Methods of treating an environmental surface by depositing a preparation including nonpathogenic bacteria on the environmental surface are disclosed. Methods of treating an environmental surface by depositing a preparation including ammonia oxidizing microorganisms on the environmental surface are disclosed. Methods of introducing nonpathogenic bacteria into a built environment are disclosed. Methods of introducing ammonia oxidizing microorganisms into a built environment are disclosed. Methods of modulating a microbiome associated with a built environment or maintaining a microbiome associated with a built environment are disclosed. Methods of treating a subject by introducing ammonia oxidizing microorganisms into the built environment are also disclosed.