scholarly journals Phototrophic Lactate Utilization byRhodopseudomonas palustrisIs Stimulated by Coutilization with Additional Substrates

2019 ◽  
Vol 85 (11) ◽  
Author(s):  
Alekhya Govindaraju ◽  
James B. McKinlay ◽  
Breah LaSarre
Keyword(s):  
Carbon Source ◽  
Organic Acids ◽  
Rhodopseudomonas Palustris ◽  
Practical Importance ◽  
Substrate Utilization ◽  
Mixed Substrate ◽  
Content Type ◽  
Bacterial Physiology ◽  
Carbon Substrates ◽  
Lactate Utilization

ABSTRACTThe phototrophic purple nonsulfur bacteriumRhodopseudomonas palustrisis known for its metabolic versatility and is of interest for various industrial and environmental applications. Despite decades of research onR. palustrisgrowth under diverse conditions, patterns ofR. palustrisgrowth and carbon utilization with mixtures of carbon substrates remain largely unknown.R. palustrisreadily 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 byR. palustris. We found that lactate was simultaneously utilized with a variety of other organic acids and glycerol in time frames that were insufficient forR. palustrisgrowth on lactate alone. Thus, lactate utilization byR. palustriswas expedited by its coutilization with additional substrates. Separately, experiments using carbon pairs that did not contain lactate revealed acetate-mediated inhibition of glycerol utilization inR. palustris. This inhibition was specific to the acetate-glycerol pair, asR. palustrissimultaneously utilized acetate or glycerol when either was paired with succinate or lactate. Overall, our results demonstrate that (i)R. palustriscommonly employs simultaneous mixed-substrate utilization, (ii) mixed-substrate utilization expands the spectrum of readily utilized organic acids in this species, and (iii)R. palustrishas the capacity to exert carbon catabolite control in a substrate-specific manner.IMPORTANCEBacterial 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 organismRhodopseudomonas palustris. Using mixtures of organic acids and glycerol, we show thatR. palustrisexhibits 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 byR. palustris. Additionally, we found thatR. palustrisutilizes acetate and glycerol sequentially, revealing that this species has the capacity to use some substrates in a preferential order. These results provide insights intoR. palustrisphysiology that will aid the use ofR. palustrisfor industrial and commercial applications.

scholarly journals Phototrophic lactate utilization by Rhodopseudomonas palustris is stimulated by co-utilization with additional substrates

2018 ◽  
Author(s):  
Alekhya Govindaraju ◽  
James B McKinlay ◽  
Breah LaSarre
Keyword(s):  
Organic Acids ◽  
Rhodopseudomonas Palustris ◽  
Substrate Utilization ◽  
Carbon Utilization ◽  
Mixed Substrate ◽  
Metabolic Versatility ◽  
Carbon Substrates ◽  
Glycerol Utilization ◽  
Lactate Utilization ◽  
Time Frames

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 co-utilization 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. palustris has the capacity to exert carbon catabolite control in a substrate-specific manner.

scholarly journals The Cyclic AMP Receptor Protein Regulates Quorum Sensing and Global Gene Expression in Yersinia pestis during Planktonic Growth and Growth in Biofilms

mBio ◽  
2019 ◽  
Vol 10 (6) ◽  
Author(s):  
Jeremy T. Ritzert ◽  
George Minasov ◽  
Ryan Embry ◽  
Matthew J. Schipma ◽  
Karla J. F. Satchell
Keyword(s):  
Gene Expression ◽  
Quorum Sensing ◽  
Carbon Source ◽  
Cyclic Amp ◽  
Yersinia Pestis ◽  
Carbon Sources ◽  
Transcriptional Regulator ◽  
Receptor Protein ◽  
Content Type ◽  
Bacterial Physiology

ABSTRACT Cyclic AMP (cAMP) receptor protein (Crp) is an important transcriptional regulator of Yersinia pestis. Expression of crp increases during pneumonic plague as the pathogen depletes glucose and forms large biofilms within lungs. To better understand control of Y. pestis Crp, we determined a 1.8-Å crystal structure of the protein-cAMP complex. We found that compared to Escherichia coli Crp, C helix amino acid substitutions in Y. pestis Crp did not impact the cAMP dependency of Crp to bind DNA promoters. To investigate Y. pestis Crp-regulated genes during plague pneumonia, we performed RNA sequencing on both wild-type and Δcrp mutant bacteria growing in planktonic and biofilm states in minimal media with glucose or glycerol. Y. pestis Crp was found to dramatically alter expression of hundreds of genes in a manner dependent upon carbon source and growth state. Gel shift assays confirmed direct regulation of the malT and ptsG promoters, and Crp was then linked to Y. pestis growth on maltose as a sole carbon source. Iron regulation genes ybtA and fyuA were found to be indirectly regulated by Crp. A new connection between carbon source and quorum sensing was revealed as Crp was found to regulate production of acyl-homoserine lactones (AHLs) through direct and indirect regulation of genes for AHL synthetases and receptors. AHLs were subsequently identified in the lungs of Y. pestis-infected mice when crp expression was highest in Y. pestis biofilms. Thus, in addition to the well-studied pla gene, other Crp-regulated genes likely have important functions during plague infection. IMPORTANCE Bacterial pathogens have evolved extensive signaling pathways to translate environmental signals into changes in gene expression. While Crp has long been appreciated for its role in regulating metabolism of carbon sources in many bacterial species, transcriptional profiling has revealed that this protein regulates many other aspects of bacterial physiology. The plague pathogen Y. pestis requires this global regulator to survive in blood, skin, and lungs. During disease progression, this organism adapts to changes within these niches. In addition to regulating genes for metabolism of nonglucose sugars, we found that Crp regulates genes for virulence, metal acquisition, and quorum sensing by direct or indirect mechanisms. Thus, this single transcriptional regulator, which responds to changes in available carbon sources, can regulate multiple critical behaviors for causing disease.

scholarly journals Triosephosphate Isomerase Is Dispensable In Vitro yet Essential for Mycobacterium tuberculosis To Establish Infection

mBio ◽  
2014 ◽  
Vol 5 (2) ◽  
Author(s):  
Carolina Trujillo ◽  
Antje Blumenthal ◽  
Joeli Marrero ◽  
Kyu Y. Rhee ◽  
Dirk Schnappinger ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Carbon Source ◽  
Triosephosphate Isomerase ◽  
Central Carbon Metabolism ◽  
Dihydroxyacetone Phosphate ◽  
Content Type ◽  
Carbon Substrates ◽  
Metabolic Conditions ◽  
Single Carbon Source

ABSTRACTTriosephosphate isomerase (TPI) catalyzes the interconversion of dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (G3P). This reaction is required for glycolysis and gluconeogenesis, andtpihas been predicted to be essential for growth ofMycobacterium tuberculosis. However, when studying a conditionally regulatedtpiknockdown mutant, we noticed that depletion of TPI reduced growth ofM. tuberculosisin media containing a single carbon source but not in media that contained both a glycolytic and a gluconeogenic carbon source. We used such two-carbon-source media to isolate atpideletion (Δtpi) mutant. The Δtpimutant did not survive with single carbon substrates but grew like wild-type (WT)M. tuberculosisin the presence of both a glycolytic and a gluconeogenic carbon source.13C metabolite tracing revealed the accumulation of TPI substrates in Δtpiand the absence of alternative triosephosphate isomerases and metabolic bypass reactions, which confirmed the requirement of TPI for glycolysis and gluconeogenesis inM. tuberculosis. The Δtpistrain was furthermore severely attenuated in the mouse model of tuberculosis, suggesting thatM. tuberculosiscannot simultaneously access sufficient quantities of glycolytic and gluconeogenic carbon substrates to establish infection in mice.IMPORTANCEThe importance of central carbon metabolism for the pathogenesis ofM. tuberculosishas recently been recognized, but the consequences of depleting specific metabolic enzymes remain to be identified for many enzymes. We investigated triosephosphate isomerase (TPI) because it is central to both glycolysis and gluconeogenesis and had been predicted to be essential for growth ofM. tuberculosis. This work identified metabolic conditions that make TPI dispensable forM. tuberculosisgrowth in culture and proved thatM. tuberculosisrelies on a single TPI enzyme and has no metabolic bypass for the TPI-dependent interconversion of dihydroxyacetone phosphate and glyceraldehyde-3-phosphate in glycolysis and gluconeogenesis. Finally, we demonstrate that TPI is essential for growth of the pathogen in mouse lungs.

scholarly journals Complete Genome Sequence of Rhodopseudomonas palustris RCB100, an Anoxygenic Phototroph That Degrades 3-Chlorobenzoate

2021 ◽  
Vol 10 (15) ◽  
Author(s):  
Irshad UI Haq ◽  
Kathryn R. Fixen
Keyword(s):  
Carbon Source ◽  
Genome Sequence ◽  
Complete Genome Sequence ◽  
Complete Genome ◽  
Rhodopseudomonas Palustris ◽  
Content Type ◽  
Purple Nonsulfur Bacterium ◽  
Insight Into

ABSTRACT The purple nonsulfur bacterium Rhodopseudomonas palustris RCB100 anaerobically degrades 3-chlorobenzoate (3-CBA), a halogenated pollutant. R. palustris RCB100 uses 3-CBA as a carbon source, while most R. palustris strains cannot. We report the complete genome sequence of strain RCB100 to help gain insight into how this bacterium degrades 3-CBA.

scholarly journals A Disjointed Pathway for Malonate Degradation by Rhodopseudomonas palustris

2020 ◽  
Vol 86 (11) ◽  
Author(s):  
Zhaobao Wang ◽  
Qifeng Wen ◽  
Caroline S. Harwood ◽  
Bo Liang ◽  
Jianming Yang
Keyword(s):  
Carbon Source ◽  
Dicarboxylic Acid ◽  
Slow Growth ◽  
Rhodopseudomonas Palustris ◽  
Carbon Sources ◽  
Value Added ◽  
Poor Growth ◽  
Content Type ◽  
Phototrophic Bacterium ◽  
Malonyl Coa

ABSTRACT The purple nonsulfur phototrophic bacterium Rhodopseudomonas palustris strain CGA009 uses the three-carbon dicarboxylic acid malonate as the sole carbon source under phototrophic conditions. However, this bacterium grows extremely slowly on this compound and does not have operons for the two pathways for malonate degradation that have been detected in other bacteria. Many bacteria grow on a spectrum of carbon sources, some of which are classified as poor growth substrates because they support low growth rates. This trait is rarely addressed in the literature, but slow growth is potentially useful in biotechnological applications where it is imperative for bacteria to divert cellular resources to value-added products rather than to growth. This prompted us to explore the genetic and physiological basis for the slow growth of R. palustris with malonate as a carbon source. There are two unlinked genes annotated as encoding a malonyl coenzyme A (malonyl-CoA) synthetase (MatB) and a malonyl-CoA decarboxylase (MatA) in the genome of R. palustris, which we verified as having the predicted functions. Additionally, two tripartite ATP-independent periplasmic transporters (TRAP systems) encoded by rpa2047 to rpa2049 and rpa2541 to rpa2543 were needed for optimal growth on malonate. Most of these genes were expressed constitutively during growth on several carbon sources, including malonate. Our data indicate that R. palustris uses a piecemeal approach to growing on malonate. The data also raise the possibility that this bacterium will evolve to use malonate efficiently if confronted with an appropriate selection pressure. IMPORTANCE There is interest in understanding how bacteria metabolize malonate because this three-carbon dicarboxylic acid can serve as a building block in bioengineering applications to generate useful compounds that have an odd number of carbons. We found that the phototrophic bacterium Rhodopseudomonas palustris grows extremely slowly on malonate. We identified two enzymes and two TRAP transporters involved in the uptake and metabolism of malonate, but some of these elements are apparently not very efficient. R. palustris cells growing with malonate have the potential to be excellent biocatalysts, because cells would be able to divert cellular resources to the production of value-added compounds instead of using them to support rapid growth. In addition, our results suggest that R. palustris is a candidate for directed evolution studies to improve growth on malonate and to observe the kinds of genetic adaptations that occur to make a metabolic pathway operate more efficiently.

Glucose utilization dependence on preferred carbon-source growth in an Arthrobacter sp.

1973 ◽  
Vol 19 (4) ◽  
pp. 541-543 ◽  
Author(s):  
R. A. Sokol ◽  
D. A. Klein
Keyword(s):  
Carbon Source ◽  
Glucose Utilization ◽  
Substrate Utilization ◽  
Mixed Substrate

Arthrobacter sp., ATCC 25581, is incapable of glucose utilization except diauxically following growth on a preferred carbon source such as succinate. This phenomenon appears to be a novel mixed substrate utilization relationship.

scholarly journals Characterization of Multiple-Substrate Utilization by Anthracene-Degrading Mycobacterium frederiksbergense LB501T

2003 ◽  
Vol 69 (10) ◽  
pp. 6133-6142 ◽  
Author(s):  
Lukas Y. Wick ◽  
Natacha Pasche ◽  
Stefano M. Bernasconi ◽  
Oliver Pelz ◽  
Hauke Harms
Keyword(s):  
Fatty Acids ◽  
Carbon Source ◽  
Cell Surface ◽  
Stable Carbon Isotope ◽  
Cell Surface Hydrophobicity ◽  
Substrate Utilization ◽  
Mycolic Acid ◽  
Mixed Substrate ◽  
Mycolic Acids ◽  
Degrading Bacteria

ABSTRACT Stable carbon isotope analysis of biomass and analyses of phospholipid fatty acids (PLFA), glycolipid fatty acids (GLFA), and mycolic acids were used to characterize mixed-substrate utilization by Mycobacterium frederiksbergense LB501T under various substrate regimens. The distinct 13C contents of anthracene and glucose as representatives of typical hydrophobic pollutants and naturally occurring organic compounds, respectively, were monitored during formation into biomass and used to quantify the relative contributions of the two carbon sources to biomass formation. Moreover, the influence of mixed-substrate utilization on PLFA, GLFA, and mycolic acid profiles and cell surface hydrophobicity was investigated. Results revealed that M. frederiksbergense LB501T degrades anthracene and forms biomass from it even in the presence of more readily available dissolved glucose. The relative ratios of straight-chain saturated PLFA to the corresponding unsaturated PLFA and the total fraction of saturated cyclopropyl-branched PLFA of M. frederiksbergense LB501T depended on the carbon source and the various rates of addition of mixed substrates, whereas no such trend was observed with GLFA. Higher proportions of anthracene in the carbon source mixture led to higher cell surface hydrophobicities and more-hydrophobic mycolic acids, which in turn appeared to be valuable indicators for substrate utilization by M. frederiksbergense LB501T. The capability of polycyclic aromatic hydrocarbon (PAH)-degrading bacteria to utilize readily available substrates besides the poorly available PAHs favors the buildup of PAH-degrading biomass. Feeding of supplementary carbon substrates may therefore promote bioremediation, provided that it sustains the pollutant-degrading population rather than other members of the microbial community.

scholarly journals Acetate Metabolism and the Inhibition of Bacterial Growth by Acetate

2019 ◽  
Vol 201 (13) ◽  
Author(s):  
Stéphane Pinhal ◽  
Delphine Ropers ◽  
Johannes Geiselmann ◽  
Hidde de Jong
Keyword(s):  
Escherichia Coli ◽  
Organic Acids ◽  
Growth Inhibition ◽  
Food Preservation ◽  
Acetate Metabolism ◽  
Overflow Metabolism ◽  
Acetyl Phosphate ◽  
Content Type ◽  
Bacterial Physiology ◽  
High Concentrations

ABSTRACTDuring aerobic growth on glucose,Escherichia coliexcretes acetate, a mechanism called “overflow metabolism.” At high concentrations, the secreted acetate inhibits growth. Several mechanisms have been proposed for explaining this phenomenon, but a thorough analysis is hampered by the diversity of experimental conditions and strains used in these studies. Here, we describe the construction of a set of isogenic strains that remove different parts of the metabolic network involved in acetate metabolism. Analysis of these strains reveals that (i) high concentrations of acetate in the medium inhibit growth without significantly perturbing central metabolism; (ii) growth inhibition persists even when acetate assimilation is completely blocked; and (iii) regulatory interactions mediated by acetyl-phosphate play a small but significant role in growth inhibition by acetate. The major contribution to growth inhibition by acetate may originate in systemic effects like the uncoupling effect of organic acids or the perturbation of the anion composition of the cell, as previously proposed. Our data suggest, however, that under the conditions considered here, the uncoupling effect plays only a limited role.IMPORTANCEHigh concentrations of organic acids such as acetate inhibit growth ofEscherichia coliand other bacteria. This phenomenon is of interest for understanding bacterial physiology but is also of practical relevance. Growth inhibition by organic acids underlies food preservation and causes problems during high-density fermentation in biotechnology. What causes this phenomenon? Classical explanations invoke the uncoupling effect of acetate and the establishment of an anion imbalance. Here, we propose and investigate an alternative hypothesis: the perturbation of acetate metabolism due to the inflow of excess acetate. We find that this perturbation accounts for 20% of the growth-inhibitory effect through a modification of the acetyl phosphate concentration. Moreover, we argue that our observations are not expected based on uncoupling alone.

scholarly journals Calvin Cycle Flux, Pathway Constraints, and Substrate Oxidation State Together Determine the H2 Biofuel Yield in Photoheterotrophic Bacteria

mBio ◽  
2011 ◽  
Vol 2 (2) ◽  
Author(s):  
James B. McKinlay ◽  
Caroline S. Harwood
Keyword(s):  
Organic Compounds ◽  
Oxidation State ◽  
Rhodopseudomonas Palustris ◽  
Calvin Cycle ◽  
Substrate Oxidation ◽  
Hydrogen Gas ◽  
Anaerobic Growth ◽  
Anoxygenic Phototrophic Bacteria ◽  
Transportation Fuel ◽  
Content Type

ABSTRACTHydrogen gas (H2) is a possible future transportation fuel that can be produced by anoxygenic phototrophic bacteria via nitrogenase. The electrons for H2are usually derived from organic compounds. Thus, one would expect more H2to be produced when anoxygenic phototrophs are supplied with increasingly reduced (electron-rich) organic compounds. However, the H2yield does not always differ according to the substrate oxidation state. To understand other factors that influence the H2yield, we determined metabolic fluxes inRhodopseudomonas palustrisgrown on13C-labeled fumarate, succinate, acetate, and butyrate (in order from most oxidized to most reduced). The flux maps revealed that the H2yield was influenced by two main factors in addition to substrate oxidation state. The first factor was the route that a substrate took to biosynthetic precursors. For example, succinate took a different route to acetyl-coenzyme A (CoA) than acetate. As a result,R. palustrisgenerated similar amounts of reducing equivalents and similar amounts of H2from both succinate and acetate, even though succinate is more oxidized than acetate. The second factor affecting the H2yield was the amount of Calvin cycle flux competing for electrons. When nitrogenase was active, electrons were diverted away from the Calvin cycle towards H2, but to various extents, depending on the substrate. When Calvin cycle flux was blocked, the H2yield increased during growth on all substrates. In general, this increase in H2yield could be predicted from the initial Calvin cycle flux.IMPORTANCEPhotoheterotrophic bacteria, likeRhodopseudomonas palustris, obtain energy from light and carbon from organic compounds during anaerobic growth. Cells can naturally produce the biofuel H2as a way of disposing of excess electrons. Unexpectedly, feeding cells organic compounds with more electrons does not necessarily result in more H2. Despite repeated observations over the last 40 years, the reasons for this discrepancy have remained unclear. In this paper, we identified two metabolic factors that influence the H2yield, (i) the route taken to make biosynthetic precursors and (ii) the amount of CO2-fixing Calvin cycle flux that competes against H2production for electrons. We show that the H2yield can be improved on all substrates by using a strain that is incapable of Calvin cycle flux. We also contributed quantitative knowledge to the long-standing question of why photoheterotrophs must produce H2or fix CO2even on relatively oxidized substrates.

Re-conceptualising call-centres as sites of control: the insider perspective

2014 ◽  
Vol 48 (1/2) ◽  
pp. 25-46 ◽  
Author(s):  
Edward Kasabov ◽  
Anna C.C.C. da Cunha
Keyword(s):  
Design Methodology ◽  
Customer Orientation ◽  
Practical Importance ◽  
Call Centre ◽  
Structured Interviews ◽  
Content Type ◽  
Call Centres ◽  
Customer Dissatisfaction ◽  
Customer Centricity

Purpose – The role of call-centres during service recovery has attracted much attention in research. However, marketers know less about controlling customers during recovery interactions and consequences of such control. In order to address this gap and empirically ascertain whether service interactions are marked by customer centricity or by employees exerting control over customers, the aim of the authors was to organise an empirical research in two Brazilian call-centres. Design/methodology/approach – The research consisted of direct, open observation and 33 semi-structured interviews with insiders (call-centre managers, supervisors and operatives). Findings – Four key findings emerged during interviews with insiders. First, control over customers may be more widely practiced than assumed in certain sections of marketing academe. Second, such control is viewed positively by call-centre insiders and is sanctioned by management. Third, control does not disempower and demoralise call-centre staff but protects operatives. Finally, control does not seem to unavoidably generate lasting customer dissatisfaction. These findings are incorporated in a framework of call-centre management which incorporates control through scripting. Research limitations/implications – The discussion calls for the revisit of certain marketing concepts and philosophies, including customer orientation, by demonstrating that control over customers is practised and should not be viewed negatively or avoided altogether in practice and as a topic of analysis. A re-conceptualisation of call-centres as sites of control over customers is proposed. Originality/value – Control and power are rarely analysed in services marketing. This is one of a few studies that makes sense of providers' (insiders') viewpoints and argues that control may play a constructive role and should be seen as a legitimate topic of services and call-centre analysis. As such it addresses a question of intellectual and practical importance which is rarely discussed and may be viewed as incongruous with an age when customers are assumed to have rights.

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