Exam 2 - Chapter 14

Types of metabolic systems in microbes

-Photo-litho-autotroph

-Chemo-organo-heterotroph

-Photo-litho-heterotroph

-Chemo-litho-autotroph

-Chemo-litho-heterotroph

-Mixotroph

Mixotroph

An organism that is capable of both autotrophy and heterotrophy

Metabolic types that are only found in prokaryotes

-Photo-litho-heterotroph

-Chemo-litho-autotroph

-Chemo-litho-heterotroph

-Mixotroph

Metabolic classifications based on energy source

Phototroph and chemotroph

Metabolic classifications based on reducing power source

Lithotroph and organotroph

Metabolic classifications based on carbon source

Autotroph and heterotroph

Phototrophy and respiration involve...

ETC and PMF

Calvin Cycle

Most widespread, globally important pathway for CO2 fixation

Calvin cycle is used by...

all oxygenic phototrophs (cyanobacteria, algae, plants), most purple bacteria, and most aerobic chemolithotrophic Bacteria

Key enzyme of the Calvin cycle in carboxysomes

RubisCO

The Calvin cycle requires...

12 NADPH and 18 ATP to synthesize 1 fructose-6-phosphate from CO2

Reverse Citric Acid (reductive TCA) cycle

Pathway in which CO2 is reduced by reversal of steps in citric acid cycle, which is more efficient than the Calvin cycle

Reverse citric acid cycle is used by...

green sulfur bacteria and many anaerobic or microaerophilic chemolithotrophic Bacteria

Reverse citric acid cycle requires...

24H and 10 ATP to fix 6 CO2

Source of energy and reducing power can be...

sunlight or chemical reactions

Patterns of photosynthesis

Oxygenic and anoxygenic

What organisms perform anoxygenic photosynthesis?

phototrophic purple and green bacteria

What organisms perform oxygenic photosynthesis?

Cyanobacteria

Anoxygenic phototrophy uses ___ for reducing power

H2S

Oxygenic phototrophy uses ___ for reducing power

H2O

In anoxygenic phototrophy, ____ is formed by reduction of the reducing power

SO₄^2-

In oxygenic phototrophy, ____ is formed by reduction of the reducing power

1/2 O2

Phototrophy in purple bacteria

Light energy converts a weak electron donor into a strong donor and cyclic electron flow generates pmf (uses Q-type RC)

Phototrophy in green sulfur bacteria

Fe-S type RC makes a stronger electron donor than Q-type

Phototrophy in cyanobacteria

Noncyclic electron flow or cyclic electron flow generates pmf; 2 different photosystems using either Fe-S type RC or Q type RC

Photophosphorylation

Sunlight -- PMF -- ATP production

Light reactions in oxygenic photosynthesis occur in...

photocomplexes in specialized photosynthetic membranes

In eukaryotes (plants and algae), the light reactions in oxygenic photosynthesis occur in...

chloroplast

In cyanobacteria, the light reactions in oxygenic photosynthesis occur in...

stacked membranes in the cytoplasm

Electron transport in oxygenic photosynthesis uses what structures in the photosynthetic membrane?

ATP synthase, PSI, Cyt b6f, and PSII

Cyanobacteria acquired both PSI and PSII via...

horizontal gene transfer

Chemolithotrophic reactions

-Sulfide to sulfate

-Sulfite to sulfate

-Thiosulfate to sulfate

How many electrons are involved in the sulfide to sulfate chemolithotrophic reaction?

8

How many electrons are involved in the sulfite to sulfate chemolithotrophic reaction?

2

How many electrons are involved in the thiosulfate to sulfate chemolithotrophic reaction?

8

Stoichiometry of the sulfide to sulfate chemolithotrophic reaction

H2S + 2 O2 -- SO4 2- + 2H+

Stoichiometry of the sulfite to sulfate chemolithotrophic reaction

SO₃^2- + 1/2 O₂ -- SO₄^2-

Stoichiometry of the thiosulfate to sulfate chemolithotrophic reaction

S₂O₃^2- + H₂O + 2 O₂ -- 2 SO₄^2- + 2 H⁺

Iron oxidation

Aerobic oxidation of ferrous iron (Fe2+) to ferric ion (Fe3+) which supports chemolithotrophic "iron-bacteria"

Many Fe oxidizers are...

strongly acidophilic

In iron oxidation, ferric hydroxide...

precipitates in water, driving down pH

Nitrification

Ammonia and nitrite are oxidized aerobically by chemolithotrophic nitrifying bacteria

Nitrifying bacteria widely distributed in...

soil, water, wastewater, and oceans

2 sets of reactions used in nitrification

Oxidation of ammonia to nitrite and oxidation of nitrite to nitrate

How many sets of reactions can most nitrifiers catalyze?

Only one set of reactions (only ammonia to nitrite or only nitrite to nitrate)

Oxidation state of organic nitrogen (-NH2)

-3

Oxidation state of ammonia (NH3)

-3

Oxidation state of nitrogen gas (N2)

0

Oxidation state of nitrous oxide (N2O)

+1 (average per N)

Oxidation state of nitric oxide (NO)

+2

Oxidation state of nitrite (NO2-)

+3

Oxidation state of nitrogen dioxide (NO2)

+4

Oxidation state of nitrate (NO3-)

+5

Steps in dissimilative reduction of nitrate

1. Nitrate reduction

2. Nitrite reduction

3. Nitric oxide reduction

4. Nitrous oxide reduction

5. Dinitrogen formed

Methanogenisis

Biological production of methane via CO2 reduction by H2

Methanogenesis is catalyzed by...

strictly anaerobic Archaea called methanogens

Methanogens are present in...

freshwater sediments, wetlands, many animal guts, sewage sludge digesters, and other bioreactors

Methanogenesis is a form of...

anaerobic respiration

Fermentation energy conservation depends on...

substrate level phosphorylation

Fermentation is defined by...

lack of external electron acceptor

Fermentation does not involve...

ETC or PMF

Redox balance is achieved in fermentation by...

donating electrons to metabolic intermediates excreted as fermentation products

Fermentation energy conservation

Conserves much less energy than respiratory organisms

Energy is conserved in fermentation via...

substrate level phosphorylation

Types of fermentation reactions

-Alcoholic

-Homolactic

-Heterolactic

-Propionic acid

-Mixed acid

-Butanediol

-Butyric acid

-Butanol

-Caproate/butyrate

Alcoholic fermentation reaction

Hexose -- 2 ethanol + 2 CO2

Homolactic fermentation reaction

Hexose -> 2 lactate + 2 H+

Heterolactic fermentation reaction

Hexose -> lactate- + ethanol + CO2 + H+

Propionic acid fermentation reaction

2 lactate- -> 2 propionate- + acetate- + CO2 + H2O

Mixed acid fermentation reaction

Hexose -> lactate- + acetate- + succinate2- + formate- + ethanol + H2 + CO2

Butanediol fermentation reaction

Hexose -> 2,3-butanediol + ethanol + lactate- + acetate- + succinate2- + formate- + H2 + CO2

Butyric acid fermentation reaction

Hexose -> butyrate- + 2 H2 + 2 CO2 + H+

Butanol fermentation reaction

2 hexose -> butanol + acetone + 5 CO2 + 4 H2

Caproate/butyrate fermentation reaction

6 ethanol + 3 acetate- -> 3 butyrate- + caproate- + 2 H2 + 4 H2O + H+

Organisms that use alcoholic fermentation

yeast, zymomonas

Organisms that use homolactic fermentation

streptococcus, some lactobacillus

Organisms that use heterolactic fermentation

leuconostoc, some lactobacillus

Organisms that use propionic acid fermentation

propionibacterium, clostridium propionicum

Organisms that use mixed acid fermentation

enteric bacteria including escheria, salmonella, shigella

Organisms that use butanediol fermentation

klebsiella, enterobacter

Organisms that use butyric acid fermentation

Clostridium butyricum

Organisms that use butanol fermentation

Clostridium acetobutylicum

Organisms that use caproate/butyrate fermentation

Clostridium kluyveri

Fermentation does not involve...

ETC or PMF