Cultivable bacterial flora of Indian oil reservoir: isolation, identification and characterization of the biotechnological potential

‘Produced water’ is a term used in oil industry to describe water produced along with oil and gas from oil reservoir. Microorganisms have been frequently isolated from produced water/oil reservoirs; however, there is paucity of information regarding the diversity and characterization of bacterial flora from Indian oil reservoirs. The present investigation was undertaken to study bacterial diversity associated with Indian oil reservoirs and to investigate their potential as a source of industrially valuable enzymes. A total of 103 strains were isolated from five oil reservoirs. PCR-based DNA fingerprinting grouped these strains into 72 genovars. These isolates were identified using morphological, phenotypical and phylogenetic analyses. Most of these isolates were thermophiles (growing at 45◦C or higher), halotolerant (growth at 5% salinity) and were distributed through a variety of genera including but not limited to Bacillus, Chelatococcus, Paenibacillus and Pseudomonas species. The 16S rRNA gene sequence of several strains shared less than 97% homology with the reference sequences in the GenBank database indicating taxonomic novelty of these strains. Assessment of the biotechnological potential of 72 genovars revealed that majority of strains produce one or many of the valuable enzymes including amylase, cellulase, xylanase, pectinase, inulinase, protease, alcohol dehydrogenase and urease. Most of the isolates also degraded crude oil or petroleum hydrocarbons. The vast pool of phenotypic, genetic and functional diversity of the strains retrieved in this study suggested oil reservoirs as yet largely untapped and potent source of taxonomically novel and biotechnologically valuable microorganisms.