Title: Phototrophic Lactate Utilization by Rhodopseudomonas palustris Is Stimulated by Coutilization with Additional Substrates

Abstract

The phototrophic purple nonsulfur bacterium Rhodopseudomonas palustris is known for its metabolic versatility and is of interest for various industrial and environmental applications. Despite decades of research on R. palustris growth under diverse conditions, patterns of R. palustris growth and carbon utilization with mixtures of carbon substrates remain largely unknown. R. palustris readily utilizes most short-chain organic acids but cannot readily use lactate as a sole carbon source. Here we investigated the influence of mixed-substrate utilization on phototrophic lactate consumption by R. palustris. We found that lactate was simultaneously utilized with a variety of other organic acids and glycerol in time frames that were insufficient for R. palustris growth on lactate alone. Thus, lactate utilization by R. palustris was expedited by its coutilization with additional substrates. Separately, experiments using carbon pairs that did not contain lactate revealed acetate-mediated inhibition of glycerol utilization in R. palustris. This inhibition was specific to the acetate-glycerol pair, as R. palustris simultaneously utilized acetate or glycerol when either was paired with succinate or lactate. Overall, our results demonstrate that (i) R. palustris commonly employs simultaneous mixed-substrate utilization, (ii) mixed-substrate utilization expands the spectrum of readily utilized organic acids in this species, and (iii) R. palustrismore » has the capacity to exert carbon catabolite control in a substrate-specific manner. IMPORTANCE. Bacterial carbon source utilization is frequently assessed using cultures provided single carbon sources. However, the utilization of carbon mixtures by bacteria (i.e., mixed-substrate utilization) is of both fundamental and practical importance; it is central to bacterial physiology and ecology, and it influences the utility of bacteria as biotechnology. Here we investigated mixed-substrate utilization by the model organism Rhodopseudomonas palustris. Using mixtures of organic acids and glycerol, we show that R. palustris exhibits an expanded range of usable carbon substrates when provided substrates in mixtures. Specifically, coutilization enabled the prompt consumption of lactate, a substrate that is otherwise not readily used by R. palustris. Additionally, we found that R. palustris utilizes acetate and glycerol sequentially, revealing that this species has the capacity to use some substrates in a preferential order. These results provide insights into R. palustris physiology that will aid the use of R. palustris for industrial and commercial applications.« less

Authors:

Govindaraju, Alekhya ^[1]; McKinlay, James B. ^[1]; LaSarre, Breah ^[1]

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+ Show Author Affiliations

1. Indiana Univ., Bloomington, IN (United States)

Publication Date:

Fri Mar 22 00:00:00 EDT 2019

Research Org.:

Indiana Univ., Bloomington, IN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER); Army Research Office (ORO); National Science Foundation (NSF)

OSTI Identifier:

1611015

Grant/Contract Number:  

SC0008131; W911NF-14-1-0411

Resource Type:

Accepted Manuscript

Journal Name:

Applied and Environmental Microbiology

Additional Journal Information:

Journal Volume: 85; Journal Issue: 11; Journal ID: ISSN 0099-2240

Publisher:

American Society for Microbiology

Country of Publication:

United States

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; Biotechnology & Applied Microbiology; Microbiology; mixed substrate utilization; Rhodopseudomonas palustris; lactate; catabolite; repression; diauxie