Characterization of the gen locus involved in β‐1,6‐oligosaccharide utilization by Enterococcus faecalis

Abstract

Summary The bicistronic genBA operon (formerly named celBA) of the opportunistic pathogen Enterococcus faecalis, encodes a 6‐phospho‐β‐glucosidase (GenA) and a phosphotransferase system permease EIIC (GenB). It resembles the cel operon of Streptococcus pyogenes, which is implicated in the metabolism of cellobiose. However, genBA mutants grew normally on cellobiose, but not (genA) or only slowly (genB) on gentiobiose and amygdalin. The two glucosides were also found to be the main inducers of the operon, confirming that the encoded proteins are involved in the utilization of β‐1,6‐ rather than β‐1,4‐linked oligosaccharides. Expression of the genBA operon is regulated by the transcriptional activator GenR, which is encoded by the gene upstream from genB. Thermal shift analysis showed that it binds gentiobiose‐6′‐P with a Kd of 0.04 mM and with lower affinity also other phospho‐sugars. The GenR/gentiobiose‐6′‐P complex binds to the promoter region upstream from genB. The genBA promoter region contains a cre box and gel‐shift experiments demonstrated that the operon is under negative control of the global carbon catabolite regulator CcpA. We also show that the orphan EIIC (GenB) protein needs the EIIA component of the putative OG1RF_10750‐OG1RF_10755 operon situated elsewhere on the chromosome to form a functional PTS transporter.

Changes in Intestinal Microbiota and Predicted Metabolic Pathways During Colonic Fermentation of Mango (Mangifera indica L.)—Based Bar Indigestible Fraction

“…In the case of the Enterococcus genus belonging to the Bacilli class, we observed a lower presence in NegativeC but higher prevalence in the MangoB treatment. Although species such as Enterococcus faecalis have been reported as responsible of health problems in the human gut [54], other species such as Enterococcus faecium have been reported as beneficial probiotic microorganisms with the capacity of starting fermented cultures, high acidity and bile salt tolerance that could contribute to reducing serum cholesterol levels [55]. Recently, Wei et al [56] reported that some species of the Enterococcus and Eubacterium genera, have been the guiding forces in the biotransformation of C-C glycosidic bonds, which are present in flavone, xanthone and phenolic acid biomolecules.…”

Insights into 6S RNA in lactic acid bacteria (LAB)

“…We found strong evidence for cre sites upstream of the 6S RNA promoter in about a third of all LAB species, mainly in Enterococcaceae but also in Streptococcaceae and some Lactobacillus subgroups. For Streptococcaceae and Enterococcaceae , the presence and regulatory importance of these cre sites has been reported and studied previously [ 59 , 60 ]. On the basis of previous reports, our findings suggest that 6S RNA expression is under the negative control of CcpA in many LAB species.…”

Gene Duplications in the Genomes of Staphylococci and Enterococci

“…Three of them code for proteins playing a role in cell metabolism, including the duplication of the gene coding for of the subunit IIB of the lactose/cellobiose PTS system. Different components of the PTS system have also been reported as relevant for E. faecalis colonization (Paulsen et al, 2003), and they have deserved special attention in the last years (Ruiz-Cruz et al, 2015;Sauvageot et al, 2017;Grand et al, 2019).…”