Enterococcus

LeBlanc, Donald J.

doi:10.1007/0-387-30744-3_6

Cited by 16 publications

(24 citation statements)

References 288 publications

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“…On the other hand, in Lactobacillus casei, malate metabolism was reported to be repressed by the presence of glucose in the medium (23). London and Meyer (27) reported in their pioneering work on malate metabolism in E. faecalis that the malate transporter and malic enzyme are induced by this substrate and apparently repressed by glucose (25). More recently, we have shown that the E. faecalis mae locus encodes the malate degradative enzymes (5).…”

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confidence: 84%

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Fine-Tuned Transcriptional Regulation of Malate Operons in Enterococcus faecalis

Mortera

Espariz

Suárez

et al. 2012

Appl Environ Microbiol

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eIn 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.

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confidence: 84%

“…This bacterium is routinely isolated from different sources, such as food, vegetables, water, and soil (6,10,25). In recent years, this organism gained considerable notoriety because it was associated with the spread of resistance against numerous antibiotics in nosocomial infections (6,10,25).…”

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confidence: 99%

Fine-Tuned Transcriptional Regulation of Malate Operons in Enterococcus faecalis

Mortera

Espariz

Suárez

et al. 2012

Appl Environ Microbiol

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“…1). Given the homolactic behaviour of this micro-organism, when carbohydrates are present in the medium, pyruvate is reduced primarily to lactate by lactic dehydrogenase, which is activated by the glycolysis intermediate fructose 1,6-bisphosphate (Leblanc, 2006). In this manner, high levels of NADH produced during glycolysis are reoxidized and redox balance is achieved.…”

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confidence: 99%

Disruption of the alsSD operon of Enterococcus faecalis impairs growth on pyruvate at low pH

2011

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Diacetyl and acetoin are pyruvate-derived metabolites excreted by many micro-organisms, and are important in their physiology. Although generation of these four-carbon (C4) compounds in Enterococcus faecalis is a well-documented phenotype, little is known about the gene regulation of their biosynthetic pathway and the physiological role of the pathway in this bacterium. In this work, we identified the genes involved in C4 compound biosynthesis in Ent. faecalis and report their transcriptional analysis. These genes are part of the alsSD bicistronic operon, which encodes a-acetolactate synthase (AlsS) and a-acetolactate decarboxylase (AlsD). Our studies showed that alsSD operon transcription levels are maximal during the exponential phase of growth, decreasing thereafter. Furthermore, we found that this transcription is enhanced upon addition of pyruvate to the growth medium. In order to study the functional role of the alsSD operon, an isogenic alsSD mutant strain was constructed. This strain lost its capacity to generate C4 compounds, confirming the role of alsSD genes in this metabolic pathway. In contrast to the wild-type strain, the alsSD-deficient strain was unable to grow in LB medium supplemented with pyruvate at an initial pH of 4.5. This dramatic reduction in growth parameters for the mutant strain was simultaneously accompanied by the inability to alkalinize the internal and external medium under these conditions. In sum, these results suggest that the decarboxylation reactions related to the C4 biosynthetic pathway give enterococcal cells a competitive advantage during pyruvate metabolism at low pH.

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“…These infections have become a leading health care concern because of increasing antibiotic resistance mediated by mobile genetic elements (12). The ability of enterococci to colonize extraintestinal sites and cause infection involves both core and variable genetic traits (3, 15) and is not fully understood.Enterococci exhibit diversity in metabolic capabilities (such as the ability of Enterococcus faecalis, but not E. faecium, to respire [11]) and in clinically relevant phenotypes such as toxin production (12) and biofilm formation (13). Enterococci can also be motile or nonmotile, and pigmented or nonpigmented (4), yet little is known about the mechanism and significance of these traits.…”

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confidence: 99%

“…Enterococci exhibit diversity in metabolic capabilities (such as the ability of Enterococcus faecalis, but not E. faecium, to respire [11]) and in clinically relevant phenotypes such as toxin production (12) and biofilm formation (13). Enterococci can also be motile or nonmotile, and pigmented or nonpigmented (4), yet little is known about the mechanism and significance of these traits.…”

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High-Quality Draft Genome Sequences of 28 Enterococcus sp. Isolates

et al. 2010

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The enterococci are low-GC Gram-positive bacteria that have emerged as leading causes of hospital-acquired infection. They are also commensals of the gastrointestinal tract of healthy humans and most other animals with gastrointestinal flora and are important for food fermentations. Here we report the availability of draft genome sequences for 28 enterococcal strains of diverse origin, including the species Enterococcus faecalis, E. faecium, E. casseliflavus, and E. gallinarum.The enterococci are ecologically diverse, Gram-positive lactic acid bacteria that are found in the gastrointestinal consortia of humans, other mammals, reptiles, amphibians, birds, and insects and are utilized in production of fermented foods and probiotics (1, 2, 16). However, they have also emerged as leading causes of hospital-acquired infection at extraintestinal sites, including the heart, urinary tract, and surgical site wounds (9, 10). These infections have become a leading health care concern because of increasing antibiotic resistance mediated by mobile genetic elements (12). The ability of enterococci to colonize extraintestinal sites and cause infection involves both core and variable genetic traits (3, 15) and is not fully understood.Enterococci exhibit diversity in metabolic capabilities (such as the ability of Enterococcus faecalis, but not E. faecium, to respire [11]) and in clinically relevant phenotypes such as toxin production (12) and biofilm formation (13). Enterococci can also be motile or nonmotile, and pigmented or nonpigmented (4), yet little is known about the mechanism and significance of these traits. Insights into basic enterococcal physiology are limited by a paucity of genome data. The genome sequences of the vancomycin-resistant bloodstream isolate E. faecalis V583 (14), the human oral isolate E. faecalis OG1RF (3), and the commercial probiotic strain E. faecalis Symbioflor (6) have been determined, and a draft genome sequence for E. faecium DO has been available in GenBank since 2002. Here we announce the availability of draft genome sequences of 28 additional enterococcal strains, including 16 E. faecalis strains, 8 E. faecium strains, 3 E. casseliflavus strains, and 1 E. gallinarum strain. In addition to expanding the Enterococcus nucleotide sequence in GenBank by approximately an order of magnitude, this is the first report of genome sequencing of the motile E. gallinarum strain and the motile, pigmented E. casseliflavus strains.Most of the enterococcal strains utilized for our genome sequencing project are of clinical origin. The remaining strains are commensal isolates or were obtained from animals or insects. E. faecalis strains selected for this project were previously described in a study of E. faecalis strain diversity (12). To maximize the information yield from genome sequencing, we selected 16 E. faecalis strains that represent the deepest phylogenetic nodes in the E. faecalis multilocus sequence typing (MLST) dendrogram from the 106 strains previously examined (12). These strains include commens...

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Enterococcus

Cited by 16 publications

References 288 publications

Fine-Tuned Transcriptional Regulation of Malate Operons in Enterococcus faecalis

Fine-Tuned Transcriptional Regulation of Malate Operons in Enterococcus faecalis

Disruption of the alsSD operon of Enterococcus faecalis impairs growth on pyruvate at low pH

High-Quality Draft Genome Sequences of 28 Enterococcus sp. Isolates

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