A novel compound from the marine bacterium Bacillus pumilus S6-15 inhibits biofilm formation in Gram-positive and Gram-negative species

Abstract

Biofilm formation is a critical problem in nosocomial infections and in the aquaculture industries and biofilms show high resistance to antibiotics. The aim of the present study was to reveal a novel anti-biofilm compound from marine bacteria against antibiotic resistant Gram-positive and Gram-negative biofilms. The bacterial extract (50 μg ml⁻¹) of S6-01 (Bacillus indicus = MTCC 5559) showed 80–90% biofilm inhibition against Escherichia coli, Shigella flexneri, Proteus mirabilis and S6-15 (Bacillus pumilus = MTCC 5560) showed 80–95% biofilm inhibition against all the 10 tested organisms. Furthermore, they also reduced the hydrophobicity index and extracellular polymeric substances (EPS) production. Structural elucidation of the active principle in S6-15 using GC-MS, ¹H NMR, and ¹³C NMR spectral data revealed it to be 4-phenylbutanoic acid. This is the first report of 4-phenylbutanoic acid as a natural product. The purified compound (10–15 μg ml⁻¹) showed potential activity against a wide range of biofilms. This study for the first time, reports a novel anti-biofilm compound from a marine bacterium with wide application in medicine and the aquaculture industry.

Keywords:

• Bacillus pumilus
• Bacillus indicus
• anti-biofilm
• 4-phenylbutanoic acid
• hydrophobicity index
• EPS production

Acknowledgements

This study was supported by a research grant from the Department of Biotechnology (DBT), the Government of India (GOI) (Grant No. BT/PR11994/ndb/52/134/2009). The authors gratefully acknowledge the computational and bioinformatics facility provided by the Alagappa University Bioinformatics Infrastructure Facility (funded by DBT, GOI; Grant No. BT/BI/25/001/2006). Financial support provided to Chari Nithya by Alagappa University in the form of Research Fellowship is thankfully acknowledged.