Arsenic efflux in Enterobacter cloacae RSN3 isolated from arsenic-rich soil
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ORIGINAL ARTICLE
Arsenic efflux in Enterobacter cloacae RSN3 isolated from arsenic-rich soil Biplab Dash 1 & Narayan Sahu 1 & Anup Kumar Singh 1 & S.B Gupta 1 & Ravindra Soni 1 Received: 8 April 2020 / Accepted: 30 August 2020 # Institute of Microbiology, Academy of Sciences of the Czech Republic, v.v.i. 2020
Abstract In the present study, bacterial isolates were screened for arsenic resistance efficiency. Environmental isolates were isolated from arsenic-rich soil samples (i.e., from Rajnandgaon district of Chhattisgarh state, India). Amplification and sequencing of 16S rRNA gene revealed that the isolates were of Bacillus firmus RSN1, Brevibacterium senegalense RSN2, Enterobacter cloacae RSN3, Stenotrophomonas pavanii RSN6, Achromobacter mucicolens RSN7, and Ochrobactrum intermedium RSN10. Arsenite efflux gene (arsB) was successfully amplified in E. cloacae RSN3. Atomic absorption spectroscopy (AAS) analysis showed an absorption of 32.22% arsenic by the RSN3 strain. Furthermore, results of scanning electron microscopy (SEM) for morphological variations revealed an initial increase in the cell size at 1 mM sodium arsenate; however, it was decreased at 10 mM concentration in comparison to control. This change of the cell size in different metal concentrations was due to the uptake and expulsion of the metal from the cell, which also confirmed the arsenite efflux system.
Introduction Heavy metal contamination in the environment is a buzzing topic nowadays. Extensive growth in the industrial activities has led to the production of several heavy metal pollutants that contaminate soil and water, thereby harming our agroecosystem (Agrawal et al. 2015). Several novel physical and chemical strategies have been adopted for solving this problem, which ultimately proved to be costly and ineffective (Ayangbenro and Babalola 2017). Over few years, different new avenues of microbial bioremediation, i.e., bioaccumulation, biosorption, bioprecipitation, bioleaching, biotransformation, biosurfactants, and siderophore formation, have emerged as a new hope (Agrawal et al. 2018; Mosa et al. 2016; Kang et al. 2016). These eco-friendly methods are quite successful in addressing the issues lacking in their predecessors. It has reported that bioremediation can save up to 50– 65% of the total cost as compared to conventional approaches (Ojuederie and Babalola 2017). Due to their widespread abun-
* Ravindra Soni [email protected] 1
Department of Agricultural Microbiology, College of Agriculture, Indira Gandhi Krishi Vishwavidyalaya, Krishak Nagar Jora, Raipur 492012, CG, India
dance, easy culturability, and varied mechanisms towards heavy metal tolerance, bacteria can be used as a suitable tool for heavy metal remediation. A typical ars operon is generally transcribed as a single unit (Rosen 1999) containing either three (arsRBC) or five (arsRDABC) genes, which can be either plasmid or chromosome borne (Diorio et al. 1995). Sequential events and their associated genes involved in detoxification of arsenic are arsC, encoding As5+ redu
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