Document Detail

Fine-tuned transcriptional regulation of malate operons in Enterococcus faecalis.
MedLine Citation:
PMID:  22247139     Owner:  NLM     Status:  MEDLINE    
In Enterococcus faecalis, the mae locus is constituted by two putative divergent operons, maePE and maeKR. The first operon encodes a putative H(+)/malate symporter (MaeP) and a malic enzyme (MaeE) previously shown to be essential for malate utilization in this bacterium. The maeKR operon encodes two putative proteins with significant similarity to two-component systems involved in sensing malate and activating its assimilation in bacteria. Our transcriptional and genetic assays showed that maePE and maeKR are induced in response to malate by the response regulator MaeR. In addition, we observed that both operons were partially repressed in the presence of glucose. Accordingly, the cometabolism of this sugar and malate was detected. The binding of the complex formed by CcpA and its corepressor P-Ser-HPr to a cre site located in the mae region was demonstrated in vitro and explains the carbon catabolite repression (CCR) observed for the maePE operon. However, our results also provide evidence for a CcpA-independent CCR mechanism regulating the expression of both operons. Finally, a biomass increment of 40 or 75% was observed compared to the biomass of cells grown only on glucose or malate, respectively. Cells cometabolizing both carbon sources exhibit a higher rate of glucose consumption and a lower rate of malate utilization. The growth improvement achieved by E. faecalis during glucose-malate cometabolism might explain why this microorganism employs different regulatory systems to tightly control the assimilation of both carbon sources.
Pablo Mortera; Martín Espariz; Cristian Suárez; Guillermo Repizo; Josef Deutscher; Sergio Alarcón; Víctor Blancato; Christian Magni
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2012-01-13
Journal Detail:
Title:  Applied and environmental microbiology     Volume:  78     ISSN:  1098-5336     ISO Abbreviation:  Appl. Environ. Microbiol.     Publication Date:  2012 Mar 
Date Detail:
Created Date:  2012-02-23     Completed Date:  2012-05-16     Revised Date:  2013-06-26    
Medline Journal Info:
Nlm Unique ID:  7605801     Medline TA:  Appl Environ Microbiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1936-45     Citation Subset:  IM    
Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET) and Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas (FCByF), Universidad Nacional de Rosario (UNR), Suipacha, Rosario, Argentina.
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MeSH Terms
Bacterial Proteins / genetics,  metabolism
Enterococcus faecalis / genetics*,  growth & development,  metabolism*
Gene Expression Regulation, Bacterial*
Glucose / metabolism
Malates / metabolism*
Transcription, Genetic*
Reg. No./Substance:
0/Bacterial Proteins; 0/Malates; 50-99-7/Glucose; 6915-15-7/malic acid

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