Bacterial MetabolismMetabolism

– Sum up all the chemical processes that occur within a cell1. 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

– After Sugars are made or obtained, they are the energy source of life.

– Breakdown of sugar(catabolism) different ways:

• Aerobic respiration• Anaerobic respiration • Fermentation

Energy Generating Patterns

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 productiv. Bacterial chlorophyll absorb light at longer W.L.

v. Similar CO2 fixationvi. 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

chainH2S 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 + FADHGDP + Pi -----> GTPGTP + ADP -----> ATP + GDP

– Electron trasnport Chain4HADH -----> 12 ATPFADH ------> 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 pathwaysa. Homolactic acid F.

P.A -----> Lactic Acideg. Streptococci, Lactobacilli

b.Alcoholic F.P.A -----> Ethyl alcoholeg. yeast

c. Mixed acid fermentationP.A -----> lactic acid

acetic acid H2 + CO2 succinic acid ethyl alcohol

eg. E.coli and some enterbacterd. Butylene-glycol F.

P.A -----> 2,3, butylene glycoleg. Pseudomonas

e. Propionic acid F.P.A -----> 2 propionic acideg. 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