This is the first demonstration that tyramine can be produced from peptides containing tyrosine and therefore that free tyrosine is not the only precursor for tyramine production. We studied the expression of the tyrDC and tyrP genes to determine whether it was growth phase-dependent and/or nitrogen source dependent. tyrDC and tyrP expression The tyrDC and tyrP genes are co-transcribed in E. faecalis[13], L. brevis[15]
and Sporolactobacillus sp. [49]. A complete transcriptional analysis of the four genes of the operon was made in Lactobacillus SCH727965 price brevis IOEB 9809 [15]. Even if tyrDC tyrP transcripts were the most abundant, other polycistronic mRNA were described as: tyrS-tyrDC-tyrP-nhaC and tyrS-tyrDC, as well as tyrP-nhaC. So tyrDC and tyrP
can be transcribed from different manner. L. plantarum IR BL0076 tdc locus sequences was analysed using ARNold, an interface allowing localization of Rho-independent terminators in any bacterial sequence. (na.igmors.u-psud.fr/toolbox/arnold/). A predicted transcription terminator (−11.70 kcal/mol) localized at the 3′ end of TyrP coding region was identified. Erpin and RNAmotif programm predict the 5′ end position of this predicted transcription terminator at the nucleotide 3402 of the locus. To check the presence of a bicistronic tyrDC-tyrP in the IR BL0076 isolate, we used Reverse-Transcription-PCR experiments and primers tdcf and tyrPLpR located inside the tyrDC and tyrP genes respectively to study their expression Ku-0059436 solubility dmso in L. plantarum. An amplicon of 1,761 bp was obtained using cDNA obtained from RNA extracted from cultures on each medium selleck screening library 1 and medium 2 as the template. The length of the RT-PCR product indicates that tyrP is part of a polycistronic mRNA including tyrDC. As the four genes of the tyrosine decarboxylase operon
are part of a genetic island, as described for L. brevis[12], they have been disseminated through lactic acid bacteria via a horizontal gene transfer [49]. So it is expected that they are regulated in the same way in all enterococci and lactobacilli including L. plantarum. To study the tyrosine transport, expression tyrP and tyrDC was similarly analyzed by RT-qPCR. The expression of tyrP increased during growth in both medium 1 and medium 2, with a maximum at OD600nm = 1.8 (Figure 3a), and was significantly stronger during the stationary phase than during early exponential growth. The expression of tyrP paralleled the accumulation of tyramine in both media (Figure 1). This is coherent with what has been found for other bacteria producing biogenic amines, for example Streptococcus thermophilus[50], which produces histamine at the end of its growth, with an increase in the expression of the decarboxylase hdcA. The expression profile of tyrDC during growth was very similar to that of tyrP (Figure 3b). Both tyrDC and tyrP were significantly more strongly expressed during the early exponential growth phase in peptide medium (medium 2) than tyrosine medium (medium 1).