Genomic Sequence and Receptor for the Vibrio cholerae Phage KSF-1Φ: Evolutionary Divergence among Filamentous Vibriophages Mediating Lateral Gene Transfer

Abstract

KSF-1⌽, a novel filamentous phage of Vibrio cholerae, supports morphogenesis of the RS1 satellite phage by heterologous DNA packaging and facilitates horizontal gene transfer. We analyzed the genomic sequence, morphology, and receptor for KSF-1⌽ infection, as well as its phylogenetic relationships with other filamentous vibriophages. While strains carrying the mshA gene encoding mannose-sensitive hemagglutinin (MSHA) type IV pilus were susceptible to KSF-1⌽ infection, naturally occurring MSHA-negative strains and an mshA deletion mutant were resistant. Furthermore, D-mannose as well as a monoclonal antibody against MSHA inhibited infection of MSHA-positive strains by the phage, suggesting that MSHA is the receptor for KSF-1⌽. The phage genome comprises 7,107 nucleotides, containing 14 open reading frames, 4 of which have predicted protein products homologous to those of other filamentous phages. Although the overall genetic organization of filamentous phages appears to be preserved in KSF-1⌽, the genomic sequence of the phage does not have a high level of identity with that of other filamentous phages and reveals a highly mosaic structure. Separate phylogenetic analysis of genomic sequences encoding putative replication proteins, receptor-binding proteins, and Zot-like proteins of 10 different filamentous vibriophages showed different results, suggesting that the evolution of these phages involved extensive horizontal exchange of genetic material. Filamentous phages which use type IV pili as receptors were found to belong to different branches. While one of these branches is represented by CTX⌽, which uses the toxin-coregulated pilus as its receptor, at least four evolutionarily diverged phages share a common receptor MSHA, and most of these phages mediate horizontal gene transfer. Since MSHA is present in a wide variety of V. cholerae strains and is presumed to express in the environment, diverse filamentous phages using this receptor are likely to contribute significantly to V. cholerae evolution.Vibrio cholerae is the host for a variety of bacteriophages (vibriophages), which include virulent phages as well as temperate phages represented by the kappa-type phages produced by most strains of the El Tor biotype (18, 36). Another group of vibriophages includes the filamentous phages, which have a single-stranded DNA (ssDNA) genome (1,8,23,25,40). Several of the V. cholerae-specific filamentous phages have been implicated in virulence gene transfer among V. cholerae strains (2,7,40). Filamentous phages of V. cholerae have also been found to be distinct from the well-characterized filamentous coliphages in that some of these phages can form lysogens (1,25,40). The most remarkable of these phages is CTX⌽ (40), which exists as a prophage in toxigenic V. cholerae and encodes cholera toxin (CT).Mechanisms associated with the induction and propagation of CTX⌽ and related phages have been a major area of interest in vibriophage biology (5,6,(9)(10)(11)(12). In toxigenic El Tor and O139 strains of V. cholerae, CTX propha...

Correlation between viral production and carbon mineralization under nitrate-reducing conditions in aquifer sediment

“…These VLPs are morphologically similar to other filamentous bacteriophage. Similarly sized filamentous phage have been identified in pure culture as well as environmental samples: KSF-1F 1200 nm long 7 nm wide (Faruque et al, 2005), Pf1 2000 nm wide (Lorieau et al, 2008), VFJF 1400 nm long 7 nm wide (Wang et al 2013), B5 620 nm long 12 nm wide (Chopin et al, 2002); alpine lake filamentous viruses 450-730 nm long 30-40 nm wide (Hofer and Sommaruga, 2001). Together, these results indicate that Pseudomonas sp.…”

Comparative genomics of clinical and environmental Vibrio mimicus

“…MSHA pilus (34), a type IV pilus (TFP), has been shown to play a role in adherence to plankton (38), the MSHA of V. mimicus may serve as a dual-function appendage, i. e., for intestinal adherence and attachment to plankton or other surfaces to form a biofilm. In addition, MSHA has been shown to serve as receptor for KSF-1Φ, VGJΦ, fs-1, fs-2, and 493 filamentous phages in V. cholerae (39)(40)(41)(42)(43). Therefore, the same family of phages may be expected to infect V. mimicus.…”

An inducible lambdoid prophage encoding cytolethal distending toxin (Cdt-I) and a type III effector protein in enteropathogenic Escherichia coli

“…CDT-1⌽ prepared from mitomycin C-induced culture supernatant of NT3363 was concentrated by ultracentrifugation (100,000 ϫ g for 1 h) and resuspension of the precipitate. The crude preparation was used to determine the morphology of the phage as described (29). The phage particles were negatively stained with 2% uranyl acetate and examined under a transmission electron microscope (model 420T; Philips, Amsterdam, The Netherlands).…”