Genomic insights and evaluation of Bacillus spizizenii Endophyte from Solanum elaeagnifolium Cav against multidrug-resistant pathogens

Secondary metabolites are promising alternatives due to their diverse biological activities, including antimicrobial and antiviral effects. Wild plants, particularly Solanum elaeagnifolium Cav (Silverleaf Nightshade), harbor endophytic microorganisms that represent an untapped source of such bioactive compounds. In the present study, four bacterial endophytes were isolated from the leaves of Solanum elaeagnifolium Cav (LS1, LS2, LS3, and LS4), and their extracts (S1, S2, S3, and S4) were prepared. Extract S4 showed both qualitative and quantitative inhibitory activity against a broad range of standard and multidrug-resistant (MDR) pathogens, including Gram-positive and Gram-negative pathogens. Moreover, it showed significant antiviral effects against Adenovirus serotype 7 and Herpes Simplex Viruses 1 and 2. The endophytic bacterium LS4 was identified microscopically, biochemically, and via whole-genome sequencing as Bacillus spizizenii CCASU-2025-89. Cytotoxic assessment of S4 revealed a CC 50 of 80.71 μg/mL and a safe concentration of 6.23 μg/mL. Whole-genome analysis revealed conserved biosynthetic gene clusters of antimicrobial peptides including bacilysin, subtilin, mycosubtilin, bacillaene, bacillibactin, subtilosin A, and Pulcherriminic acid. Overall, this study demonstrates that endophytic bacterium Bacillus spizizenii from Solanum elaeagnifolium represents a promising resource for developing new antimicrobial and antiviral therapeutics.