Rhamnolipid (RL) from Pseudomonas aeruginosa OBP1: A novel chemotaxis and antibacterial agent

• Published in: Colloids and surfaces, B, Biointerfaces B, Biointerfaces, 2013-03, Vol.103, p.502-509
• Main Authors: Bharali, P., Saikia, J.P., Ray, A., Konwar, B.K.
• Format: Article
• Language: English
• Subjects: Anti-Bacterial Agents - pharmacology; antibacterial properties; antibiotics; bacteria; Cell Membrane Permeability - drug effects; cell membranes; Cell wall; cell wall components; Chemo-attractant; chemoattractants; chemotaxis; Chemotaxis - drug effects; colloids; Colony Count, Microbial; Fourier transform infrared spectroscopy; gentian violet; glucose; Glycolipids - isolation & purification; Glycolipids - pharmacology; Hydrogen-Ion Concentration - drug effects; Hydrophobic and Hydrophilic Interactions - drug effects; hydrophobicity; Klebsiella pneumoniae; Klebsiella pneumoniae - cytology; Klebsiella pneumoniae - drug effects; Klebsiella pneumoniae - growth & development; Klebsiella pneumoniae - ultrastructure; membrane permeability; micelles; Microbial Sensitivity Tests; Microbial Viability - drug effects; minimum inhibitory concentration; Permeability; Pseudomonas aeruginosa; Pseudomonas aeruginosa - chemistry; Rhamnolipid; scanning electron microscopy; Spectroscopy, Fourier Transform Infrared; Staphylococcus aureus; Staphylococcus aureus - cytology; Staphylococcus aureus - drug effects; Staphylococcus aureus - growth & development; Staphylococcus aureus - ultrastructure; Streptomycin - pharmacology
• ISSN: 0927-7765; 1873-4367
• DOI: 10.1016/j.colsurfb.2012.10.064

[Display omitted] ► Novel chemotaxis activity on bacteria was shown by RL (of Pseudomonas aeruginosa). ► RL alters the cell permeability leading to leakage of cellular contents. ► Gram positive bacterial cells were more sensitive to RL. ► The RL start its activity within 30min of incubation at 37°C. ► pH (5–9) did not have any significant effect on RL activity. In the present study, the interaction of rhamnolipid produced by Pseudomonas aeruginosa OBP1 with the cell surfaces of Staphylococcus aureus (MTCC 3160) and Klebsiella pneumoniae (MTCC 618) were studied. Rhamnolipid concentration below critical micelle concentration (CMC) did not exhibit significant antibacterial activity. However, on increasing rhamnolipid concentration beyond CMC a prominent antibacterial activity was observed. The results demonstrated different degree of rhamnolipid interaction with both the bacteria. This might be due to the changes in their cell wall composition. The antibacterial activity determined by minimum inhibitory concentration (MIC). The antibacterial activity is prominent within 30min of incubation. The antibacterial property of rhamnolipid was effective in all tested pH levels (5–9). The rhamnolipid was effective in almost all tested pH levels and showed better chemoattractant property against both the tested bacteria in comparison to glucose. The increase in the membrane permeability was evidenced by increase in the release of protein, enhancement in cell surface hydrophobicity and raises in the retention of crystal violet dye. Further, leakage of 260nm absorbing intracellular materials, fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis confirmed the disruptive action of rhamnolipid. The above evidences support the idea that rhamnolipid significantly alters the cell membrane/envelop that leads to cell damage and enhances membrane permeability. Such activity of rhamnolipid could be used as an additive in the formulation of antibiotic and other antimicrobial agents for enhancing the effectiveness of chemotherapeutics.