Abstract
Gram-negative bacteria are important food spoilage and pathogenic
bacteria. Their unique outer membrane (OM) provides them with a hydrophilic
surface structure, which makes them inherently resistant to many antimicrobial
agents, thus hindering their control. However, with permeabilizers, compounds
that disintegrate and weaken the OM, Gram-negative cells can be sensitized to
several external agents. Although antimicrobial activity of plant-derived
phenolic compounds has been widely reported, their mechanisms of action have
not yet been well demonstrated. The aim of our study was to elucidate the role
of selected colonic microbial metabolites of berry-derived phenolic compounds
in the weakening of the Gram-negative OM. The effect of the agents on the OM
permeability of Salmonella was studied utilizing a fluorescence probe uptake
assay, sensitization to hydrophobic antibiotics, and lipopolysaccharide (LPS)
release. Our results show that 3,4-dihydroxyphenylacetic acid,
3-hydroxyphenylacetic acid, 3-(3,4-dihydroxyphenyl)propionic acid (3,4-diHPP),
3-(4-hydroxyphenyl)propionic acid, 3-phenylpropionic acid, and
3-(3-hydroxyphenyl)propionic acid efficiently destabilized the OM of
Salmonella enterica subsp. enterica serovar Typhimurium and S. enterica subsp.
enterica serovar Infantis as indicated by an increase in the uptake of the
fluorescent probe 1-N-phenylnaphthylamine (NPN). The OM-destabilizing activity
of the compounds was partially abolished by MgCl2 addition, indicating that
part of their activity is based on removal of OM-stabilizing divalent cations.
Furthermore, 3,4-dihydroxyphenylacetic acid, 3-hydroxyphenylacetic acid, and
3,4-diHPP increased the susceptibility of S. enterica subsp. enterica serovar
Typhimurium strains for novobiocin. In addition, organic acids present in
berries, such as malic acid, sorbic acid, and benzoic acid, were shown to be
efficient permeabilizers of Salmonella as shown by an increase in the NPN
uptake assay and by LPS release.
Original language | English |
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Pages (from-to) | 3905 - 3912 |
Journal | Journal of Agricultural and Food Chemistry |
Volume | 55 |
Issue number | 10 |
DOIs | |
Publication status | Published - 2007 |
MoE publication type | A1 Journal article-refereed |
Keywords
- Permeability
- Gram-negative
- Salmonella
- phenolic compounds
- metabolites
- organic acid