Effect of bile salts stress on protein synthesis of Lactobacillus casei Zhang revealed by 2-dimensional gel electrophoresis

Abstract

Lactobacillus casei Zhang, isolated from koumiss in Inner Mongolia of China, is known from previous findings to be tolerant to bile salts. Bile salts secreted by mammals act as a natural antibacterial barrier and may serve as a component of innate immunity, as they have limited antagonistic effect against resident microflora. In this work, we compared the growth and protein expression patterns of L. casei Zhang with and without bile salts. Twenty-six proteins were found to be differentially expressed using 2-dimensional gel electrophoresis. Peptide mass fingerprinting was used to identify these proteins. Further verification by using real-time, quantitative reverse transcription-PCR and bioinformatics analysis showed that the implicated pathways are involved with a complex physiological response under bile salts stress, particularly including cell protection (DnaK and GroEL), modifications in cell membranes (NagA, GalU, and PyrD), and key components of central metabolism (PFK, PGM, CysK, LuxS, PepC, and EF-Tu). These results provide insight on the protein expression pattern of L. casei under bile salts stress and offer a new perspective for the molecular mechanisms involved in stress tolerance and adaptation of bacteria.

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

“…However, at the transcriptional level, no significant differences were observed in any of the genes encoding the subunits of the ATPase. Wu et al (2010) did not observe this effect, whereas Hamon et al (2012) observed modest increments in the abundance of subunit d in some L. casei strains. However, it cannot be ascertained whether this is due to different experimental designs or methodologies.…”

“…Activation of stress proteins in response to bile has been observed in L. casei Zhang (Wu et al, 2010) and its close relative L. rhamnosus GG (Koskenniemi et al, 2011). In contrast, a clear activation of stress proteins was not observed by Hamon et al (2012).…”

“…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.…”

“…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).…”