1. Foundations in Microbiology
PowerPoint to accompany
Foundations in Microbiology
Fifth Edition
Talaro
Chapter 7
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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

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

4. 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

5. 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

14. Carbon source
Energy source
photoautotrophs
CO2
sunlight
chemoautotrophs
Simple inorganic chemicals
photoheterotrophs
organic
chemoheterotrophs
Metabolizing organic cpds

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

18. diffusion

19. osmosis

21. passive transport

22. Active transport

23. Bulk transport

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

25. 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

26. 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

27. 3 temperature adaptation groups

28. Oxygen requirements

30. 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

31. 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

32. Binary Fission

33. Population growth

34. Growth curve

35. 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

36. Turbidity

37. Direct microscopic count

38. Electronic counting