A SPECIES-SPECIFIC PROBE AND A PCR ASSAY FOR THE MARINE BACTERIUM, PSEUDOMONAS-STUTZERI STRAIN ZOBELL

The cloning, sequencing, and analysis of a Pseudomonas stutzeri Zobell 23S rRNA gene is described. Three variable regions were identified, a nd oligonucleotides homologous to portions of these regions were synth esized. The oligonucleotides were used as probes to screen DNA from va rious cultured bacteria to identify a species-specific probe. All prob es were found to hybridize strongly with P. stutzeri Zobell DNA under stringent conditions and did not hybridize with other Pseudomonas spec ies. One probe showed slight cross-reactivity with DNA from four other bacteria under the hybridization conditions used. Finally, PCR condit ions were optimized for detection of P. stutzeri Zobell in mixed cultu re with a detection limit of 400 cells. The assay detected P. stutzeri Zobell rDNA in coastal seawater samples sampled over a 20-month perio d. In the future, these probes could be used to quantify the 23S rRNA and rDNA from P. stutzeri Zobell in mixed culture and in environmental samples.