Lactobacillus piscicola, a New Species from Salmonid Fish

Abstract

The name Lactobacillus piscicola sp. nov. is proposed for a group of 17 bacterial strains that were isolated from diseased rainbow trout (Salmo gairdneri), cutthroat trout (Salmo clarki), and chinook salmon (Oncorhynchus tshawytscha). This bacterium was found most frequently in infected fish which had suffered some form of stress, such as that which occurs at spawning. Occasionally, pathological signs in the internal organs or skin were observed. Phenotypically, L. piscicola belongs to the family Lactobacillaceae and can be distinguished from other species of Lactobacillus by its morphology and physiological characteristics. dl-Lactic acid was produced homofermentatively from glucose. Diaminopimelic acid was present in the cell wall peptidoglycan. The 17 isolates were closely related genetically, as demonstrated by similar percent guanine-plus-cytosine contents (35 mol%) and high deoxyribonucleic acid reassociation values, both characteristics of a single species. The isolates exhibited less than 10% deoxyribonucleic acid reassociation with other reference Lactobacillus strains with similar guanine-plus-cytosine contents. Strain B270 (= ATCC 35586), which was isolated in 1970 from diseased cutthroat brood trout at Bandon Hatchery in Oregon, is designated the type strain of this new species of Lactobacillus.