30
pathogenic lactobacilli, with similarities to Lactobacillus alimentarius and
Lactobacillus homohiochi, have been recovered from post-spawning rainbow trout
in the USA (Starliper et al. 1992 ).
In most respects, all the isolates bore similarities, and by comparison of the phenotypic traits with conventional identifi cation schemes, it is apparent that an identifi cation of Lactobacillus or Streptococcus could result. Furthermore, the
photomicrographs of cells, published by Ross and Toth ( 1974 ), could be interpreted
as chains of cocci rather than short rods, which would be more in keeping with an
identifi cation of Streptococcus. The isolates recovered from England and Canada, by
Austin and Stemke, respectively, possessed more of the characteristics attributable to
Lactobacillus or the related genera. Cultures comprised Gram-positive, non- motile,
fermentative rods of approximately 3.0 × 1.0 μm in size, forming round, raised entire
white colonies on TSA after incubation for 48 h at 20 °C. Growth occurred at 4–26 °C
but not 37 °C, and in 2.5 % but not 7.5 % (w/v) sodium chloride. A resemblance to
Car. piscicola is readily apparent. Indeed, the only differences refl ect growth at 37 °C
and acid production from lactose. Both the Canadian isolates of Stemke and the US
isolates of Hiu et al. ( 1984 ) and Starliper et al. ( 1992 ) produced lactic acid from the
fermentation reactions. It is possible that these lactobacilli may all belong in the
same taxon, i.e. Car. piscicola , but it will be necessary for further study to determine
the true relationship of the English and Canadian isolates to those of Hiu et al. ( 1984 ).
The cell wall peptidoglycan of Car. piscicola was found to comprise diaminopimelic acid, alanine and glutamic acid, but no lysine. DNA:DNA hybridisation
revealed negligible, i.e. 10 %, homology with the reference cultures of Lactobacillus
acidophilus, Lactobacillus crispatus, Lactobacillus jensenii, Lactobacillus salivarius and Lactobacillus yamanashiensis, compared to 70 % re-association between
isolates of Car. piscicola (Hiu et al. 1984 . Thus in their publication, it was concluded that the fi sh pathogens were most closely related to Lactobacillus
yamanashiensis subsp. yamanashiensis in terms of G + C ratio of the DNA and
Box 2.4: Carnobacterium piscicola
On TSA, Car. piscicola produces small round, entire, shiny, opaque colonies
that develop within 48 h. These contain non-motile, non-acid-fast, Grampositive fermentative cocco-bacilli or rods of approximately 1.1–1.4 × 0.5–
0.6 μm in size. Other phenotypic traits of the lactobacilli include the inability
to produce catalase (catalase-positive isolates were described by Starliper
et al. 1992 ), H 2 S, indole, gelatinase, urease, the Voges Proskauer reaction,
arginine hydrolysis, or lysine or ornithine decarboxylases or reduce nitrates.
However, the isolates produce acid from fructose, galactose, glucose, glycerol, inulin, lactose, maltose, mannitol, melibiose, salicin, starch, sucrose and
trehalose, but not raffi nose, sorbitol or xylose (Schmidtke and Carson 1994 ).
There are a few differences between the Californian and Canadian isolates,
namely hydrolysis of aesculin, and acid production from lactose. Growth
occurs at 10 °C but not 40 °C, in 6.5 % (w/v) sodium chloride, and at pH 9.6.
2 Gram-Positive Bacteria (Anaerobes and ‘Lactic Acid’ Bacteria)
pathogenic lactobacilli, with similarities to Lactobacillus alimentarius and
Lactobacillus homohiochi, have been recovered from post-spawning rainbow trout
in the USA (Starliper et al. 1992 ).
In most respects, all the isolates bore similarities, and by comparison of the phenotypic traits with conventional identifi cation schemes, it is apparent that an identifi cation of Lactobacillus or Streptococcus could result. Furthermore, the
photomicrographs of cells, published by Ross and Toth ( 1974 ), could be interpreted
as chains of cocci rather than short rods, which would be more in keeping with an
identifi cation of Streptococcus. The isolates recovered from England and Canada, by
Austin and Stemke, respectively, possessed more of the characteristics attributable to
Lactobacillus or the related genera. Cultures comprised Gram-positive, non- motile,
fermentative rods of approximately 3.0 × 1.0 μm in size, forming round, raised entire
white colonies on TSA after incubation for 48 h at 20 °C. Growth occurred at 4–26 °C
but not 37 °C, and in 2.5 % but not 7.5 % (w/v) sodium chloride. A resemblance to
Car. piscicola is readily apparent. Indeed, the only differences refl ect growth at 37 °C
and acid production from lactose. Both the Canadian isolates of Stemke and the US
isolates of Hiu et al. ( 1984 ) and Starliper et al. ( 1992 ) produced lactic acid from the
fermentation reactions. It is possible that these lactobacilli may all belong in the
same taxon, i.e. Car. piscicola , but it will be necessary for further study to determine
the true relationship of the English and Canadian isolates to those of Hiu et al. ( 1984 ).
The cell wall peptidoglycan of Car. piscicola was found to comprise diaminopimelic acid, alanine and glutamic acid, but no lysine. DNA:DNA hybridisation
revealed negligible, i.e. 10 %, homology with the reference cultures of Lactobacillus
acidophilus, Lactobacillus crispatus, Lactobacillus jensenii, Lactobacillus salivarius and Lactobacillus yamanashiensis, compared to 70 % re-association between
isolates of Car. piscicola (Hiu et al. 1984 . Thus in their publication, it was concluded that the fi sh pathogens were most closely related to Lactobacillus
yamanashiensis subsp. yamanashiensis in terms of G + C ratio of the DNA and
Box 2.4: Carnobacterium piscicola
On TSA, Car. piscicola produces small round, entire, shiny, opaque colonies
that develop within 48 h. These contain non-motile, non-acid-fast, Grampositive fermentative cocco-bacilli or rods of approximately 1.1–1.4 × 0.5–
0.6 μm in size. Other phenotypic traits of the lactobacilli include the inability
to produce catalase (catalase-positive isolates were described by Starliper
et al. 1992 ), H 2 S, indole, gelatinase, urease, the Voges Proskauer reaction,
arginine hydrolysis, or lysine or ornithine decarboxylases or reduce nitrates.
However, the isolates produce acid from fructose, galactose, glucose, glycerol, inulin, lactose, maltose, mannitol, melibiose, salicin, starch, sucrose and
trehalose, but not raffi nose, sorbitol or xylose (Schmidtke and Carson 1994 ).
There are a few differences between the Californian and Canadian isolates,
namely hydrolysis of aesculin, and acid production from lactose. Growth
occurs at 10 °C but not 40 °C, in 6.5 % (w/v) sodium chloride, and at pH 9.6.
2 Gram-Positive Bacteria (Anaerobes and ‘Lactic Acid’ Bacteria)