Physiology of Bacteria

1. Physiology of Bacteria Bacterial Growth (Page 291)

2. Bacterial Colony • “a visible group of bacteria growing on a solid medium, presumably arising from a single microorganism”

3. Requirements for Growth • Physical: temperature, pH, light, osmotic pressure, moisture • Chemical: carbon, nitrogen, sulfur, phosphorus, trace elements, oxygen

4. Temperature • Page 294 • Readings question one: What are psychrophiles, mesophiles, and thermophiles?

5. Psychrophiles • Desulfofrigusoceanense(Arctic and Antarctic Oceans)

6. Mesophiles E. coli

7. Thermophiles Fossilized Microbes from Yellowstone’s Hot Springs

8. 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”

9. What are the embalming implications associated with the temperature preference of bacteria?

10. pH • Page 295 • Readings question two: Describe the pH scale. Acidophiles: bacteria that are remarkably tolerant of acidity

11. Light • Cyanobacteria: oxygen producing prokaryotes • thrive in the presence of light • Yeasts and Molds • prefer dark areas • Some bacteria are destroyed by ultraviolet light.

12. 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 • Figure 22-1A page 296

13. Moisture • Page 293 • 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.

14. Chemical Requirements • Page 292 • Readings question three: Describe the differences between autotrophic bacteria and heterotrophic bacteria.

15. 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

16. 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

17. Nitrogen, Sulfur, and Phosphorus • needed by microorganisms for the synthesis of cellular material • e.g. protein, DNA, RNA, ATP

18. Trace Elements • iron, copper, and zinc • essential for the function of certain enzymes

19. Oxygen • Page 293 • 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.

20. Microaerophilic Organisms • Page 293 • “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

21. 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, Corneybacteriumdiphtheriae, Escherichia coli

22. Aerotolerant Organisms • can grow in the presence or absence of oxygen • e.g. Streptococcus pyogenes

23. Microbial Associations • Page 296 • 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

24. 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

25. Commensalism • Page 297 • “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

26. 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

27. Readings Question #5 What is the synergistic effect?

28. 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)