Newly identified SpoVAF/FigP complex: the role in Bacillus subtilis spore germination at moderate high pressure and influencing factors
The SpoVAF/FigP complex, a newly identified ion channel, has been shown to amplify the response of germinant receptors (GRs) to nutrient germinants. However, its contribution to high-pressure-induced germination remains unexplored. In this study, we discovered that the 5AF/FigP complex plays an important role in the GRs-dependent germination of Bacillus subtilis spores under moderate high pressure (MHP) by facilitating the release of ions such as potassium (K+), a mechanism in parallel with its role in nutrient-induced germination. Despite its predicted function as an ion channel, the 5AF/FigP complex fails to respond to MHP in the absence of GerA-type GRs. We quantitatively examined the factors that influence the 5AF/FigP complexs function in MHP-induced germination using modeling and fitting techniques. Our results indicate that the complexs amplification effect is both enhanced and accelerated as pressure levels increase from 50 to 200 MPa. However, raising the MHP treatment temperature from 22 to 30{degrees}C only speeds up the complexs function without enhancing its effectiveness. Moreover, extreme conditions of higher pressure (300 MPa) and temperature (34-37{degrees}C) can diminish the complexs functionality. Additionally, the amplification effect is weakened in spores produced at both elevated and reduced sporulation temperatures. Taken together, our findings highlight the essential role of the 5AF/FigP complex in boosting the efficiency of MHP-induced germination. This revelation has enriched our understanding of the intricate mechanisms underlying GRs-dependent germination in Bacillus spores, offering valuable insights that can be utilized to refine the germination-inactivation strategies within the food industry.