Inactivation of Escherichia coli enhanced by anaerobic microbial iron reduction
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GREEN TECHNOLOGIES FOR SUSTAINABLE WATER
Inactivation of Escherichia coli enhanced by anaerobic microbial iron reduction Lavane Kim 1
&
Tao Yan 2 & Van Toan Pham 1
Received: 13 May 2020 / Accepted: 9 October 2020 # The Author(s) 2020
Abstract Microbial iron reduction (MIR) is an important and ubiquitous natural process in the biogeochemical cycling of iron and carbon in anaerobic sedimentary and subsurface environments. The objectives of this study were (1) to determine if the MIR process can enhance the inactivation of Escherichia coli cells under anaerobic conditions and (2) to identify potential inactivation mechanisms. Laboratory microcosm experiments showed that the presence of MIR activity significantly enhanced E. coli inactivation, and the inactivation rate under the MIR condition was significantly larger than those under other anaerobic redox conditions. Under anoxic condition, higher Fe2+concentrations exhibited a linear function to larger E. coli inactivation rates, indicating that the production of Fe2+by MIR was one of the important roles in E. coli inactivation. When E. coli cells were amended as the sole electron source to the MIR process, increased Fe2+ production was observed, which corresponded to decreasing TOC concentration. Together, the results suggest that MIR enhanced E. coli inactivation through the production of Fe2+ as metabolic waste, and the inactivation benefited the MIR process as the inactivated cells were used as an electron source, which represents a potential new mechanism for bacterial inter-species competition. This knowledge could further improve our understanding of the fate of fecal bacteria in natural environments where the MIR process is prevalent, and may also be explored for enhanced removal of bacterial pathogens in engineering processes. Keywords Inactivation . E. coli . Microbial iron reduction
Introduction Microbial iron reduction (MIR) is an important and ubiquitous natural process in the biogeochemical cycling of iron and the oxidation of organic matter in anaerobic sedimentary and subsurface environments (Lovley 1991). Although nonenzymatic reduction of Fe(III) under anaerobic conditions can occur (Lovley et al. 1991), dissimilatory MIR by ironResponsible Editor: Robert Duran Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-020-11209-w) contains supplementary material, which is available to authorized users. * Lavane Kim [email protected] 1
Department of Environmental Engineering, College of Environment and Natural Resources, Can Tho University, 3/2 Street, Xuan Khanh Ward, Ninh Kieu District, Can Tho City, Vietnam
2
Department of Civil and Environmental Engineering, University of Hawaii at Manoa, Honolulu, HI 96822, USA
reducing bacteria (IRBs), which use Fe(III) as the terminal electron acceptor in respiration, is considered the most important mechanism in converting Fe(III) to Fe(II) aq (Lovley 1991; Weber et al. 2006). During the MIR process, IRBs can oxidize and mineralize a large variety of organi
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