Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Physiology of Bacteria Bacterial Growth Bacterial Colony • “a visible group of bacteria growing on a solid medium, presumably arising from a single microorganism” Requirements for Growth • Physical: temperature, pH, light, osmotic pressure, moisture • Chemical: carbon, nitrogen, sulfur, phosphorus, trace elements, oxygen Temperature • Readings question one: What are psychrophiles, mesophiles, and thermophiles? Psychrophiles • Desulfofrigus oceanense (Arctic and Antarctic Oceans) Mesophiles E. coli Thermophiles Fossilized Microbes from Yellowstone’s Hot Springs Temperatures • Minimum: “temperature below which bacterial growth will not take place” • Optimum: “temperature at which organisms grow best” • Maximum: “temperature above which bacterial growth will not take place” • What are the embalming implications associated with the temperature preference of bacteria? pH • Readings question two: Describe the pH scale. Acidophiles: bacteria that are remarkably tolerant of acidity Light • Cyanobacteria: oxygen producing prokaryotes – thrive in the presence of light • Yeasts and Molds – prefer dark areas • Some bacteria are destroyed by ultraviolet light. Osmotic Pressure • “pressure that develops when two solutions of different concentrations are separated by a semi-permeable membrane” • microorganisms require water for growth and are made up of 80-90% water • high osmotic pressure removes necessary water from a cell • plasmolysis • hypertonic solutions Moisture • maximum, optimum and minimum requirement for all microorganisms • Pathogenic bacteria are usually found in the body’s tissues • Fungal diseases are usually found on the body surface. Chemical Requirements • Readings question three: Describe the differences between autotrophic bacteria and heterotrophic bacteria. Heterotrophic Bacteria • 3 categories: – 1) strict (obligate) saprophyte – 2) strict (obligate) parasite – 3) facultative bacteria: • Facultative saprophyte: “prefers live organic matter as a source of nutrition but can adapt to the use of dead organic matter under certain conditions” • Facultative parasite: capable of living and growing with the nutrients that its host provides Carbon • one of the most important requirements for microbial growth • structural backbone of living matter • needed for all the organic compounds that make up a living cell • ½ of the “dry weight” of a bacterial cell is carbon Nitrogen, Sulfur, and Phosphorus • needed by microorganisms for the synthesis of cellular material • e.g. protein, DNA, RNA, ATP Trace Elements • iron, copper, and zinc • essential for the function of certain enzymes Oxygen • Microbes that use molecular oxygen (aerobes) produce more energy from nutrients than microbes that do not use oxygen (anaerobes) • Reading question four: Describe the difference between obligate aerobes and obligate anaerobes. Microaerophilic Organisms • “a microorganism that requires very little free oxygen” • only grow in oxygen concentrations that are lower than those in air • require about 2 – 10% free oxygen Facultative Organisms • Facultative Aerobes: “a microorganism that prefers an environment devoid of oxygen but has adapted so that it can live and grow in the presence of oxygen” • Facultative Anaerobes: “a microorganism that prefers an oxygen environment but is capable of living and growing in its absence” – E.g. Bacillus anthracis, Corneybacterium diphtheriae, Escherichia coli Aerotolerant Organisms • can grow in the presence or absence of oxygen – e.g. Streptococcus pyogenes Microbial Associations • normal flora (microbiota) • transient microbiota • symbiotic relationship: “organisms live in close nutritional relationships; required by one or both members” – distinguished by the degree to which the host organism is harmed Mutualism • “a symbiotic relationship in which organisms of two different species live in close association to the mutual benefit of each” – e.g. E. coli in the human digestive tract Commensalism • “the symbiotic relationship of two organisms of different species in which one gains some benefit such as protection or nourishment and the other is not harmed or benefited” – e.g. bacteria on skin surface; microorganisms within the digestive tract Parasitism • “an interactive relationship between two organisms in which one is harmed and the other benefits” • many disease-causing bacteria are parasites • typically the host is macroscopic and the parasite is microscopic • roundworms and flatworms are parasites that are large multi-cellular organisms • Readings question five: What is the synergistic effect? Antagonism • “mutual opposition or contrary action. The inhibition of one microorganism by another.” • Involves competition among microbes • normal microbiota protect the host against colonization by potentially pathogenic microbes • normal flora produce substances harmful to the invading microbes (pH, oxygen)