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

Pyruvate + 4NAD + FAD -----> 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