Transcript analysis of multiple copies of amo (encoding ammonia monooxygenase) and hao (encoding hydroxylamine oxidoreductase) in Nitrosomonas europaea

The genes encoding ammonia monooxygenase (amoCAB), hydroxylamine oxidoreduc tase (hao), and the c-type cytochrome c-554 (hcy) are present in multiple c opies in the genome of Nitrosomonas europaea. The upstream regions of the t wo copies of amoC, the three copies of hao, and one copy of hey were cloned and sequenced. Primer extension reactions were done to identify transcript ion start sites for these genes, as well as for amoA. Putative sigma (70) p romoter sequences were found associated with ail but one of the mapped tran scription start sites. Primer extensions were done with amoC primers using RNA harvested from cells incubated with and without ammonium, The experimen ts suggested that N, europaea cells may be able to use different promoters in the presence and absence of ammonium.