Tyrosine decarboxylase activity of Enterococcus mundtii: new insights into phenotypic and genetic aspects. Issue 6 (14th September 2016)

• Record Type: Journal Article
• Authors: Gatto, Veronica; Tabanelli, Giulia; Montanari, Chiara; Prodomi, Valentina; Bargossi, Eleonora; Torriani, Sandra; Gardini, Fausto
• Is Part Of: Microbial biotechnology. Volume 9:Issue 6(2016:Nov.)
• Page Start: 801
• Page End: 813
• Publication Date: 2016-09-14
• Subjects: Microbial biotechnology -- Periodicals; Biotechnology; Microbiology; 660.62
• DOI: 10.1111/1751-7915.12402
• Languages: English
• ISSNs: 1751-7915

Abstract

Summary: Few information is available about the tyraminogenic potential of the species Enterococcus mundtii . In this study, two plant‐derived strains of E. mundtii were selected and investigated to better understand the phenotypic behaviour and the genetic mechanisms involved in tyramine accumulation. Both the strains accumulated tyramine from the beginning of exponential phase of growth, independently on the addition of tyrosine to the medium. The strains accumulated also 2‐phenylethylamine, although with lower efficiency and in greater extent when tyrosine was not added. Accordingly, the tyrosine decarboxylase ( tyrDC ) gene expression level increased during the exponential phase with tyrosine added, while it remained constant and high without precursor. The genetic organization as well as sequence identity levels of tyrDC and tyrosine permease ( tyrP ) genes indicated a correlation with those of phylogenetically closer enterococcal species, such as E. faecium, E. hirae and E. durans ; however, the gene Na+/H+ antiporter ( nhaC ) that usually follow tyrP is missing. In addition, BLAST analysis revealed the presence of additional genes encoding for decarboxylase and permease in the genome of several E. mundtii strains. It is speculated the occurrence of a duplication event and the acquisition of different specificity for these enzymes that deserves further investigations. Abstract : This study showed that the accumulation of tyramine and 2‐phenylethylamine by two plant‐derived strains of Enterococcus mundtii was linked to the growth phase and the precursor present in the growth medium. New insights into the genetic basis of the tyraminogenic potential of E. mundtii were revealed, analyzing the tyrosine decarboxylase gene expression, and the characteristics of the TDC operon region. Noteworthy, additional genes encoding for decarboxylase and permease were detected in the E. mundtii genome, suggesting the occurrence of a duplication event.