Diazotrophic activity and ferric phosphate mineralizing ability in estuarine sulfate reducing bacteria

Abstract

Twenty strainsofsulfate reducing bacteria were isolated from water and sediments of Cochin backwaters, India. Five of them were identified as Desulfovibrio desulfuricans and fifteen as Desulfotomaculum orientis. All the Desulfovibrio were isolated from sediments whereas Desulfotomaculum was present in both water and sediment. All the bacteria grew at pH of slightly alkaline reaction and lowered the Eh from -105 to - 270 m V of the growth medium. Complete reduction of sulfate to sulfide by the bacteria was evidenced by blackening of Post gate culture media. All isolates were able to fix dinitrogen in anaerobic N-free modified Postgate broth. In addition to nitrogen fixing ability, 5 of the Desulfotomaculum and 3 of the Desulfovibrio were able to produce soluble phosphorus in growth medium from insoluble FePO4. A scheme for FePO4 mineralization in marine and estuarine sediments has been proposed.