Advances in Biology & Earth Sciences

Probiotics are living microorganisms that provide beneficial physiological functions to the host. The objectives of this study were to isolate and characterize probiotic candidates from mangrove forest sediments with antibacterial activity against pathogens. From ten sediment samples, 45 bacterial isolates were obtained, of which five exhibited antimicrobial activity against pathogens (Staphylococcus aureus, Bacillus cereus, Escherichia coli O157:H7 and Vibrio parahaemolyticus EMS). Based on 16S rRNA gene sequencing, 3 isolates of the Bacillus altitudinis/pumilus complex (WU5S01, WU5S02, WU5S03; 96.22-98.34% similarity) and 2 of Bacillus cereus (WU5S04, WU5B01; 97.79-98.10% similarity) were obtained. These isolates displayed high tolerance to gastrointestinal enzymes (trypsin, pepsin, pancreatin) and bile salts. Additionally, WU5S01 and WU5S02 showed a high survival rate under acidic conditions. All strains demonstrated effective auto-aggregation (49.32-59.85% within 5 h) and strong adhesion ability. LC-MS analysis of the selected probiotic metabolites detected 35 compounds, of which 11 exhibited potential antimicrobial properties. The LCFS of WU5S02 showed antibacterial activity against the tested pathogens, with the MIC values of 15.625-125 mg/mL. Furthermore, LCFS showed strong antibiofilm activity at sub-MIC levels (68.83-89.27%). This study provides a preliminary characterization of probiotic candidates from mangrove sediments, demonstrating that their metabolites can suppress both the growth and biofilm-forming abilities of foodborne pathogens.