Fig. 1. Length heterogeneity–polymerase chain reaction applied to the intergenic region between the amoC and the amoA genes of the ammonia monooxygenase operon. The top panel is the electropherogram from soil treated with composted manure, the middle panel is the electropherogram from fresh cow manure, and the bottom panel is unamended soil (no manure) where the genes are either below detection or absent. The numbers in the box are the lengths of the amplicons in base pairs.