The role of integrating conjugative elements in Helicobacter pylori: a review

Langgeng Agung Waskito,Jeng Yih-Wu,Yoshio Yamaoka

doi:10.1186/s12929-018-0489-2

Abstract

The genome of Helicobacter pylori contains many putative genes, including a genetic region known as the Integrating Conjugative Elements of H. pylori type four secretion system (ICEHptfs). This genetic regions were originally termed as “plasticity zones/regions” due to the great genetic diversity between the original two H. pylori whole genome sequences. Upon analysis of additional genome sequences, the regions were reported to be extremely common within the genome of H. pylori. Moreover, these regions were also considered conserved rather than genetically plastic and were believed to act as mobile genetic elements transferred via conjugation. Although ICEHptfs(s) are highly conserved, these regions display great allele diversity, especially on ICEHptfs4, with three different subtypes: ICEHptfs4a, 4b, and 4c. ICEHptfs were also reported to contain a novel type 4 secretion system (T4SS) with both epidemiological and in vitro infection model studies highlighting that this novel T4SS functions primarily as a virulence factor. However, there is currently no information regarding the structure, the genes responsible for forming the T4SS, and the interaction between this T4SS and other virulence genes. Unlike the cag pathogenicity island (PAI), which contains CagA, a gene found to be essential for H. pylori virulence, these novel T4SSs have not yet been reported to contain genes that contribute significant effects to the entire system. This notion prompted the hypothesis that these novel T4SSs may have different mechanisms involving cag PAI.

Highlights

Helicobacter pylori is one of the most successful pathogenic bacteria that colonizes the human stomach, an organ that had previously been considered to be sterile
Since the discovery of this particular gene region in the H. pylori genome, there have been a variety of proposed names including the plasticity region, plasticity zones, transposon of plasticity zones (TnPZ), and ICEHptfs, which has led to the confusion regarding the terminology
With the increasing number of available genome sequences, it has been reported that this region is commonly present in H. pylori genome with some variability in the different geographic areas

Summary

Introduction

Helicobacter pylori is one of the most successful pathogenic bacteria that colonizes the human stomach, an organ that had previously been considered to be sterile. In addition to the cag PAI, another intriguing putative gene cluster is the Integrating Conjugative Elements (ICEs) of H. pylori of type four secretion system (ICEHptfs), which has not been studied as much as other virulence factors such as cag PAI and VacA. The cag PAI had a similar features to ICEHptfs, such as low G + C content, and was flanked by a 31 bp motif representing the integration site [19] and contained the VirB homologue forming cag T4SS to translocate CagA [8, 20].

Results

Conclusion