”. Lack the following structures:  Nuclear membrane around DNA  Membrane bound organelles  Mitochondria  Chloroplasts  Golgi apparatus  Endoplasmic reticulum  Lysosomes BACTERIA ⦿ Size of Bacteria - 0.2 – 1.5 µm in diameter - 3 – 5 µm in length  Diversity of Microorganisms I. Bacteria (Sing. Bacterium) Include two groups:  Eubacteria: Peptidoglycan cell walls.  Archaebacteria: Lack peptidoglycan cell walls. Shapes: Several forms:  Bacilli: Rod like. (Sing. Bacillus)  Cocci: Spherical. (Sing. Coccus)  Spiral: Corkscrew or curved  Square  Star shaped  Diversity of Microorganisms I. Bacteria (Sing. Bacterium) Divide by binary fission (not mitosis). Source of nutrients varies:  Heterotrophs: Consume organic chemicals.  Autotrophs: Make their own food. Include photosynthetic bacteria. Motility: Many can “swim” by using moving appendages:  Cilia: Small hair like structures  Flagella: Large whip like structures. ⦿ Shape of Bacteria Cocci – spherical/ oval shaped Bacilli – rod shaped Coccobacilli – rods with spherical ends Vibrios – comma shaped Spirilla – rigid spiral forms Spirochetes – flexible spiral forms Actinomycetes – branching filamentous bacteria Comma shaped Spirilla Spirochetes  Coccus Cocci in pair – Diplococcus Tetrad – groups of four Cocci in chain - Streptococci Cocci in cluster - Staphylococci ⦿ Anatomy of Bacterial Cell Outer layer - two components: 1. Rigid cell wall 2. Cytoplasmic (Cell/ Plasma) membrane – present beneath cell wall Cytoplasm - gel-like substance enclosed within the cell membrane contains cytoplasmic inclusions, ribosomes, mesosomes and nucleoid Additional structures - plasmid, slime layer, capsule, flagella, fimbriae (pili) and spores. ⦿ Structure & Function of Cell Components CELL WALL Outermost layer, encloses cytoplasmic membrane 1. Confers shape and rigidity 2.Peptidoglycan is responsible for the rigidity of the bacterial cell wall and for the determination of cell shape. 3. Composed of Mucopeptide (peptidoglycan/ murein): formed by N-acetyl glucosamine (NAG) & N-acetyl muramic acid (NAM) alternating in chains, held by peptide chains. 4. Can not be seen by direct light microscopy and do not stain with simple stains. 5. Carries bacterial antigens – important in virulence & immunity. 6. Chemical nature of the cell wall helps to divide bacteria into two broad groups – Gram positive & Gram negative. 7. Gram +ve bacteria have simpler chemical nature than Gram –ve bacteria. 8. Several antibiotics may interfere with cell wall synthesis e.g. Penicillin, Cephalosporins ⦿ Gram positive cell wall The Gram-positive cell composed of a thick, wall is peptidoglycan multilayered sheath outside of cytoplasmic membrane. the Teichoic acids are linked to and embedded in the peptidoglycan, and lipoteichoic acids extend into the cytoplasmic membrane ⦿ Gram negative cell wall The Gram-negative cell wall is composed of an outer membrane linked to thin single-layered peptidoglycan by lipoproteins. The peptidoglycan is located within the periplasmic space that is created between the outer and inner membranes. The outer membrane includes *porins, which allow the passage of small hydrophilic molecules across the membrane, and **lipopolysaccharide molecules that extend into extracellular space. Property of bacteria Gram Positive Gram Negative Thickness of wall 20-80 nm 10 nm Number of layers in wall 1 2 Peptidoglycan content >50% 10-20% Teichoic acid in wall + - Lipid & lipoprotein content 0-3% 58% Protein content 0% 9% Lipopolysaccharide 0 13% Sensitive to penicillin Yes Less sensitive Digested by lysozyme Yes Weakly Cytoplasmic (Plasma) membrane Thin layer 5-10 nm, separates cell wall from cytoplasm. Acts as a semi-permeable membrane: controls the inflow and outflow of metabolites. Composed of lipoproteins with small amounts of carbohydrates. Cytoplasm Colloidal system of variety of organic & inorganic solutes in viscous watery solution = Cytoplasmic Components 1. Ribosomes: place of protein synthesis (70 S) 2. Mesosomes: 1. Multi-laminated structures formed as invaginations of plasma membrane. 2. Principal sites of respiratory enzymes. 3. Coordinate nuclear & division during cytoplasmic binary fission 4. More prominent in Gram +ve bacteria 3. Intracytoplasmic inclusions: Reserve of energy & phosphate for cell metabolism e.g. Metachromatic granules in diphtheria bacilli  4. Nucleus: No nucleolus No nuclear membrane Oval or elongated bodies generally 1 per cell Genome – single, circular double stranded DNA (one chromosome). Divides by binary fission =Additional Organelles 1. Plasmid Extra-nuclear genetic elements consisting of DNA Transmitted to daughter cells during binary fission May be transferred from one bacterium to another by conjugation Not essential for life of the cell Confer certain properties e.g. drug resistance because the plasmid carries some genes responsible for drug resistance 2. Capsule & Slime layer: Viscous layer secreted around the cell wall. Polysaccharide / polypeptide in nature a) Capsule – sharply defined structure, antigenic in nature Protects bacteria from lytic enzymes Inhibits phagocytosis Stained by negative staining using India Ink Can be demonstrated by Quellung reaction (capsule swelling reaction). b) Slime layer – is loosely associated with the bacterium and can be easily washed off, whereas a capsule is attached tightly to the bacterium and has definite boundaries.  3. Flagella Long (3 to 12 µm) filamentous surface appendages Organs of locomotion Composed of proteins called flagellins The number and distribution of flagella on the bacterial surface are characteristic for a given species - hence are useful in identifying and classifying bacteria Flagella may serve as antigenic determinants (e.g. the H antigens of Gram-negative enteric bacteria) Presence shown by e.g. hanging drop motility preparation test. Each flagellum consists of 3 1. parts: Filament 2. Hook 3. Basal body Polar/ Monotrichous – single flagellum at one pole Lophotrichous – tuft of flagella at one pole Amphitrichous – flagella at both poles Peritrichous – flagella all over Amphilophotrichous – tuft of flagella at both ends 4. Fimbriae/ Pili Thin, hair like appendages on the surface of many Gram negative bacteria 10-20µ long, acts as organs of adhesion (attachment) - allowing bacteria to colonize environmental surfaces or cells and resist flushing Made up of proteins called pilins. Pili can be of two types A. Common pili - short & abundant B. Sex pili - very long pili & small number (one to six), helps in conjugation (process of transfer of DNA) 5. Spores : Highly resistant resting stages formed during adverse environment (depletion of nutrients). Formed inside the parent cell, hence called Endospores Very resistant to heat, radiation and drying and can remain dormant for hundreds of years. Formed by bacteria like Clostridium and Bacillus Shape & position of bacterial spore Oval central Spherical central Non- bulging Oval sub terminal Oval sub terminal Oval terminal Bulging Spherical terminal Free spore Character Prokaryotes Eukaryotes Nucleus Nuclear Absent Present membrane Nucleolus Absent Present Chromosome One circular One or more paired and linear Cell division Binary fission Mitosis Cytoplasmic Structure and phospholipid bilayer, phospholipid bilayer membrane Composition lacks sterols containing sterols Function Incapable of Capable of endocytosis endocytosis and (phagocytosis and exocytosis pinocytosis) and exocytosis Character Prokaryotes Eukaryotes Cytoplasm Mitochondria Absent Present Lysosomes Absent Present Golgi Absent Present apparatus Endoplasmic Absent Present reticulum Vacuoles Absent Present Ribosomes 70 S 80 S Character Prokaryotes Eukaryotes Cell Wall Present Animals & Protozoans – Absent Plants, Fungi & Algae - Present Composition Peptidoglycan – Cellulose or chitin complex carbohydrate Locomotor Flagella Flagella/ Cilia organelles Bacterial Colonial Characteristics ♣ Appearance in petri dish. ♣ Appearance in test tube. ♣ Affecting factor on growth ♣Culturing of anaerobic bacteria ♣features of bacterial growth on media  * Colony morphology in petri dish A colony is a large number of bacterial cells on solid medium, which is visible to the naked eye as a separate unit. Colony is derived from one bacterial cell. Different species of bacteria can produce very different colonies. In the identification of bacteria and fungi much Focus is placed on how the organism grows in or on media. Appearance of bacterial colony on culture medium is  * Bacterial Colonial Features on Petri dish Shape – Circular, irregular, rhizoid or filamentous. Size –can be categorised as large (>1 mm), medium (=1 mm), small (