This study reveals the quorum sensing inhibition (QSI) activity of Bacillus species isolated from South African marine sponges against Pseudomonas aeruginosa virulence factors, demonstrating their potential as anti-virulence therapeutics. It systematically evaluates the impact of different culture media on metabolite production and confirms absence of cytotoxicity, providing novel insights for antimicrobial strategies.
Literature Overview
Published in the journal Antibiotics, the study 'Quorum Sensing Inhibition by Sponge-Associated Bacillus Species: Suppressing Pseudomonas aeruginosa Virulence Factors' reviews Bacillus species' QSI activity against Pseudomonas aeruginosa virulence factors. The research isolates Bacillus strains from South African marine sponges, assessing their virulence suppression capabilities while examining culture medium effects on metabolite production and QSI activity.
Background Knowledge
Pseudomonas aeruginosa is a multidrug-resistant Gram-negative pathogen whose virulence is regulated through a complex quorum sensing (QS) system comprising four major pathways: Las, Rhl, PQS, and IQS. The QS system controls virulence factors including pyocyanin, pyoverdine, elastase, protease, rhamnolipids, biofilm formation, and motility, making it a critical target for anti-virulence therapies. Marine Bacillus species, particularly those in sponge symbiotic systems, possess 5-15% of their genome dedicated to secondary metabolite synthesis, suggesting potential for interfering with QS systems. However, studies on Bacillus-mediated QS inhibition against Pseudomonas aeruginosa remain limited. This research fills this gap by systematically evaluating Bacillus QS inhibition capabilities and metabolite variations. The findings highlight Bacillus species' potential as anti-virulence agents, particularly for treating multidrug-resistant pathogens.
Research Methods and Experiments
Bacteria from seven South African intertidal marine sponges were isolated, yielding 98 bacterial strains. These strains were screened for QS inhibitory activity using Chromobacterium violaceum biosensors, identifying 15 QS-inhibitory strains including 5 Bacillus species. Metabolites from Bacillus strains cultured in Mannitol and 5294 media were tested for virulence factor suppression. Metabolite profiles were analyzed via FTIR and GC-MS, while molecular analysis confirmed the presence of aiiA lactonase genes responsible for QS signal degradation.
Key Conclusions and Perspectives
Research Significance and Prospects
This study represents the first systematic evaluation of South African sponge-associated Bacillus species' QSI activity. The absence of cytotoxicity combined with potent virulence suppression suggests these strains as promising candidates for developing novel anti-virulence therapeutics. Future research should focus on characterizing specific metabolites and evaluating in vivo anti-virulence efficacy to realize their therapeutic potential against drug-resistant infections.
Conclusion
This study systematically demonstrates sponge-associated Bacillus species' QS inhibitory activity against Pseudomonas aeruginosa, identifying five strains (B. thuringiensis SP-AB2, B. cereus SP1-AB4, B. mobilis SP2-AB7, B. pumilus SP2-W6, B. wiedmannii SP5-AB7) with consistent virulence suppression across media. These strains exhibited up to 93% inhibition of Las/Rhl-regulated virulence factors including pyocyanin, pyoverdine, elastase, protease, and rhamnolipids. The presence of aiiA genes supports QS signal degradation mechanisms. FTIR/GC-MS analyses revealed significant medium-dependent metabolite variations, emphasizing culture conditions' critical role in anti-virulence drug development. Future studies should focus on metabolite characterization and in vivo anti-virulence validation to advance these Bacillus species as anti-resistance therapeutic agents.
