Microbial diversity: Substrate utilization

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Microbial diversitySubstrate utilization

• Dr Paul Brown
• paul.brown_at_uwimona.edu.jm
• BC10M Introductory Biochemistry
• Lecture 9

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METABOLIC DIVERSITY
Diversity of energy harvesting pathways in
microorganisms
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Physiological diversity of bacteria
Physiological type Energy source Carbon source Example
chemoorganotroph or heterotroph organic compounds organic compounds E. coli, Staphylococcus
chemolithotroph or chemoautotroph inorganic chemicals inorganic C (CO2) Thiobacillus sp.
photoautotroph light inorganic C (CO2) cyanobacteria
photoorganotroph or photoheterotroph light organic compounds purple non-sulfur bacteria
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Diversity of phototrophic microorganisms
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Anoxygenic photophosphorylation
Purple and green sulfur and non-sulfur bacteria -
bacteriochlorophylls
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Oxygenic photophosphorylation
Cyanobacteria, Prochlorophytes, chloroplasts -
chlorophyll a or ab
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Organization of an anoxygenic photosystem in the
bacterial membrane
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Chemoautotrophic energy harvesting
pathways oxidation of H2, S/S2-, Fe2, NH4,
NO2- ALL ARE AEROBIC RESPIRATION
Oxidation of hydrogen H21/2 O2-? H2O ATP
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Sulfur oxidation electron flow and CO2 fixation
reduced S oxygen ? oxidized S water ATP
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Internal sulfur granules in Beggiatoa
Sulfolobus (archaea) cells attached to sulfur
crystals
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Electron flow and CO2 fixation in iron oxidizing
bacteria.
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Anaerobic respiration Relative energy of final
electron acceptors used in respiration and the
products of their reduction during respiration.
Anaerobic respirers are mainly organotrophic. Fac
ultative or obligate anaerobes
Aerobic respiration
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Methanogenesis and acetogenesis Methanogens may
be autotrophic or organotrophic obligate
anaerobic archaea
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Fermentation ATP is produced only by
substrate-level phosphorylation NAD is
regenerated by formation of fermentation products
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Many organic compounds in addition to sugars can
be metabolized by fermentation under anaerobic
conditions.
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Growth on organic compounds other than sugars or
amino acids. Hydrocarbon oxidation.
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oxidation of fatty acids Acetyl CoA enters
central metabolism (citric acid cycle)
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Methane oxidation in methanotrophs. Methane is
used as an energy and a carbon source.
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Bacteria require extracellular enzymes when they
use large molecules as substrates. protein
starch lipids DNA
The End!
Bacteria are osmotrophs