RESTRICTION-ENDONUCLEASE ANALYSIS OF ATYPICAL AEROMONAS-SALMONICIDA ISOLATES FROM GOLDFISH CARASSIUS-AURATUS, SILVER PERCH BIDYANUS-BIDYANUS, AND GREENBACK FLOUNDER RHOMBOSOLEA-TAPIRINA IN AUSTRALIA

Total genomic DNA samples of atypical isolates of Aeromonas salmonicid a from goldfish Carassius auratus L., silver perch Bidyanus bidyanus ( Mitchell), and greenback flounder Rhombosolea tapirina Gunther from Au stralia and isolates from goldfish from the USA and Singapore were dig ested with the restriction enzyme CfoI, separated in 3.5% acrylamide g els and visualised by silver staining. Isolates from goldfish and silv er perch comprised an homogenous group while those from greenback flou nder formed a second group. Within the goldfish and silver perch isola tes there were minor differences in restriction endonuclease fragment pattern. Isolates from Australian goldfish obtained between 1977 and 1 989 were indistinguishable from isolates from goldfish from the USA bu t slightly different from an isolate from a Singaporean goldfish. Thes e and other data suggest that A. salmonicida probably crossed a specie s barrier from goldfish to silver perch on the same farm but that farm ed greenback flounder in Tasmania have acquired a distinct strain of A . salmonicida probably from wild-caught marine fish.