A Bioinformatic Study of the Distribution of Mn Oxidation Proteins in Sequenced Bacterial Genomes

1.BackgroundWhile many species of bacteria have been identified that can convert soluble, reduced manganese (Mn+2) into insoluble, oxidized Mn+4 oxides, the mechanisms these bacteria employ and their distribution throughout the bacterial domain are less well understood. One of the best characterized MnOB is the gamma-proteobacterium Pseudomonas putida GB-1, which uses three distinct proteins (PpMnxG, McoA and MopA) to oxidize Mn+2. The best characterized Mn oxidase enzyme is the MnxG homolog of Bacillus sp. PL-12 (BaMnxG), which appears to be the only Mn oxidase in this species. MofA, found in Leptothrix discophora sp SS-1 is an additional putative Mn oxidase. ResultsBy querying publicly available databases of bacterial genome sequences for homologs to these Mn oxidase proteins, it was possible to determine the distribution of the proteins within bacteria. The overwhelming majority of homologs were found in just three phyla: proteobacteria, actinobacteria and firmicutes. These data do not preclude the possibility of novel Mn oxidase mechanisms in other as yet uncharacterized groups of bacteria. Each of the homologs had a statistically significant probability of being present as the solo Mn oxidase in a genome. When genomes did have more than one oxidase, they were present in the same combinations as in P. putida GB-1. ConclusionsThese results do not support the initial hypothesis that multiple enzymes are required to complete the two-electron oxidation of Mn+2 to Mn+4. Alternatively, the various Mn oxidase enzymes may be optimized to function under different environmental conditions; organisms like P. putida GB-1 may need to oxidize Mn at different temperatures, nutritional states or oxygen conditions.