Genomic Analysis of Shewanella sp. O23S-The Natural Host of the pSheB Plasmid Carrying Genes for Arsenic Resistance and Dissimilatory Reduction.

Witold Uhrynowski,Monika Radlinska,Lukasz Drewniak

doi:10.3390/ijms20051018

Witold Uhrynowski, Monika Radlinska + Show 1 more

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https://doi.org/10.3390/ijms20051018

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Abstract

Shewanella sp. O23S is a dissimilatory arsenate reducing bacterial strain involved in arsenic transformations within the abandoned gold mine in Zloty Stok (SW Poland). Previous physiological studies revealed that O23S may not only release arsenic from minerals, but also facilitate its immobilization through co-precipitation with reduced sulfur species. Given these uncommon, complementary characteristics and the application potential of the strain in arsenic-removal technologies, its genome (~5.3 Mbp), consisting of a single chromosome, two large plasmids (pSheA and pSheB) and three small plasmid-like phages (pSheC-E) was sequenced and annotated. Genes encoding putative proteins involved in heavy metal transformations, antibiotic resistance and other phenotypic traits were identified. An in-depth comparative analysis of arsenic respiration (arr) and resistance (ars) genes and their genetic context was also performed, revealing that pSheB carries the only copy of the arr genes, and a complete ars operon. The plasmid pSheB is therefore a unique natural vector of these genes, providing the host cells arsenic respiration and resistance abilities. The functionality of the identified genes was determined based on the results of the previous and additional physiological studies, including: the assessment of heavy metal and antibiotic resistance under various conditions, adhesion-biofilm formation assay and BiologTM metabolic preferences test. This combined genetic and physiological approach shed a new light on the capabilities of O23S and their molecular basis, and helped to confirm the biosafety of the strain in relation to its application in bioremediation technologies.

Highlights

Extreme environments, including heavy metal polluted mining sites, constitute important research areas plentiful in species with interesting adaptive traits [1]
Members of Shewanellaceae are known for their involvement in the cycle of arsenic in the environment, most of them being related to mobilization of this element
O23S was isolated from microbial mats from the Zloty Stok mine (SW Poland), an environment strongly contaminated with arsenic

Summary

Introduction

Extreme environments, including heavy metal polluted mining sites, constitute important research areas plentiful in species with interesting adaptive traits [1]. Dissimilatory arsenate reducing bacteria (DARB) are considered the main arsenic mobilizers in the environment [5,6], and their presence usually contributes to increasing of the concentration of arsenic in waters, and especially underground waters, such as mine effluents [7,8,9]. DARB may find application in bioremediation, as they can facilitate controlled removal of arsenic from solid material, including minerals, waste residues [11], and contaminated soil [12] This capability of mobilization of heavy metals by DARB can be used to selectively remove the toxic species by applying adequate red-ox potential, for example in redox-stat reactors [13]

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