pH stability during fermentation is associated with sustained antibacterial metabolite production in marine sediment

Globally, the rise in antibiotic-resistant pathogens has underscored the urgent need for new strategies to discover antimicrobials, with emphasis on microbial producers of secondary metabolites. The influence of pH on bacterial recovery, metabolite expression, and antibacterial activity in isolates from marine sediments was evaluated in this study. Three culture media were used to isolate sediment bacteria across a pH gradient (5.0-8.0), and conventional biochemical methods were employed for putative identification of the bacterial isolates. The agar plug assay was used for primary antibacterial screening, while the disk diffusion assay of the cell-free and sonicated extracts was used for secondary screening after 7 days of submerged fermentation of the isolates at their different culture pH levels. The results revealed the predominance of IMPORTANCE: Marine environments are important reservoirs of bacteria capable of producing bioactive secondary metabolites; however, many promising antimicrobial producers identified during initial screening fail to retain activity during fermentation. This study demonstrates that pH stability during fermentation, rather than pH value alone, is a key determinant of sustained antibacterial metabolite production in marine sediment-derived