Cyanobacterial diversity in hydrocarbon-polluted sediments and their possible role in bioremediation

•This is the first study dealing with cyanobacterial diversity in crude oil sludge contaminated terrestrial sediments.•The sediments and microbial mats harbours a number of cyanobacterial strains dominated by Leptolyngbya spp and Panktothrix spp.•Increase in CO2 evolution activity suggest a role of cyanobacteria in hydrocarbon degradation.•DGGE analysis of soil sediment samples revealed sequences of uncultured cyanobacterial strains.

The cyanobacterial diversity in crude-oil-contaminated mats and soil sediments from the Guwahati refinery, in Guwahati, India, was studied using a polyphasic approach. Sequencing of the 16S rRNA gene of the isolated cyanobacterial strains and of denaturing gradient gel electrophoresis bands of the environmental samples revealed dominance of the genera Leptolyngbya and Planktothrix and the presence of Tolypothrix sp., Anabaena sp., Oscillatoriales sp., and Arthronema sp. These strains exhibited wide variation in their transferase glutamine synthetase activity and ammonia excretion activity. Treatment of isolates with hydrocarbon sludge caused a sharp decrease in photosynthetic oxygen evolution activity followed by time-dependent recovery, which ranged from 18.6% to 153.1% after 4 h. The CO2 evolution activity remained unaffected or exhibited stimulation after 1% or 2% oil sludge treatment.