Growth and membrane fluidity of food-borne pathogen Listeria monocytogenes in the presence of weak acid preservatives and hydrochloric acid

Abstract

This study addresses a major issue in microbial food safety, the elucidation of correlations between acid stress and changes in membrane fluidity of the pathogen Listeria monocytogenes. In order to assess the possible role that membrane fluidity changes play in L. monocytogenes tolerance to antimicrobial acids (acetic, lactic, hydrochloric acid at low pH or benzoic acid at neutral pH), the growth of the bacterium and the gel-to-liquid crystalline transition temperature point (Tm) of cellular lipids of each adapted culture was measured and compared with unexposed cells. The Tm of extracted lipids was measured by differential scanning calorimetry. A trend of increasing Tm values but not of equal extent was observed upon acid tolerance for all samples and this increase is not directly proportional to each acid antibacterial action. The smallest increase in Tm value was observed in the presence of lactic acid, which presented the highest antibacterial action. In the presence of acids with high antibacterial action such as acetic, hydrochloric acid or low antibacterial action such as benzoic acid, increased Tm values were measured. The Tm changes of lipids were also correlated with our previous data about fatty acid changes to acid adaptation. The results imply that the fatty acid changes are not the sole adaptation mechanism for decreased membrane fluidity (increased Tm). Therefore, this study indicates the importance of conducting an in-depth structural study on how acids commonly used in food systems affect the composition of individual cellular membrane lipid molecules.

A comparative study of fatty acid profile and formation of biofilm inGeobacillus gargensisexposed to variable abiotic stress

“…Thermophiles, as extremophiles, are a good source of thermostable enzymes and have been exploited for pharmaceutical and many other industrial applications (Lin et al 2013;Oliveira et al 2013;Panda et al 2013;Park et al 2013). It is known that microbial adaptation is regulated by changes in cellular enzymes, membrane lipids, and their morphology, leading to a variation in functional dynamics and plasticity through redox and signaling systems of the organism (Contera et al 2010;Pocock et al 2011;Diakogiannis et al 2013).…”

CgMED3 Changes Membrane Sterol Composition To Help Candida glabrata Tolerate Low-pH Stress

“…Levels of long-chain fatty acids, UFAs, and ergosterol were restored or increased upon CgMED3AB overexpression, which might contribute to improve the membrane fluidity and integrity at pH 2.0. Note that squalene accumulated in the Cgmed3ABΔ strain at pH 2.0, inhibiting ergosterol synthesis and resulting in increased membrane permeability and significantly defective growth at low pH (48,49). Previous reports found that ergosterol was essential for maintaining membrane integrity and rigidity, both of which play a vital role against acid stress (42,50,51).…”

Identification of Novel Raft Marker Protein, FlotP in Bacillus anthracis

“…Cells adapt to the changes in environment through modulation of membrane properties and lipid composition resulting in altered membrane fluidity (Barrera et al, 2012 ). Cell membrane serves as a barrier for entry or exit of biomolecules across the cells and intrinsic (inherent) or acquired cellular changes due to alteration in structure may accompany the cells to modulate the pathogenicity and virulence of the organism (Diakogiannis et al, 2013 ). In order to determine the effects of endogenous sterol derivatives on membrane fluidity, the biophysical properties of the B. anthracis membrane was accessed in presence of ZA using fluorescence polarization and TRFS.…”