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Appl. Environ. Microbiol., Sep 1997, 3628-3636, Vol 63, No. 9
MH Bennik, A Verheul, T Abee, G Naaktgeboren-Stoffels, LG Gorris and EJ Smid
The natural variation in the susceptibilities of gram-positive bacteria
towards the bacteriocins nisin and pediocin PA-1 is considerable. This
study addresses the factors associated with this variability for closely
related lactic acid bacteria. We compared two sets of nonbacteriocinogenic
strains for which the MICs of nisin and pediocin PA-1 differed 100- to
1,000-fold: Lactobacillus sake DSM20017 and L. sake DSM20497 and
Pediococcus dextrinicus and Pediococcus pentosaccus. Strikingly, the
bacteriocin-sensitive and -insensitive strains showed a similar
concentration-dependent dissipation of their membrane potential (delta psi)
after exposure to these bacteriocins. The bacteriocin- induced dissipation
of delta psi below the MICs for the insensitive strains did not coincide
with a reduction of intracellular ATP pools and glycolytic rates. This was
not observed with the sensitive strains. Analysis of membrane lipid
properties revealed minor differences in the phospho- and glycolipid
compositions of both sets of strains. The interactions of the bacteriocins
with strain-specific lipids were not significantly different in a lipid
monolayer assay. Further lipid analysis revealed higher in situ membrane
fluidity of the bacteriocin- sensitive Pediococcus strain compared with
that for the insensitive strain, but the opposite was found for the L. sake
strains. Our results provide evidence that the association of bacteriocins
with the cell membrane and their subsequent insertion take place in a
similar way for cells that have a high or a low natural tolerance towards
bacteriocins. For insensitive strains, overall membrane constitution rather
than mere membrane fluidity may preclude the formation of pores with
sufficient diameters and lifetimes to ultimately cause cell death.
Copyright © 1997, American Society for Microbiology
Interactions of nisin and pediocin PA-1 with closely related lactic acid bacteria that manifest over 100-fold differences in bacteriocin sensitivity
Agrotechnological Research Institute (ATO-DLO), Wageningen, The Netherlands. bennik@mbcrr.harvard.edu
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