Organization of the adenyl cyclase (cya) locus of Rhizobium meliloti

Abstract

A cya-like gene encoding adenyl cyclase from Rhizobium meliloti was localized to a 0.8-kb PstI-EcoRI fragment by subcloning experiments. Experiments in Escherichia coli 'maxicells' identified a R. meliloti cya gene product of 28 kDa, which is significantly smaller than the corresponding protein from enteric bacteria. A control region for the expression of the cya gene in E. coli was found on an adjacent 2.6-kb BglII-BamHI sequence by insertional mutagenesis with Tn5 and phage MudI (ApR lac). The direction of transcription of the cya gene was also determined using a cya::MudIlac fusion. Promoter activity of this cya::lac fusion was not decreased when glucose was added to the culture. The R. meliloti cya gene is conserved among R. meliloti strains but no homology could be detected to other Rhizobium species or to E. coli in DNA hybridization experiments.