INVESTIGADORES
BLANCATO Victor Sebastian
congresos y reuniones científicas
Título:
Regulation of the maeEP operon encoding the Malate utilization pathway in Enterococus faecalis
Autor/es:
MORTERA, P; ESPARIZ, M; REPIZO, GD; BLANCATO, VS; ALARCÓN, S; MAGNI, C
Lugar:
Tucumán - Argentina
Reunión:
Simposio; III Simposio Internacional de Bacterias Lácticas y Segundo encuentro Red BAL (Bacterias Lácticas) Argentina; 2009
Institución organizadora:
CERELA
Resumen:
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Malic enzymes are
disseminated from eukaryotes to prokaryotes. In Lactic Acid Bacteria (LAB)
three different types of malic enzymes were described. Only two genes coding
for this family of proteins were identified in Enterococcus faecalis chromosome.citM gene encoding an oxaloacetate decarboxylase associated to the
citrate metabolism and maeE (EF1207), which is linked to maeP
(EF1206, encoding a malate transporter). maePE operon was identified on
the E. faecalis V583 chromosome nearby to the maeS (EF1209) and maeR
(EF1210) genes, which encode the two-component system involved in the positive
activation of this operon. MaeS and MaeR present homology to citrate/malate
sensor kinases and response regulators, respectively, found in several microorganisms. In this
communication we analysed the regulation of the malate utilization in E.
faecalis and present evidence for the role of the mae locus.
Inactivation of the maePE operon or the sensor-regulator pair maeSR
caused complete loss of malate utilization in E. faecalis. Malate
utilization was analysed in E. faecalis by measuring the cytoplasmic
alkalinization of the cells, which is associated to its consumption. In order
to achieve that, we evaluated resting cells internal pH changes in enterococcal
cells grown in different media by using the fluorescent probe BCECF. No signal
was found in the absence of malate or when glucose (or other PTS sugars) were
added to the growth medium. Moreover, by a bioinformatic approach we identified
multiple cre sites (catabolite- responsive element)
in the intergenic region between the maePE and maeRS operons and
in the coding region of maeP and maeR. This strongly support the
PTS sugar hierarchical preference over malate above described. Finally, the
effect of pH in malate growing E. faecalis cells was evaluated.
Surprisingly, for acid pre-adapted bacteria the metabolism of malate was only
observed when the initial external pH of the growth medium was set above 4.5
units.