FY participated in the CLSM analysis. JL participated in the RNA extractions. YW participated in the design of the study, performed the statistical analysis Epigenetics Compound Library cost and edited the manuscript. AF, PF, and JS performed and analyzed microarray experiments. DQ participated in the study design and coordination and helped to draft and edit the manuscript. All authors read and approved the final manuscript.”
“Background The Lactobacillus sakei species belongs to the lactic acid bacteria (LAB), a group of Gram-positive organisms with a low G+C content which produce lactic acid as the main end product of carbohydrate fermentation. This trait has, throughout history, made LAB suitable for

production of food. Acidification suppresses the growth and survival of undesirable spoilage bacteria and human pathogens. L. sakei is naturally associated with the meat and fish environment, and is important in the meat industry where it is used as starter culture

for sausage fermentation [1, 2]. The bacterium shows great potential as a protective culture and biopreservative to extend storage life and ensure microbial safety of meat and fish products [3–6]. The genome screening assay sequence of L. sakei strain 23K has revealed a metabolic repertoire which reflects the bacterium’s adaption to meat products and the ability to flexibly use meat components [7]. Only a few carbohydrates are available in meat and fish, and L. sakei can utilize mainly glucose and ribose for growth, a utilization biased in favour of glucose [7–9]. The species has been observed as a transient member of the human gastrointestinal tract (GIT) [10, 11], and ribose may be described as a commonly accessible carbon source in the gut environment [12]. Transit through the GIT of axenic mice gave mutant strains

which grow faster on ribose compared with glucose [13]. Glucose is primarily transported and phosphorylated by the phosphoenolpyruvate (PEP)-dependent carbohydrate phosphotransferase system (PTS). A phosphorylation cascade is driven from PEP through the general components enzyme I (EI) and the histidine protein (HPr), then via the mannose-specific enzyme II complex (EIIman) to find more the incoming sugar. Moreover, glucose is fermented through glycolysis leading to lactate [7, 8, 14]. Ribose transport and subsequent phosphorylation are induced by the ribose itself and mediated by a ribose transporter (RbsU), a D-ribose pyranase (RbsD), and a ribokinase (RbsK) encoded by rbsUDK, respectively. These genes form an operon with rbsR which encodes the local repressor RbsR [15, 16]. The phosphoketolase pathway (PKP) is used for pentose fermentation ending with lactate and other end products [8, 17]. L. sakei also has the ability to catabolize arginine, which is abundant in meat, and to catabolize the nucleosides inosine and adenine, a property which is uncommon among lactobacilli [7, 18].