Sphingomonas sp. MIM37 possessing aerobic anoxygenic photosynthetic gene cluster and xanthorhodopsin-like gene: its genome draft and growth stimulation by illumination

Abstract:

[Objective] The genome of the photoheterotrophic bacterium MIM37, possessing anoxygenic photosynthetic gene cluster (PGC) and xanthorhodopsin-like gene, was sequenced and the stimulated growth by illumination was determined, which is helpful in shedding light upon the diversity of photosynthetic pathway and phototrophic bacteria, and the evolution and role of photosynthesis. [Methods] The isolation was performed by the traditional plate spread and streak. To classify and identify the isolate preliminarily, the morphological feature and, the homology and phylogeny of 16S rRNA gene, pufM and rhodopsin genes were analyzed. Spectrophotometry and fluorescence microscopy were employed separately to reveal the concentration and size shifts of the cell cultured under illumination or dark. Illumina PE library of 300?500 bp fragments was constructed for Illumina Hiseq2000 genome sequencing. Sequences were assembled through the software of SOAPdenovo and GapCloser and the online software of RAST was used to annotate. [Results] We obtained a bacterial strain MIM 37 from Lake Swan in Desert Tenggeli in Inner Mongolia. The homology and phylogeny analysis based on 16S rRNA gene, pufM and rhodopsin genes respectively, showed that the strain most closely related to the members of Sphingomonas genus. Compared with the dark condition, light condition increased the maximum of the cell concentration and volume by 1.2 and 5.6 folds respectively. The genome draft sequence demonstrated that MIM37 has diverse metabolic pathways with electron transport chain of the typical aerobic respiration, intact aerobic phototrophic photosynthetic gene cluster and xanthorhodopsin-like genes, siderophore biosynthesis, heavy metal reduction, the degradation of microcystin and polyaromatic hydrocarbon and etc. [Conclusion] The strain MIM37 is a member of the genus Sphingomonas and possesses two different phototrophic pathways. Light may stimulate its growth markedly. The diverse metabolic pathways may be helpful for the strain in the survival and wide distribution in natural ecosystems, and make strain MIM37 useful in environmental pollutes bioremediation.

Key words:Aerobic anoxygenic phototrophic bacteria, Photosynthetic gene cluster, Rhodopsin, 16S rRNA, pufM, genome