Investigation of Biomarkers of Bile Tolerance in Lactobacillus casei Using Comparative Proteomics

Abstract

The identification of cell determinants involved in probiotic features is a challenge in current probiotic research. In this work, markers of bile tolerance in Lactobacillus casei were investigated using comparative proteomics. Six L. casei strains were classified on the basis of their ability to grow in the presence of bile salts in vitro. Constitutive differences between whole cell proteomes of the most tolerant strain (L. casei Rosell-215), the most sensitive one (L. casei ATCC 334), and a moderately tolerant strain (L. casei DN-114 001) were investigated. The ascertained subproteome was further studied for the six strains in both standard and bile stressing conditions. Focus was on proteins whose expression levels were correlated with observed levels of bile tolerance in vitro, particularly those previously reported to be involved in the bile tolerance process of lactobacilli. Analysis revealed that 12 proteins involved in membrane modification (NagA, NagB, and RmlC), cell protection and detoxification (ClpL and OpuA), as well as central metabolism (Eno, GndA, Pgm, Pta, Pyk, Rp1l, and ThRS) were likely to be key determinants of bile tolerance in L. casei and may serve as potential biomarkers for phenotyping or screening purposes. The approach used enabled the correlation of expression levels of particular proteins with a specific probiotic trait.

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

“…Furthermore, those studies focused on the differences observed between cells grown in the presence or absence of bile, whereas our experimental design aimed to determine the response of L. casei BL23 to a bile challenge. Therefore, differences in the results obtained are to be expected, especially considering the differences between strains observed by Hamon et al (2012). The same argument applies to studies conducted with other species.…”

“…Our results show that the bile response is a complex process that involves significant physiological changes in this bacterium. Earlier studies on the response of L. casei strains to bile made use only of a proteomic approach (Hamon et al, 2012;Wu et al, 2010). Furthermore, those studies focused on the differences observed between cells grown in the presence or absence of bile, whereas our experimental design aimed to determine the response of L. casei BL23 to a bile challenge.…”

“…A number of studies have dealt with the response of lactobacilli to bile exposure (Bron et al, 2004;Burns et al, 2010;Hamon et al, 2011Hamon et al, , 2012Koskenniemi et al, 2011;Lee et al, 2008;Pfeiler et al, 2007;Pfeiler & Klaenhammer, 2009;Whitehead et al, 2008;Wu et al, 2010). These studies have spanned several species of lactobacilli and have detected considerable variability in the response, although it must be kept in mind that experimental conditions varied from one study to another.…”

“…These studies have spanned several species of lactobacilli and have detected considerable variability in the response, although it must be kept in mind that experimental conditions varied from one study to another. Furthermore, a comparative study conducted with six L. casei strains has shown significant differences between strains (Hamon et al, 2012). Therefore, extrapolation of results from other strains is of limited use in understanding the bile response of a certain strain.…”

“…Earlier studies on the bile response of L. casei strains have not included strain BL23 and used exclusively a proteomic approach (Hamon et al, 2012;Wu et al, 2010). The study of strain BL23 is of special interest, since it has been used as a model strain for physiological studies (Monedero et al, 2007) and for its probiotic properties (Bäuerl et al, 2010).…”