Some strains of Vibrio harveyi are known to be pathogenic for fish and many invertebrates including crustaceans. Despite their importance, their modes of virulence have yet to be fully elucidated. Here, we present a previously unreported bacteriophage extracted from a toxin‐producing strain of V. harveyi isolated from moribund prawn larvae in tropical Australia. Classification into the family Myoviridae was based upon morphological characteristics (an icosahedral head, a neck/collar region and a sheathed rigid tail) and nucleic acid characteristics (double‐stranded linear DNA). We have termed the bacteriophage VHML (Vibrio Harveyi Myovirus Like). VHML is a temperate bacteriophage that has a narrow host range and shows an apparent preference for V. harveyi above other vibrios (63 Vibrio isolates tested) and other genera (10 other genera were tested). The conventional methods for phage concentration and extraction of nucleic acids from phage particles were not efficient and the alternative methods that were used are discussed.
Aims: To determine the complete nucleotide sequence of the bacteriophage VHML and establish a hypothesis for the virulence conversion caused by VHML infection of Vibrio harveyi. Methods and Results: The complete nucleotide sequence of VHML was determined (43 193 bp) and used to identify putative genes. The translated products of these genes were compared with reported sequences to assign hypothetical functions. All anticipated structural genes and putative genes for lysogeny were identified. In addition, we found a complete N6-adenine methyltransferase (Dam) gene that appeared to have an essential site for ADPribosylating toxins at the C-terminal of the translated product. Conclusions: Virulence conversion of V. harveyi by VHML may be associated with Dam transcriptional regulation. The Dam gene may also encode for a toxin component similar to ADP-ribosylating toxins. Significance and Impact of Study: This manuscript lays the foundation for understanding the virulence of toxin-producing V. harveyi. Further research into aspects discussed here will lead to a greater comprehension regarding the invertebrate disease vibriosis and its control in the farming of these animals.
Aims: Vibrio harveyi is an important pathogen, causing potential devastation to marine aquaculture. This organism, however, is extremely difficult to identify because it is phenotypically diverse. Biochemical identification can involve many tests and take weeks to perform. The aim of this work is to develop a PCR that can reduce the number of biochemical tests, and the time taken, to get a definitive identification of this organism. Methods and Results: The PCR was developed using 16S rDNA sequences from a number of V. harveyi strains, and other vibrios. The described test gave positive results for all strains of V. harveyi tested. However, some strains of V. alginolyticus also gave positive results and a small number of biochemical tests were required to differentiate between these two species. This indicated that preisolation of the bacteria was needed and therefore the test was not applicable to the testing of mixed populations directly. Conclusion, Significance and Impact of the Study: The duration of identification of this species was significantly reduced from a number of weeks to a few days. Hence, diagnosis of affected animals will be faster and earlier treatment can be administered which may increase the survival rate from vibriosis.
Random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) was used to investigate the differentiation of the genus Aeromonas at the genomospecies level. Of 20 primers evaluated, six produced profiles which contained multiple bands capable of differentiating the genomospecies. These six primers were also used in RAPD-PCR analyses of clinical and environmental isolates of the different genomospecies. In most cases, each strain gave a unique fingerprint, illustrating genetic heterogeneity at the genomospecies level. However, some homogeneity in fragment sizes was seen among strains within a genomospecies which was not apparent in strains from different genomospecies. This study therefore complements and supports the current classification of Aeromonas into genomospecies. These results also show that RAPD-PCR has the potential to differentiate between the genomospecies of Aeromonas.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.