Hydrogen Sulfide: A Toxic Gas Produced by Dissimilatory Sulfate and Sulfur Reduction and Consumed by Microbial Oxidation - The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment - page 234

3.1 Eubacterial Sulfur Reductase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

3.1.1 Sulfur Reductase in Desulfovibrio and Desulfomicrobium Species . ...... 262

3.1.2 Polysulfide Reductase from Wolinella succinogenes ...................... 263

3.1.3 Polysulfide Reductase from Desulfuromonas acetoxidans ................ 263

3.1.4 Sulfur Oxidoreductase from Sulfurospirillum deleyianum ................ 265

3.2 Archaebacterial Sulfur Reductase .................................................. 265

3.2.1 Membraneous Sulfur Reductase Complex from Acidianus ambivalens . . 265

3.2.2 Sulfur-Reducing Complex from Pyrodictium abyssi ...................... 265

3.2.3 Sulfur Reductase from Pyrococcus furiosus ............................... 266

4 MICROBIAL OXIDATION OF HYDROGEN SULFIDE TO SULFATE . . . . . . . . . . . . . 266

4.1 Archaebacterial Inorganic Sulfur Compound Oxidation . . . ........................ 266

4.2 Eubacterial Inorganic Sulfur Compound Oxidation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267

4.2.1 Oxidation of Sulfide ......................................................... 268

4.2.2 Oxidation of Polysulfides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268

4.2.3 Oxidation of Stored Sulfur to Sulfite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269

4.2.4 Oxidation of Sulfite to Sulfate . ............................................. 269

4.2.5 Oxidation of Thiosulfate . . . ................................................. 269

5 CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270

ABBREVIATIONS AND DEFINITIONS . . . . . .............................................. 271

ACKNOWLEDGMENTS ..................................................................... 272

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272

Abstract Sulfur is an essential element for the synthesis of cysteine, methionine,
and other organo-sulfur compounds needed by living organisms. Additionally,
some prokaryotes are capable of exploiting oxidation or reduction of inorganic
sulfur compounds to energize cellular growth. Several anaerobic genera of Bacteria
and Archaea produce hydrogen sulfide (H 2 S), as a result of using sulfate (SO 2

),

4

elemental sulfur (S 0 ), thiosulfate (S 2 O 2

3 ), and tetrathionate (S 4 O 2 6 ) as terminal
electron acceptors. Some phototrophic and aerobic sulfur bacteria are capable of
using electrons from oxidation of sulfide to support chemolithotrophic growth. For
the most part, biosulfur reduction or oxidation requires unique enzymatic activities
with metal cofactors participating in electron transfer. This review provides an
examination of cytochromes, iron-sulfur proteins, and sirohemes participating in
electron movement in diverse groups of sulfate-reducing, sulfur-reducing, and
sulfide-oxidizing Bacteria and Archaea.

Keywords hydrogen sulfide production • sulfate reduction • sulfide oxidation
• sulfite reduction • sulfur cycle

Please cite as: Met. Ions Life Sci . 14 (2014) 237-277

1 Introduction

Sulfur is one of the most versatile elements in life due to its reactivity in different
reduction and oxidation states. Sulfur is the element with the highest number of
allotropes (about 30), but only a few are found in nature and occur in biological