Zonula occludens toxins and their prophages in Campylobacter species

BACKGROUND: We previously showed that zonula occludens toxin (Zot) encoded by Campylobacter concisus zot(808T) gene has the potential to initiate inflammatory bowel disease. This Zot protein caused prolonged intestinal epithelial barrier damage, induced intestinal epithelial and macrophage production of tumor necrosis factor-α and enhanced the responses of macrophages to other microbes. In order to understand the potential virulence of Zot proteins in other Campylobacter species, in this study we examined their presence, similarities, motifs and prophages. METHODS: The presence of Zot proteins in Campylobacter species was examined by searching for the Zot family domain in multiple protein databases. Walker A and Walker B motifs in Zot proteins were identified using protein sequence alignment. A phylogenetic tree based on Campylobacter zot genes was constructed using maximum-likelihood method. Campylobacter Zot proteins were compared using protein sequence alignment. The zot-containing prophages in Campylobacter species were identified and compared with known prophage proteins and other viral proteins using protein sequence alignment and protein BLAST. RESULTS: Twelve Zot proteins were found in nine Campylobacter species/subspecies. Among these Campylobacter species, three species had two Zot proteins and the remaining six species/subspecies had one Zot protein. Walker A and Walker B motifs and a transmembrane domain were found in all identified Campylobacter Zot proteins. The twelve Campylobacter zot genes from the nine Campylobacter species/subspecies formed two clusters. The Zot(CampyType_1) proteins encoded by Cluster 1 Campylobacter zot genes showed high similarities to each other. However, Zot(CampyType_2) proteins encoded by Cluster 2 Campylobacter zot genes were more diverse. Furthermore, the zot-containing Campylobacter prophages were identified. CONCLUSION: This study reports the identification of two types of Campylobacter Zot proteins. The high similarities of Zot(CampyType_1) proteins suggest that they are likely to have similar virulence. Zot(CampyType_2) proteins are less similar to each other and their virulent properties, if any, remain to be examined individually. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13099-016-0125-1) contains supplementary material, which is available to authorized users.