Title: An electrochemical investigation of interfacial electron uptake by the sulfur oxidizing bacterium Thioclava electrotropha ElOx9

Abstract

Extracellular electron transfer (EET) allows microbes to acquire energy from solid state electron acceptors and donors, such as environmental minerals. Here, this process can also be harnessed at electrode interfaces in bioelectrochemical technologies including microbial fuel cells, microbial electrosynthesis, bioremediation, and wastewater treatment. Improving the performance of these technologies will benefit from a better fundamental understanding of EET in diverse microbial systems. While the mechanisms of outward (i.e. microbe-to-anode) EET is relatively well characterized, specifically in a few metal-reducing bacteria, the reverse process of inward EET from redox-active minerals or cathodes to bacteria remains poorly understood. This knowledge gap stems, at least partly, from the lack of well-established model organisms and general difficulties associated with laboratory studies in existing model systems. Recently, a sulfur oxidizing marine microbe, Thioclava electrotropha ElOx9, was demonstrated to perform electron uptake from cathodes. However, a detailed analysis of the electron uptake pathways has yet to be established, and electrochemical characterization has been limited to aerobic conditions. Here, we report a detailed amperometric and voltammetric characterization of ElOx9 cells coupling cathodic electron uptake to reduction of nitrate as the sole electron acceptor, even in the absence of any added inorganic carbon source. By comparing this cellularmore » activity to spent media controls and using medium exchange experiments, we demonstrate that one of the pathways by which ElOx9 facilitates inward EET is by a direct-contact mechanism through a redox center with a formal potential of -94 mV vs SHE, rather than soluble intermediate electron carriers. In addition to the implications for understanding microbial sulfur oxidation in marine environments, this study highlights the potential for ElOx9 to serve as a convenient and readily culturable model organism for understanding the molecular mechanisms of inward EET.« less

Authors:

Karbelkar, Amruta A. ^[1]; Rowe, Annette R. ^[2]; El-Naggar, Mohamed Y. ^[1]

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+ Show Author Affiliations

1. Univ. of Southern California, Los Angeles, CA (United States)
2. Univ. of Cincinnati, OH (United States)

Publication Date:

Fri Sep 06 00:00:00 EDT 2019

Research Org.:

Univ. of Southern California, Los Angeles, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division; National Science Foundation (NSF); National Aeronautics and Space Administration (NASA); USDOE

OSTI Identifier:

1802137

Alternate Identifier(s):

OSTI ID: 1562180

Grant/Contract Number:  

SC0010609; FG02-13ER16415; DEB-1542527; NNA13AA92A; NSF-STC OCE0939564

Resource Type:

Accepted Manuscript

Journal Name:

Electrochimica Acta

Additional Journal Information:

Journal Volume: 324; Journal Issue: C; Journal ID: ISSN 0013-4686

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; electrochemistry; electromicrobiology; extracellular electron transfer; lithotrophy; biocathodes