Inferring pathways leading to organic-sulfur mineralization in the Bacillales

Microbial organic sulfur mineralization to sulfate in terrestrial systems is poorly understood. The process is often missing in published sulfur cycle models. Studies on microbial sulfur cycling have been mostly centered on transformations of inorganic sulfur, mainly on sulfate-reducing and inorgani...

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Bibliographic Details
Published in:Critical reviews in microbiology 2016-01, Vol.42 (1), p.31-45
Main Authors: Santana, Margarida M., Gonzalez, Juan M., Clara, Maria I.
Format: Article
Language:English
Subjects:
Aspartate transaminase
Bacillales - classification
Bacillales - genetics
Bacillales - metabolism
dissimilatory organic-sulfur oxidation
enzymes of cysteine and methionine pathways
Genes, Bacterial
Metabolic Networks and Pathways
Multigene Family
Phylogeny
Sulfates - metabolism
sulfite oxidase
sulfite reductase
Sulfur - metabolism
Temperature
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Summary:Microbial organic sulfur mineralization to sulfate in terrestrial systems is poorly understood. The process is often missing in published sulfur cycle models. Studies on microbial sulfur cycling have been mostly centered on transformations of inorganic sulfur, mainly on sulfate-reducing and inorganic sulfur-oxidizing bacteria. Nevertheless, organic sulfur constitutes most sulfur in soils. Recent reports demonstrate that the mobilization of organic-bound-sulfur as sulfate in terrestrial environments occurs preferentially under high temperatures and thermophilic Firmicutes bacteria play a major role in the process, carrying out dissimilative organic-sulfur oxidation. So far, the determinant metabolic reactions of such activity have not been evaluated. Here, in silico analysis was performed on the genomes of sulfate-producing thermophilic genera and mesophilic low-sulfate producers, revealing that highest sulfate production is related to the simultaneous presence of metabolic pathways leading to sulfite synthesis, similar to the ones found in mammalian cells. Those pathways include reverse transsulfuration reactions (tightly associated with methionine cycling), and the presence of aspartate aminotransferases (ATs) with the potential of 3-sulfinoalanine AT and cysteine AT activity, which ultimately leads to sulfite production. Sulfite is oxidized to sulfate by sulfite oxidase, this enzyme is determinant in sulfate synthesis, and it is absent in many mesophiles.
ISSN:1040-841X
1549-7828
DOI:10.3109/1040841X.2013.877869