RESUMO
A study was performed to investigate the genomic variations in the shrimp farm isolates of Vibrio alginolyticus and V. harveyi when the isolates were subjected to environmental stress. Samples of shrimps, water and sediment were collected from Southern Indian coastal shrimp farms. Vibrio isolates were biochemically identified and confirmed using 16S rDNA and gyrB gene specific PCR. The bacterial strains were genotyped by PCR fingerprinting using GTG(5) and IS (Insertion Sequence) primers. Seven strains each of V. alginolyticus and V. harveyi were subjected to 10 passages through trypticase soya broth (TSB), which contained different NaCl concentrations (3, 6 and 8%) and trypticase soya agar (TSA). V. alginolyticus was also passaged through TSB with a 12% NaCl concentration. PCR fingerprinting, which was performed on the strains that were passaged through different salt concentrations, confirmed that V. alginolyticus and V. harveyi could affect the genomic variations, depending on the environmental conditions of the culture. The study highlights the complex genotypic variations that occur in Vibrio strains of tropical aquatic environment because of varied environmental conditions, which result in genetic divergence and/or probable convergence. Such genetic divergence and/or convergence can lead to the organismal adaptive variation, which results in their ability to cause a productive infection in aquatic organisms or generation of new strains.
Assuntos
Animais/genética , Animais/crescimento & desenvolvimento , Animais/isolamento & purificação , Animais/microbiologia , Aquicultura/genética , Aquicultura/crescimento & desenvolvimento , Aquicultura/isolamento & purificação , Aquicultura/microbiologia , Primers do DNA/genética , Primers do DNA/crescimento & desenvolvimento , Primers do DNA/isolamento & purificação , Primers do DNA/microbiologia , DNA Bacteriano/genética , DNA Bacteriano/crescimento & desenvolvimento , DNA Bacteriano/isolamento & purificação , DNA Bacteriano/microbiologia , Ecossistema/genética , Ecossistema/crescimento & desenvolvimento , Ecossistema/isolamento & purificação , Ecossistema/microbiologia , Penaeidae/genética , Penaeidae/crescimento & desenvolvimento , Penaeidae/isolamento & purificação , Penaeidae/microbiologia , Reação em Cadeia da Polimerase/genética , Reação em Cadeia da Polimerase/crescimento & desenvolvimento , Reação em Cadeia da Polimerase/isolamento & purificação , Reação em Cadeia da Polimerase/microbiologia , Vibrio alginolyticus/genética , Vibrio alginolyticus/crescimento & desenvolvimento , Vibrio alginolyticus/isolamento & purificação , Vibrio alginolyticus/microbiologia , Vibrio/genética , Vibrio/crescimento & desenvolvimento , Vibrio/isolamento & purificação , Vibrio/microbiologiaRESUMO
Abstract Yellow pigmented, filamentous, Gram-negative bacteria belonging to genus Flavobacterium are commonly associated with infections in stressed fish. In this study, inter-species diversity of Flavobacterium was studied in apparently healthy freshwater farmed fishes. For this, ninety one yellow pigmented bacteria were isolated from skin and gill samples (n = 38) of three farmed fish species i.e. Labeo rohita, Catla catla and Cyprinus carpio. Among them, only twelve bacterial isolates (13.18%) were identified as Flavobacterium spp. on the basis of morphological, biochemical tests, partial 16S rDNA gene sequencing and phylogenetic analysis. On the basis of 16S rDNA gene sequencing, all the 12 isolates were 97.6-100% similar to six different formally described species of genus Flavobacterium. The 16S rDNA based phylogenetic analysis grouped these strains into six different clades. Of the 12 isolates, six strains (Fl9S1-6) grouped with F. suncheonense, two strains (Fl6I2, Fl6I3) with F. indicum and the rest four strains (Fl1A1, Fl2G1, Fl3H1 and Fl10T1) clustered with F. aquaticum, F. granuli, F. hercynium and F. terrae, respectively. None of these species except, F. hercynium were previously reported from fish. All the isolated Flavobacterium species possessed the ability of adhesion and biofilm formation to colonize the external surface of healthy fish. The present study is the first record of tropical freshwater farmed fishes as hosts to five environmentally associated species of the Flavobacterium.
