Survival of ammonia oxidising bacteria in air-dried soil

Natural populations of ammonia oxidising bacteria survived in air-dried soils for periods greater than 3 months. Recovery of a laboratory strain of Nitrosomonas europaea, grown and stored under similar conditions, was not possible after only 10 weeks. Pure cultures of natural isolates from the nitrifier enrichments possessed significant amounts of extracellular polymeric substances as capsular material, which was absent from cells of the laboratory strain, suggesting production of such material as a survival strategy during periods of desiccation stress in the soil.