Published online by Cambridge University Press: 05 December 2011
The physiology of three nitrate respiring bacteria, identified as Klebsiella strain K312, Pseudomonas strain P388 and Vibrio strain V25, obtained from Kingoodie Bay sediments in the River Tay by enrichment techniques, have been studied in continuous culture. In glycerol limited anaerobic cultures Klebsiella K312 produced NO2 as the primary product of nitrate reduction whereas under N-limited conditions NH4+ was excreted into the culture medium. Nitrate reduction in this organism was accompanied by the synthesis of a paniculate nitrate reductase (NR) whilst under N-limitation a soluble nitrite reductase (NiR) was also produced. In contrast, Pseudomonas P388 dissimilates NO3 directly to gaseous products under anaerobic conditions and was associated with the synthesis of a particulate NR and under N-limited conditions a NiR. Nitrite never accumulated as an intermediate. Vibrio V25 would only reduce NO3 as far as NO2 and was therefore restricted in its use of NO3 under anaerobic conditions. Klebsiella K312 was the most versatile of the three organisms studied and since Klebsiella spp were found in significant numbers in the Kingoodie sediments they may account in part for the high interstitial NH4+ levels found there.