Colonisation of the gastrointestinal tract (GIT) is a key factor in the ability of pathogenic bacteria to cause disease in humans, where the GIT’s mucous layers form a barrier against infection. The chemotaxis properties of gut colonising bacteria, like Escherichia coli and Campylobacter jejuni have been well studied. Motility and attraction of C. jejuni to components of the GIT mucous layer have been regarded as facilitators for penetration of the gut epithelial cells. However, chemotaxis genes of hydrogen-requiring Campylobacter species, known to colonise the GIT, have not been thoroughly investigated.
This study compared the presence and location of chemotaxis related genes in the genomes of C. concisus, C. curvus, C. mucosalis and C. showae. The 3-D predicted protein structure and ligand binding domains were analysed to assess their colonisation capabilities. Whole genome sequences for E. coli (K-12, MG1655), C. jejuni (NCTC 11168) and C. concisus (ATCC 33237), C. curvus (525.92), C. showae (B91 SC ) and C. mucosalis (ATCC 43265) were downloaded from the NCBI website and annotated using DFAST. Protein identity was established by multiple sequence alignment using Clustal-omega. The predicted chemotaxis-related genes and their encoded protein structures were compared to those previously identified in E. coli.
Several chemotaxis-related genes similar to those previously identified in the E. coli model were found, in some form, in all of the analysed Campylobacter spp genome sequences. Two groups of these gene clusters were close enough in their location to possibly be in operons. Furthermore, the high similarity between the size and the predicted 3-D protein structures of Campylobacter spp and E. coli suggests that chemotaxis in these GIT colonisers, operates in a similar manner, and show the conservation of chemotaxis genes in these selected enteric bacterial species. However, differences in the binding sites of chemotaxis receptor proteins suggests variation in the sensed substances, and may indicate their colonisation potential and pathogenic properties, which is worth of further investigation.