Effect of oxygen tension, salinity, temperature and organic matter concentration on the growth and nitrifying activity of an estuarine strain of Nitrosomonas

Abstract

The effects of O2 tension, temperature, salt concentration and organic matter concentration on the growth and nitrifying activity of Nitrosomonas N3 isolated from Tay Estuary sediments have been investigated. Chemostat-grown cultures were able to grow and nitrify at dissolved O2 concentrations as low as 0.1 mg O2· 1−1 (cell population densities were 15% of those obtained in fully aerated cultures). This bacterium was sensitive to reduced temperatures as chemostat-grown cultures washed out at growth temperatures below 15°C, at dilution rates > 0.025 · h−1. Batch-grown cultures of Nitrosomonas N3 were used to study the effects of NaCl and complex organic matter concentration on nitrifying activity. Maximum rates of NH+4 oxidation were recorded at NaCl concentrations of 1% w/v, whilst tryptone soya broth (TSB), nutrient broth (NB), yeast extract broth (YEB) and peptone were inhibitory at concentrations > 10 mg · 1−1.