Molecular and taxonomic characterization of arsenic (As) transforming Bacillus sp. strain IIIJ3–1 isolated from As-contaminated groundwater of Brahmaputra river basin, India

Abstract

Background: Microbe-mediated redox transformation of arsenic (As) leading to its mobilization has become a serious environmental concern in various subsurface ecosystems especially within the alluvial aquifers. However, detailed taxonomic and eco-physiological attributes of indigenous bacteria from As impacted aquifer of Brahmaputra river basin has remained under-studied. Results: A newly isolated As-resistant and-transforming facultative anaerobic bacterium IIIJ3-1 from Ascontaminated groundwater of Jorhat, Assam was characterized. Near complete 16S rRNA gene sequence affiliated the strain IIIJ3-1 to the genus Bacillus and phylogenetically placed within members of B. cereus sensu lato group with B. cereus ATCC 14579(T) as its closest relative with a low DNA-DNA relatedness (49.9%). Presence of iC17:0, iC15:0 fatty acids and menaquinone 7 corroborated its affiliation with B. cereus group, but differential hydroxy-fatty acids, C18:2 and menaquinones 5 & 6 marked its distinctiveness. High As resistance [Maximum Tolerable Concentration = 10 mM As 3+ , 350 mM As 5+ ], aerobic As 3+ (5 mM) oxidation, and near complete dissimilatory reduction of As 5+ (1 mM) within 15 h of growth designated its physiological novelty. Besides O 2 , cells were found to reduce As 5+ , Fe 3+ , SO 4 2− , NO 3 − , and Se 6+ as alternate terminal electron acceptors (TEAs), sustaining its anaerobic growth. Lactate was the preferred carbon source for anaerobic growth of the bacterium with As 5+ as TEA. Genes encoding As 5+ respiratory reductase (arr A), As 3+ oxidase (aioB), and As 3+ efflux systems (ars B, acr3) were detected. All these As homeostasis genes showed their close phylogenetic lineages to Bacillus spp. Reduction in cell size following As exposure exhibited the strain's morphological response to toxic As, while the formation of As-rich electron opaque dots as evident from SEM-EDX possibly indicated a sequestration based As resistance strategy of strain IIIJ3-1.

Adsorption Isotherm, Kinetic and Thermodynamic Modelling of <i>Bacillus subtilis</i> ATCC13952 Mediated Adsorption of Arsenic in Groundwaters of Selected Gold Mining Communities in the Wassa West Municipality of the Western Region of Ghana

“…The rationale for the optimization process was to determine conditions of contact time, amount of the Bacillus subtilis ATCC13952, the concentration of arsenic (III) solution, the pH and the temperature that would give optimum removal of arsenic [47]. Three separate laboratory Experiments (I, II and III) were conducted on laboratory simulated arsenic (III) contaminated aqueous system using the Bacillus subtilis ATCC13952 as biosorbent for the arsenic.…”

Unraveling the Underlying Heavy Metal Detoxification Mechanisms of Bacillus Species

“…like B. megaterium [ 83 , 84 ], B. aryabhattai [ 85 ], and B. cereus strain W2 was studied by Miyatake and Hayashi [ 86 ]. Anaerobic respiration of As 5+ by B. cereus was reported by Ghosh et al [ 71 ]. Various other studies conducted over the years have reported the ability of Bacillus spp.…”

“…Among them, As 3+ and As 5+ are the most abundant forms. As 3+ is more toxic and mobile in aqueous and oxic environments than As 5+ , which is mostly adsorbed to the sediments in an anoxic state [ 70 , 71 ]. The histidine part of cellular proteins is a target site for the interaction of thiols of cysteine residues and/or imidazolium nitrogen with As 3+ , which results in the inactivation of enzymes [ 72 ].…”

“…Above 0.5 ppm, it is toxic for living systems resulting in symptoms of skin cancer [ 75 ], loss of appetite, weakness, weight loss, lethargy, chronic respiratory disorders, gastrointestinal disorders, enlargement of liver, spleen disorders, anemia [ 76 ], and cardiovascular disease [ 77 ]. Introduction of arsenic into the food chain and ground water may lead to serious concerns of arsenicosis [ 71 ].…”

A Review on the Resistance and Accumulation of Heavy Metals by Different Microbial Strains

“…Metal ions were utilized as electron donors for generating energy by bacterial isolates. Example: S. aureus strain for resistance of arsenic (As 5+ /As 3+ ) [52], Klebsiella pneumonia for resistance of mercury (Hg 2+ /Hg) [53].…”