Characterization and identification of lactic acid bacteria from freshwater fishes Original Research Article

This work reports on the characterization and identification of 249 strains of lactic acid bacteria (237 rods and 12 cocci) isolated from freshwater fish (mainly wild brown trout) and their surrounding environments. Approximately 90% (226 strains), not able to grow on Acetate (Rogosa) agar, exhibited a high degree of phenotypic homogeneity and were assigned to the genus Carnobacterium. Only a reduced number of strains (22) were allocated to the generaLactobacillus, Enterococcus, Lactococcus or Vagococcus. One strain remained unidentified at genus level. Most Carnobacteria were identified as C. piscicola (156), whereas the species C. divergens was represented only by 10 strains. A total of 59 carnobacteria remained unidentified at species level. After a numerical taxonomy classification based on phenotypic features, at a similarity level of 86% (SSM), and with an average linkage algorithm (UPGMA) of clustering, 13 clusters were formed, seven of which contained three or more strains (regarded as significant clusters). Clusters I and II were labelled as Enterococcus durans and Lactobacillus spp, respectively. Clusters III to VI were assigned to C. piscicola, whereas cluster VII was adscribed to the species C. divergens. An accurate discrimination among Carnobacteria and Lactobacillus was achieved through the use of numerical taxonomy, although the separation betweenCarnobacterium species was not so clearly defined. Phenotypically, the distinction between both species relied only on a reduced number of tests (growth at 40°C and mannitol fermentation). The ability of Carnobacteria to degrade proteinaceous and lipidic compounds was scarce.