julia vorholt lecture 8 - eth zn.ethz.ch/~nielssi/download/3....

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings

Brock Biology of Microorganisms, Twelfth Edition – Madigan / Martinko / Dunlap / Clark

752-4001-00L Mikrobiologie

Julia Vorholt Lecture 8: Nov 12, 2012



1) Nutrients and microbial growth 2) Introduction to principles of metabolism 3) Chemoorganotrophy 4) Chemolithotrophy 5) Phototrophy 6) Autotrophy, nitrogen fixation 7) Global carbon, nitrogen, sulfur cycles


Glycolysis and Citric Acid Cycle

Fig. 4.14

Glucose

Pyruvate

2 Pyruvate

2 lactate

Substrate-level-phosphorylation

Electron transport-coupled phosphorylation

Pyruvate (three carbons)

Acetyl-CoA

Oxalacetate2

Malate2

Fumarate2

Succinate2

Succinyl-CoA

Citrate3

Aconitate3

Isocitrate3

-Ketoglutarate2

C2

C4

C5

C6

Electron transport-coupled

phosphorylation


Aerobic Respiration

Complex I (NADH:quinone oxidoreductase) NADH donates e- to FMN FMN donates e- to quinone

Complex II (succinate dehydrogenase complex) Bypasses Complex I Feeds e- and H+ from FADH directly to quinone pool

Complex III (cytochrome bc1 complex)

Transfers e- from quinones to cytochrome c Cytochrome c shuttles e- to cytochromes a and a3

Complex IV (cytochromes a and a3) Terminal oxidase; reduces O2 to H2O

Electron transport process in the membrane of

Paracoccus denitrificans

Chap. 4.10 Fig. 4.19

CYTOPLASMENVI

RONM

ENT

Complex IISuccinate

Fumarate

Q cycle

0.22

0.0

0.1

0.36

0.39

E0(V)

E0(V)


Aerobic Respiration

Electron transport process in the membrane of

Escherichia coli

Fig. 14.13a Chap. 4.11


Anaerobic Respiration

The use of electron acceptors other than oxygen

Examples include nitrate (NO3-), ferric iron (Fe3+), sulfate

(SO42-), carbonate (CO3

2-), certain organic compounds

Less energy released compared to aerobic respiration

Energy released from redox reactions can be determined by comparing reduction potentials of each electron acceptor

Dependent on electron transport, generation of a proton motive force, and ATPase activity

Chap. 4.12, 14.6


Major Forms of Anaerobic Respiration

Thermodynamic hierarchy of

electron acceptors

Organisms: (many) Pseudomonas

Paracoccus

Organisms: Enterobacteria,

e.g. E. coli

Chap. 14.6 Fig. 14.11

0.42

0.3

0.27

0.25

0.22

0

0.2

0.3

0.4

0.75

0.82

Anoxic

Oxic(oxygenpresent)

Anoxic Proton reduction;Pyrococcus furiosus,obligate anaerobe

E0(V)

Carbonate respiration;acetogenic bacteria,obligate anaerobes

Sulfur respiration;facultative aerobes andobligate anaerobes

Carbonate respiration;methanogenic Archaea;obligate anaerobes

Sulfate respiration(sulfate reduction);obligate anaerobes(SO4

2- SO32-, E0 0.52)

Fumarate respiration;facultative aerobes

Iron respiration; facultativeaerobes and obligateanaerobes

Reductive dechlorination;facultative aerobes andobligate anaerobes

Nitrate respiration;facultative aerobes (somereduce NO3

- to NH4)

Denitrification;facultative aerobes

Manganese reduction;facultative aerobes

Aerobic respiration;obligate andfacultative aerobes


Dissimilative Reduction of Nitrate

-> Denitrification is a biological source of gaseous N2

Chap. 14.7 Fig. 14.12

Nitrate

Nitrite

Nitric oxide

Nitrous oxide

Dinitrogen

Gases

Nitratereduction (Escherichiacoli)

Denitrification (Pseudomonasstutzeri)

NO3

NO2

NO

N2O

N2

Nitrate reductase

Nitrite reductase

Nitric oxide reductase

Nitrous oxide reductase

NH4+


Respiration and Anaerobic Respiration

Chap. 14.7 Fig. 14.13

Periplasm

Q cycle

Cytoplasm

Aerobic respiration

Denitrification

Nitrate reduction

Periplasm

Q cycle

Cytoplasm

Nitrate reductase complex

Nitr

ate

re

duct

ase

Nitr

ate

re

duct

ase

Nitr

ic o

xide

re

duct

ase

Periplasm Nitrate reductase complex

Q cycle

Cytoplasm

N2O reductase

NO2

reductase



Chap. 14.6 Fig. 14.11

0.42

0.3

0.27

0.25

0.22

0

0.2

0.3

0.4

0.75

0.82

Anoxic

Oxic(oxygenpresent)


E0(V)





2- SO32-, E0 0.52)





- to NH4)




Organisms: Shewanella Geobacter


Microbial Fuel Cell

www.microbialfuelcell.org


Electricigens – Potential mechanisms for electron transfer



Chap. 14.6 Fig. 14.11

0.42

0.3

0.27

0.25

0.22

0

0.2

0.3

0.4

0.75

0.82

Anoxic

Oxic(oxygenpresent)


E0(V)





2- SO32-, E0 0.52)





- to NH4)




Organisms: Methanosarcina

Methanobacterium Methanococcus Methanopyrus


Methanogenesis and Acetogenesis

at 1-10 Pa H2: G‘ = - 17 kJ/mol)

Some methanogens also use acetate or methanol as substrate

Chap. 14.10 Fig. 14.16

Proton or sodium motive force (plus

substrate-level phosphorylation for

acetogens)

Methanogenesis ( G0 136 kJ)

Acetogenesis ( G0 105 kJ)


Methanogenesis

Methanogenesis is the only way that methanogenic archaea can obtain energy for growth. => Specialization

Methanogens are the only organisms known to produce methane (CH4) as a catabolic end product.

They are strict anaerobes.

Atmospheric concentrations of methane have doubled since 200 years.


Anoxic Decomposition


Rumen and Gastrointestinal System of a Cow

Chap. 24.10 Fig. 24.27

The rumen contains 1010-1011

microbes/g of rumen constituents

Microbial fermentation in the rumen is mediated by celluloytic microbes that hydrolyze cellulose to free glucose that is then fermented, producing volatile fatty acids (e.g., acetic, propionic, butyric) and the CH4 and CO2

Fatty acids pass through rumen wall into bloodstream and are utilized by the animal as its main energy source


Biochemical Reactions in the Rumen

Rumen microbes also synthesize amino acids and vitamins for their animal host

Rumen microbes themselves can serve as a source of protein to their host when they are directly digested

Chap. 24.10 Fig. 24.28


Rumen and Gastrointestinal System of a Cow

Chap. 25.7 Fig. 25.26

The rumen contains 1010-1011

microbes/g of rumen constituents

Microbial fermentation in the rumen is mediated by celluloytic microbes that hydrolyze cellulose to free glucose that is then fermented, producing volatile fatty acids (e.g., acetic, propionic, butyric) and the CH4 and CO2

Fatty acids pass through rumen wall into bloodstream and are utilized by the animal as its main energy source


Biochemical Reactions in the Rumen

Rumen microbes also synthesize amino acids and vitamins for their animal host

Rumen microbes themselves can serve as a source of protein to their host when they are directly digested

Chap. 25.7 Fig. 25.27

FEED, HAY, etc.

Cellulose, starch, sugars

Fermentation Fermentation

Cellulolysis, amylolysis

Formate

Pyruvate Succinate

Lactate Propionate CO2

Removed byeructation toatmosphere

Acetate

Rum

inan

t blo

odst

ream

Rum

en w

all

VFAs

AcetatePropionateButyrate

Overall stoichiometry of rumen fermentation:

SUGARS



1) Nutrients and microbial growth 2) Introduction to principles of metabolism 3) Chemoorganotrophy 4) Chemolithotrophy 5) Phototrophy 6) Autotrophy, nitrogen fixation 7) Global carbon, nitrogen, sulfur cycles


Chemolithotrophy: Beggiatoa


Sergej Winogradsky: Concept of Chemolithotrophy 1887

Drawings made by Winogradsky of Beggiatoa. Fig. 1. The tip of a filament of Beggiatoa alba: (a) in sulfurous [sulfide-containing] water, (b) after 24 h in water nearly depleted in H2S, (c) after 48 h in water without H2S. Fig. 2. The tip of a filament of Beggiatoa media. Fig. 3. The tip of a filament of Beggiatoa minima. From Winogradsky, S. 1949. Microbiologie du Sol. Masson, Paris.

Sulfur oxidizers

Fig. 1.2


Chemolithotrophy

Chemolithotrophs are organisms that obtain energy

from the oxidation of inorganic compounds

Most chemolithotrophs obtain their carbon from CO2 (autotrophs)

Many sources of reduced molecules exist in the

environment

The oxidation of different reduced compounds yields

varying amounts of energy

Chap. 13.6


Chemolithotrophic processes

Chap. 13.6


Energy Yields from Oxidation of Inorganic Electron Donors

Chap. 13.6


Hydrogen Oxidizers (aerobic) / Knallgas bacteria

Chap. 13.7

> Large amounts of hydrogen are formed during the anaerobic biological degradation of organic material.

> Low amounts are also released during geochemical processes and are found in vulcanic gases.

H2 + 0.5 O2 -> H2O (G°‘ = - 237 kJ/mol) Key enzyme: Hydrogenase (Fe, S) (Ni, Fe) „Knallgasbakterien“ – aerobic hydrogen oxidizing microorganisms: Ralstonia eutropha (Alcaligenes), Paracoccus (usually facultative chemolithotroph)


Hydrogenases of Aerobic Hydrogen oxidizing Bacteria

Chap. 13.7 Fig. 13.20

Membrane-integrated hydrogenase

Cytoplasmic hydrogenase

Cell material

Out

In


Nitrification

NH3 and NO2- are oxidized by nitrifying bacteria (and archaea) during the process of nitrification

Two groups of bacteria work in concert to fully oxidize ammonia to nitrate

The nitrifiers are widespread in soil and water. They can be found in nature wherever ammonium is liberated and oxygen is available.

Like many other chemolithotrophs, the nitrifiers are particularly active at the oxic/anoxic interface of sediments and water bodies.

Only small energy yields from this reaction

=> Growth of nitrifying bacteria is very slow

Nitrite-oxidizing

Ammonium-oxidizing

Chap. 13.10


Oxidation of Ammonia by Ammonia-Oxidizing Bacteria

Chap. 13.10 Fig. 13.26

AMO, ammonia monooxygenase

HAO, hydroxylamine oxidoreductase

Cyt aa3, terminal cyt c oxidase (complex IV)

Oxidation ofhydroxylamine

Out

Oxidation ofammonia

Reductionof oxygen

In


Oxidation of Nitrite to Nitrate by Nitrifying Bacteria

Chap. 13.10 Fig. 13.27

NXR, nitrite oxidoreductase

Cyt aa3, terminal cyt c oxidase (complex IV)

Periplasm

Cytoplasm

Oxidation of nitrite

Reductionof oxygen

Reverse e flowto make NADH


Degradation of limestone

NH3 NO2- NO3

-

Salpeter- säure

Nitric acid

salpetrige Säure

Nitrous acid

Agriculture

Ca(CO3)2


Nitrifiers in waste-water treatment

The chemolithoautotrophic ammonium- and nitrite-oxidizing bacteria play a vital role in modern waste-water treatment for nitrogen removal.


Anammox

Chap. 13.11 Fig. 13.28

Anammox: anoxic ammonia oxidation (to N2 gas)

NH4+ + NO2

- -> N2 + H2O Performed by unusual group of

obligate aerobic bacteria (Plantomycetes)

Anammoxosome is compartment where anammox reactions occur

Protects cell from reactions occuring during anammox

Hydrazine (H2N-NH2) is an intermediate of anammox

Anammox is very beneficial in the treatment of wastewater Anammoxosome

membraneElectrontransport

Out In

julia vorholt lecture 8 - eth zn.ethz.ch/~nielssi/download/3....

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