Abstract
BackgroundEnterococcus mundtii is a yellow-pigmented microorganism rarely found in human infections. The draft genome sequence of E. mundtii was recently announced. Its genome encodes at least 2,589 genes and 57 RNAs, and 4 putative genomic islands have been detected. The objective of this study was to compare the genetic content of E. mundtii with respect to other enterococcal species and, more specifically, to identify genes coding for putative virulence traits present in enterococcal opportunistic pathogens.ResultsAn in-depth mining of the annotated genome was performed in order to uncover the unique properties of this microorganism, which allowed us to detect a gene encoding the antimicrobial peptide mundticin among other relevant features. Moreover, in this study a comparative genomic analysis against commensal and pathogenic enterococcal species, for which genomic sequences have been released, was conducted for the first time. Furthermore, our study reveals significant similarities in gene content between this environmental isolate and the selected enterococci strains (sharing an “enterococcal gene core” of 805 CDS), which contributes to understand the persistence of this genus in different niches and also improves our knowledge about the genetics of this diverse group of microorganisms that includes environmental, commensal and opportunistic pathogens.ConclusionAlthough E. mundtii CRL1656 is phylogenetically closer to E. faecium, frequently responsible of nosocomial infections, this strain does not encode the most relevant relevant virulence factors found in the enterococcal clinical isolates and bioinformatic predictions indicate that it possesses the lowest number of putative pathogenic genes among the most representative enterococcal species. Accordingly, infection assays using the Galleria mellonella model confirmed its low virulence.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-489) contains supplementary material, which is available to authorized users.
Highlights
Enterococcus mundtii is a yellow-pigmented microorganism rarely found in human infections
E. mundtii CRL1656 phylogeny was analyzed with a tree generated from the concatenated sequences of 805 core proteins from nine enterococci and the outgroup L. lactis SK11 (Figure 2A)
We observed that E. mundtii is more related to E. faecium, which is frequently associated with nosocomial infections
Summary
Enterococcus mundtii is a yellow-pigmented microorganism rarely found in human infections. Enterococci are nutritionally fastidious microorganisms, which are associated with a large variety of human activities. Enterococcus mundtii was described as a non-motile, yellow-pigmented enterococcus typically isolated from plant material, soil, cow teats and milker’s hands [4,5] and infrequently associated to human infection [6]. We have recently announced the draft genome sequence of E. mundtii strain CRL1656 [7]. This strain was isolated from stripping milk of an Argentinean cow and, given its bacteriocinogenic capacity, it has been proposed as a probiotic microorganism to prevent mastitis in these mammals [8]
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