A comparative study of coastal and clinical isolates of <italic>Pseudomonas aeruginosa</italic>

<italic>Pseudomonas aeruginosa</italic> is a ubiquitous Gram-negative bacterium having a versatile metabolic potential and great ecological and clinical significance. The geographical distribution of <italic>P. aeruginosa</italic>has revealed the existence of an unbiased genetic arrangement in terrestrial isolates. In contrast, there are very few reports about <italic>P. aeruginosa</italic> strains from marine environments. The present work was aimed at studying the distribution of <italic>P. aeruginosa</italic> in coastal waters along the Indian Peninsula and understanding the environmental influence on genotypic, metabolic and phenotypic characteristics by comparing marine and clinical isolates. Of the 785 marine isolates obtained on selective media, only 32 (~4.1%) were identified as <italic>P. aeruginosa</italic>, based on their fatty acid methyl ester profiles. A low Euclidian distance value (< 2.5) obtained from chemotaxonomic analysis suggested that all the environmental (coastal and marine) isolates originated from a single species. While UPGMA analyses of AP-PCR and phenotypic profiles separated the environmental and clinical isolates, fatty acid biotyping showed overlapping between most clinical and environmental isolates. Our study revealed the genetic diversity among different environmental isolates of <italic>P. aeruginosa.</italic> While biogeographical separation was not evident based solely on phenotypic and metabolic typing, genomic and metatranscriptomic studies are more likely to show differences between these isolates. Thus, newer and more insightful methods are required to understand the ecological distribution of this complex group of bacteria.