Pentavalent Arsenate Reductase Activity in Cytosolic Fractions of Pseudomonas sp., Isolated from Arsenic-Contaminated Sites of Tezpur, Assam

Abstract

Pentavalent arsenate reductase activity was localized and characterized in vitro in the cytosolic fraction of a newly isolated bacterial strain from arsenic-contaminated sites. The bacterium was gram negative, rod-shaped, nonmotile, non-spore-forming, and noncapsulated, and the strain was identified as Pseudomonas sp. DRBS1 following biochemical and molecular approaches. The strain Pseudomonas sp. DRBS1 exhibited enzymatic machinery for reduction of arsenate(V) to arsenite(III). The suspended culture of the bacterium reduced more than 97% of As(V) (40-100 mM) to As(III) in 48 h. The growth rate and total cellular yield decreased in the presence of higher concentration of arsenate. The suspended culture repeatedly reduced 10 mM As(V) within 5 h up to five consecutive inputs. The cell-free extracts reduced 86% of 100 microM As(V) in 40 min. The specific activity of arsenate reductase enzyme in the presence of 100 microM arsenate is 6.68 micromol/min per milligram protein. The arsenate reductase activity is maximum at 30 degrees C and at pH 5.2. The arsenate reductase activity increased in the presence of electron donors like citrate, glucose, and galactose and metal ions like Cd(+2), Cu(+2), Ca(+2), and Fe(+2). Selenate as an electron donor also supports the growth of strain DRBS1 and significantly increased the arsenate reduction.

Metagenomic Evidence for a Methylocystis Species Capable of Bioremediation of Diverse Heavy Metals

“…AAP120 has not been reported, its relative R. palustris C1 was found to reduce As(V), with a specific activity of 12.07 U mg -1 protein, which was comparable to that of the As(V)-reducing bacterium Pseudomonas sp. (12.15 U mg -1 protein) (Srivastava et al, 2010; Nookongbut et al, 2017). Based on the similarity of the proteins in HL18 to proteins with known As(V)-reducing activity, it is very likely that these proteins in HL18 are active as well.…”

Arsenic resistance genes of As‐resistant purple nonsulfur bacteria isolated from As‐contaminated sites for bioremediation application

“…Whilst As(V) reduction is mediated by ars C gene the reductase activity detected in strain C1 is highly significant and is comparable to the activity by Pseudomonas sp. (12.15 U mg −1 protein) . As(V) reduction contributes to mobilization of As(III) which can be easily desorbed from solid phases such as in soils therefore, the strain C1 had potential for its use in bioleaching of As from contaminated soils.…”

Statistical design of experiments for optimization of arsenate reductase production by Kocuria palustris (RJB-6) and immobilization parameters in polymer beads

“…9 Energy dispersive X-ray analysis (Inca Penta FETx3, Oxford Instruments, UK) of the pristine and As(V)-treated bacteria (RJB-6) was further performed in order to conrm the intracellular accumulation of arsenic. The arsenate reductase activity in the cell-free extract (CFE) in the presence of 100 mM As(V) was found to be 31.86 U mL À1 , while no activity was detected in the membrane fraction.…”

“…7 Systems are present in bacteria that allow detoxication of intracellular As(III) or As(V), which penetrate through aquaglyceroporins and phosphate transporters respectively. 5,9,10 Statistical optimization of the process parameters has long been used to improve the yield of any bioprocess. 8 Reduction of arsenate in various bacteria also occurs due to the presence of the cytoplasmic arsenate reductase (arsC) gene that belongs to the arsenic resistance system.…”

“…8 Reduction of arsenate in various bacteria also occurs due to the presence of the cytoplasmic arsenate reductase (arsC) gene that belongs to the arsenic resistance system. 5,9,10 Statistical optimization of the process parameters has long been used to improve the yield of any bioprocess. Optimization with the one variable at a time method is quite lengthy and tedious and oen fails to elucidate the interactive behavior of the operating factors resulting in misinterpretation of the obtained responses.…”