1. Chapter 5
Microbial Nutrition

2. Nutrient Requirements
Macroelements (macronutrients)
C, O, H, N, S, P, K, Ca, Mg, and Fe
required in relatively large amounts
Micronutrients (trace elements)
Mn, Zn, Co, Mo, Ni, and Cu
required in trace amounts
often supplied in water or in media components

3. All Organisms Require Carbon, Hydrogen, Oxygen and Electron Source

4. Heterotrophs Autotrophs
use organic molecules as carbon sources which often also serve as energy sourc
Autotrophs
use carbon dioxide as their sole or principal carbon source
must obtain energy from other sources

5. Sources of Carbon, Energy and Electrons
Table 5.1

6. Nutritional Types of Organisms
based on energy source
phototrophs use light
chemotrophs obtain energy from oxidation of chemical compounds
based on electron source
lithotrophs use reduced inorganic substances
organotrophs obtain electrons from organic compounds

7. Nutritional Types of Microorganisms
Table 5.2

8. Nitrogen, Phosphorus, and Sulfur
Needed for synthesis of important molecules (e.g., amino acids, nucleic acids)
Nitrogen usually supplied as organic and inorganic N-source (NH3 , NO3-)
Phosphorus usually supplied as inorganic phosphate (H3PO4)
Sulfur usually supplied as sulfate (SO42-)

9. Growth Factors Organic compounds
Essential cell components (or their precursors) that the cell cannot synthesize
Must be supplied by environment if cell is to survive and reproduce

10. Classes of growth factors
Amino acids
needed for protein synthesis
Purines and pyrimidines
needed for nucleic acid synthesis
Vitamins
function as enzyme cofactors

12. Uptake of Nutrients Some nutrients enter by passive diffusion
Most nutrients enter by:
facilitated diffusion
active transport
group translocation

13. Passive Diffusion
Molecules move from region of higher concentration to one of lower concentration
H2O, O2 and CO2 often move across membranes this way

14. rate of facilitated
diffusion increases
more rapidly and
at a lower
concentration
diffusion rate
reaches a plateau
when carrier
becomes
saturated
Figure 5.3

15. Facilitated Diffusion
Similar to passive diffusion
movement of molecules is not energy dependent
direction of movement is from high concentration to low concentration
size of concentration gradient impacts rate of uptake

16. Facilitated diffusion…
Differs from passive diffusion
uses carrier molecules (permeases)
smaller concentration gradient is required for significant uptake of molecules
effectively transports glycerol, sugars, and amino acids
more prominent in eucaryotic cells than in procaryotic cells

17. note conformational change of carrier
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note conformational change of carrier
possible mechanism of action of permease used for facilitated diffusion; movement is down the gradient; note higher concentration of transported molecule on outside of cell
Figure 5.4

18. Active Transport Energy-dependent process
ATP or PMF
Carrier proteins needed (permeases)
carrier saturation effect is observed at high solute concentrations

19. ABC transporters ATP-binding cassette transporters
observed in bacteria, archaea, and eucaryotes
active transport system; solute-binding protein is located in periplasm of gram-negative bacteria but is attached to external surface of cytoplasmic membrane in gram-positive bacteria; solute-binding proteins may also participate in chemotaxis
Figure 5.5

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Figure 5.4: active transport using proton and sodium gradients
Figure 5.6

21. Group Translocation
Chemically modifies molecule as it is brought into cell
Best known system: transports a variety of sugars while phosphorylating them using phosphoenolpyruvate: sugar phosphotransferase system (PTS)
Phosphoenolpyruvate (PEP) as the phosphate donor 21

22. Group Translocation energy-dependent process Figure 5.7
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Group Translocation
energy-dependent process
Figure 5.7

23. Iron Uptake ferric iron is very insoluble so uptake is difficult
microorganisms use siderophores to aid uptake
siderophore complexes with ferric ion
complex is then transported into cell
Figure 5.6: siderophore ferric iron complexes
Figure 5.6a: ferrichrome is a cyclic hydroxamat molecule formed by many fungi
Figure 5.6b: E. coli produces enterobactin, a cyclic catacholate derivative
Figure 5.6c: ferric iron probably complexes with three siderophore groups to form a six-coordinate, octahedral complex (enterobactin-iron complex is shown)
Figure 5.8

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Types of Media
Table 5.4

25. Defined or Synthetic Media
all components and their concentrations are known
Table 5.5

26. Complex Media
contain some ingredients of unknown composition and/or concentration
Table 5.6

27. Some media components peptones extracts agar
protein hydrolysates prepared by partial digestion of various protein sources
extracts
aqueous extracts, usually of beef or yeast
agar
sulfated polysaccharide used to solidify liquid media

28. Types of Media General purpose media Enriched media
support the growth of many microorganisms
e.g., tryptic soy agar
Enriched media
general purpose media supplemented by blood or other special nutrients
e.g., blood agar

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Figure 5.9

30. Types of media… Selective media
favor the growth of some microorganisms and inhibit growth of others
e.g., MacConkey agar

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Table 5.7

32. Types of media… Differential media
distinguish between different groups of microorganisms based on their biological characteristics
e.g., blood agar
hemolytic versus nonhemolytic bacteria
e.g., MacConkey agar
lactose fermenters versus nonfermenters

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Table 5.7

34. Isolation of Pure Cultures
Spread plate, streak plate, and pour plate are techniques used to isolate pure cultures

35. Spread-plate technique
1. dispense cells onto
medium in petri dish
4. spread cells
across surface
sterilize spreader
Figure 5.10 (a)

36. Appearance of a Spread Plate
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Appearance of a Spread Plate
Figure 5.10 (b)

37. Streak plate technique
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Streak plate technique
Figure 5.11

38. The Pour Plate Sample is diluted several times
Diluted samples are mixed with liquid agar
Mixture of cells and agar are poured into sterile culture dishes

39. Figure 5.12 Figure 5.9: pour-plate technique
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Figure 5.9: pour-plate technique
Figure 5.12

40. Bacterial Colony Morphology
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Bacterial Colony Morphology
Figure 5.13 (a)

41. Bacterial Colony Morphology
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Bacterial Colony Morphology
Figure 5.13 (b) and (c)