Isolation and Identification of Unique Arsenotolerant Exiguobacterium indicum DSAM62 from Arsenic Rich Environment

Debanjana Sengupta,Sayak Ganguli,Siddhartha Chakraborty,Sudeshna Shyam Choudhury,Arup Kumar Mitra

doi:10.13189/azb.2020.080403

Abstract

Arsenic infiltration via bio-geological and anthropogenic mean's has been a global concern in the developing countries due to the severe toxic effects of the compound which leaches to the ecological niche. Herein, we report one such arsenotolerant bacteria isolated from a contaminated soil collected from a district in West Bengal (India), where an arsenic concentration of the soil sample was found to be 0.51 mg/kg. In the present study, several bacteria were isolated from the soil sample, out of which LD50 value of arsenic for the novel tolerant bacteria was found to be 500 mg./l which was also determined by INT assay. The efficacy of arsenate uptake by this bacterium was 52.20% from its respective LD50 concentration. After 16S rDNA sequencing, the bacteria showed 99% similarity with Exiguobacterium indicum based on nucleotide homology and meta-phylogenetic analysis. LCMS FAME revealed that the unique fatty acids were monosaturated C:10:03 OH (0.53%), C12:1 (0.16%), C11:03 OH (0.38%), terminally branched Anteiso C14:0 (0.74%), monosaturatedC15:1w5C, monosaturatedC16:0 N Alcohol, Anteiso 16:0 (0.36%), Iso- C16:0 3OH (0.33%), Iso- C18:1 H (0.25%), C18:3w6C (6,9,12) (0.53%), C18:1 2OH (0.52%), which lead us to conclude that the bacteria was a new and unique bacterial strain. So, on the basis of FAME analysis, the unique bacteria were named as Exiguobacterium indicum Strain DSAM62, which can be used as a potential bio accumulator in agricultural fields for bioremediation of arsenic. The fully annotated sequence of the genome and the plasmid of the novel strain revealing key regulatory genes were also investigated and results can be correlated with this tolerant behavior. The annotated sequence was submitted to NCBI genome database which currently having an accession number of PRJNA555453.

Highlights

IntroductionArsenic is a toxic element of the environment and it is a member of group V of the periodic table
Arsenic is a toxic element of the environment and it is a member of group V of the periodic table. It is classified as a heavy metal (Wackett, 2004)
According to Castro-Severyn et al, 2017 and Albarracin et al, 2016, psychrophilic bacteria Exiguobacterium was normally found in the extreme environmental condition of Chilean Altiplano, Atacama desert, Antarctic ice (Carneiro et al, 2012), Himalayan glaciers (Chaturvedi and Shivaji, 2006), soda lakes (Borsodi et al, 2005), hyperthermophilic hot springs (Vishnivetskaya et al, 2009), and deep-sea hydrothermal vents (Vishnivetskaya et al, 2009 and Crapart, 2007)

Summary

Introduction

Arsenic is a toxic element of the environment and it is a member of group V of the periodic table. It is classified as a heavy metal (Wackett, 2004). The most common way for heavy metal removal techniques from industrial effluents are chemical precipitation, chemical oxidation or reduction, ion exchange, filtration, electrochemical treatment, reverse osmosis, membrane technologies and evaporation recovery (Ahluwalia and Goyal, 2007). These methods are expensive and have some drawbacks in the higher concentration of heavy metal removal (Nourbakhsh et al, 1994).

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