The marine chemolithotrophic ammonium-oxidizing bacterium Nitrosomonas crytolerans was monitored during recovery after 5 weeks of energy-source deprivation. The organism responded immediately to the addition of [Formula: see text], producing [Formula: see text] at a constant rate. The cells used stored energy sources (ATP) and reducing equivalents (possibly NAD(P)H + H+) to immediately begin biosynthesis. However, these sources were quickly exhausted. Consequently, anabolism (14CO2 incorporation) decreased until levels of ATP and reducing potential were increased through oxidation of [Formula: see text]. Electron transport system activity steadily increased after the addition of [Formula: see text]. The increases in activities were greater than the increase in the total number of cells, suggesting that the increase in activity of the whole culture was due to either a physiological change in each cell or a reactivation of cells which had entered dormancy during energy-source deprivation. These results indicate that N. cryotolerans is well adapted to oligotrophic environments.
