Diversity and detection of nitrate assimilation genes in marine bacteria

A PCR approach was used to construct a database of nasA genes (called narB genes in cyanobacteria) and to detect the genetic potential for heterotroph ic bacterial nitrate utilization in marine environments. A nasA-specific PC R primer set that could be used to selectively amplify the nasA gene from h eterotrophic bacteria was designed. Using seawater DNA extracts obtained fr om microbial communities in the South Atlantic Bight, the Barents Sea, and the North Pacific Gyre, we PCR amplified and sequenced nasA genes. Our resu lts indicate that several groups of heterotrophic bacterial nasA genes are common and widely distributed in oceanic environments.