MICR2000 Revision - Microbiology Notes PDF

MICR2000 revision LEC 1 Microbiology is the study of microscopic living organisms: bacteria, archaea, viruses, fungi, algae and protozoa Microbes have a major impact on all aspects of life: Health ecology agriculture biotechnology, the environment etc. Microbes play an important role in medicin...

MICR2000 revision LEC 1 Microbiology is the study of microscopic living organisms: bacteria, archaea, viruses, fungi, algae and protozoa Microbes have a major impact on all aspects of life: Health ecology agriculture biotechnology, the environment etc. Microbes play an important role in medicine, agriculture and industry Shapes of different cells: morphology Key structures of a bacterial cell - Cytoplasmic (cell) membrane : barrier that separates the inside of the cell from the outside environment - Cytoplasm: fluid that fills cells - Nucleus: machinery for cell growth and function - Cell wall: confers structural strength Characteristics of all bacterial cells - Metabolism : cells take up nutrients, transform them, and expel wastes. - Growth: Nutrients from the environment are converted into new cell materials to form new cells - Evolution: cells evolve to display new properties. Phylogenetic tress capture evolutionary relationships Louis Pasteur (1822-1895) Showed that microbes are responsible for fermentation Demonstrated that bacteria which caused the spoilage of wine (and food) could be killed by heat that was not hot enough to evaporate the alcohol in wine (Pasteurization). Disproved theory of spontaneous generation – Led to the development of methods for controlling the growth of microorganisms Developed vaccines for anthrax, fowl cholera, and rabies To disprove spontaneous generation (i.e. microbes appeared out of thin air), Francesco Redi covered meat with a cheese cloth to prevent flies landing on it, and showed that this meat did not grow maggots like uncovered meat. Is this a perfect experiment? Does it have any flaws? The defeat of spontaneous generation Robert Koch Lec 2 Cytoplasmic membrane: Gram positive cells have a thicker peptidoglycan layer and no outer membrane A. How are bacteria identified? B. What types of clinical diagnostic tests are available to do this? Some bacteria can produce more than one type of fimbriae. Different fimbriae can be expressed at the same time, or independently regulated to be produced in the correct biological niche. Some types of fimbriae may also may have adhesive domains along the shaft that anchor the cell by a zippering effect. CELL INCLUSIONS Many bacteria can synthesise carbon and energy storage compounds such as poly-beta-hydroxybutyric acid (lipid) or glycogen (glucose polymer) Some bacteria can accumulate inorganic phosphate (PO4 3- ) for nucleic acid, phospholipid and ATP synthesis. Stored polyphosphate is accumulated in phosphate rich environments, then used when phosphate is limiting. Other bacteria can oxidise H2S either to produce energy or as part of a CO2 fixation process. Elemental sulphur (S0) is stored in sulfur globules in the periplasm. Magnetosomes: intracellular particles of magnetite (Fe3O4) that enable bacteria to orientate themselves in a specific arrangement within a magnetic field. The function of magnetosomes is unknown, however the presence of magnetosomes in aquatic bacteria may allow the bacteria to orientate in a water column. GAS VESICLES Gas vesicles: confer buoyancy in planktonic cells (eg. Cyanobacteria) Spindle-shaped gas-filled structures made of protein Gas vesicle membrane impermeable to water Allows photosynthetic bacteria to optimise position in water column ENDOSPORES Endospores: highly differentiated cells that is resistant to dessication, heat, harsh chemicals, and radiation “Dormant” stage of bacterial life cycle Ideal for dispersal via wind, water, or animal gut Only present in some gram-positive bacteria (eg. Bacillus and Clostridium) HOW DO ENDOSPORES PROMOTE SURVIVAL? Endospore structure differs markedly from that of the vegetative cell. The exosporium is the outermost covering consisting of protein Several spore coats may then be found The cortex consists of a peptidoglycan layer The “core” contains the core wall, cytoplasmic membrane, cytoplasm, DNA and ribosomes. Lec 4 !!!!!!! Viewing biofilms Light microscope Scanning confocal laser microscope !!!! !!! !!! !!! !!! !!!! !!! !!! Feeding & life cycles blood suckers; with elaborate mouth parts for penetrating host skin. Many ticks secrete cement to aid attachment during feeding. Usually 3 individual hosts in the life of a tick