Increased survival of <i>Parageobacillus thermoglucosidasius</i>, a thermophilic soil bacterium, in a rhizosphere milieu

Previous studies have highlighted the widespread presence of thermophilic bacterial genera in upper soil layers, their role in biogeochemical cycles, and their potential application in soil fertilization. However, the mechanisms by which these thermophiles maintain cell viability in temperate soils remain largely unknown. The isolation of thermophilic bacteria from rhizospheric soils has been reported, hence it may be hypothesized that the rhizosphere environment plays a role in their survival. In this study, we developed a hydroponic system to introduce the thermophilic bacterium Parageobacillus thermoglucosidasius into the rhizosphere of tomato plants, demonstrating that this environment increased bacterial survival rates at 20°C-25°C by over 23-fold. The rhizosphere exudates contributed to this increase, as their addition boosted bacterial survival in pure cultures at 25°C by up to twofold. We propose that the rhizosphere and its exudates, characterized through targeted metabolomics, support the persistence of thermophilic bacteria in temperate soils during colder periods, ensuring viable cells that contribute to soil fertilization during warmer seasons.