Phenol, 2,4-bis(1,1-dimethylethyl) of marine bacterial origin inhibits quorum sensing mediated biofilm formation in the uropathogen Serratia marcescens

Abstract

Intercellular communication in bacteria (quorum sensing, QS) is an important phenomenon in disease dissemination and pathogenesis, which controls biofilm formation also. This study reports the anti-QS and anti-biofilm efficacy of seaweed Gracilaria gracilis associated Vibrio alginolyticus G16 against Serratia marcescens. Purification and mass spectrometric analysis revealed the active principle as phenol, 2,4-bis(1,1-dimethylethyl) [PD]. PD affected the QS regulated virulence factor production in S. marcescens and resulted in a significant (p < 0.05) reduction in biofilm (85%), protease (41.9%), haemolysin (69.9%), lipase (84.3%), prodigiosin (84.5%) and extracellular polysaccharide (84.62%) secretion without hampering growth, as evidenced by XTT [2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide] assay. qPCR analysis confirmed the down-regulation of the fimA, fimC, flhD and bsmA genes involved in biofilm formation. Apart from biofilm inhibition and disruption, PD increased the susceptibility of S. marcescens to gentamicin when administered synergistically, which opens another avenue for combinatorial therapy where PD can be used to enhance the efficacy of conventional antibiotics.

Keywords:

• anti-biofilm
• phenol, 2,4-bis(1,1-dimethylethyl)
• seaweed associated bacteria
• quorum sensing inhibition
• biofilm disruption

Acknowledgements

This work was supported in part by ICMR research grant [Sanction No. 58/20/2011-BMS] sanctioned to SKP. The authors also acknowledge the computational facilities provided by the Bioinformatics Infrastructure Facility, Alagappa University [funded by the Department of Biotechnology, Government of India; grant number BT/BI/25/001/2006]. AP thanks ICMR for the financial assistance provided in the form of a senior research fellowship.