Title: Single-genotype syntrophy by Rhodopseudomonas palustris is not a strategy to aid redox balance during anaerobic degradation of lignin monomers

Abstract

Rhodopseudomonas palustris has emerged as a model microbe for the anaerobic metabolism of p-coumarate, which is an aromatic compound and a primary component of lignin. However, under an aerobic conditions, R.palustris must actively eliminate excess reducing equivalents through a number of known strategies (e.g., CO₂ fixation, H₂ evolution) to avoid lethal redox imbalance. Others had hypothesized that to ease the burden of this redox imbalance, a clonal population of R.palustris could functionally differentiate into a pseudo-consortium. Within this pseudo-consortium, one sub-population would perform the aromatic moiety degradation into acetate, while the other sub-population would oxidize acetate, resulting in a single-genotype syntrophy through acetate sharing. Here, the objective was to test this hypothesis by utilizing microbial lelectrochemistry as a research tool with the extrac ellular-electron-transferring bacterium Geobacter sulfurreducens as a reporter strain replacing the hypothesized acetate-oxidizing sub-population. We used a 2×4 experimental design with pure cultures of R. palustris in serum bottles and co-cultures of R. palustris and G.sulfurreducens in bioelectrochemical systems.This experimental design included growth medium with and without bicarbonate to induce non-lethal and lethal redox imbalance conditions, respectively, in R. palustris. Finally, the design also included a mutant strain (NifA*) of R. palustris, which constitutively produces H₂, to servemore » both as a positive control for metabolite secretion (H₂) to G. sulfurreducens, and as a non-lethal redox control for without bicarbonate conditions. Our results demonstrate that acetate sharing between different sub-populations of R. palustris does not occur while degrading p-coumarate under either non-lethal or lethal redox imbalance conditions. Furthermore, this work highlights the strength of microbial electrochemistry as a tool for studying microbial syntrophy.« less

Authors:

Doud, Devin F. R. ^[1]; Angenent, Largus T. ^[2]

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+ Show Author Affiliations

1. Cornell Univ., Ithaca, NY (United States); The DOE Joint Genome Institute, Walnut Creek, CA (United States)
2. Cornell Univ., Ithaca, NY (United States)

Publication Date:

Thu Jul 14 00:00:00 EDT 2016

Research Org.:

Cornell Univ., Ithaca, NY (United States)

Sponsoring Org.:

USDOE Advanced Research Projects Agency - Energy (ARPA-E)

OSTI Identifier:

1312683

Grant/Contract Number:  

AR0000312

Resource Type:

Accepted Manuscript

Journal Name:

Frontiers in Microbiology

Additional Journal Information:

Journal Volume: 7; Journal ID: ISSN 1664-302X

Publisher:

Frontiers Research Foundation

Country of Publication:

United States

Language:

English

Subject:

60 APPLIED LIFE SCIENCES; single-genotype syntrophy; Rhodopseudomonas palustris; microbial electrochemistry; lignin degradation; redox balance