1. Chapter 6
Microbial Nutrition 1 1

2. The Common Nutrient Requirements
macroelements (macronutrients)
Large amounts are needed
C, O, H, N, S, P – carbohydrates, proteins, lipids, nucleic acids
K, Ca, Mg, enzyme activity
Fe –part of cytochrome – electron transport
micronutrients (trace elements) – small amounts
Mn, Zn, Co, Mo, Ni, and Cu (manganese, molybdenum)
required in trace amounts
often supplied in water or in media components
Part of enzymes or cofactors 2 2

3. All Organisms Require Carbon, Hydrogen, Oxygen and Electron Source
carbon is backbone of all organic components present in cell
hydrogen and oxygen are also found in organic molecules
electrons play a role in energy production and reduction of CO2 to form organic molecules 3 3

4. Requirements for Carbon, Hydrogen, and Oxygen
often satisfied together
carbon source often provides H, O, and electrons
heterotrophs
use organic molecules as carbon sources which often also serve as energy source
autotrophs
use carbon dioxide as their sole or principal carbon source
must obtain energy from other sources 4 4

5. Nutritional Types of Organisms
based on energy source
phototrophs use light
chemotrophs obtain energy from oxidation of chemical compounds (organic or inorganic)
based on electron source
lithotrophs use reduced inorganic substances
organotrophs obtain electrons from organic compounds 5 5

6. Requirements for Nitrogen, Phosphorus, and Sulfur
needed for synthesis of important molecules (e.g., amino acids, nucleic acids)
nitrogen supplied in numerous ways
phosphorus - phosphate
Sulfur – sulfate ion 6 6

7. Sources of nitrogen organic molecules ammonia
nitrogen gas via nitrogen fixation 7 7

8. 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 8 8

9. Classes of growth factors
amino acids
needed for protein synthesis
purines and pyrimidines
needed for nucleic acid synthesis
vitamins
function as enzyme cofactors 9 9

10. Practical Applications of growth factors
industrial production of growth factors by microorganisms – manufacture vitamins
Riboflavin (B2) - Clostridium 10 10

11. Uptake of Nutrients by the Cell
Some nutrients enter by passive diffusion
Most nutrients enter by:
facilitated diffusion
active transport
group translocation 11 11

12. Passive Diffusion
molecules move from region of higher concentration to one of lower concentration
H2O, O2 and CO2 often move across membranes this way 12 12

13. Facilitated Diffusion
similar to passive diffusion
movement of molecules is not energy dependent
direction of movement is from high concentration to low concentration 13 13

14. Facilitated diffusion…
differs from passive diffusion
uses carrier molecules (permeases)
effectively transports glycerol, sugars, and amino acids
more prominent in eucaryotic cells than in procaryotic cells 14 14

15. 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 15 15

16. Active Transport energy-dependent process moves molecules low to high
ATP or proton motive force used
moves molecules low to high
concentrates molecules inside cell
involves carrier proteins (permeases) 16 16

17. ABC transporters - active transporters
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ABC transporters - active 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
Maltose,
galactose, ribose, amino acids
Figure 5.5 17 17

18. Group Translocation Low to high Energy is used Transport protein
chemically modifies molecule as it is brought into cell 18 18

19. Group Translocation energy-dependent process Figure 5.7
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Group Translocation
energy-dependent process
Phosphoenol pyruvate: sugar
Phosphotransferase system
PTS
Sugars
Figure 5.7 19 19

20. Iron Uptake siderophores (organic molecues) secreted to aid uptake
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Iron Uptake
siderophores (organic molecues) secreted 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)
For cytochrome
Binds to receptor
Iron released
Figure 5.8 20 20