Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Physiological diversity
• Principles
• Energetic considerations
• Biochemical pathways
• Organisms
• Ecological relevance
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Physiological diversity
• Sulfate- and nitrate reducers (5. Nov.)
• Methanogens and homoacetogens (10. Nov.)
• Chemolithotrophs (11. Nov.)
• Photosynthesis (12. Nov.)
• Recapitulation (13. Nov.)
• Written test II (16. Nov.)
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Sulfate and nitrate reducers
Martin Könneke
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Recommended text books
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Aerobic respiration vs fermentation
Glycolysis
NADH
ATP
NADH
Pyruvic acid
Acetyl CoA
Pyruvic acid
NADH
ATP
TCA
(Krebs)
cylce
Formation of
fermentation end
products
CO2
NADH
Electrons
Substrate level phosphorilation
ATP
Electron transport chain and chemiosmosis
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Aerobic respiration
Chemiosmosis
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Fermentation
Substrate-level phosphorylation
Organic compounds
Fermentation
product
NAD+
NADH
Energy-rich
compounds
Oxidized
compound
ADP
ATP
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Complex polymers
(polysaccharides, lipids, proteins)
Hydrolysis
Monomers
(sugars, fatty acids, amino acids)
Fermentation
H2 + CO2
Formate
Short chain fatty acids and alcohols
(lactate, butyrate, propionate, ethanol)
Acetate
???
???
???
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Anaerobic respiration
• Utilization of terminal electron acceptors others than oxygen
• Electron transport systems analog to aerobes
(cytochromes, quinones, iron-sulfur and other proteins)
• Strict anaerobes (sulfate reducers + nitrate reducers)
• Facultative anaerobes (nitrate reducers)
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Anaerobic respiration
Electron-donating
reaction
Membrane associated
electron transport
Terminal electronaccepting reaction
Reduced organic and
Inorganic compounds
Proton motive force
Oxidized compounds
others than O2
Generation of ATP
Less energy than aerobic respiration,
but usually more than fermentation!
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Complex polymers
(polysaccharides, lipids, proteins)
Hydrolysis
Monomers
(sugars, fatty acids, amino acids)
Fermentation
H2 + CO2
Formate
Short chain fatty acids and alcohols
(lactate, butyrate, propionate, ethanol)
Acetate
CO2 + Sulfide
CO2 + Methane
CO2 + NH4/N2
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Examples for
anaerobic respirations
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Dissimilatory
nitrate reducers
Brock Biology of Microorganisms: Chapter 12, 17, 18
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
The biological nitrogen cycle
NO3Nitrate reduction
NO
Nitrite
Ammonification
DNRA
N2O
N2
Nitrification
Denitrification
NO2-
Anammox
Nitrogen fixation
NH2OH
NH4+
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
The biological nitrogen cycle
NO3Nitrate reduction
Denitrification
NO2NO
N2O
Nitrite
ammonification
N2
NH4+
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Denitrification - Reduction of nitrate to nitrogen
Anaerobic respiration with anorganic nitrate as electron acceptor
Formation of gaseous compounds nitrous oxide (N2O), nitric oxide (NO)
und nitrogen (N2)
Results in a loss of nitrogen in the environment (agriculture - wastewater
treatment)
Initial step is catalyzed by the nitrate reductase
Many facultative anaerobic prokaryotes are denitrifiers
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Oxidation state
Nitrate (NO3-)
+V
Nitrite (+III)
Reduction
5 electrons (e-)
Nitric oxide (+II)
Nitrous oxide (av. +I)
Denitrification
2NO3- + 10e- + 12H+ ! N2 + 6H2O
0
Nitrogen (N2)
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Denitrification in
Pseudomonas stutzeri
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Oxygen- and nitrate respiration in E. coli
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Haloferax denitrificans (facultatic aerobe)
Ferroglobus placidus (strict anaerobe)
Widespread among the Bacteria
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Oxidation state
Nitrate (NO3-)
+V
2 electrons (e-)
Nitrite (+III)
6 electrons (e-)
Nitrate
ammonification
- III
Ammonia (NH3)
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Nitrate ammonification Reduction of nitrate to ammonia
Anaerobic respiration with inorganic nitrate as electron acceptor
(energy yielding step)
Temporary accumulation of nitrite
Reduction of nitrite to ammonia is an exergonic reaction (kind of
fermentation process)
Removal of reduction equivalents
Common in facultative anaerobes (Enterobacter, E. coli) and strict
anaerobes (Ammonifex, Wolinella, certain sulfate reducers)
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Examples for
anaerobic respirations
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Relation of free energy to
reduction potential
!G0’ = - nF ! E0’
n
F
= Number of electrons
= Faraday’s constant (96.48 kJ/V)
! E0 = Difference in potentials of half-reactions
= E0 electron-accepting - E0 electron-donating
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Vertical profile of potential electron
acceptors in marine sediments
Eo’ [mV]
O2/H2O +820 Aerobic respiration
NO3-/N2 +751 Denitrification
NO3-/NH4+ +363 Nitrate ammonification
MnO2/Mn2++390 Manganese reduction
FeOOH +150 Iron reduction
SO42-/HS- -218 Sulfate reduction
So/HS-240 Sulfur reduktion
CO2/CH4 -244 Methanogenesis
O2
NO3MnO2
Fe(III)
SO42-
CH4
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Complex polymers
(polysaccharides, lipids, proteins)
Hydrolysis
Monomers
(sugars, fatty acids, amino acids)
Fermentation
H2 + CO2
Formate
Short chain fatty acids and alcohols
(lactate, butyrate, propionate, ethanol)
Acetate
CO2 + Sulfide
CO2 + Methane
CO2 + NH4/N2
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Complex polymers
(polysaccharides, lipids, proteins)
Hydrolysis
Monomers
(sugars, fatty acids, amino acids)
Fermentation
H2 + CO2
Formate
Short chain fatty acids and alcohols
(lactate, butyrate, propionate, ethanol)
Acetate
CO2 + Sulfide
Sulfidogenesis
(Dissimilatory sulfate reduction)
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Dissimilatory
sulfate reducers
Heterogenous group of prokaryotes that gain energy
by the reduction of sulfate to sulfide
SO42- + 8e- ! S2-
Brock Biology of Microorganisms:
Chapter 12, 17, 18
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Sulfate-reducing prokaryotes
Sulfate-reducing prokaryotes (Desulfo-)
(in contrast to sulfur-reducing prokaryotes (Desulfuro-))
1864
H2S is product of a biological process (Meyer)
1886
anaerobic degradation of cellulose
with gypsum (CaSO4) (Hoppe-Seyler)
1895
first isolate (Bejerinck)
1953
detection of cytochrom (Postgate)
1980
complete oxidization of acetate (Widdel)
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Oxidation state
Sulfate (SO4-)
+ VI
Reduction
8 electrons (e-)
Sulfite (+IV)
Thiosulfate (av. +II)
Sulfur (0)
- II
Hydrogen sulfide (H2S)
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Biochemical pathway
Uptake of sulfate
Activation of sulfate
Sulfate reduction
Generation of proton motive force
Release of sulfide
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Activation of sulfate
ATP sulfurylase
APS kinase
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Activation of sulfate on the expense of energy (ATP)
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Dissimilatory
sulfite reductase
Dsr
A specific
biomarker
for SRB!
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Lateral gene transfer of dsrAB genes
16S rRNA
DsrAB
delta
proteobacteria
LGC
Klein et al., (2001) J Bac 183(20): 6028-35
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Incomplete oxidation of lactate
1 "m
Desulfovibrio desulfuricans
Incomplete oxidation of lactate (e.g. Desulfovibrio spec.)
2 CH2CHOHCOO- + SO42- ! 2 CH3COO- + 2 HCO3- + HS- + H+
!G0’ = -160 kJ/ mol sulfate
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Electron transport
and
energy conservation
in incomplete-oxidizing
Sulfate-reducing
bacteria (SRB)
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Oxidation of acetate
CH3COO- + SO42- ! 2 HCO3- + HSElectron accepting reaction
SO42- + H+! HSElectron donating reaction
CH3COO- ! 2 HCO3- + H+
10 "m
Desulfobacter postgatei
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Oxidation of acetate
CH3COO- + SO42- ! 2 HCO3- + HS-
Electron accepting reaction
SO42- + H+! HS+ VI
- II
Electron donating reaction
CH3COO- ! 2 HCO3- + H+
+ IV
Aver. 0
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Complete oxidation of acetate
CH3COO- + SO42- ! 2 HCO3- + HS-
Electron accepting reaction
SO42- + 8 e- + H+! HS+ VI
E0 ’
- 0.217 V
- II
Electron donating reaction
CH3COO- ! 2 HCO3- + 8 e- + H+
Aver. 0
+ IV
!G0’ = - nF ! E0’
- 0.29 V
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Complete oxidation of acetate (e.g. Desulfobacter spec.)
CH3COO- + SO42- ! 2 HCO3- + HS!G0’ = -47.6 kJ/ mol sulfate
Complete oxidation of lactate (e.g. Desulfosarcina spec.)
2 CH2CHOHCOO- +3 SO42- ! 6 HCO3- +3 HS- + H+
!G0’ = -85 kJ/ mol sulfate
!G0’ = -127 kJ/ mol lactate
Incomplete oxidation of lactate (e.g. Desulfovibrio spec.)
2 CH2CHOHCOO- + SO42- ! 2 CH3COO- + 2 HCO3- + HS- + H+
!G0’ = -160 kJ/ mol sulfate
!G0’ = -80 kJ/ mol lactate
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Electron-donors
Hydrogen, fatty acids, alkenes, aromatic compounds
sugars,amino acids, alcohols
Alternative electron acceptors
sulfur, thiosulfate, sulfite
nitrate, iron, uranium
Fermentation
Sulfur Disproportionation
(S2O32- + H2O ! SO42- + H2S)
Autotrophic growth
A) Reverse tricarboxylic cycle (Desulfobacter spp.)
B) Acetyl-CoA pathway
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Desulfovibrio
desulfuricans
Desulfonema
limicola
Desulfobulbus
propionius
Desulfobacter
postgatei
Desulfosarcina
variabilis
Desulfuromonas
acetoxidans
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Hyperthermophilic sulfate-reducing archaea
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Physiology and Diversity of Prokaryotes WS 2009/2010 (www.icbm.de/pmbio/)
Habitats of sulfate-reducing bacteria
Almost in all anoxic environment where sulfate is available
A) Marine sediments
B) Freshwater sediments
C) Biofilms and microbial mats
D) Anaerobic sewage sludge
E) Related to human diseases
F)
Geothermal sources
Temperature range: - 1.8ºC to 105ºC