Sequence Analyses of Type IV Pili from Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus

Abstract

Bacterial surface structures called pili have been studied extensively for their role as possible colonization factors. Most sequenced Vibrio genomes predict a variety of pili genes in these organisms, including several types of type IV pili. In particular, the mannose-sensitive hemagglutinin (MSHA) and the PilA pili, also known as the chitin-regulated pilus (ChiRP), are type IVa pili commonly found in Vibrio genomes and have been shown to play a role in the colonization of Vibrio species in the environment and/or host tissue. Here, we report sequence comparisons of two type IVa pilin subunit genes, mshA and pilA, and their corresponding amino acid sequences, for several strains from the three main human pathogenic Vibrio species, V. cholerae, V. parahaemolyticus, and V. vulnificus. We identified specific groupings of these two genes in V. cholerae, whereas V. parahaemolyticus and V. vulnificus strains had no apparent allelic clusters, and these genes were strikingly divergent. These results were compared with other genes from the MSHA and PilA operons as well as another Vibrio pili from the type IVb group, the toxin co-regulated pilus (TCP) from V. cholerae. Our data suggest that a selective pressure exists to cause these strains to vary their MSHA and PilA pilin subunits. Interestingly, V. cholerae strains possessing TCP have the same allele for both mshA and pilA. In contrast, V. cholerae isolates without TCP have polymorphisms in their mshA and pilA sequences similar to what was observed for both V. parahaemolyticus and V. vulnificus. This data suggests a possible linkage between host interactions and maintaining a highly conserved type IV pili sequence in V. cholerae. Although the mechanism underlying this intriguing diversity has yet to be elucidated, our analyses are an important first step towards gaining insights into the various aspects of Vibrio ecology.

Implications of Chitin Attachment for the Environmental Persistence and Clinical Nature of the Human Pathogen Vibrio vulnificus

“…For many bacterial species, including numerous pathogens, type IV pili have been implicated in environmental survival as well as host colonization. Aagesen and Hase proposed that the heterogeneities among pilA and mshA sequences are likely a result of positive selective pressures, which would be expected to have ecological implications for the bacterium (29). Sequence alignment of V. vulnificus type IV pilus genes (pilA, pilD, and mshA) as well as gbpA revealed a considerable number of genetic polymorphisms, many of which correlate with genotype.…”

“…GbpA also contributes to the persistence of V. cholerae within bivalve tissues, particularly through colonization of mussel hepatopancreas cells (28). Two type IV pili have been identified in V. vulnificus, the mannose-sensitive hemagglutinin pilus (MSHA) and the PilA pilus (also referred to as the chitin-regulated pilus ChiRP in some Vibrio species), both of which are processed by a unique prepilin peptidase (PilD) to form a mature pilus structure that extends from the surface of the cell and interacts with the environment (29). In V. vulnificus, the type IV pilin subunit PilA has been shown to play a role in biofilm formation, adherence to human epithelial cells, and oyster colonization (30,31).…”

Are type IV pili involved in <i>Vibrio anguillarum</i> virulence towards sea bass (<i>Dicentrarchus labrax</i> L.) larvae?

“…A possible explanation for this observation is the identification of a second type IV pilus system in the V. anguillarum genome, the mannose-sensitive hemagglutinin pilus (MSHA) system, which may complement the PilA deficiency. This system is very similar to the V. cholerae MSHA pilus and has been previously identified in other Vibrio species such as V. vulnificus and V. parahaemolyticus [45]. However, in V. vulnificus, the presence of the MSHA pilus was not able to complement for the loss of the PilA pilus, as the pilA knock out mutant was severely attenuated in biofilm formation and virulence in mice [28].…”

Genome Sequence of the Human-Pathogenic Bacterium Vibrio vulnificus Type Strain ATCC 27562

“…These genes have long been reported by many research papers (1,9,15). Overall, as this strain has long been used in the labs all over the world, the genome sequence of Vibrio vulnificus ATCC 27562 T provides an excellent foundation for disease control and comparative and basic research.…”