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
The effect of increasing concentrations of Vibrio alginolyticus on survival of Mytilus galloprovincialis larvae was studied in a 48 h static bioassay in 1 l glass bottles. Five bacterial densities were tested ranging from 10(2) to 10(6) bacteria ml(-1). Larval survival and normality (veliger larvae with the typical D-shape) were evaluated after 48 h. An inverse relationship between bacterial concentration and larval survival and normality was observed. In spite of high larval survival (79%) under conditions of high bacterial density (10(5) bacteria ml(-1)), the percent of normal larvae was 11%. Besides an irregular shape, abnormal larvae also presented velum reduction. Results from this study suggest that concentrations of V. alginolyticus lower than 10(3) bacteria ml(-1) should be maintained during M. galloprovincialis larval culture.