THESE Maryse Bonnin Jusserand - Université de Bourgogne

Résultats
strains, do not carry the genes of the tdc pathway. However a partial sequence of 333 bp, from
the tdc gene of a L. plantarum strain isolated from wine, was cloned and sequenced by Arena
et al (2007). But nothing is known about the genetic organization of these genes in this LAB.
tyrP expression
In order to study the transport of the L-tyrosine either with free tyrosine or in the presence of
peptides, tyrP expression was measured by RT-qPCR. In both cases, the influence of the
growth phase was evaluated. The expression of tyrP was observed at low levels until the
stationary growth phase was reached. Then there was an increase of about three times of the
expression in both culture conditions, with a maximum at OD600nm = 1.8 (Fig 2). We observed
that the expression of tyrP is in accordance with the accumulation of tyramine in both media.
It is actually the case for other bacteria producing biogenic amines like Streptococcus
thermophilus (Calles-Enriquez et al, 2010), which produces histamine at the end of its
growth, with an increase in the expression of the decarboxylase hdcA. But to our knowledge,
the expression of a biogenic amines transporter has never been studied neither correlated to
BA production in LAB isolated from wine. Therefore, this experiment clearly showed the link
between the increase in tyramine production and tyrP expression in L. plantarum IR BL0076,
and that this expression is induced at the stationary growth phase whatever the source of
nitrogen studied.
Figure 2: Relative expression of the tyramine transporter tyrP of L. plantarum IR BL0076
grown with free tyrosine or tyrosine containing peptides. Expression was measured at three
different OD600nm.
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