Enrichment, enumeration and characterisation of nitrate-reducing bacteria present in sediments of the River Tay Estuary

Abstract

SynopsisSediments from the River Tay contained higher concentrations of ammonia than nitrate throughout an 18 month sampling cycle. Sediments from Kingoodie Bay and from the North Sea off the Tay Estuary produced nitrite and ammonia when incubated in the presence of nitrate.The nitrate-reducing bacteria present in Kingoodie Bay sediments were Aeromonasj Vibrio organisms with smaller numbers of enterobacteria and pseudomonads and even smaller numbers of acinetobacters. Continuous culture enrichments of sediments showed that in media containing no added NaCl, acinetobacters predominated anaerobically in the presence of nitrate and acetate while enterobacteria predominated in the presence of nitrate and glycerol. With 0.2M NaCl added to media enterobacteria were predominant, irrespective of carbon source, while with 0.4M NaCl addition pseudomonads predominated in acetate and enterobacteria in glycerol media.These results indicate that, at the salinities observed in the Tay Estuary at Kingoodie Bay, fermentative bacteria are most likely to be active in nitrate reduction.