Various Bacillus and Paenibacillus Spp. Isolated From Soil Produce Compounds With Potent Antimicrobial Activity Against Clinically Relevant Pathogens.

The increasing prevalence of antibiotic resistance among clinically significant pathogens necessitates the discovery of novel antimicrobial agents. This study investigated 29 Bacillus and Paenibacillus isolates from the soil for antimicrobial activity against multidrug-resistant clinical pathogens, including methicillin-resistant Staphylococcus aureus (MRSA) and carbapenem-resistant Enterobacterales (CRE). In both agar- and broth-based antimicrobial assays, Paenibacillus profundus strains 7.5 and M4.5 exhibited potent broad-spectrum activity, including significant inhibition of many CREs. Species identification was performed through 16S rRNA sequencing, and genome mining of three producer strains using antiSMASH revealed biosynthetic gene clusters associated with a variety of nonribosomal peptide synthetases (NRPSs), polyketide synthases (PKSs), and ribosomally synthesized and post-translationally modified peptides (RiPPs). While many of these clusters were not associated with known antimicrobial compounds, several of them displayed high similarity to known compounds such as polymyxin B, paenilan, colistin, and paenibacterin. These findings reinforce numerous previous studies highlighting the potential of soil-derived Bacillus and Paenibacillus species as valuable sources of novel antimicrobials to address the global antibiotic resistance crisis.