In Silico and In Vitro Characterization of Fecal Spore-Forming Bacteria with Probiotic Potential

The search for next-generation probiotics derived from the human gut microbiota has intensified due to their potential beneficial effects in modulating immunity and preventing diseases. Spore-forming bacteria are attractive probiotic candidates due to their functional traits and unique resilience, which offer high stability to commercial formulations. In this study, spore-forming bacteria isolated from human fecal samples were screened. Two strains, Bacillus spizizenii A1 and Priestia megaterium F6, were identified as non-hemolytic and not resistant to a panel of antibiotics relevant for spore formers. Both strains were characterized by using in silico and in vitro approaches, demonstrating relevant probiotic potential. The comparative analysis indicated B. spizizenii A1 as the most promising probiotic candidate due to the resistance of its spores to simulated gastric conditions and for its antioxidant, antimicrobial, and antibiofilm activities. Strain A1 combines a safety profile with functional probiotic traits and is therefore a strong candidate for further in vivo evaluation and future development as a next-generation probiotic.