A multicopper oxidase gene, cumA, required for Mn(II) oxidation was recently identified in Pseudomonas putida strain GB-1. In the present study, degenerate primers based on the putative copper-binding regions of the cumAgene product were used to PCR amplify cumA gene sequences from a variety of Pseudomonas strains, including both Mn(II)-oxidizing and non-Mn(II)-oxidizing strains. The presence of highly conserved cumA gene sequences in several apparently non-Mn(II)-oxidizing Pseudomonasstrains suggests that this gene may not be expressed, may not be sufficient alone to confer the ability to oxidize Mn(II), or may have an alternative function in these organisms. Phylogenetic analysis of both CumA and 16S rRNA sequences revealed similar topologies between the respective trees, including the presence of several distinct phylogenetic clusters. Overall, our results indicate that both thecumA gene and the capacity to oxidize Mn(II) occur in phylogenetically diverse Pseudomonas strains.