Chapter 8. Microbial metabolism

- metabolism : “metaballein” = change

- microbial metabolism : all chemical changes occurring in a microbe during its growth

and development for healthy and stable maintenanceand development for healthy and stable maintenance

- occurring for activities such as movement, growth, synthesis, foodstuff, reproduction

-> highly organized and responsive to cellular control in its local environment

-> rxn of metabolism are used efficiently, economically

Light energy Chemical energyLight energy

PhotolithoautotrophChemolithoautotroph

Chemical energy

CO2Chemolithoautotroph

CH2Oenergy worksmicrobes

Chemoorganoheterotroph(energy, biosynthesis)

Chapter 8. Microbial metabolism

1. Enzyme

- all metabolic rxns are catalyzed and regulated by enzyme- enzyme : organic molecules, catalysts

-> catalyst : speed up the rxn without being chemically transformed by itself

* Enzyme reaction

Chapter 8. Microbial metabolism* Enzyme reaction

- enzyme provide a site for substrate binding -> active site- enzyme-substrate complex is formed at transition state- end products is released

Chapter 8. Microbial metabolism

☞ enzyme-substrate complex

2. Energy

Chapter 8. Microbial metabolism2. Energy

- major goal of metabolism :

-> supply energy-storing substances and release when needed

(photosynthesis) vs (respiration)

- ATP : energy carrier molecule

-> adenosine triphosphate

-> universal energy currency

l l ( l l )

Chapter 8. Microbial metabolism

3. Glycolysis (glyco + lysis)

- primary central pathway for all living organisms

- starts from six-carbon organic molecule glucose- starts from six-carbon organic molecule, glucose

- produce three-carbon molecule, pyruvate, as end product

- pyruvate is utilized for three different destination

take place in the cytoplasm of microbes- take place in the cytoplasm of microbes

- not require oxygen

- catalyzed by enzymes

2 l l f ATP i t d d 4 ATP d d- 2 molecules of ATP are invested and 4 ATP are produced

Glycolysis (Embden-Meyerhof)Glycolysis (Embden-Meyerhof)

Phase I Phase II

Pentose phosphate pathwayPentose phosphate pathway

Entner-Doudoroff pathwayEntner-Doudoroff pathway

P d Rhi biPseudomonas, Rhizobium

4 F t ti

Chapter 8. Microbial metabolism

4. Fermentation

- side step of glycolysis -> takes place in the absence of oxygen

- pyruvate is transformed into other organic products -> alcohol, acid, CO2py g p , , 2

- Yeast : Mag-gul-li, wine Streptococcus, Lactobacillus : yogurt

FermentationFermentation

Microbial fermentations

*공통특징 :공통특징 : - NADH는 NAD+로 산화- Pyruvate나 그 유도체가 전자수용체

1: lactate 발효1 lactate 발효- homolactic: 모든 pyruvate를 lactate로- heterolactic: lactate 이외의 산물 생산2: alcohol 발효3: propionate 발효3 propionate 발효4: butanediol 발효5: formic acid 발효6: acetate 발효

Chapter 8. Microbial metabolism

5 A bic spi ti n5. Aerobic respiration

- pyruvate의 분해과정

- mitochondria 내에서 acetyl-coA로 변환 후 Krebs cycle 에 투입y y

- mitochondria 없으면 세포막에서 진행

1) Krebs cycle :

- one cycle : one acetyl-coA -> two CO2

- citric acid cycle, TCA(tricarboxylic acid) cycle

- produce NADH, FADH2, ATPproduce NADH, FADH2, ATP

- intermediate products -> precursor of biosynthesis

Chapter 8. Microbial metabolism

)2) Electron transport and chemiosmosis :

- take place in mitochondria or cell membrane

serious of losses & gains of electron- serious of losses & gains of electron

between electron carrier molecules

- beginning with NADH and FADH2

- final electron acceptor : O2 ->produce H2O

- what if there is no O2 ?

- released energy is used to make proton gradient

cross the membrane

- proton gradient is utilized to synthesis ATP

산화환원, 환원전위, 전자이동산화환원, 환원전위, 전자이동

E’o(standard reduction potential) : affinity for electron+ : 전자를 받아들이는 경향이 큼- : 전자를 내어놓는 경향이 큼

Chapter 8. Microbial metabolism

☞ energy level of electron carriers

Chapter 8. Microbial metabolism

☞ electron transport and chemiosmosis☞ electron transport and chemiosmosis

Chapter 8. Microbial metabolism

3) ATP synthetase

Chapter 8. Microbial metabolism

☞ Total ATP production during aerobic respiration

Chapter 8. Microbial metabolism

6 A bi i ti6. Anaerobic respiration

- take place under anaerobic condition

- use alternatives to oxygen as an final electron acceptoruse alternatives to oxygen as an final electron acceptor

산화환원, 환원전위, 전자이동산화환원, 환원전위, 전자이동

Photosynthesis in microbes

M t b li f th t i tM t b li f th t i tMetabolism of other nutrientsMetabolism of other nutrients

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