Outer Membrane Protein OmpW Is the Receptor for Typing Phage VP5 in the Vibrio cholerae O1 El Tor Biotype

Abstract

Phage typing is used for the subtyping of clones of epidemic bacteria. In this study, we identified the outer membrane protein OmpW as the receptor for phage VP5, one of the typing phages for the Vibrio cholerae O1 El Tor biotype. A characteristic 11-bp deletion in ompW was observed in all epidemic strains resistant to VP5, suggesting that this mutation event can be used as a tracing marker in cholera surveillance. Seven cholera pandemics have been recorded historically. The first six pandemics were putatively caused by the classical biotype of Vibrio cholerae serogroup O1, whereas the ongoing seventh pandemic is caused by the O1 El Tor biotype (1). Subtyping of V. cholerae strains is useful in epidemiological and microbiological studies. A phage-biotyping scheme, in which five typing phages (VP1 to VP5) were included, was established for El Tor strain subtyping in the 1970s in China (2). During surveillance of V. cholerae strains, almost all El Tor strains from epidemics were found to be sensitive to all five of these typing phages and are designated phage type 1 (PT1) strains. However, during the 1998 cholera epidemic in Sichuan Province, some patient strains were resistant to phage VP5. These strains belong to the PT6 group and coexisted with PT1 strains. PT6 strains became predominant in 1999 and 2000 but disappeared after 2001 (3), which makes them unique among the epidemic strains.Phages infect susceptible bacterial strains, beginning with binding to receptors on the surfaces of bacteria. OmpW is an outer membrane protein that serves as a receptor for Escherichia coli colicin S4 (4). The ompW gene has served as a species-specific gene of V. cholerae in many detection studies (5, 6). This gene was found to have an 11-bp deletion in the PT6 strains, but the deletion was not detected in any PT1 strain (3). Therefore, a role for OmpW in VP5 infection was suspected.In this study, ompW genes from 44 strains isolated from 1998 to 2001, including 22 PT6 and 11 PT1 strains from Sichuan and 11 PT1 strains from other provinces, were sequenced. The same 11-bp deletion was in all PT6 strains (Fig. 1). The deletion corresponds to nucleotides (nt) 298 to 308 of ompW and causes a shift in the reading frame. A new stop codon is generated at 350 nt, ahead of the original stop codon (Fig. 1). All the PT1 strains had intact and identical ompW sequences.To assess the possible role of the ompW gene in VP5 infection, we constructed an ompW deletion mutant, designated N16961-dompW, with suicide plasmid pWM91 (7) from the VP5-sensitive strain N16961. The N16961-dompW mutant lost sensitivity to VP5 ( Fig. 2A). This sensitivity was restored when it was complemented with plasmid pBR322-ompW (designated strain N16961-dompW-R) containing the intact ompW gene cloned from N16961 but not when it obtained pBR322-ompW(del) containing ompW with an 11-bp deletion cloned from the PT6 strain VC631. VC631 became sensitive to VP5 when it obtained plasmid pBR322-ompW but remained resistant when it obtained pBR322-ompW(del) ( Fig. 2A), indicating t...

Key Residues of S. flexneri OmpA Mediate Infection by Bacteriophage Sf6

“…For example, many archaeal, eukaryotic, and bacterial viruses require proteinaceous receptors on the host surface used for attachment [2][3][4][5][6][7][8][9][10][11][12]. In addition, many of these viruses demonstrate plasticity in their binding mechanisms [3,13].…”

The Resistance of Vibrio cholerae O1 El Tor Strains to the Typing Phage 919TP, a Member of K139 Phage Family

“…The Phage-Biotyping Scheme was used to subtype V. cholerae O1 El Tor strains based on their phenotype since the 1970s ( Wang et al, 2007 ; Deng et al, 2008 ). Some genetic mutations of the El Tor strains that were resistant to the typing phages, mainly on the receptor genes ( Zhang et al, 2009 ; Xu et al, 2013 , 2014 ), had been identified. Based on phage resistance and receptor gene mutations, the appearance and spread of a distinct clone was identified in some specific geographical regions ( Xu et al, 2014 ).…”

“…Some genetic mutations of the El Tor strains that were resistant to the typing phages, mainly on the receptor genes ( Zhang et al, 2009 ; Xu et al, 2013 , 2014 ), had been identified. Based on phage resistance and receptor gene mutations, the appearance and spread of a distinct clone was identified in some specific geographical regions ( Xu et al, 2014 ). V. cholerae strains in different epidemics or outbreaks also presented different sensitivities to phage 919TP.…”

“…A Phage-Biotyping Scheme was developed for the subtyping of O1 El Tor strains and has been used in the cholera surveillance in China since the 1970s ( Gao et al, 1984 ; Xiao et al, 2013 ). In the phage typing part of the scheme, five typing phages (named VP1 to VP5, respectively; Gao et al, 1984 ; Zhang et al, 2009 ; Li et al, 2013 ; Xu et al, 2013 , 2014 ) are used and El Tor strains can be clustered into 32 distinct phage types (from 1 to 32) according to their lytic patterns to these five phages. In the biological typing part, El Tor strains can be grouped into 12 biotypes (from a to l) according to their biological performance in lysogenicity, susceptibility to temperate phage 919TP, sorbitol fermentation, and hemolysis ( Gao, 1988 ; Wang et al, 2009 ; Xiao et al, 2013 ).…”

“…The phenotype change from sensitivity to resistance to the phage infection always results from gene mutations. In our previous studies, we found that mutations in the receptor genes (e.g., ompW , core oligosaccharide genes, and O -antigen genes) of V. cholerae El Tor strains may render the strains resistant to the typing phages used in the Phage-Biotyping Scheme ( Zhang et al, 2009 ; Xu et al, 2013 , 2014 ). Bacteria commonly avoid phage infection using mechanisms associated with phage adsorption, injection, gene replication, assembly, and release ( Hyman and Abedon, 2010 ; Labrie et al, 2010 ).…”