Phenotypic and Molecular Characterisation of Rhamnolipids in Clinical, Animal and Environmental Potential Mutant LasR of P. aeruginosa

Background: Rhamnolipids (RL) are natural glycolipids produced by Pseudomonas aeruginosa. Despite their use in the agricultural, environmental, bioremediation, petroleum, pharmaceutical and food industries, these rhamnolipid biosurfactants have not been characterised in clinical, animal or environmental strains. Objective: The aim of this study was to characterise the rhamnolipids produced by P. aeruginosa strains of diverse origin. Methodology: A total of 97 P. aeruginosa strains of clinical (30), environmental (32) and animal (35) origin were identified using bacteriological methods and PCR followed by sequencing. The sensitive, semi-quantitative blue agar test and detection of the RhlI and RhlR genes by PCR were used to characterise the phenotypic and molecular production of rhamnolipids, respectively. Potential LasR mutants were identified from iridescent and autolytic metallic colonies on the same agar. Results: In order of decreasing importance, P. aeruginosa strains of clinical (83.3%), environmental (78.1%) and animal (62.9%) origin produced different levels of rhamnolipids. Rhamnolipid-producing strains showed patches of autolysis (63.9%), iridescence (51.4%) and autolytic iridescence (41.7%). The RhlI synthase and the RhlR regulator were mainly detected in environmental strains with an identical prevalence of 66.4%. The prevalence of RhlI (47.2%) and RhlR (47.2%) detected was also identical for clinical and animal strains. Conclusions: This study shows the need to study the factors controlling rhamnolipid production in P. aeruginosa.