Metabolic adaptation of Staphylococcus xylosus to meat substrates

National audienceStaphylococcus xylosus is commonly used as meat starter. S. xylosus genome analysis and its gene expression profiling in a meat model miming sausage batter, revealed that it can use diverse substrates as sources of carbon, nitrogen and iron. S. xylosus possesses the genetic potential for transport of 18 carbohydrates. In meat model, S. xylosus imports the added glucose by a PTS-independent system and then glucose is catabolized through the EMP and the PP pathways. The lactate, naturally present in meat, is simultaneously imported by a lactate permease and catabolized to pyruvate. Proteins, the main components of meat, are hydrolysed in peptides by endogenous proteinases during maturation. Peptides play a key role in bacterial nutrition. In S. xylosus, two gene clusters encoding peptide import and 20 genes encoding peptidases are present. In meat model, S. xylosus overexpresses genes encoding one peptide import and four peptidases. The free amino acids availability in the meat model leads to the down regulation of many genes involved the amino acid biosynthesis. In S. xylosus, arginine can be catabolised by arginase then by urease leading to NH3, a nitrogen source. Genes involved in glutamate transport and catabolism are overexpressed in meat model. In meat, nucleosides such as xanthine and uracil can be released from ATP hydrolysis. S. xylosus overexpresses thirteen genes involved in purine and pyrimidine catabolism that generate ribose, which can fuel the EMP pathway resulting in energy production. Meat is rich in hemic and non-hemic iron sources. S. xylosus has six systems to acquire iron. One of them is involved in the acquisition of iron from ferritin, an important substrate in meat. It can produce one siderophore to extract complexed iron. This analysis establishes that S. xylosus is well equipped with all functions necessary for its adaptation to the meat substrates