Enrichment and diversity analyis of arsenite-resistant bacteria in deep sea sediment samples from southwest Indian Ocean ridge

Abstract:

[Objective] The aim of this study was to assess the diversity of arsenite-resistant bacteria in deep sea sediment of the southwest Indian Ocean Ridge. [Method] Arsenite-resistant bacteria in the deep-sea sediment were enriched with 2×10-3 mol/L NaAsO2 and isolated on plates. Their diversity was further examined by Denaturing gradient gel electrophoresis (DGGE) and 16S rDNA library analysis. Furthermore, the gene encoding putative arsenite efflux pump was detected with degenerate primers among these isolates. [Result] Eight arsenite-resistant isolates were obtained; they belonged to five different genera of γ-proteobacteria. One isolate named As-I1-3 can grow in presence of 26×10-3 mol/L NaAsO2, showed highest similarity to Pseudoalteromonas tetraodonis IAM (100%). DGGE result showed that As-I1-3 was dominant in arsenite enriched community, followed by isolate As-I1-5 (Halomonas meridiana,100%) and Mn-I1-6 (Marinobacter vinifirmus, 99%). 16S rDNA library analysis reconfirmed the result of DGGE, which showed that the three bacteria occupied 72.5%, 10% and 7.5% of the total OTUs (operational taxonomic units), respectively. However, only from other two isolates which were not dominant, the gene encoding a putative arsenite efflux pump was obtained. [Conclusion] Different bacteria of arsenite-resistance inhabited in deep sea environment, among which P. tetraodonis (100%) showed highest resistance; they might play a certain role in the geobiocycling of arsenic element in marine environments.

Key words:Indian Ocean; deep-sea sediment; arsenite-reistant bacteria; diversity