Proteomic Investigations on Interaction of Silver Nanoparticles with Halophilic Bacillus sp. EMB9

Background: With the recent advances of nanotechnological interventions, nanoparticles have found immense importance in various sectors of water, energy, health, agriculture and environment. Concurrently, there has been an increasing concern about their toxicity on living systems. The bactericidal role of silver nanoparicle is well established. The present work explores the interaction of silver nanoparticles with halophilic bacteria Bacillus sp. EMB9. Given that halophiles thrive under saline/ hypersaline habitats and retain their structural and functional integrity under such high salt conditions, they present a new and interesting model system for understanding their interactions with metals in nanoparticulate form. Methods: Bacillus sp. EMB9 was incubated in the presence and absence of 1.0 mM silver nanoparticles and their growth profile monitored. Their responses towards the nano-stress environment were further evaluated using a proteomic approach. Result: Despite initial nanotoxic effects, Bacillus sp. EMB9 was able to resist silver mediated nanotoxicity and grow with a high specific growth rate. Proteomic analysis showed striking global changes in the intracellular bacterial proteome with almost a 50% reduction in the number of expressed proteins in the cells grown in presence of silver nanoparticles. Out of a total of 261 protein spots detected, 24 were newly expressed and expression of 132 spots was suppressed completely in the nanoparticle treated cells. Conclusion: The differential expression patterns are indicative of adaptive strategies being employed by the bacteria for functioning of the cellular machinery amidst nano-stress. A comprehensive understanding of the response of halophilic Bacillus sp. EMB9 to silver nanoparticles will provide significant insight into mechanistic interpretations of bacteriananoparticle interactions.