Ammonia-dependent differential regulation of the gene cluster that encodes ammonia monooxygenase in Nitrosococcus oceani ATCC 19707

Authors

  • Amal F. El Sheikh,

    1. Evolutionary and Genomic Microbiology Laboratory, Department of Biology and
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    • Present address: Department of Microbiology, Miami University, Oxford, OH 45056, USA.

  • Martin G. Klotz

    Corresponding author
    1. Evolutionary and Genomic Microbiology Laboratory, Department of Biology and
    2. Department of Microbiology and Immunology, University of Louisville, Louisville, KY 40292, USA.
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*E-mail martin.klotz@louisville.edu; Tel. (+1) 502 8527 779; Fax (+1) 502 8520 725.

Summary

Molecular analysis of the ammonia monooxygenase-encoding gene cluster in Nitrosococcus oceani revealed that the amo genes are differentially expressed from three promoters dependent on the external ammonia concentration. Whereas a distal amoRCABD operon promoter, pC1, is active only in the presence of ammonia, identified proximal amoC (pC2) and amoA (pA) sigma-70-type promoters are constitutive. Promoter region pC2 also contains a consensus sequence for binding of RpoN, usually involved in nitrogen starvation response. Additional regulation of transcript stability by anti-termination and mRNA degradation are proposed and discussed.

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