One of the representatives of the AOB group is Nitrosomonas mobilis species. Although a few pure strains of this species have been isolated so far, approaches to their preservation in pure culture have not been established. Here, we report isolation of novel members of the N. mobilis species from autotrophic nitrifying granules used for ammonia-rich wastewater treatment. We developed an isolation method focusing on microcolonies formation of nitrifying bacteria.If you really want to enriche or isolate Nitrosomonas species you can used relatively high concentration of ammonium, up to 5mM. But the process of enrichment is a long-term, you have to make a lot of circles of reinoculation and dilution steps.