Abstract
The effect of lactic acid on the outer membrane permeability ofEscherichia coli O157:H7, Pseudomonas aeruginosa, and Salmonella enterica
serovar Typhimurium was studied utilizing a fluorescent-probe uptake
assay and sensitization to bacteriolysis. For control purposes, similar
assays were performed with EDTA (a permeabilizer acting by chelation)
and with hydrochloric acid, the latter at pH values corresponding to
those yielded by lactic acid, and also in the presence of KCN. Already 5
mM (pH 4.0) lactic acid caused prominent permeabilization in each
species, the effect in the fluorescence assay being stronger than that
of EDTA or HCl. Similar results were obtained in the presence of KCN,
except for P. aeruginosa, for which an increase in the effect
of HCl was observed in the presence of KCN. The permeabilization by
lactic and hydrochloric acid was partly abolished by MgCl2. Lactic acid sensitized E. coli
and serovar Typhimurium to the lytic action of sodium dodecyl sulfate
(SDS) more efficiently than did HCl, whereas both acids sensitized P. aeruginosa to SDS and to Triton X-100. P. aeruginosawas
effectively sensitized to lysozyme by lactic acid and by HCl.
Considerable proportions of lipopolysaccharide were liberated from
serovar Typhimurium by these acids; analysis of liberated material by
electrophoresis and by fatty acid analysis showed that lactic acid was
more active than EDTA or HCl in liberating lipopolysaccharide from the
outer membrane. Thus, lactic acid, in addition to its antimicrobial
property due to the lowering of the pH, also functions as a
permeabilizer of the gram-negative bacterial outer membrane and may act
as a potentiator of the effects of other antimicrobial substances.
Original language | English |
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Pages (from-to) | 2001 - 2005 |
Number of pages | 5 |
Journal | Applied and Environmental Microbiology |
Volume | 66 |
Issue number | 5 |
DOIs | |
Publication status | Published - 2000 |
MoE publication type | A1 Journal article-refereed |