Abstract
Ensifer (Sinorhizobium) sp. M14 is an efficient arsenic-oxidizing bacterium (AOB) that displays high resistance to numerous metals and various stressors. Here, we report the draft genome sequence and genome-guided characterization of Ensifer sp. M14, and we describe a pilot-scale installation applying the M14 strain for remediation of arsenic-contaminated waters. The M14 genome contains 6874 protein coding sequences, including hundreds not found in related strains. Nearly all unique genes that are associated with metal resistance and arsenic oxidation are localized within the pSinA and pSinB megaplasmids. Comparative genomics revealed that multiple copies of high-affinity phosphate transport systems are common in AOBs, possibly as an As-resistance mechanism. Genome and antibiotic sensitivity analyses further suggested that the use of Ensifer sp. M14 in biotechnology does not pose serious biosafety risks. Therefore, a novel two-stage installation for remediation of arsenic-contaminated waters was developed. It consists of a microbiological module, where M14 oxidizes As(III) to As(V) ion, followed by an adsorption module for As(V) removal using granulated bog iron ores. During a 40-day pilot-scale test in an abandoned gold mine in Zloty Stok (Poland), water leaving the microbiological module generally contained trace amounts of As(III), and dramatic decreases in total arsenic concentrations were observed after passage through the adsorption module. These results demonstrate the usefulness of Ensifer sp. M14 in arsenic removal performed in environmental settings.
Highlights
The development and implementation of bioremediation technologies based on bioaugmentation requires the selection of appropriate microbial strains
We were interested in the genetic basis of the strains arsenic oxidation and resistance capabilities, resistance to arsenic and other heavy metals, and the biosafety of the strain for use in biotechnological applications
M14 that are not found in related species, and these genes are often colocalized in genomic islands
Summary
The development and implementation of bioremediation technologies based on bioaugmentation requires the selection of appropriate microbial strains. Genes 2018, 9, 379 bioaugmentation agents is their ability to survive in the environment into which they are introduced Such strains are usually characterized by high tolerance to heavy metals [1,2], resistance and ability to use organic (sometimes toxic) compounds [3,4], resistance to antibiotics [5], and an ability to thrive in the presence of local bacteriophages and microorganisms. M14 in the context of its release to the environment (e.g., determination of the presence of virulence and antibiotic resistance genes) These analyses revealed hints about the potential application of this strain in biotechnological applications; for example, the ability of it to survive environmental stresses, and whether it is likely to pose a safety risk. The results support that the developed low-cost approach is an efficient method for the removal of arsenic from contaminated water
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