Phenotypic characterization ofBeneckea anguillara biotypes I and II

Pathogenicity of members of the vibrionaceae family to cultured juvenile sablefish

Sablefish Anoplopoma fimbria are a prized seafood species due to their high oil content and white flaky flesh. Raising these species in culture can help to provide an important source of protein for humans and relief to declining wild fish populations. Understanding the environmental factors that influence the production of Sablefish is important for successful culturing. The significance of host-pathogen interactions in Sablefish culture and the resulting environmental implications are unknown. Pathogens could potentially cause losses of cultured Sablefish stocks due to disease, while Sablefish cultured in net pens may also serve as reservoirs for pathogens and potentially transmit disease to wild fish species. In this initial study, the susceptibility of juvenile Sablefish to three bacterial pathogens from the family Vibrionaceae was examined. Listonella anguillarum, Vibrio ordalii, and V. splendidus can pose serious economic threats to cultured fish and shellfish. Groups of juvenile Sablefish were exposed to five concentrations of each of the pathogens. Sablefish were susceptible to L. anguillarum, but were resistant to V. ordalii and V. splendidus at exposure concentrations of ≤ 1.32 × 10⁷ CFU/mL and ≤ 3.57 × 10⁶ CFU/mL, respectively. The greatest L. anguillarum concentration examined (8.7 × 10⁶ CFU/mL) resulted in 24% mortality in juvenile Sablefish. A 24% loss of Sablefish stock could significantly influence an aquaculture program. As determined by multiple logistic regression, the survival of Sablefish to L. anguillarum exposure was significantly affected by their body mass, and larger fish had a greater probability of survival. Aquaculture operations could employ various strategies to minimize the loss of juvenile Sablefish by accounting for their size and known susceptibilities to pathogens.

Distribution of ultramicrobacteria in a gulf coast estuary and induction of ultramicrobacteria

The abundance of ultramicrobacteria (i.e., bacteria that pass through a 0.2μm filter) in a subtropical Alabama estuary was determined during a 1-year period. Although phenotypic and molecular characterization indicated that the population of ultramicrobacteria was dominated byVibrio species, species ofListonella andPseudomonas were also abundant. Vibrios occurred with the greatest frequency in waters whose salinities were less than 14‰, and were the most abundant species of the total ultramicrobacterial population year-round, whilePseudomonas species were absent or considerably reduced during the winter months. The total number of ultramicrobacteria showed an inverse relationship to total heterotrophic bacteria as measured by colony-forming units (CFU)/ml and to water quality as measured by several parameters. Analysis by generic composition indicated that both salinity and temperature significantly affected the distribution of these organisms. Laboratory studies revealed that strains of vibrios under starvation in both static and continuous-flow microcosms could be induced to form cells that passed through 0.2 and/or 0.4μm filters. Cells exposed to low nutrients became very small; some grew on both oligotrophic (5.5 mg carbon/liter) and eutrophic (5.5 g carbon/liter) media; and some few cells grew only on oligotrophic media. By passing selected vibrio strains on progressively diluted nutrient media, cells were also obtained that were small, that passed through 0.4μm filters, and that could grow in oligotrophic media. These results suggest that ultramicrobacteria in estuaries (at least some portion of the population) may be nutrientstarved or low nutrient-induced forms of certain heterotrophic, eutrophic, autochthonous, estuarine bacteria.

A numerical taxonomic study of species of Vibrio isolated from the aquatic environment and birds in Kent, England

A numerical taxonomic study has been carried out to confirm the identity of strains of the family Vibrionaceae isolated during an ecological study. A total of 237 strains were studied including 148 from the aquatic environment, 6 from estuarine birds, 1 from sheep faeces, and 61 control cultures. Duplicates of 21 of the strains were randomly selected and included to estimate test and operator error. Taxonomic resemblance was estimated on the basis of 148 characters using Euclidean distance. The taxonomic position of some strains was reevaluated using the pattern different coefficient. Strains were clustered by three methods, all of which gave similar results. The estimated average probability of test error was 1.5%. Strains previously identified as Vibrio anguillarum fell into four distinct phenons corresponding to V. anguillarum biovar I, 'V. anguillarum biovar II', V. diazotrophicus, and strains pathogenic to oyster larvae. The latter group characteristically degraded xanthine and probably represents a new species. The phenon corresponding to V. cholerae included the type strain, strains of human origin, and strains isolated in the United Kingdom from birds and the aquatic environment. Some strains of V. cholerae were luminous. Other phenons were identified as V. metschnikovii, V. fluvialis, and Aeromonas spp.