Effects on Rhamnolipid Biosurfactant on Cell Surface Properties of Antibiotic Resistant Bacteria

Abstract

This study was aimed to study the effect of rhamnolipid on different antibiotic resistant gram positive and gram negative bacteria. 10.02 mgmL-1of rhamnolipid was produced using the strain P. aeruginosa MTCC 2297 which had high surface tension (29.02mNm-1) and emulsification activity (84.85%). The potential of biosurfactant on antibiotic resistant bacterial cells of Pseudomonas aeruginosa, Escherichia coli and Bacillus subtilis was studied. Biosurfactant was shown to have a decreasing effect on the growth of Gram-positive strain, and this was dependent on the surfactant concentration. Complete inhibition of growth was observed at the concentration of 300μgml-1 in B. subtilis. However in case of Gram negative strains; rhamnolipid at increasing concentrations provoked a multi-component response of the bacterial cells without affecting their growth and viability. There was an increase in the protein release of 44% and 24% at the highest concentrations in P. aeruginosa and E.coli respectively and a decrease of approximately 100 % was observed in Gram positive strain at increasing rhamnolipid concentration. The rhamnolipid caused a two fold increase of LPS in the culture supernatant in case of P. aeruginosa whereas only 32% of LPS release was observed in E.coli. The increasing LPS release can be associated with increased cell hydrophobicity. The observations conclude that E.coli had very less effect of rhamnolipid even at higher concentrations. It can be due to the low permeability membrane barrier of the strain conferring to its antibiotic resistance potential.The results indicated that the rhamnolipid-biosurfactant from Pseudomonas aeruginosa has a potential application in the relatively new field of biomedicine and combating the problem of antibiotic resistance.