Population dynamics of the nitrifying bacterium Nitrosolobus in soil.
Ammonium-oxidizing bacteria (Nitrosolobus sp.) were counted every 2 days for 28 days in the top 5 cm of a soil at Rothamsted. The population density fluctuated with an amplitude of 1.7 X 104 cells g-1. These fluctuations were mainly associated with changes in soil moisture content. The mean standing crop was 8.7 X 103 cells g-1 (15 ng g-1; 9.3 g ha-1 freshweight). Mean cumulative biomass production was at least 79 ng g-1 (51 g ha-1) per 28 days; net biomass production was negligible. Doubling times for populations were 8-78 h (mean 32.5 h).