demonstrates clearly that the organisms are suited to low temperature

Demonstrates clearly that the organisms are suited to

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demonstrates clearly that the organisms are suited to low-temperature, freshwater environments. The organisms are capable of degrading autoclaved cells of Esch. coli (Pacha, 1968). The G + C ratio of the DNA is 32.5-34 mol %. The original 10
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120 Bacterial Fish Pathogens isolates of Pacha (1968) were deemed to be serologically homogeneous. Yet, later work identified two major serogroups, with Ol accommodating isolates from Japan and the U.S.A. and 02 comprising only Japanese cultures (Wakabayashi et al, 1994). This number increased to three, with European isolates included in one major serogroup (Lorenzen and Olesen, 1997). Seven antigenic types have been recognised among Finnish isolates, with results suggesting a new serogroup (Madetoja et ciL, 2001). Furthermore, a novel serotype has been described for cultures recovered from amago in Japan (Tzumi et ciL, 2003). Several ribotypes have been recognised among 85 isolates, with most harbouring one or more plasmids (11 plasmid profiles defined) (Chakroun et ciL, 1998). In comparison, 13 ribotypes were recognised among Finnish cultures (Madetoja et ciL, 2001). PCR and RFLP led to the recognition of genetic heterogeneity among 242 isolates (Tzumi et ciL, 2003a). On the basis of the phenotypic characteristics, the conclusion was reached that the causal agent of coldwater disease could be equated with the genus Cytophaga, as defined by Stanier (1942), but was sufficiently distinct from existing species to warrant description as a new species. Hence, Cyt.psychrophila was named (Borg, 1960). How- ever, Lewin and Lounsberry (cited in Leadbetter, 1974) disagreed with this notion, and proposed that the organisms would be better classified in the genus Flexibacter, as Fie. aurantiacus. Bernardet and Grimont (1989) agreed with the opinion that the organisms belong in the genus Flexibacter, but proposed Fie. psychrophilum. Then, with general improvements in the understanding of the yellow-pigmented bacteria resulting from phylogenetic data, the taxon was transferred to Flavobacterium, as Fla. psychrophilum (Bernardet et al., 1996). It is agreed that the taxon comprises a homogeneous group of bacteria (Lorenzen et al., 1997). Flavobacterium piscicida Only a poor description of Fla. piscicida exists in the fisheries Hterature. Therefore, further discussion will not be attempted. Flexibacter spp. The fish pathology literature abounds with references to unspeciated Flexibacter. Pyle and Shotts (1980, 1981) studied 17 strains for phenotypic traits, as determined by use of the API 20E rapid identification system, and by DNA homology. The conclusion reached was that the isolates from warm-water fish were distinct to those recovered from cold-water fish. At least three separate groups were recognised. However, whether or not these organisms belong in existing species or represent new taxa must await further study.
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Characteristics of the pathogens: Gram-negative bacteria 121 Tenacibaculum maritimum (= Flexibacter maritimus = Cytophaga marina) Tenacihaculum maritimum A very homogeneous group (Bernardet et ciL, 1994), with cultures forming pale yellow, flat, thin colonies, containing strictly aerobic. Gram-negative rods of 2-
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