Chemolithotrophs Sulfur and Iron Oxidizing bacteria
Oxidation state of thiosulfate S2O3 2- (+2)
+2
Oxidation state of SO4 2-
+6
Sulfur and Iron Oxidizing bacteria
Chemolithotrophs that grow using reduced sulfur as electron donors are also capable of using iron compounds (Fe++) as an electron donor as long as they can grow under acidic conditions
Sulfur dispropotionation
Desulfovibrio and others
Sulfate reduction (anaerobic)
Desulfovibrio, Desulfobacter
Sulfur reduction (anaerobic)
Desulfuromonas, Many hyperthermophillic Archaea
Species growing poorly if at all in organic media
Thiobacillus thioparus Thiobacillus denitrificans Halothiobacillus neapolitanus Acidithiobacillus thiooxidans Acidithiobacillus ferrooxidans
If S is deposited inside the cell, it is
Transient as it will eventually be oxidized to sulfate
Physiology of sulfur and iron
Obligate autotrophs (calvin cycle), facultative heterotrophs, neutrophilres, acidophiles, mesophiles to thermophiles, and most are aerobes.
Because these cells live in environments with 1-2 pH and their insides are 6 pH, there is a natural
Proton gradient from outside to inside the cells.
Sulfide/sulfur oxidation (H2S=>S^0=>SO4^2-) Anaerobic
Purple and Green phototrophic bacteria, some chemolithotrophs
Starkeya novella and Thiomonas intermedia inorganic donor
S2O3^2-
Thiomicrospira inorganic electron donor
S2O3^2-, H2S
Acidithiobacillus thiooxidans
S^0
Halothiobacillus neapolitanus Inorganic electron donor
S^0, S2O3^2-
Acidithiobacillus ferrooxidans
S^0, metal sulfides, Fe^2+
Ferrous rapidly oxidizes (____________)to ferric forms and is very ________.
Spontaneous; insoluble
Species growing well in organic media
Starkeya novella Thiomonas intermedia
Sulfide/sulfur oxidation (H2S=>S^0=>SO4^2-) Aerobic
Sulfur chemolithotrophs (Thiobacillus, Beggiatoa, many others)
The proton motive force generated by the natural proton gradient cannot
be used to generate ATP by the cells.
Autotrophy
calvin cycle
In thiosulfate oxidation, extensive oxidation after the initial steps in the periplasm happens within the
cytoplasm
Depending upon the nature of the substrate S may be
deposited inside the cell or not
Cells growing on elemental sulfur
grow attached to the element and gradually liberate S
Beggiatoa can grow into
long mats that cause bulking problems in many industries (sewage treatment, paper mill)
Ferrous iron is stable under
low pH and anaerobic conditions.
The initial steps of thiosulfate oxidation are
periplasmic
Fe++ and Fe+++ is a
poor redox pair. So e- transport is short.
Desulfurylation
Many organisms
Organic sulfur compound oxidation or reduction
Many organisms
Oxidation state of H2S
-2
Oxidation state of elemental S^0
0
Chemolithotrophic rxn: Sulfite to sulfate
2 electrons
Range of growth for Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans
2-4 pH
Range of growth for Thiomonas intermedia
3-7pH
pH of cytoplasm
6
Range of growth for Beggiatoa and Thiothrix
6-8
Range of growth for Starkeya novella
6-8 pH
Range of growth for Thiobacillus thioparus, Thiobacillus denitrificansb, and Halothiobacillus neapolitanus
6-8 pH
Range of growth for Thiomicrospira, Thiosphaerad, and Thiovulum
6-8pH
Range of growth for Thermothrix
6.5-7.5pH
Chemolithotrophic rxn: Sulfide to sulfate
8 electrons
Other genera
Achromatium, Thiomicrospira, Thiosphaera, Thermothrix, Thiovulum
Phylogenetic Group of Thiosphaera
Alpha
Phylogenetic group of Starkeya novella
Alpha
Sulfur oxidizing bacteria and Dissimilatory Sulfur metabolism
Aquificae, Deinoccus-Thermus, and Proteobacteria
Filamentous sulfur chemolithotrophs
Beggiatoa, Thiothrix, Thioploca
Phylogenetic Group of Thermothrix
Beta
Phylogenetic group of Thiomonas intermedia
Beta
Phylogentic group of Thiobacillus thioparus and Thiobacillus denitrificansb
Beta
Phylogenetic Group of Thiovulum
Epsilon
Iron oxidation
Ferrous (Fe++) to Ferric(Fe+++)
Phylogenetic Group of Achromatium and Thiomicropira
Gamma
Phylogenetic group of Beggiatoa, Thiothrix, and Thioploca
Gamma
Phylogenetic group of Halothiobacillus neapolitanus, Acidithiobacillus thiooxidans, and Acidithiobacillus ferrooxidans
Gamma
Achromatium inorganic electron donor
H2S
Thiothrix inorganic electron donor
H2S
Beggiatoa inorganic electron donor
H2S, S2O3^2-
Thiosphaerad inorganic electron donor
H2S, S2O3^2-, H2
Thioploca inorganic electro donor
H2S, S^0
Thiovulum inorganic electron donor
H2S, S^0
Sulfur compounds commonly used include
H2S, S^0, S2O3 which are all oxidized to SO4 which is released as sulfuric acid. Ample energy yield from oxidation of common reduced sulfur compounds
Thiobacillus denitrificansb Inorganic electron donor
H2S, S^0, S2O3^2-
Thiobacillus thiparus Inorganic electron donor
H2S, Sulfides, S^0, S2O3^2-
Thermothrix inorganic electron donor
H2s, S2O3^2-, SO3^-
Sulfur is one of the most ______ materials in the world
Insoluble
Iron oxidation is very ____ energy yield oxidation
Low