Elements of Microbial Nutrition, Ecology and Growth Chapter 7

1. Elements of Microbial Nutrition, Ecology and Growth Chapter 7

2. Microbial nutrition • Macronutrients – required in large quantities; play principal roles in cell structure & metabolism • proteins, carbohydrates • Micronutrientsor trace elements – required in small amounts; involved in enzyme function & maintenance of protein structure • manganese, zinc, nickel

3. Nutrients • Inorganic nutrients– atom or molecule that contains a combination of atoms other than carbon and hydrogen • metals and their salts (magnesium sulfate, ferric nitrate, sodium phosphate), gases (oxygen, carbon dioxide) and water • Organic nutrients- contain carbon and hydrogen atoms and are usually the products of living things • methane (CH4), carbohydrates, lipids, proteins, and nucleic acids

4. Chemical composition of cytoplasm • 70% water • proteins • 96% of cell is composed of 6 elements • Carbon • Hydrogen • Oxygen • Phosphorous • Sulfur

6. Obtaining Carbon • Heterotroph – an organism that must obtain carbon in an organic form made by other living organisms such as proteins, carbohydrates, lipids and nucleic acids • Autotroph - an organism that uses CO2, an inorganic gas as its carbon source • not dependent on other living things

7. Nitrogen • Main reservoir is nitrogen gas (N2) • 79% of earth’s atmosphere is N2 • Nitrogen is part of the structure of proteins, DNA, RNA & ATP – these are the primary source of N for heterotrophs • Some bacteria & algae use inorganic N nutrients (NO3-, NO2-, or NH3) • Some bacteria can fix N2 • Regardless of how N enters the cell, it must be converted to NH3, the only form that can be combined with carbon to synthesis amino acids, etc.

8. Oxygen • major component of carbohydrates, lipids and proteins • plays an important role in structural & enzymatic functions of cell • component of inorganic salts (sulfates, phosphates, nitrates) & water • O2 makes up 20% of atmosphere • essential to metabolism of many organisms

9. Hydrogen • major element in all organic compounds & several inorganic ones (water, salts & gases) • gases are produced & used by microbes • roles of hydrogen • maintaining pH • forming H bonds between molecules • serving as the source of free energy in oxidation-reduction reactions of respiration

10. Phosphorous • main inorganic source is phosphate (PO4-3) derived from phosphoric acid (H3PO4) found in rocks & oceanic mineral deposits • key component of nucleic acids, essential to genetics • serves in energy transfers (ATP)

11. Sulfur • widely distributed in environment, rocks, sediments contain sulfate, sulfides, hydrogen sulfide gas and sulfur • essential component of some vitamins and the amino acids: methionine & cysteine • contributes to stability of proteins by forming disulfide bonds

12. Important mineral ions • Potassium • Sodium • Calcium • Magnesium • Iron

13. Growth factors • organic compounds that cannot be synthesized by an organism & must be provided as a nutrient • essential amino acids, vitamins

15. Saprobes – decompose dead organisms, recycle elements, release enzymes to digest materials • Parasites – utilize tissues and fluids of a living host and cause harm

16. saprobes

17. Transport mechanisms • Passive transport –do not require energy, substances exist in a gradient and move from areas of higher concentration towards areas of lower concentration • Diffusion • Osmosis - water • Facilitated diffusion – requires a carrier • Active transport – require energy and carrier proteins, gradient independent • Carrier-mediated active transport • Group translocation – transported molecule chemically altered • Bulk transport – endocytosis, exocytosis, pinocytosis

19. Environmental influences on microbial growth • temperature • oxygen requirements • pH • electromagnetic radiation • barometric pressure

20. 3 cardinal temperatures • Minimum temperature – lowest temperature that permits a microbe’s growth and metabolism • Maximum temperature – highest temperature that permits a microbe’s growth and metabolism • Optimum temperature – promotes the fastest rate of growth and metabolism

22. 3 temperature adaptation groups • Psychrophiles – optimum temperature below 15oC, capable of growth at 0oC • Mesophiles – optimum temperature 20o-40oC, most human pathogens • Thermophiles – optimum temperature greater than 45oC

23. 3 temperature adaptation groups

25. Oxygen requirements

27. Microbial associations • Symbiotic – organisms live in close nutritional relationships; required by one or both members • Mutualism – obligatory, dependent; both members benefit • Commensalism – commensal member benefits, other member not harmed • Parasitism – parasite is dependent and benefits; host is harmed

28. Microbial associations • Non-symbiotic – organisms are free-living; relationships not required for survival • Synergism – members cooperate and share nutrients • Antagonism – some member are inhibited or destroyed by others

29. Binary Fission

30. Population growth

32. Growth curve

33. Growth curve • Lag phase – “flat” period of adjustment, enlargement; little growth • Exponential growth phase – a period of maximum growth will continue as long as cells have adequate nutrients & a favorable environment • Stationary phase – rate of cell growth equals rate of cell death cause by depleted nutrients & O2, excretion of organic acids & pollutants • Death phase – as limiting factors intensify, cells die exponentially in their own wastes

34. Turbidity

35. Direct microscopic count

36. Electronic counting

37. Standard Plate Count