Pseudomonas see Cowan 1974 Kersters and De Ley 1984 Palleroni 2005 In some

Pseudomonas see cowan 1974 kersters and de ley 1984

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Pseudomonas (see Cowan, 1974; Kersters and De Ley, 1984; Palleroni, 2005). In some respects, the G + C ratio and the inability to produce acid in peptone water sugars is more conducive to the concept of Alcaligenes or Deleya, although the pathogen is clearly distinct from existing nomenspecies (Kersters and De Ley, 1984). Moreover, it may not be ruled out that the causal agent of Sekiten-byo should be classified in a newly described genus. Certainly, the distinctive micro- morphology adds weight to this supposition. Maybe this explains the pronounced dissimilarity of Ps. anguilliseptica to other species of Pseudomonas as revealed by analyses of fatty acids and outer-membrane proteins (Nakajima et al., 1983). Pseudomonas chlororaphis To date, there has been only one report of Pseudomonas chlororaphis as a fish pathogen. This involved a heavy mortahty among farmed Amago trout (Onco- rhynchus rhodurus) in Japan (Hatai et al., 1975). For the present, it is uncertain whether Ps. chlororaphis represents an emerging problem, or a secondary (opportu- nistic) invader of already diseased hosts. The isolates matched the description of Ps. chlororaphis, insofar as cultures comprised Gram-negative motile rods, which produced distinctive colonies. These produced green pigment, which crystallised as needles in the colonies (Stanier et al., 1966; Palleroni, 1984). Other phenotypic traits were not reported, although the authors inferred that further tests had been carried out, and that these agreed with the definition of Ps. chlororaphis.
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134 Bacterial Fish Pathogens Pseudomonas fluorescens Ps. fluorescens is a dominant component of the freshwater ecosystem (Allen et ai, 1983b). At various times, Ps. fluorescens has been considered as a fish spoilage organism (Shewan et al, 1960), a contaminant or secondary invader of damaged fish tissues (Otte, 1963), as well as a primary, but poor pathogen (Roberts and Home, 1978). All the pubHshed descriptions of the organism (e.g. Bullock, 1965; Csaba et ai, 1981b; Ahne et ai, 1982) agree closely with the definition of Ps. fluorescens (Stanier et al., 1966; Palleroni, 2005). Pseudomonas fluorescens Cultures comprise Gram-negative, oxidative, arginine dihydrolase-, catalase- and oxidase-producing rods, which are motile by polar flagella. Growth occurs at 4°C, but not at 42°C. Fluorescent pigment (fluorescein) and gelatinase, but not (3- galactosidase, H2S, indole, amylase or urease, are produced. The Voges Proskauer reaction is negative. Citrate is utilised, and acid is produced from arabinose, inositol, maltose, mannitol, sorbitol, sucrose, trehalose and xylose, but not from adonitol or salicin. It seems Hkely that other fish-pathogenic pseudomonads, as discussed by Li and Flemming (1967) and Li and Traxler (1971), correspond to Ps. fluorescens. Pseudomonas plecoglossicida The pathogen was regarded as having phenetic similarities with Ps. putida biovar A, but on the basis of 16S rRNA sequencing was regarded as distinct, and elevated into a new species, as Ps. plecoglossicida (Nishimori et al., 2000).
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