Glucose is transported and phosphorylated by the phosphoenolpyruvate

(PEP)-dependent phosphotransferase system (PTS) encoded by the ptsHI operon, and by one or more additional non-PTS permeases [18]. A unique L. sakei rbsUDKR (LSA0200-0203) gene cluster responsible for ribose catabolism has been described, which encodes a ribose transporter (RbsU), a D-ribose pyranase (RbsD), a ribokinase (RbsK) and the ribose FK506 price operon transcriptional regulator (RbsR) [16, 17, 21]. RbsR was shown to function as a local repressor on rbsUDK, and as a ptsI mutant increased transport and phosphorylation of ribose, the PTS was suggested to negatively control ribose utilization [16, 17, 21, 22]. Moreover, regulation by carbon catabolite repression (CCR) mediated by catabolite control protein A (CcpA) has been suggested, as a putative catabolite responsive element (cre) site, the binding site of CcpA, was found preceding rbsD [23–25]. It has been proposed that the species can be divided into two subspecies described as L. sakei subsp. sakei and L. sakei subsp. carnosus based on results from numerical analyses of total cell soluble protein content and randomly

amplified polymorphic DNA (RAPD) patterns [26–28]. L. sakei species display a large genomic diversity with more than 25% variation in genome size between isolates [29]. In a previous study, we investigated the diversity of ten L. sakei strains by phenotypic and Lonafarnib solubility dmso genotypic methods, and could report a wide phenotypic heterogeneity and the presence of two genetic groups which coincide with the subspecies [30]. The growth rates of the strains on glucose MLN0128 in vitro and ribose varied, indicating different abilities to metabolize the two sugars. Acidification properties in a meat model also showed differences between the strains, possibly reflecting that some are more suited as starter or protective cultures than others [30]. In this study, we used a proteomic approach to compare the same ten strains, which are isolates from meat and fermented meat

products, saké, and fermented fish [30]. We investigated their metabolic routes when growing in a defined medium [31] supplemented with glucose and ribose. Two-dimensional gel electrophoresis (2-DE) combined with mass spectrometry (MS) allowed identification of proteins, the expression of which varied depending on the carbon source used for growth. Previous studies used 2-DE to obtain an overview of global changes in the L. sakei proteome as function of uracil deprivation [32], anaerobiosis [33], adaption to cold temperatures and addition of NaCl [34], and high hydrostatic pressure [35]. However, studies on the global protein expression patterns during growth of this bacterium on various carbohydrates have not been reported, and importantly, studies to detect specific differences between strains of L. sakei are needed.