title: 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.
authors.affiliation: Centre for Nanobiotechnology, VIT University, Vellore, Tamil Nadu, India.
authors.forename: Jastin
authors.initials: J
authors.lastname: Samuel
authors.forename: Madona Lien
authors.initials: ML
authors.lastname: Paul
authors.forename: Harish
authors.initials: H
authors.lastname: Ravishankar
authors.forename: Ankita
authors.initials: A
authors.lastname: Mathur
authors.forename: Dipti Priya
authors.initials: DP
authors.lastname: Saha
authors.forename: Chandrasekaran
authors.initials: C
authors.lastname: Natarajan
authors.forename: Amitava
authors.initials: A
authors.lastname: Mukherjee
mesh_terms: D000222:Adaptation, Physiological; D001412:Bacillus subtilis / Q000166:cytology / Q000302:isolation & purification / Q000502:physiology* / Q000648:ultrastructure; D001673:Biodegradation, Environmental; D002857:Chromium / Q000302:isolation & purification; D017608:Chromium Compounds / Q000302:isolation & purification*; D004926:Escherichia coli / Q000166:cytology / Q000302:isolation & purification* / Q000502:physiology* / Q000648:ultrastructure; D005978:Glutathione / Q000378:metabolism; D008906:Mining; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D017550:Spectroscopy, Fourier Transform Infrared; D013312:Stress, Physiological; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D017608:Chromium Compounds; D002857:Chromium; C074702:chromium hexavalent ion; D013482:Superoxide Dismutase; D005978:Glutathione