Zooplankton act as cruise ships promoting the survival and pathogenicity of pathogenic bacteria.

Bacteria in general interact with zooplankton in aquatic ecosystems. These zooplankton-bacterial interactions help to shape the bacterial community by regulating bacterial abundances. Such interactions are even more significant and crucially in need of investigation in the case of pathogenic bacteria, which cause severe diseases in humans and animals.

Preyssler-type phosphotungstate is a new family of negative-staining reagents for the TEM observation of viruses.

Transmission electron microscopy (TEM) is an essential method in virology because it allows for direct visualization of virus morphology at a nanometer scale. Negative staining to coat virions with heavy metal ions must be performed before TEM observations to achieve sufficient contrast. Herein, we report that potassium salts of Preyssler-type phosphotungstates (K[PWOM], M = Na, Ca, Ce, Eu, Bi, or Y) are high-performance negative staining reagents.

Environmental factors affecting Edwardsiella ictaluri-induced mortality of riverine ayu, Plecoglossus altivelis (Temminck & Schlegel).

We analysed the predisposing factors for Edwardsiella ictaluri infection in the riverine ayu Plecoglossus altivelis on the basis of environmental and epidemiological data obtained in a tributary to and the lower reaches of the Tama River, Japan, in July and August 2011-2015. Mortality of ayu due to E. ictaluri infection was observed only in the tributary in August 2012 and 2013; both periods were unusually hot.

Continuation and replacement of Vibrio cholerae non-O1 clonal genomic groups isolated from Plecoglossus altivelis fish in freshwaters.

The dissemination and abundances of Vibrio species in aquatic environments are of interest, as some species cause emerging diseases in humans and in aquatic organisms like fish. It is suggested that Vibrio cholerae non-O1 infections of Plecoglossus altivelis ('ayu') were spread to various parts of Japan through the annual transplantation of juvenile fish. To investigate this, we used genome-aided tracing of 17 V.

Pathological and immunohistochemical studies following the experimental infection of ayu (Plecoglossus altivelis) by Edwardsiella ictaluri.

In recent decades, several mass mortalities were recorded in riverine ayu (Plecoglossus altivelis) in Tokyo Metropolis, Hiroshima Prefecture, and Yamaguchi Prefecture, Japan; in these outbreaks, microbiological and pathological examinations revealed Edwardsiella ictaluri as the causative agent. In this study, histopathological findings and immunohistochemical localization of the bacteria following experimental infection of ayu were discussed. Infection experiments were performed using 44 healthy cultured ayu fingerlings using E.

Comparative immunohistological study on using capsaicin, piperine, and okadaic acid for the transepithelial passage of the inactivated viral and bacterial vaccines in fish.

The practical difficulty of parenteral application of fish vaccines against devastating fish diseases diverted the interest toward oral vaccination. Search for effective methods to enhance the oral uptake of viral and bacterial vaccines is continuing. The current research focus on a new role of mucosal fish vaccine adjuvants inducing the antigen uptake by enhancing vascularity or increasing intestinal permeability.

A novel jumbo Tenacibaculum maritimum lytic phage with head-fiber-like appendages.

A novel jumbo bacteriophage (myovirus) is described. The lytic phage of Tenacibaculum maritimum, which is the etiological agent of tenacibaculosis in a variety of farmed marine fish worldwide, was plaque-isolated from seawater around a fish aquaculture field in Japan. The phage had an isometric head 110-120 nm in diameter, from which several 50- to 100-nm-long flexible fiber-like appendages emanate, and a 150-nm-long rigid contractile tail.

Comparative genomic analysis of three lytic Lactococcus garvieae phages, novel phages with genome architecture linking the 936 phage species of Lactococcus lactis.

To date, a number of bacteriophages that infect Lactococcus garvieae isolated from marine fish have been identified. However, the evolutionary insight between L. garvieae phages and other viral community have not yet been immersedly investigated.

Host range and influence of a cell capsule on the phage efficacy of three Lactococcus garvieae lytic phages.

Three lytic phages (PLgW-1, PLgY-16, and PLgY-30) were previously used for phage-typing Lactococcus garvieae, a bacterial pathogen of various marine fish species, and were demonstrated to be potential therapeutants for infections caused by L. garvieae. The morphology, host range, and efficacy of these phages have not been investigated in detail, however.

Complete Genome Sequence of the Lytic Giant Bacteriophage pT24 Infecting spp., Isolated from a Shrimp Culture Pond.

The lytic bacteriophage pT24, which infects spp., was isolated from the water of a whiteleg shrimp () culture pond in Thailand. This giant bacteriophage with myovirus morphology comprised 234,670 bp with 296 predicted genes.

ORF13 in the Type III secretion system gene cluster of Edwardsiella tarda binds to the mammalian factor Cugbp2.

The Type III secretion system (TTSS) is essential for the intracellular replication of Edwardsiella tarda in phagocytes of fish and mammals, and a hypothetical gene (orf13) located in the TTSS gene cluster is required for intracellular replication and virulence of E. tarda. Here, we show that under TTSS-inducing conditions, the protein ORF13 was secreted into culture supernatant.

Identification of genes associated with the penetration activity of the human type of Edwardsiella tarda EdwGII through human colon epithelial cell monolayers.

Edwardsiella tarda is a Gram-negative pathogen with a broad host range including fish and humans. E. tarda causes gastrointestinal and extraintestinal infections in humans.

Cell Culture Isolation of Piscine Nodavirus (Betanodavirus) in Fish-Rearing Seawater.

Piscine nodavirus (betanodavirus) is the causative agent of viral nervous necrosis (VNN) in a variety of cultured fish species, particularly marine fish. In the present study, we developed a sensitive method for cell culture isolation of the virus from seawater and applied the method to a spontaneous fish-rearing environment. The virus in seawater was concentrated by an iron-based flocculation method and subjected to isolation with E-11 cells.

V-GAP: Viral genome assembly pipeline.

Next-generation sequencing technologies have allowed the rapid determination of the complete genomes of many organisms. Although shotgun sequences from large genome organisms are still difficult to reconstruct perfect contigs each of which represents a full chromosome, those from small genomes have been assembled successfully into a very small number of contigs. In this study, we show that shotgun reads from phage genomes can be reconstructed into a single contig by controlling the number of read sequences used in de novo assembly.

Full-genome sequence of a novel myovirus, GF-2, infecting Edwardsiella tarda: comparison with other Edwardsiella myoviral genomes.

Edwardsiellosis, which is caused by Edwardsiella tarda, a Gram-negative bacterium, is one of the most serious infectious diseases in both marine and freshwater fish farms worldwide. Previously, we reported the complete genome sequences of three E. tarda-lytic bacteriophages (two podoviruses and a myovirus), which were isolated from fish tissues and fish-rearing seawater.

Complete genome sequence analysis of two Pseudomonas plecoglossicida phages, potential therapeutic agents.

Pseudomonas plecoglossicida is a lethal pathogen of ayu (Plecoglossus altivelis) in Japan and is responsible for substantial economic costs to ayu culture. Previously, we demonstrated the efficacy of phage therapy against P. plecoglossicida infection using two lytic phages (PPpW-3 and PPpW-4) (S.

Type III secretion system genes of Edwardsiella tarda associated with intracellular replication and virulence in zebrafish.

The Type III secretion system (T3SS) is essential for intracellular replication of Edwardsiella tarda in phagocytes of fish and mammals. Two possible effector candidate genes (eseE and eseG) and 7 hypothetical genes (esaB, escC, orf13, orf19, orf26, orf29, and orf30) located in the T3SS gene cluster were inactivated by an allelic exchange method, and we found that E. tarda strains carrying insertion mutations in escC, orf13, orf19, orf29, and orf30 were unable to replicate within J774 macrophages and HEp-2 epithelial cells.

Complete Genome Sequence of the Edwardsiella ictaluri-Specific Bacteriophage PEi21, Isolated from River Water in Japan.

We present the complete genome sequence for a novel Edwardsiella ictaluri-specific bacteriophage, PEi21, isolated from river water in Japan. An initial comparative genome analysis revealed that the phage was closely related to the previously reported Edwardsiella tarda phage MSW-3 isolated from a red sea bream farm in Japan.

Complete Genome Sequence of a Novel Myovirus Which Infects Atypical Strains of Edwardsiella tarda.

We present the genome sequence of a novel -lytic bacteriophage, MSW-3, which specifically infects atypical strains. The morphological and genomic features of MSW-3 suggest that this phage is a new member of the dwarf myoviruses, which have been much less studied than other groups of myoviruses.

Complete Genome Sequences of Edwardsiella tarda-Lytic Bacteriophages KF-1 and IW-1.

We report the complete genome sequences of two Edwardsiella tarda-lytic bacteriophages isolated from flounder kidney (KF-1) and seawater (IW-1). These newly sequenced phage genomes provide a novel resource for future studies on phage-host interaction mechanisms and various applications of the phages for control of edwardsiellosis in aquaculture.

Identification of RNA regions that determine temperature sensitivities in betanodaviruses.

Betanodaviruses, the causative agents of viral nervous necrosis in marine fish, have bipartite positive-sense RNA genomes. The larger genomic segment, RNA1 (~3.1 kb), encodes an RNA-dependent RNA polymerase (protein A), and the smaller genomic segment RNA2 (~1.

Plasmid profiling of Flavobacterium psychrophilum isolates from ayu (Plecoglossus altivelis altivelis) and other fish species in Japan.

In order to evaluate the genetic variability of the causative agent of cold water disease (CWD), plasmid profiling was used to characterize Flavobacterium (F.) psychrophilum isolates (n = 169). Size analysis of plasmids in F.

Isolation and identification of bacteriophages infecting ayu Plecoglossus altivelis altivelis specific Flavobacterium psychrophilum.

In order to investigate methods for controlling systemic bacterial coldwater disease (CWD), bacteriophages that infect Flavobacterium psychrophilum were isolated by the enrichment method from pond water collected from Japanese ayu farms. The five phages isolated were classified as members of Myoviridae (PFpW-3, PFpC-Y), Podoviridae (PFpW-6, PFpW-7), and Siphoviridae (PFpW-8) and had highly variable patterns of infectivity for different F. psychrophilum isolates (n=128).

Characterization of proteins secreted from a type III secretion system of Edwardsiella tarda and their roles in macrophage infection.

The Type III secretion system is essential for intracellular replication of Edwardsiella tarda in phagocytes of fish and mammals. We identified the secreted proteins of the Type III secretion system by comparing the wild-type strain and the Type III mutant mET1229. The wild-type strain secreted 55, 25, and 22 kDa proteins into the culture supernatant, whereas the Type III mutant did not.