Microbial Nutrition and Growth

1. Microbial Nutrition and Growth Nutrition = Obtaining Required Substances from the Environment

2. Essential Nutrients Must be Provided for an Organism to Survive and Reproduce

3. Nutrients • Inorganic nutrients– atoms, ions or molecules 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 bonded to hydrogen and are usually the products of living things • methane (CH4), carbohydrates, lipids, proteins, and nucleic acids

4. Macronutrients • Required in Large Quantities • Play principle roles in cell structure and metabolism • Proteins (source of amino acids) • Carbohydrates

5. Micronutrients Needed in Small Amounts – like Minerals

6. Points about Bacterial Cytoplasm • Mostly water • Large proportion of protein • 97% of dry weight is organic matter • 96% of bacterial cell is composed of C, H, N, O, P and S

7. Challenge for Bacteria How to get enough nutrients in forms that they can use to make cell components

8. Bacteria Must Make • Proteins • Carbohydrates • Lipids • Nucleic Acids

9. Sources of Essential Nutrients • Carbon – obtain in organic form, or reduce CO2 • Nitrogen – Fix N2 or obtain as NO3-- NO2-, or NH3 • Oxygen – Atmospheric or dissolved in water • Hydrogen – Minerals, water, organic compounds

10. Nutrient Sources - Continued • Phosphorous – Mineral deposits • Sulfur – Minerals, H2S • Metal Ions - Minerals

11. Mineral Nutrients Important in Microbial Metabolism • Potassium – essential to protein synthesis and membrane function • Sodium – used in some types of cell transport • Calcium – cell wall and endospore stabilizer • Magnesium – component of chlorophyll; membrane and ribosome stabilizer • Iron – component of proteins of cellular respiration • Zinc, copper, nickel, manganese, etc.

12. Growth Factors • Organic compounds that cannot be synthesized by an organism & must be provided as a nutrient • essential amino acids, vitamins

13. Nutritional Types • Autotrophs - use CO2, an inorganic gas as carbon source • Heterotrophs - obtain carbon in an organic form made by other living organisms

14. Autotrophs – “Self-Feeding” • Phototrophs use light energy to reduce carbon or make ATP • Chemotrophs use energy stored in inorganic chemical bonds to reduce carbon or make ATP

15. Heterotrophs • Obtain reduced carbon compounds made by another organism • Chemoheterotrophs – oxidize reduced carbon to make ATP

16. Two Kinds of Bacterial Heterotrophs • Saprobes – Obtain nutrients from dead, decaying matter • Parasites – Feed off a host organism

17. Environmental Influences on Microbial Growth • Temperature • Oxygen requirements • pH • Barometric pressure

18. 3 Cardinal Temperatures • Minimum temperature • Maximum temperature • Optimum temperature

19. 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

20. Ecological Groups by Temperature of Adaptation

21. Oxygen in the Microbial Environment • Oxygen required by aerobic species (Bacillus, Pseudomonas) but produces toxic by-products; these species have efficient de-tox enzymes • Facultative anaerobes can exist in presence of oxygen but have no requirement for it (E. coli, Staphylococcus, etc.)

22. Anaerobes – no Need for Oxygen • Strict anaerobes cannot tolerate oxygen (Clostridium sp.) • Aerotolerant anaerobes have atypical oxygen detox systems (Lactobacillus sp.) • Capnophiles require higher CO2 pressures (Neisseria, Brucella, S. pneumoniae)

23. pH Effects on Growth • Acidophiles require low pH (Thermoplasma) • Alkalinophiles require high pH (Proteus)

24. Osmotic Effects • Most microbes exist under hypotonic or isotonic conditions • Halophiles – require a high concentration of salt • Osmotolerant – do not require high concentration of solute but can tolerate it when it occurs

25. Miscellaneous Environmental Factors • Barophiles require high environmental pressure (like deep sea Archae) • Dehydrated Cell Stages – Spores • Extreme radiation conditions - Dinococcus radiodurans

26. Ecological Relationships • Symbiosis – existing together • Mutualism – both parties benefit • Commensalism – one party benefits without impacting the other • Parasitism – one party benefits at expense of the other • Synergism – multiple organisms working together

27. Microbial Biofilms • Biofilms result when organisms attach to a substrate by some form of extracellular matrix that binds them together in complex organized layers • Dominate the structure of most natural environments on earth • Microorganisms communicate and cooperate in the formation and function of biofilms – quorum sensing

29. Ecological Relationships - Continued • Antagonism – one party acts to inhibit or eliminate the other • Example of antagonism: Antibiosis – producing substances toxic to other organisms

30. Microbial Growth Growth of a population at an exponential rate under optimal conditions

31. Stages in Normal Growth • Lag phase • Exponential/log phase • Stationary phase • Death or decline

32. Mathematics of Population Growth

33. Growth Curve

34. Methods for Monitoring Growth • Dilution Plating • Turbidity analysis using spectrophotometer • Direct count with hemacytometer • Optical detection – Coulter Counter

35. Turbidity

36. Direct Microscopic Count

37. Electronic Counting

38. It is Ideal to Perform Most Manipulations of a Culture When it is Growing in Log Phase