Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 1 Chapter 6 Microbial Nutrition

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 2 Elements of Life - 1 macroelements (macronutrients) –C, O, H, N, S, P found in organic molecules such as proteins, lipids, carbohydrates, and nucleic acids –K, Ca, Mg, and Fe cations and serve in variety of roles including enzymes, biosynthesis –required in relatively large amounts

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Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 4 Elements of Life - 2 micronutrients (trace elements) –Mn, Zn, Co, Mo, Ni, and Cu –required in trace amounts –often supplied in water or in media components –ubiquitous in nature –serve as enzymes and cofactors some unique substances may be required

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 5 Carbon, Hydrogen, Oxygen, and Electrons 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 CO 2 to form organic molecules

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 6 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 –can use a variety of carbon sources autotrophs –use carbon dioxide as their sole or principal carbon source –must obtain energy from other sources

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Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 8 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

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 9 Classes of Major Nutritional Types majority of microorganisms known –photolithoautotrophs (photoautotrophs) –chemoorganoheterotrophs (chemoheterotrophs) majority of pathogens ecological importance –photoorganoheterotrophs –chemolithoautotrophs –chemolithotrophs

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Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 12 Microorganisms May Change Nutritional Type some have great metabolic flexibility based on environmental requirements provides distinct advantage if environmental conditions change frequently

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Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 14 Requirements for Nitrogen, Phosphorus, and Sulfur needed for synthesis of important molecules (e.g., amino acids, nucleic acids) nitrogen supplied in numerous ways phosphorus usually supplied as inorganic phosphate sulfur usually supplied as sulfate via assimilatory sulfate reduction

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 15 Sources of Nitrogen organic molecules ammonia nitrate via assimilatory nitrate reduction nitrogen gas via nitrogen fixation

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 16 Sources of Phosphorus and Sulfur phosphorus –most organisms use inorganic phosphorus which is directly incorporated into their cells sulfur –most organisms use sulfate and reduce it by assimilatory sulfate reduction

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 17 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

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 18 Classes of Growth Factors amino acids –needed for protein synthesis purines and pyrimidines –needed for nucleic acid synthesis vitamins –function as enzyme cofactors heme

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Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 20 Microbial Production of Growth Factors microorganisms can synthesize many growth factors large-scale industrial production of growth factors, such as vitamins

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 21 Uptake of Nutrients microbes can only take in dissolved particles across a selectively permeable membrane some nutrients enter by passive diffusion microorganisms use transport mechanisms –facilitated diffusion – all microorganisms –active transport – all microorganisms –group translocation – Bacteria and Archaea –endocytosis – Eukarya only

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 22 Passive Diffusion molecules move from region of higher concentration to one of lower concentration between the cell’s interior and the exterior H 2 O, O 2, and CO 2 often move across membranes this way

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 23 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

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 24 Facilitated Diffusion… differs from passive diffusion –uses membrane bound carrier molecules (permeases) –smaller concentration gradient is required for significant uptake of molecules –effectively transports glycerol, sugars, and amino acids more prominent in eukaryotic cells than in bacteria or archaea

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 25 Figure 6.3 rate of facilitated diffusion increases more rapidly and at a lower concentration diffusion rate reaches a plateau when carrier becomes saturated

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Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 27 Active Transport energy-dependent process –ATP or proton motive force used move molecules against the gradient concentrates molecules inside cell involves carrier proteins (permeases) –carrier saturation effect is observed at high solute concentrations

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 28 ABC Transporters primary active transporters use ATP ATP-binding cassette transporters observed in Bacteria, Archaea, and eukaryotes Consist of –2 hydrophobic membrane spanning domains –2 cytoplasmic associated ATP-binding domains –Substrate binding domains

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Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 30 Secondary Active Transport major facilitator superfamily (MFS) use ion gradients to cotransport substances –protons –symport – two substances both move in the same direction –antiport – two substances move in opposite directions

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Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 32 Group Translocation energy dependent transport that chemically modifies molecule as it is brought into cell best known translocation system is phosphoenolpyruvate: sugar phosphotransferase system (PTS) –many anaerobic bacteria transport sugars while phosphorylating them using phosphoenolpyruvate (PEP) as the phosphate donor

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 33 Figure 6.7

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 34 Iron Uptake microorganisms require iron ferric iron is very insoluble so uptake is difficult microorganisms secrete siderophores to aid uptake siderophore complexes with ferric ion complex is then transported into cell Figure 6.8

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 35 Culture Media need to grow, transport, and store microorganisms in the laboratory culture media is solid or liquid preparation must contain all the nutrients required by the organism for growth classification –chemical constituents from which they are made –physical nature –function

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Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 37 Chemical and Physical Types of Culture Media Defined or synthetic Complex

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 38 Defined or Synthetic Media all components and their concentrations are known Table 6.6

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 39 Complex Media contain some ingredients of unknown composition and/or concentration Table 6.7

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 40 Some Media Components peptones –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; most microorganisms cannot degrade it

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 41 Functional Types of Media Supportive Enriched Selective Differential

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 42 Functional Types of Media supportive or general purpose 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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Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 44 Selective Media favor the growth of some microorganisms and inhibit growth of others e.g., MacConkey agar –selects for gram-negative bacteria

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 45 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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Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 47 Isolation of Pure Cultures population of cells arising from a single cell developed by Robert Koch allows for the study of single type of microorganism in mixed culture spread plate, streak plate, and pour plate are techniques used to isolate pure cultures

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 48 The Streak Plate involves technique of spreading a mixture of cells on an agar surface so that individual cells are well separated from each other –involves use of bacteriological loop each cell can reproduce to form a separate colony (visible growth or cluster of microorganisms)

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Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 50 The Spread Plate and Pour Plate spread plate –small volume of diluted mixture containing approximately 30–300 cells is transferred –spread evenly over surface with a sterile bent rod pour plate –sample is serially diluted –diluted samples are mixed with liquid agar –mixture of cells and agar are poured into sterile culture dishes both may be used to determine the number of viable microorganisms in an original sample

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Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 53 Microbial Growth on Solid Surfaces colony characteristics that develop when microorganisms are grown on agar surfaces aid in identification microbial growth in biofilms is similar differences in growth rate from edges to center is due to –oxygen, nutrients, and toxic products –cells may be dead in some areas

Copyright © McGraw-Hill companies, Inc. Permission required for reproduction or display. 54 Figure 6.13