Prevention of Acyl homoserine lactone (AHL) mediated biofilm formation by selected flora of Andaman & Nicobar Islands

Acyl homoserine lactones (AHL) are inter-cellular signal molecules and it controls the population density dependent growth behavior of bacteria in a biofilm. The AHL mediated biofilm formation and its inhibition was evaluated using methanol (MeOH), ethyl acetate (EtOAc), n-butanol (n-BuOH) and aqueous (H2O) fractions of 12 marine flora of Andaman and Nicobar Islands with fouling Vibrio sp., isolated from root surface of mangrove. The 12 fractions were assayed for inhibition of AHL promoted biofilm formation of Vibrio sp. and the results showed that seven fractions possess AHL inhibitory potential. The extracts of mangroves Avicennia marina, Rhizophora mucronata and macroalgae Sargassum ilicifolium, Actinotrichia fragilis, Amphiroa anceps and Padina tetrastromatica had anti-biofilm activity at least in one of the four solvent fractions. Out of these, EtOAc fraction of Padina tetrastromatica (60% inhibition at 50 mu g) showed higher inhibition on AHL mediated antibiofilm activity. The concentration dependent (10-200 mu g) study of this fraction showed that there was a significant reduction in biofilm formation by increase in concentration with an IC50 (50 % inhibitory concentration) of 40 mu g. Thus it was concluded that the AHL mediated biofilm inhibitory compound from Padina tetrastromatica can be used for the development of anti-quorum sensing antifoulants.