Diversity within the Campylobacter jejuni type I restriction-modification loci

Area of Science:

• Microbiology
• Genetics
• Molecular Biology

Background:

• Campylobacter jejuni is a significant foodborne pathogen.
• Restriction-modification (R-M) systems, including type I (hsd) systems, play crucial roles in bacterial genome regulation and defense.
• Understanding R-M system diversity is key to deciphering bacterial evolution and adaptation.

Purpose of the Study:

• To characterize the type I restriction-modification (hsd) systems in a collection of Campylobacter jejuni strains.
• To identify novel genes associated with hsd loci and compare them with known sequences.
• To classify the identified C. jejuni type I R-M systems into distinct families.

Main Methods:

• DNA and amino acid sequence analysis of hsd systems from 73 C. jejuni strains.
• Gene organization analysis.
• Parsimony analysis of amino acid sequences for phylogenetic classification.

Main Results:

• Identification of new genes not present in the reference strain NCTC 11168.
• Absence of evidence for multiple type I systems in C. jejuni, unlike Helicobacter pylori.
• Discovery of intervening ORFs (rloA-H, mloA-B) between hsd genes in some strains.
• Classification of C. jejuni type I R-M systems into three families: 'IAB', 'IC', and 'IF'.
• High conservation of HsdM proteins within families, but low homology between families.
• High nucleotide identity within 'IC' and 'IF' loci.
• Significant nucleotide sequence variation in 'IAB' hsdS and rlo genes, suggesting recombination.

Conclusions:

• The study provides a comprehensive classification of C. jejuni type I R-M systems.
• Sequence diversity within the 'IAB' family suggests ongoing recombination, contributing to the evolution of these systems.
• The identified novel genes and organizational variations highlight the complexity and adaptability of C. jejuni hsd systems.