Chapter 5 Microbial Nutrition

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

All Organisms Require Carbon, Hydrogen, Oxygen and Electron Source

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

Sources of Carbon, Energy and Electrons Table 5.1

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

Nutritional Types of Microorganisms Table 5.2

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-)

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

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

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

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

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

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

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

note conformational change of carrier Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 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

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

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

Copyright © McGraw-Hill companies, Inc Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. Figure 5.4: active transport using proton and sodium gradients Figure 5.6

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

Group Translocation energy-dependent process Figure 5.7 Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. Group Translocation energy-dependent process Figure 5.7

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

Copyright © McGraw-Hill companies, Inc Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. Types of Media Table 5.4

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

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

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

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

Copyright © McGraw-Hill companies, Inc Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. Figure 5.9

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

Copyright © McGraw-Hill companies, Inc Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. Table 5.7

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

Copyright © McGraw-Hill companies, Inc Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. Table 5.7

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

Spread-plate technique 1. dispense cells onto medium in petri dish 4. spread cells across surface 2. - 3. sterilize spreader Figure 5.10 (a)

Appearance of a Spread Plate Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. Appearance of a Spread Plate Figure 5.10 (b)

Streak plate technique Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. Streak plate technique Figure 5.11

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

Figure 5.12 Figure 5.9: pour-plate technique Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. Figure 5.9: pour-plate technique Figure 5.12

Bacterial Colony Morphology Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. Bacterial Colony Morphology Figure 5.13 (a)

Bacterial Colony Morphology Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. Bacterial Colony Morphology Figure 5.13 (b) and (c)