Characterization of siderophore producing arsenic-resistant Staphylococcus sp. strain TA6 isolated from contaminated groundwater of Jorhat, Assam and its possible role in arsenic geocycle
BMC MICROBIOLOGY
Authors: Das, Saurav; Barooah, Madhumita
Abstract
Background: Microorganisms specifically bacteria play a crucial role in arsenic mobilization and its distribution in aquatic systems. Although bacteria are well known for their active participation in the different biogeochemical cycles, the role of these bacteria in regulating the concentration of arsenic in Brahmaputra valley has not been investigated in detail. Results: In this paper, we report the isolation of an arsenic resistant bacterium TA6 which can efficiently reduce arsenate. The isolate identified as Staphylococcus sp. TA6 based on the molecular and chemotaxonomic identification (FAME) showed resistance to the high concentration of both arsenate and arsenite (As(III) = 30 mM; As(V) = 250 mM), along with cross-tolerance to other heavy metals viz, Hg2+, Cd2+, Co2+, Ni2+, Cr2+. The bacterium also had a high siderophore activity (78.7 +/- 0.004 mu mol) that positively correlated with its ability to resist arsenic. The isolate, Staphylococcus sp. TA6 displayed high bio-transformation ability and reduced 2 mM As(V) initially added into As(III) in a period of 72 h with 88.2% efficiency. The characterization of arsenate reductase enzyme with NADPH coupled assay showed the highest activity at pH 5.5 and temperature of 50 degrees C. Conclusions: This study demonstrates the role of an isolate, Staphylococcus sp. TA6, in the biotransformation of arsenate to arsenite. The presence of ars operon along with the high activity of the arsenate reductase and siderophore production in this isolate may have played an important role in mobilizing arsenate to arsenite and thus increasing the toxicity of arsenic in the aquatic systems of the Brahmaputra valley.
Broadband tunable mid-IR Cr2+:CdSe lasers for medical applications
SARATOV FALL MEETING 2017: LASER PHYSICS AND PHOTONICS XVIII; AND COMPUTATIONAL BIOPHYSICS AND ANALYSIS OF BIOMEDICAL DATA IV
Authors: Tarabrin, Mikhail K.; Lasarev, Vladimir A.; Tomilov, Sergey M.; Karasik, Valery E.; Tuchin, Valery V.
Abstract
Currently, lasers are widely used for surgery, medical diagnostics and oncology research. Unfortunately, most of the used laser sources have a significant drawback - the lack of operating wavelength tuning possibility, which imposes significant limitations on the investigation of biological tissue spectral properties and searching for the optimal mode of their treatment. Comparison between different promising mid-IR sources was made. We report on development of mid-infrared (mid-IR) tunable lasers based on the Cr2+:CdSe single-crystals. These lasers operate in CW mode with the maximum output power of up to 2 W and possible tuning range from 2.2 to 3.6 mu m.