Effects of selenite and tellurite on growth, physiology, and proteome of a moderately halophilic bacterium.

We isolated a moderately halophilic bacterium with high level of tolerance to two toxic oxyanions, selenite and tellurite, from hypersaline soil in Garmsar, Iran. 16s rRNA sequence analysis revealed that the isolate, strain MAM, had 98% similarity with Halomonas elongate, and is closely related to other species of the genus Halomonas. We observed that the tolerance to tellurite and its removal increased significantly when both selenite and tellurite were added to the culture media, suggesting a positive synergism of selenite on tellurite tolerance and removal. We applied a proteomic approach to study the proteome response of Halomonas sp. strain MAM to selenite, tellurite, and selenite + tellurite. Out of approximately 800 protein spots detected on 2-DE gels, 208 spots were differentially expressed in response to at least one of treatments. Of them, 70 CBB stained spots were analyzed by MALDI TOF/TOF mass spectrometry, leading to identification of 36 proteins. Our results revealed that several mechanisms including fatty acid synthesis, energy production, cell transport, oxidative stress detoxification, DNA replication, transcription and translation contributed in bacterial response and/or adaptation. These results provided new insights into the general mechanisms on the tolerance of halophilic bacteria to these two toxic oxyanions and the use of them for bioremediation of contaminated saline soils and wastes discharge sites.