bacterial metabolism

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					      Bacterial Metabolism
Metabolism
–   Sum up all the chemical processes that
    occur within a cell
    1. Anabolism: Synthesis of more complex
       compounds and use of energy
    2. Catabolism: Break down a substrate and
       capture energy
Overview of cell metabolism
Bacterial Metabolism
–   Autotroph:
     Photosynthetic bacterial
     Chemoautotrophic bacteria
–   Heterotroph:
     Parasite
     Saprophyte
     Energy Generating Patterns

–   After Sugars are made or obtained, they are
    the energy source of life.
–   Breakdown of sugar(catabolism) different
    ways:
        • Aerobic respiration

        • Anaerobic respiration

        • Fermentation
Photosynthesis
(1) Higher plants

–   Light reaction:
     Photolysis of H2O produce ATP and NADPH
–   Two photosystem (I & II)
    Dark fixation: use the production from light
    reaction (ATP and NADPH) to fix CO2
       Reaction:
       6CO2 + 6H2O -----> C6H12O6 +6O2
       (Light and chloroplast)
Bacteria Photosynthesis
 i. Only one photosystem can not do
      photolysis of H2O
 ii. H2O not the source of electron donor
 iii. O2 never formed as a product
 iv. Bacterial chlorophyll absorb light at longer
      W.L.
 v. Similar CO2 fixation
 vi. Only has cyclic photophosphorylation
    How the Bacteria synthesize NADPH
   Grow in the presence of the H2 gas
H2 + NADP+ ------------- NADPH2
           hydrogenase
   Reverse the electron flow in the e-
    transport chain
H2S                    S
S     + NADP+-------- SO4-2 + NADPH2
Succinate             Fumarate
   Simple non-cyclic photosynthetic e- flow
 Chlorophyll a and
bacteriochlophyll a(1)
 Chlorophyll a and
bacteriochlophyll a(2)
Anoxygenic photosynthesis
  Anoxygenic versus
oxygenic phototrophs(2)
  Anoxygenic versus
oxygenic phototrophs(1)
     Photosynthetic bacteria
(1) Chlorobium-green sulfur bacteria
   Use green pigment chlorophyll
   Use H2S (hydrogen sulfide), S (sulfur), Na2S2O3 (sodium
   thiosulfate) and H2 as e- donors.
(2) Chromatium-purple sulfur bacteria
   Use purple carotenoid pigment, same e-donors
(3) Rhodospirillum-non sulfur purple bacteria
  Use H2 and other organic compounds such as isopropanol etc,
  as e-donors.

Reaction: CO2 + 2H2A -----> CH20 + H20 +2A
 A is not O
         Chemautotroph
–   Some bacteria use O2 in the air to oxidize
    inorganic compounds and produce ATP
    (energy). The energy is enough to convert
    CO2 into organic material needed for cell
    growth.
–   Examples:
    Thiobacillus (sulfur S)
    Nitorsomonas (ammonia)
    Nitrobacter (nitrite)
–   Various genera (hydrogen etc.)
       Aerobic respiration
–  Most efficient way to extract energy from
   glucose.
– Process: Glycolysis
            Kreb Cycle
             Electron transport chain
– Glycolysis: Several glycolytic pathways
– The most common one:
glucose-----> pyruvic acid + 2 NADH + 2ATP
       Aerobic respiration
–   Euk.
     glucose -----> G-6-P----->F-6-P----->
           …... 2 pyruvate +2ATP + 2NADH
–   Prok.
     glucose-----> G-6-P------>F-6-P
–   Process take places during transport of the
    substrate. Phosphate is from
    phosphoenolpyruvate (PEP)
      .....-----> 2 pyruvate +2ATP + 2NADH
–   Kreb cycle:
    Pyruvate + 4NAD + FAD ----->
                      3CO2 +4NADH + FADH
    GDP + Pi -----> GTP
    GTP + ADP -----> ATP + GDP

–   Electron trasnport Chain
    4HADH -----> 12 ATP
    FADH ------> 2 ATP        Total 15 ATP
    Glycolysis -----> 8 ATP

–   Total equation:
    C6H12O6 + 6O2 ------> 6CO2 + 6H2O + 38 ATP
Generation of a proton-motive force(1)
Generation of a proton-motive force(2)
Mechanism of ATPase
      Anaerobic respiration
–   Final electron acceptor : never be O2
   Sulfate reducer: final electron acceptor is sodium
    sulfate (Na2 SO4)
   Methane reducer: final electron acceptor is CO2
   Nitrate reducer : final electroon acceptor is
    sodium nitrate (NaNO3)
O2/H2O coupling is the most oxidizing, more energy
    in aerobic respiration.

Therefore, anaerobic is less energy efficient.
           Fermentation
 Glycosis:
Glucose ----->2 Pyruvate + 2ATP + 2NADH

  Fermentation pathways
a. Homolactic acid F.
   P.A -----> Lactic Acid
   eg. Streptococci, Lactobacilli
b.Alcoholic F.
   P.A -----> Ethyl alcohol
   eg. yeast
c. Mixed acid fermentation
   P.A -----> lactic acid
             acetic acid
             H2 + CO2
             succinic acid
             ethyl alcohol
   eg. E.coli and some enterbacter
d. Butylene-glycol F.
   P.A -----> 2,3, butylene glycol
   eg. Pseudomonas
e. Propionic acid F.
   P.A -----> 2 propionic acid
   eg. Propionibacterium
Alternative energy generating
          patterns(1)
Alternative energy generating
          patterns(2)
Alternative energy generating
          patterns(3)
Alternative energy generating
          patterns(4)
Energy/carbon classes of organisms
Chlorophyll a and
bacteriochlophyll a(3)
Comparison of reaction centers
of anoxyphototrophs

				
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posted:1/15/2012
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