Bile salts and cholesterol induce changes in the lipid cell membrane of Lactobacillus reuteri

Abstract

Aims: The objective of this study was to evaluate the effect of bile salts and cholesterol in the lipid profile of Lactobacillus reuteri CRL 1098 and to determine the relationship existing between these changes: the in vitro removal of cholesterol and the tolerance of the cells to acid and cold stress. Methods and Results: Lactobacillus reuteri CRL 1098 was grown in the following media: MRS (deMan Rogosa Sharpe; M C , control medium), M B (M C with bile salts), M CH (M C with sterile cholesterol) and M BCH (M C with bile salts and cholesterol). Fatty acids were determined by analytical gas-liquid chromatography, and phospholipids and glycolipids by colorimetric techniques. The cells from different culture media were subjected to cold and acid stress. The M B cultures displayed a decrease in phospholipids and a low ratio of saturated : unsaturated fatty acids. The presence of the unusual C18 : 0,10-OH and C18 : 0,10-oxo fatty acids was the prominent characteristic of the bile salts growing cells. The relative increase in glycolipids and the changes in the fatty acids profiles of the M B cells would be responsible for the cholesterol remotion. The changes induced by bile salts in the lipid profile did not improve the tolerance of L. reuteri CRL 1098 to freezing and acid stress. Conclusions: The changes in lipid profiles reported in this study would play a key role in the response of Lactobacilli to environmental stress. Significance and Impact of the Study: This work provides useful information about the effect of bile salts on the cell membrane of L. reuteri, a probiotic enterolactobacillus. The steady-state response of the cells subjected to bile stress seems to be the appropriate model for evaluating the bacterial behaviour in detergent-containing gastrointestinal tracts, where the bile salts stress would presumably be continuous.

Proteomic and transcriptomic analysis of the response to bile stress of Lactobacillus casei BL23

“…Our results therefore suggest that L. casei and other lactobacilli lower their rates of fatty acid synthesis in response to bile stress. A number of studies have shown that exposure to bile leads to significant changes in the fatty acid composition of the membrane of different bacteria (Ruiz et al, 2007;Taranto et al, 2003Taranto et al, , 2006. However, the data available are not sufficient to determine whether L. casei also changes the membrane fatty acid composition in response to bile stress.…”

Distribution and Stress Resistance of Resident Lactobacilli in Mouse Intestinal Tract

“…Several pathways, such as deconjugation by bile salt hydrolase and the multidrug resistance transporter system are thought to be involved in bile salt resistance in lactic acid bacteria (26). Recently, Taranto et al reported that bile salts and cholesterol induce changes in the lipid profile of the cell membrane and play key roles in the response of L. reuteri to environmental stress (24). It is worth investigating whether the reduced bile resistance of L. reuteri is restored by culturing with bile salts.…”

Hypocholesterolaemic Effects of Probiotics

“…They also observed a difference in the fatty acid distribution pattern for Lactococcus grown with or without cholesterol. Later Taranto et al [74] reported modifications in the lipid profile of L. reuteri grown with cholesterol, while Liong and Shah [75] also observed alteration in the fatty acid profiles of lactobacilli grown in the presence of cholesterol in the growth medium. Pigeon et al [29] suggested that cholesterol removal by L. delbrueckii and Streptococcus thermophilus strains were due to binding of free bile acids to their cell membranes through exocellular polysaccharide (EPS).…”