Genetic correlation between chromium resistance and reduction inBacillus brevisisolated from tannery effluent

Abstract

Aims: To investigate the genetic basis of Cr(VI) resistance and its reduction to Cr(III) in indigenous bacteria isolated from tannery effluent. Methods and Results: Four bacteria resistant to high Cr(VI) levels were isolated and identified as Bacillus spp. Their Cr(VI) reduction ability was tested. To assess the genetic basis of Cr(VI) resistance and reduction, plasmid transfer and curing studies were performed. Among all, B. brevis was resistant to 180 μg Cr(VI) ml−1 and showed the greatest degree of Cr(VI) reduction (75·8%) within 28 h and its transformant was resistant to 160 μg Cr(VI) ml−1 and reduced 69·9% chromate. It harboured a stable 18 kb plasmid DNA. Transfer and curing studies revealed that both the chromate resistance and reduction were plasmid mediated. The presence of other metal cations did not have any significant effect on Cr(VI) bioreduction. Conclusions: Bacillus brevis was resistant to elevated Cr(VI) levels and may potentially reduce it in short time from an environment where other metal ions are also present in addition to chromium ions. The strain tested shows a positive correlation between genetic basis of Cr(VI) resistance and reduction. Significance and Impact of the Study: To our knowledge, this is the first study on the genetic correlation between chromium resistance and reduction in bacteria. Such strains may potentially be useful in biotechnological applications and in situ Cr(VI) bioremediation.

Remediation of chromium contaminants using bacteria

“…Three of the isolates belonged to uropathogenic E. coli serotype 04 (Verma et al 2004). In another study, B. brevis showed good plasmid-mediated resistance and reduction potential as established by transfer and curing studies (Verma et al 2009). …”

Chromate-Reducing Profile of Bacterial Strains Isolated from Industrial Effluents

“…Identified subject sequences with their GenBank accession numbers used in pintail analysis of the isolates for the detection of chimeric sequences. Resistance to antibiotics is also considered an adaptive strategy of bacteria to survive at contaminated sites [24]. Isolates KS1W and MWM82 are resistant to the maximum number of antibiotics, i.e., these could survive metal as well as antibiotic stress.…”

“…At most times, nontoxic and toxic compounds coexist at natural territory and it is essential to determine the effects of other metals on bacteria growth [24]. So organisms were tested for their ability to resist several heavy metals (HgCl 2 , ZnSO 4 , CuSO 4 , MnSO 4, CdCl 2 , and Na 2 HAsO 4 ).…”

“…Growth curve of organisms was studied, both in the presence (Cr(VI); 500 µg ml -1 ) and absence of chromium. O.D (600 nm) of inoculated LB broth was taken after 2,4,8,12,18,24,36,48,60,72, and 96 hours. Triplicate cultures were used for each strain [15].…”

Characterization and Metal Detoxification Potential of Moderately Thermophilic Bacillus cereus from Geothermal Springs of Himalaya

“…Selenate and selenite are toxic while elemental selenium being the insoluble in water is less mobile and usually remains in the soils posing a smaller risk to the environment (Fesharaki et al 2010). Biological methods for the remediation of toxic forms of chromium and selenium are environment friendly (Hunter 2007;Hunter and Manter 2008;Verma et al 2009). Bioremediation is inexpensive and established technology, which is commonly used in the environment without posing any damaging effects to the ecosystem (Khan et al 2009).…”