Chemolithotrophs Sulfur and Iron Oxidizing bacteria

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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


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