1Fisheries Experiment Station, Okayama Prefecture, Setouchi, Okayama 701-4303, 2Okayama Prefecture Fisheries Development Association, Urayasuminami, Okayama 702-8024, Japan
In the autumn of 2006, an unknown disease occurred among conchocelis of Porphyra (nori) mass-cultured using common scallop shells in Okayama Prefecture Fish Farming Center. An early symptom of the disease is tiny reddish brown spots; the color of diseased conchocelis finally turned yellowish-white. The bacterium isolated from the discolored area was confirmed to be the causative agent of this disease by artificial infection to healthy free conchocelis. When attacked by this isolate, the color of young Porphyra gametophytes turned green. The isolate was gram negative rod, strict aerobe, motile by a single flagellum, proliferated at 12-37°C , and required sea water for full growth. The bacterium is presumably a member of Pseudomonas or its closely related genus.