ISOLATION OF NEW BACTERIA FROM ARSENIC CONTAMINATED SOILS BY ARSENITE ENRICHMENT CULTURE METHOD

Microbes play a significant role in geochemical cycling of elements. For example, soil arsenite oxidation is primarily controlled by microbial activity. However, our understanding of the process is heavily limited by our knowledge on microbial arsenite oxidation. In another word, microbial arsenite oxidation is far more widespread in both known and unknown organisms, or we know too little of soil microbiology, only less than 10% of soil microbes were cultured. To better understand the geochemical process, i.e., who is responsible for the soil arsenite oxidation? arsenite enrichment culture method was used to isolate microbes with this capability from arsenic contaminated soils. Solution and agar containing 500 ppm As(III) were used as enrichment cultures. Around 40 bacteria isolates were obtained. The isolates’ DNA was extracted, and their 16S rDNA was amplified by polymerase chain reaction (PCR) and sequenced, the obtained sequences from each isolates were assembled into one sequence using BioEdit software. The closest sequence match was determined by BLASTing against GenBank and using the “SEQMATCH” option against the Ribosomal Database Project. From the results, two new species were proposed: FLCPS7 has creamy colony on arsenite-spiked agar, its partial 16S rDNA sequence (1338 base pairs) has closest similarity of 94.17% with known bacteria Sphingomonas wittichii Yabuuchi et al. 2001, sp. nov. FLCPS7 is proposed to represent a new genus. PA2 has a pink colony on arsenite-spiked agar, its partial 16S rDNA sequence (1388 base pairs) has closest similarity of 96.25% with known bacteria Herbaspirillum seropedicae Baldani et al. 1986, sp. nov. PA2 is proposed as a new species. Further characterization are being conducted. These bacteria have arsenite-oxidizing or arsenic resistant capability.