Adaptation of Staphylococcus xylosus to Nutrients and Osmotic Stress in a Salted Meat Model

Abstract

Staphylococcus xylosus is commonly used as starter culture for meat fermentation. Its technological properties are mainly characterized in vitro, but the molecular mechanisms for its adaptation to meat remain unknown. A global transcriptomic approach was used to determine these mechanisms. S. xylosus modulated the expression of about 40–50% of the total genes during its growth and survival in the meat model. The expression of many genes involved in DNA machinery and cell division, but also in cell lysis, was up-regulated. Considering that the S. xylosus population remained almost stable between 24 and 72 h of incubation, our results suggest a balance between cell division and cell lysis in the meat model. The expression of many genes encoding enzymes involved in glucose and lactate catabolism was up-regulated and revealed that glucose and lactate were used simultaneously. S. xylosus seemed to adapt to anaerobic conditions as revealed by the overexpression of two regulatory systems and several genes encoding cofactors required for respiration. In parallel, genes encoding transport of peptides and peptidases that could furnish amino acids were up-regulated and thus concomitantly a lot of genes involved in amino acid synthesis were down-regulated. Several genes involved in glutamate homeostasis were up-regulated. Finally, S. xylosus responded to the osmotic stress generated by salt added to the meat model by overexpressing genes involved in transport and synthesis of osmoprotectants, and Na+ and H+ extrusion.

Nonconventional starter cultures of coagulase-negative staphylococci to produce animal-derived fermented foods, a SWOT analysis

“…; Vermassen et al . ). They possess mechanisms to cope with osmotic stress, including the accumulation of glycine betaine and via voltage‐gated channels and membrane pumps (Jeong et al .…”

“…Modification of the lipoteichoic and teichoic acids has been reported for a S. xylosus strain (Vermassen et al . ), whereas in S. epidermidis the ammonia‐ and ATP‐generating arginine deiminase (ADI) pathway relates to pH homeostasis (Lindgren et al . ; Sánchez Mainar et al .…”

The Use of Starter Cultures in Traditional Meat Products

“…xylosus C2a strain response to nitrosative [184] or nutrients and osmotic stress [185] has been investigated through DNA microarrays. S. xylosus has been shown to counteract nitrosative stress by developing several oxidative stress resistance mechanisms, such as modulation of the expression of genes involved in iron homeostasis, detoxifying enzymes, and DNA and protein repairs [184].…”

“…S. xylosus adapted its metabolism to the meat nutrients and anaerobic conditions by simultaneously using glucose and lactate as carbon sources and by using meat peptides and amino acids. S. xylosus responded to the osmotic stress caused by the addition of salt (NaCl) by overexpressing genes involved in transport and synthesis of osmoprotectants, particularly glycine betaine, and Na + and H + extrusion [185]. To overcome the damaging effects of oxidative and nitrosative stress, staphylococci have developed protection, detoxification, and repair mechanisms controlled by a network of regulators [186].…”

Acid stress response ofStaphylococcus xylosuselicits changes in the proteome and cellular membrane

“…Production of acetate has previously been shown for S. xylosus C2a under salt stress conditions (Vermassen et al . ). Acetate was also identified as one major metabolite, produced by S. xylosus TMW 2·1523.…”