Screening, stability and antibacterial potential of rhamnolipids from Pseudomonas sp., isolated from hydrocarbon contaminated soil.

Surfactant plays an important role in industrial application such as oil recovery, lubricants and emulsifier. But chemical surfactants are toxic to human and other small animals. In recent years, biological based surfactants have gained increasing attention due to their ecofriendly in nature. The present study was focused to isolate biosurfactant producing bacteria, their stability and antibacterial ability from hydrocarbon contaminated and uncontaminated soil collected from different locations in Kanchipuram, Tamil Nadu, India. Biosurfactant producing bacteria were screened by following the haemolytic activity, drop collapsing test, emulsion against kerosene and was further confirmed through surface activity. The stability of the biosurfactant was determined by different physic-chemical conditions like pH, temperature and salinity. A total of 37 strains were selected in three different samples based on cultural characters and finally only 7 strains were confirmed as positive for biosurfactant. Among these strain H11 was considered as potential based on emulsification index (44%), surface activity (34.45 x 10-3 nm-1) and surface tension (23.17 x 10-3 nm-1) and was identified as Pseudomonas sp. The emulsification activity was stable at broad range of pH (4-12), temperature (4-120°C) and salt concentration (0-10%). The biosurfactant was further characterized in HPLC and one major peak was observed at a retention time of 2.033. The antibacterial activity of biosurfactant was high against gram positive pathogenic bacteria than gram negative bacteria. The rhamnolipid produced Pseudomonas sp. may be used as a tool to manage the oil pollution and to control the disease causing bacteria.

Prevalence of Vibrio cholerae and Other Vibrios from Environmental and Seafood Sources, Tamil Nadu, India.

Aims: The aim of this study was to investigate the prevalence of diarrhoea causing human pathogen V. cholerae and other vibrios from different environmental and seafood samples in Tamil Nadu, India. Place and Duration of Study: Laboratory of Clinical Microbiology, Department of Bio- Medical Science, School of Basic Medical Sciences, Bharathidasan University, Tiruchirappalli, Tamil Nadu, India between 2012 and 2013. Methodology: Seafood, water and plankton samples were collected at different locations of Tamil Nadu, India. All the samples were primarily enriched with alkaline peptone water (APW). 2-3 loopful of overnight cultures were streaked onto Thiosulphate Citrate Bile salt Sucrose (TCBS) agar plates. Suspected Vibrio cholerae, V. parahaemolyticus and other vibrios were picked up and identified by using standard biochemical and serological characterization and also by molecular methods. Results: Among the various samples that includes freshwater, coastal water, plankton and various seafoods, only plankton and seafood samples were found to be harbored with V. cholerae, V. parahaemolyticus and V. fluvialis. The remaining samples were negative for vibrios. All V. cholerae, V. parahaemolyticus and V. fluvialis strains possessed outer membrane protein W (ompW), thermostable direct haemolysin (tdh) and toxin regulatory protein (toxR) gene respectively. Hemolytic activity of V. cholerae exihibited different reaction isolated from seafood and plankton. The median lethal dose (LD50) of some V. cholerae strains was generally high. Conclusion: The result of the study suggested that the seafoods may act as an important reservoir of pathogenic vibrios and pose threat to human health.