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Scientific
Publications - Work Done by Microbiology Reader L. Nilsson, T.B. Hansen, P. Garrido, C. Buchrieser, P. Glaser, S. Knøchel, L.
Gram and A. Gravesen,
ABSTRACT Aims: This study elucidates the mechanisms by which a nonbacteriocinogenic Carnobacterium piscicola inhibits growth of Listeria monocytogenes. Methods and Results: Listeria monocytogenes
was exposed to live cultures of a bacteriocin-negative variant of C.
piscicola A9b in co-culture, in a diffusion chamber system, and to a
cell-free supernatant. Suppression of maximum cell density (0 Conclusions: A nonbacteriocinogenic C. piscicola reduced growth of L. monocytogenes partly by glucose depletion. Significance and Impact of the Study: Understanding the mechanism of microbial interaction enhances prediction of growth in mixed communities as well as use of bioprotective principles for food preservation.
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3·5 log
units) of L. monocytogenes was proportional to initial levels of C.
pisciola (103
1).
Cell-to-cell contact was not required to cause inhibition. The cell-free C.
piscicola supernatant caused a decrease in L. monocytogenes maximum
cell density, which was abolished by glucose addition but not by amino acid,
vitamin or mineral addition. The fermentate also gave rise to a longer lag phase
and a reduction in growth rate. These effects were independent of glucose and
may have been caused by acetate production by C. piscicola. 2D
gel-electrophoretic patterns of L. monocytogenes exposed to C.
piscicola or to L. monocytogenes fermentate did not differ. Treatment
with C. piscicola fermentate resulted in down-regulation (twofold) of
genes involved in purine- or pyrimidine metabolism, and up-regulation (twofold)
of genes from the regulon for vitamin B12 biosynthesis and
propanediol and ethanolamine utilization.