scholarly journals Metabolic Regulation as a Consequence of Anaerobic 5-Methylthioadenosine Recycling inRhodospirillum rubrum

mBio ◽  
2016 ◽  
Vol 7 (4) ◽  
Author(s):  
Justin A. North ◽  
Jaya Sriram ◽  
Karuna Chourey ◽  
Christopher D. Ecker ◽  
Ritin Sharma ◽  
...  
Keyword(s):  
Rhodospirillum Rubrum ◽  
Anaerobic Growth ◽  
Sulfur Source ◽  
Salvage Pathway ◽  
Anaerobic Conditions ◽  
Protein Levels ◽  
Methionine Salvage Pathway ◽  
Sulfur Containing ◽  
In Cells ◽  
Methionine Salvage

ABSTRACTRhodospirillum rubrum possesses a novel oxygen-independent, aerobic methionine salvage pathway (MSP) for recycling methionine from 5-methylthioadenosine (MTA), the MTA-isoprenoid shunt. This organism can also metabolize MTA as a sulfur source under anaerobic conditions, suggesting that the MTA-isoprenoid shunt may also function anaerobically as well. In this study, deep proteomics profiling, directed metabolite analysis, and reverse transcriptase quantitative PCR (RT-qPCR) revealed metabolic changes in response to anaerobic growth on MTA versus sulfate as sole sulfur source. The abundance of protein levels associated with methionine transport, cell motility, and chemotaxis increased in the presence of MTA over that in the presence of sulfate. Purine salvage from MTA resulted primarily in hypoxanthine accumulation and a decrease in protein levels involved in GMP-to-AMP conversion to balance purine pools. Acyl coenzyme A (acyl-CoA) metabolic protein levels for lipid metabolism were lower in abundance, whereas poly-β-hydroxybutyrate synthesis and storage were increased nearly 10-fold. The knownR. rubrumaerobic MSP was also shown to be upregulated, to function anaerobically, and to recycle MTA. This suggested that other organisms with gene homologues for the MTA-isoprenoid shunt may also possess a functioning anaerobic MSP. In support of our previous findings that ribulose-1,5-carboxylase/oxygenase (RubisCO) is required for an apparently purely anaerobic MSP, RubisCO transcript and protein levels both increased in abundance by over 10-fold in cells grown anaerobically on MTA over those in cells grown on sulfate, resulting in increased intracellular RubisCO activity. These results reveal for the first time global metabolic responses as a consequence of anaerobic MTA metabolism compared to using sulfate as the sulfur source.IMPORTANCEIn nearly all organisms, sulfur-containing byproducts result from many metabolic reactions. Unless these compounds are further metabolized, valuable organic sulfur is lost and can become limiting. To regenerate the sulfur-containing amino acid methionine, organisms typically employ one of several variations of a “universal” methionine salvage pathway (MSP). A common aspect of the universal MSP is a final oxygenation step. This work establishes that the metabolically versatile bacteriumRhodospirillum rubrumemploys a novel MSP that does not require oxygen under either aerobic or anaerobic conditions. There is also a separate, dedicated anaerobic MTA metabolic route inR. rubrum. This work reveals global changes in cellular metabolism in response to anaerobic MTA metabolism compared to using sulfate as a sulfur source. We found that cell mobility and transport were enhanced, along with lipid, nucleotide, and carbohydrate metabolism, when cells were grown in the presence of MTA.

scholarly journals Microbial pathway for anaerobic 5′-methylthioadenosine metabolism coupled to ethylene formation

2017 ◽  
Vol 114 (48) ◽  
pp. E10455-E10464 ◽  
Author(s):  
Justin A. North ◽  
Anthony R. Miller ◽  
John A. Wildenthal ◽  
Sarah J. Young ◽  
F. Robert Tabita
Keyword(s):  
Rhodospirillum Rubrum ◽  
Rhodopseudomonas Palustris ◽  
Anaerobic Bacteria ◽  
Sulfur Source ◽  
Salvage Pathway ◽  
Ethylene Formation ◽  
Cellular Processes ◽  
Anoxic Environments ◽  
Class Ii Aldolase

Numerous cellular processes involvingS-adenosyl-l-methionine result in the formation of the toxic by-product, 5′-methylthioadenosine (MTA). To prevent inhibitory MTA accumulation and retain biologically available sulfur, most organisms possess the “universal” methionine salvage pathway (MSP). However, the universal MSP is inherently aerobic due to a requirement of molecular oxygen for one of the key enzymes. Here, we report the presence of an exclusively anaerobic MSP that couples MTA metabolism to ethylene formation in the phototrophic bacteriaRhodospirillum rubrumandRhodopseudomonas palustris. In vivo metabolite analysis of gene deletion strains demonstrated that this anaerobic MSP functions via sequential action of MTA phosphorylase (MtnP), 5-(methylthio)ribose-1-phosphate isomerase (MtnA), and an annotated class II aldolase-like protein (Ald2) to form 2-(methylthio)acetaldehyde as an intermediate. 2-(Methylthio)acetaldehyde is reduced to 2-(methylthio)ethanol, which is further metabolized as a usable organic sulfur source, generating stoichiometric amounts of ethylene in the process. Ethylene induction experiments using 2-(methylthio)ethanol versus sulfate as sulfur sources further indicate anaerobic ethylene production from 2-(methylthio)ethanol requires protein synthesis and that this process is regulated. Finally, phylogenetic analysis reveals that the genes corresponding to these enzymes, and presumably the pathway, are widespread among anaerobic and facultatively anaerobic bacteria from soil and freshwater environments. These results not only establish the existence of a functional, exclusively anaerobic MSP, but they also suggest a possible route by which ethylene is produced by microbes in anoxic environments.

scholarly journals Effect of Anaerobiosis on Expression of Virulence Factors in Vibrio cholerae

2004 ◽  
Vol 72 (7) ◽  
pp. 3961-3967 ◽  
Author(s):  
H. H. Krishnan ◽  
Amalendu Ghosh ◽  
Kalidas Paul ◽  
Rukhsana Chowdhury
Keyword(s):  
Vibrio Cholerae ◽  
Virulence Factors ◽  
Regulatory Gene ◽  
Growth Conditions ◽  
Anaerobic Growth ◽  
Anaerobic Conditions ◽  
Regulatory Cascade ◽  
Significant Difference ◽  
In Cells

ABSTRACT In Vibrio cholerae, the transmembrane DNA binding proteins, ToxR and TcpP, activate expression of the regulatory gene toxT in response to specific environmental signals. The resulting enhanced level of ToxT leads to a coordinated increase in the production of a subset of virulence factors, including cholera toxin (CT) and toxin-coregulated pilus (TCP). The effect of anaerobiosis on expression of the V. cholerae virulence regulatory cascade was examined. The expression of the major regulatory genes, tcpP, toxR, and toxT, in anaerobically grown V. cholerae was comparable to that in cells grown under aerobic conditions, and no significant difference in the ToxT-dependent expression of tcpA was detected when aerobic and anaerobic cultures were compared. However, in spite of the presence of functional ToxT, ctxAB expression was drastically reduced, and practically no CT was detected in cells grown under anaerobic conditions. In a V. cholerae hns mutant, however, high levels of ctxAB expression occurred even under anaerobic conditions. Also, deletion of the H-NS binding site from the ctxAB promoter eliminated anaerobic repression of ctxAB expression. These results suggest that H-NS directly represses ctxAB expression under anaerobic growth conditions. It has been reported that in the first stage of infection of infant mice by V. cholerae, tcpA is expressed but ctxAB expression is shut off (S. H. Lee, D. L. Hava, M. K. Waldor, and A. Camilli, Cell 99: 625-634, 1999). This pattern is similar to the pattern in anaerobic cultures of V. cholerae. Under all other in vitro conditions, ctxAB and tcpA are known to be coordinately expressed.

scholarly journals The effect of trichloroethylene metabolites on the hepatic vitamin B12-dependent methionine salvage pathway and its relevance to increased excretion of formic acid in the rat

2020 ◽  
Vol 9 (2) ◽  
pp. 117-126
Author(s):  
Noreen Yaqoob ◽  
Katarzyna M Bloch ◽  
Andrew R Evans ◽  
Edward A Lock
Keyword(s):  
Formic Acid ◽  
Vitamin B12 ◽  
Prior Treatment ◽  
Methionine Synthase ◽  
Acid Excretion ◽  
Salvage Pathway ◽  
Methionine Salvage Pathway ◽  
F344 Rats ◽  
Male F344 Rats ◽  
Methionine Salvage

Abstract The industrial solvent trichloroethylene (TCE) and its two major metabolites trichloroethanol (TCE-OH) and trichloroacetic acid (TCA) cause formic aciduria in male F344 rats. Prior treatment of male F344 rats with 1-aminobenzotriazole a cytochrome P450 inhibitor, followed by TCE (16mk/kg, po), completely prevented formic aciduria, but had no effect on formic acid excretion produced by TCA (8 or 16 mg/kg, po), suggesting TCA may be the proximate metabolite producing this response. Dow and Green reported an increase in the concentration of 5-methyltetrahydrofolate (5-MTHF) in the plasma of rats treated with TCE-OH, suggesting a block in the cycling of 5-MTHF to tetrahydrofolate (THF). This pathway is under the control of the vitamin B12-dependent methionine salvage pathway. We therefore treated rats with three daily doses of methylcobalamin (CH3Cbl) or hydroxocobalamin (OHCbl), a cofactor for methionine synthase, or L-methionine, followed by TCE (16 mg/kg) to determine if they could alleviate the formic aciduria. These pretreatments only partially reduced the excretion of formic acid in the urine. Although prior treatment with S-adenosyl-L-methionine had no effect on formic acid excretion. Consistent with these findings, the activity of methionine synthase in the liver of TCE-treated rats was not inhibited. Transcriptomic analysis of the liver-identified nine differential expressed genes, of note, was downregulation of Lmbrd1 involved in the conversion of vitamin B12 into CH3Cbl, a cofactor for methionine synthase. Our findings indicate that the formic aciduria produced by TCE-OH and TCA may be the result of a block in the recycling of 5-MTHF to THF, the effect on the methionine salvage pathway being a secondary response following acute exposure.

scholarly journals Plausible Novel Ribose Metabolism Catalyzed by Enzymes of the Methionine Salvage Pathway inBacillus subtilis

2013 ◽  
Vol 77 (5) ◽  
pp. 1104-1107 ◽  
Author(s):  
Toshihiro NAKANO ◽  
Yohtaro SAITO ◽  
Akiho YOKOTA ◽  
Hiroki ASHIDA
Keyword(s):  
Salvage Pathway ◽  
Methionine Salvage Pathway ◽  
Methionine Salvage
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