5 110 Nitrates are reduced to ammonia Acid is produced from arabinose

5 110 nitrates are reduced to ammonia acid is

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also at pH 5.5-11.0. Nitrates are reduced to ammonia. Acid is produced from arabinose, cellobiose, glucose, lactose, mannitol, raffinose, sucrose and xylose. The G + C content of the DNA is 33.7 mol %. Chemical analyses have established that the major pigments are similar to the ''flexirubin" of Fie. elegans (Strohl and Tait, 1978). On the basis of the micromorphology, ghding movement, G + C ratio and the ability to degrade complex molecules, this group was considered to represent a previously undescribed species of Cytophaga, for which the name of Cyt. aquatilis was proposed (Strohl and Tait, 1978). However, on the basis of phylogenetics, the species was transferred to Flavobacterium, as Fla. hydatis (Bernardet et al., 1996).
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Characteristics of the pathogens: Gram-negative bacteria 119 Flavobacterium johnsoniae (= Cytophaga johnsonae) Fla. johnsoniae was identified by an examination of phenotypic tests, and associated with mortalities in salmonids (Rintamaki-Kinnunen et ai, 1997). The characteristics for the fish isolates were as follows: Fla vohac terium Johnson iae Colonies are yellow (flexirubin pigment) and contain Gram-negative, ghding filaments. Catalase, P-galactosidase and oxidase are produced, but not H2S or indole. Nitrates are reduced. Acid is produced from glucose. Growth occurs at 10-30°C, but not at 37°C, and in 0.5-1.0% (w/v) sodium chloride. Casein, chitin, DNA, gelatin, starch, tributyrin, Tween 20, Tween 40 and tyrosine (with pigment production) are degraded, but not Tween 80. Ammonium, asparagine, glutamate, potassium nitrate and urea are utilised as sole sources of nitrogen (Carson et aL, 1993). Flavobacterium psychrophilum (= Cytophaga psychrophila = Flexibacter psychrophilum) The best of the descriptions of this organism stems from the work of Pacha (1968), Bernardet and Kerouault (1989), Bernardet and Grimont (1989) and Schmidtke and Carson (1995). Opinion is that this pathogen comprises a phenotypically homo- geneous group (Madsen and Dalsgaard, 2000; Madetoja et al, 2001). Plasmid profil- ing was carried out to evaluate genetic variability among 104 isolates, most of which were recovered from Japan. Most (72/104 = 69%) possessed plasmids of 2.8, 3.4, 4.1 and 5.6kb. The 3.4kb plasmid was mostly recovered from cultures obtained from rainbow trout; the 4.1 and 5.6 kb plasmids were from Japanese isolates (Izumi and Aranashi, 2004). Fla vohac terium psychroph Hum Cultures produce non-diffusible, yellow-pigmented (flexirubin pigment) colonies with thin, spreading margins. Cells are strictly aerobic. Gram-negative, slender, flexible rods of 1.5-7.5 x 0.75 |im in size. With increasing age, the cefls appear to be shorter. As with Fla. hydatis, gUding movement is exhibited, and fruiting bodies and microcysts are absent. Catalase is produced, oxidase may appear to be pos- itive, but H2S, indole, and lysine and ornithine decarboxylase are not produced. Nitrates are not reduced, and the Voges Proskauer reaction is negative. Casein, gelatin and tributyrin are degraded; tyrosine is attacked by some isolates, and aesculin, chitin, starch and xanthine not at all. Generally, growth occurs at 4-23°C, but not at 30°C, and in 0.8%, but not 2% (w/v), sodium chloride. This
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