Vitamin K2 production by Staphylococcus shinii IMDO-S216 is affected by high oxygen exposure

Abstract

Abstract Microbial production of vitamin K2 (MK-n), particularly MK-7, is of interest because of its health-associated benefits. While oxygen favors vitamin K2 yields in lactic acid bacteria and in the genus Bacillus, less is known about its effects on food-grade staphylococci. Staphylococcus shinii IMDO-S216, a strain belonging to a recently described species genetically similar to Staphylococcus xylosus and isolated from fermented meat, was grown under high oxygen supply in brain heart infusion at pH 7.0 and 30 °C for 48 h. Its MK-7 production dynamics were followed alongside transcriptomic analysis of genes related to vitamin K2 biosynthesis, electron transport chain (owing to the participation of vitamin K2 in electron transfer), and antioxidant defenses. Over time, intracellular MK-7 concentrations decreased, while concentrations in the supernatant remained stable. This decrease was not accompanied by differential expression of MK-n biosynthetic genes, suggesting that oxidative degradation rather than reduced biosynthesis was responsible. This hypothesis was further supported by the increased expression of oxidative stress–associated genes (cydAB, crtO, crtP, crtQ, and crtM) and ROS-detoxifying genes (sodA, katB, katC, bsaA, and ohrA). Furthermore, the qorA gene, which is linked to semiquinone radical and superoxide anion formation from quinones, was hypothesized to contribute to the initial stages of menaquinones degradation. Finally, increasing relative abundance of MK-6/MK-7 ratio over time may reflect an adaptive survival strategy in S. shinii IMDO-S216. Key points High aeration disfavors MK-7 production by Staphylococcus shinii IMDO-S216.qorA expression suggests a role in initiating menaquinone degradation via redox-mediated mechanisms.MK-6/MK-7 ratios increase over time, potentially reflecting an adaptive survival strategy.