Affiliation:
1. Department of Microbiology, University of Minnesota, St. Paul, Minnesota, USA
2. BioTechnology Institute, University of Minnesota, St. Paul, Minnesota, USA
Abstract
ABSTRACT
The current understanding of dissimilatory metal reduction is based primarily on isolates from the proteobacterial genera
Geobacter
and
Shewanella
. However, environments undergoing active Fe(III) reduction often harbor less-well-studied phyla that are equally abundant. In this work, electrochemical techniques were used to analyze respiratory electron transfer by the only known Fe(III)-reducing representative of the
Acidobacteria
,
Geothrix fermentans
. In contrast to previously characterized metal-reducing bacteria, which typically reach maximal rates of respiration at electron acceptor potentials of 0 V versus standard hydrogen electrode (SHE),
G. fermentans
required potentials as high as 0.55 V to respire at its maximum rate. In addition,
G. fermentans
secreted two different soluble redox-active electron shuttles with separate redox potentials (−0.2 V and 0.3 V). The compound with the lower midpoint potential, responsible for 20 to 30% of electron transfer activity, was riboflavin. The behavior of the higher-potential compound was consistent with hydrophilic UV-fluorescent molecules previously found in
G. fermentans
supernatants. Both electron shuttles were also produced when cultures were grown with Fe(III), but not when fumarate was the electron acceptor. This study reveals that
Geothrix
is able to take advantage of higher-redox-potential environments, demonstrates that secretion of flavin-based shuttles is not confined to
Shewanella
, and points to the existence of high-potential-redox-active compounds involved in extracellular electron transfer. Based on differences between the respiratory strategies of
Geothrix
and
Geobacter
, these two groups of bacteria could exist in distinctive environmental niches defined by redox potential.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
74 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献