A Filamentous Phage Associated with Recent PandemicVibrio parahaemolyticus O3:K6 Strains

Abstract

A specific serotype, O3:K6, of Vibrio parahaemolyticus has recently been causing epidemics of gastroenteritis in Southeast Asia, Japan, and North America. To examine whether the new O3:K6 strains possess characteristics that may exacerbate outbreaks, we compared V. parahaemolyticus O3:K6 strains with non-O3:K6 strains using strains isolated from individuals with traveler's diarrhea at Kansai Airport Quarantine Station, Osaka, Japan. All 24 O3:K6 strains possessed a common plasmid, pO3K6 (DNA size, 8,782 bp, with 10 open reading frames [ORFs]). The gene organization of pO3K6 was similar to that of Vf33, a filamentous phage previously described in V. parahaemolyticus. We isolated a phage (phage f237) from the culture supernatant of V. parahaemolyticus O3:K6 strain KXV237, which formed a turbid plaque on an indicator strain. The genome of f237 was single-stranded DNA, and the double-stranded DNA obtained by treatment of the genome with DNA polymerase was identical to that of pO3K6 when analyzed by agarose gel electrophoresis after HindIII digestion. Furthermore, the N-terminal amino acid sequence of the f237 major coat protein was found in ORF4 of pO3K6. Our results showed that pO3K6 is a replicative form of f237. Among the ORFs found in the f237 genome, the sequence of ORF8 had no significant homology to those of any proteins in databases. ORF8 was located on a region corresponding to the distinctive region of Vf33, and its G؉C content was apparently lower than that of the remaining DNA sequence of f237. By colony hybridization, ORF8 was detected only in O3:K6 strains isolated since 1996 and was not found in O3:K6 strains isolated before 1996 and clinical V. parahaemolyticus strains other than those of serotype O3:K6. Thus, this study shows that f237 is exclusively associated with recent V. parahaemolyticus O3:K6 strains. The ORF8 gene can be a useful genetic marker for the identification of the recently widespread O3:K6 strains of V. parahaemolyticus.

Temporal shifts of the Norway lobster (Nephrops norvegicus) gut bacterial communities

“…Phylotypes clustering within the genus Vibrio were present in most of the samples, showing low (3.5%) to moderate (19.0%) relative abundance. The majority of their closest relatives originated from marine animals (Nasu et al, 2000;Nishiguchi & Nair, 2003;Jensen et al, 2009). This genus is often found in associations with the gut of marine animals varying from parasitism to mutualism and showing diverse metabolic capabilities (Thompson et al, 2004).…”

The contribution of mobile genetic elements to the evolution and ecology of Vibrios

“…A number of studies have examined the diversity of vibriophages associated with Vibrios isolated from coastal environments (Chang et al, , 2002Nasu et al, 2000;Miller et al, 2003;Seguritan et al, 2003), and a few studies have determined the diversity and distribution of plasmids among environmental Vibrios (Shehane & Sizemore, 2002;Roig & Amaro, 2009). In a previous study, we characterized three plasmids isolated from diverse environmental Vibrios including V. mediterranei, V. campbellii, and V. fluvialis .…”

A unique and common restriction fragment pattern of the nucleotide sequences homologous to the genome of Vf33, a filamentous bacteriophage, in pandemic strains of Vibrio parahaemolyticus O3:K6 O4:K68, and O1:K untypeable

“…The additional fragments of KX-V226 may be derived from the RF of a Vf33-like phage because a band corresponding to an extrachromosomal DNA of about 8.5 kb in size was detected only in this strain when the undigested total cellular DNAs of the pandemic strains were hybridized with the Vf33 DNA (data not shown). During the course of our study, Nasu et al [17] reported a 8782-bp plasmid present in the pandemic O3:K6 strain isolated at the quarantine station in Japan is the RF DNA of a Vf33-like ¢lamentous phage (designated as f237). The hybridization pro¢le shared by most pandemic strains was di¡erent from those of other test strains.…”

“…1). Nasu et al [17] reported that an orf8 gene located on the morphogenesis region of f237 may be associated with virulence of the pandemic strains. Therefore, the nucleotide sequence of the morphogenesis region in the pandemic strains may encode the virulence function or survival function.…”