Metal Transformation by a Novel Pelosinus Isolate From a Subsurface Environment.

Allison E Ray,Andrew L Neal,Yoshiko Fujita,Jani C Ingram,Stephanie A Connon,David E Cummings,Timothy S Magnuson

doi:10.3389/fmicb.2018.01689

Abstract

The capability of microorganisms to alter metal speciation offers potential for the development of new strategies for immobilization of toxic metals in the environment. A metal-reducing microbe, “Pelosinus lilae” strain UFO1, was isolated under strictly anaerobic conditions from an Fe(III)-reducing enrichment established with uncontaminated soil from the Department of Energy Oak Ridge Field Research Center, Tennessee. “P. lilae” UFO1 is a rod-shaped, spore-forming, and Gram-variable anaerobe with a fermentative metabolism. It is capable of reducing the humic acid analog anthraquinone-2,6-disulfonate (AQDS) using a variety of fermentable substrates and H2. Reduction of Fe(III)-nitrilotriacetic acid occurred in the presence of lactate as carbon and electron donor. Ferrihydrite was not reduced in the absence of AQDS. Nearly complete reduction of 1, 3, and 5 ppm Cr(VI) occurred within 24 h in suspensions containing 108 cells mL−1 when provided with 10 mM lactate; when 1 mM AQDS was added, 3 and 5 ppm Cr(VI) were reduced to 0.1 ppm within 2 h. Strain UFO1 is a novel species within the bacterial genus Pelosinus, having 98.16% 16S rRNA gene sequence similarity with the most closely related described species, Pelosinus fermentans R7T. The G+C content of the genomic DNA was 38 mol%, and DNA-DNA hybridization of “P. lilae” UFO1 against P. fermentans R7T indicated an average 16.8% DNA-DNA similarity. The unique phylogenetic, physiologic, and metal-transforming characteristics of “P. lilae” UFO1 reveal it is a novel isolate of the described genus Pelosinus.

Highlights

The pollution of groundwater by metal and radionuclide contaminants continues to pose a clear threat to public health (EPA, 2003), and remediation of subsurface environments is a growing environmental and economic challenge (White et al, 1997; NABIR, 2003)
“Pelosinus lilae” UFO1 was isolated under strictly anaerobic conditions from dilution-to-extinction cultivation experiments, and was capable of AQDS reduction, as evident by a color change in growth medium from transparent, pale yellow to bright orange
After restreaking at least three times, a colony was transferred to FW medium containing lactate and AQDS, and the culture reduced AQDS

Summary

Introduction

The pollution of groundwater by metal and radionuclide contaminants continues to pose a clear threat to public health (EPA, 2003), and remediation of subsurface environments is a growing environmental and economic challenge (White et al, 1997; NABIR, 2003). The goal of metal remediation is to limit contaminant mobility. The potential for immobilization of a given metal in the environment is principally dependent upon its chemical speciation. The aim is to either induce or maintain chemical conditions that result in metal species with reduced mobility. Depending on the ambient redox conditions, many toxic metals and radionuclides can be highly soluble, and mobile, in groundwater (Lovley, 2001). Microorganisms are capable of altering chemical speciation via redox reactions, thereby influencing solubility, transport properties, and bioavailability of metallic contaminants in subsurface environments. Bioreduction of highly soluble Cr(VI) and U(VI) can result in conversion to insoluble species [e.g., Cr(III) and U(IV)] that precipitate from solution (Tabak et al, 2005)

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