The differential stress response of adapted chromite mine isolates Bacillus subtilis and Escherichia coli and its impact on bioremediation potential

Abstract

In the current study, indigenous bacterial isolates Bacillus subtilis VITSUKMW1 and Escherichia coli VITSUKMW3 from a chromite mine were adapted to 100 mg L(-1) of Cr(VI). The phase contrast and scanning electron microscopic images showed increase in the length of adapted E. coli cells and chain formation in case of adapted B. subtilis. The presence of chromium on the surface of the bacteria was confirmed by energy dispersive X-ray spectroscopy (EDX), which was also supported by the conspicuous Cr-O peaks in FTIR spectra. The transmission electron microscopic (TEM) images of adapted E. coli and B. subtilis showed the presence of intact cells with Cr accumulated inside the bacteria. The TEM-EDX confirmed the internalization of Cr(VI) in the adapted cells. The specific growth rate and Cr(VI) reduction capacity was significantly higher in adapted B. subtilis compared to that of adapted E. coli. To study the possible role of Cr(VI) toxicity affecting the Cr(VI) reduction capacity, the definite assays for the released reactive oxygen species (ROS) and ROS scavenging enzymes (SOD and GSH) were carried out. The decreased ROS production as well as SOD and GSH release observed in adapted B. subtilis compared to the adapted E. coli corroborated well with its higher specific growth rate and increased Cr(VI) reduction capacity.

Exploration of NPK Activity Showing Chromium Resistant Bacteria from Sukinda Mining Area

“…(Table 4). Moreover, several studies have reported utilization of chromium resistant and plant growth promoting rhizobacteria (PGPR) for the bioremediation of toxic metals (Samuel et al, 2013;Sobariu et al, 2016;Ndeddy and Babalola, 2016) to reclaim and restore soil properties.…”

“…Such activities of soil microbes are largely affected by pollutants released to the soil, as plant growth is regulated by soil fertility (Hansda et al, 2014). Several studies have reported the utilization of plant growth promoting rhizobacteria (PGPR) for the bioremediation of toxic metals (Samuel et al, 2013;Sobariu et al, 2016;Ndeddy and Babalola, 2016 …”

REMOVAL OF CADMIUM AND LEAD BY ADAPTED STRAINS OF Pseudomonas aeruginosa AND Enterobacter cloacae

“…The OD readings were taken after 12 and 24 h, since preliminary experiments with adapted and non-adapted strains showed that in both cases, these periods of time marked the end of exponential growth and the onset of the stationary phase of growth, respectively. Adaptation was assumed when growth rates and OD values of the adapted strains were significantly higher than those determined in the non-adapted strain (Samuel et al 2013).…”

Tolerance and Reduction of Chromium(VI) by Bacillus sp. MNU16 Isolated from Contaminated Coal Mining Soil

“…The behavior of micro-organisms toward Cr(VI) was studied previously which demonstrated the significant alleviative impact of many microorganisms, including strains of Pseudomonas, Enterobacter, Bacillus , and Shewanella (Samuel et al, 2013; Ahemad, 2015). Microorganisms were found to reduce hexavalent chromium by different mechanisms either by utilizing the hexavalent chromium as final electron acceptor or by secreting certain soluble enzymes (Samuel et al, 2013; Ahemad, 2015).…”

“…Microorganisms were found to reduce hexavalent chromium by different mechanisms either by utilizing the hexavalent chromium as final electron acceptor or by secreting certain soluble enzymes (Samuel et al, 2013; Ahemad, 2015). However, the availability of efficient hexavalent chromium reducing microorganisms is a crucial requirement for the bioremediation of soils contaminated with hexavalent chromium.…”