GENOMIC AND PROTEOMIC ANALYSES OF THE POTENTIAL MEAT STARTER STAPHYLOCOCCUS XYLOSUS DSM 20266T

Staphylococcus xylosus, is found among microbiota involved in dry cured sausages and used as starter due its ability to enhance flavour and reduce nitrite content. Few studies reported the adaptation mechanisms in response to the changes of salami en¬vironment throughout seasoning (acidification, oxygen starvation, oxidative stress). To this goal, we carried out a genomic characterization and proteomic analysis of S. xylosus DSM 20266T cultured under anaerobiosis and nitrite exposure. Such conditions occur during dry sausage seasoning and affect both its adaptability and its ability to com¬pete with the indigenous microbiota. The results highlighted the presence of genes involved in several stress responses (osmotic, oxidative, acid), proteases and lipases. Overall, 1,907 of 2,487 predicted coding genes were assigned to the clusters of orthol¬ogous groups (COG) classification. Among COG categories amino acid/carbohydrate transport and metabolism, and energy production and conversion were the largest. Nitrate/nitrite genes are organized in operons (narGHJI and nir operons) like in other Staphylococcus species. The putative functionality suggested by the genomic endow¬ment was confirmed by proteomic analysis. Indeed, under anaerobiosis DSM 20266T activated fermentative pathways (acetate, lactate fermentation) triggered proteolysis (M42, PepP) and increased the amount of proteins involved in the adaptation to stress¬es (AhpC/AhpF, CodY, CspA, Gsh). The presence of nitrite, allowed the strain to better adapt itself to oxygen starvation restoring some metabolic pathways (TCA cycle) un¬derlying the aerobic behaviour of the strain (Quintieri et al., 2018). Omics results confirmed the potential of DSM2066T as a meat starter to improve safety and organoleptic characteristic of salami.