Comparative Genomic Analysis Identifies a Campylobacter Clade Deficient in Selenium Metabolism

Area of Science:

• Microbiology
• Genomics
• Bacterial Taxonomy

Background:

• The nonthermotolerant Campylobacter species Campylobacter fetus, Campylobacter hyointestinalis, Campylobacter iguaniorum, and Campylobacter lanienae form a distinct phylogenetic cluster.
• These species are primarily isolated from livestock and cause infrequent human illness.
• Previous studies suggested the existence of three novel Campylobacter lanienae-related taxa.

Purpose of the Study:

• To further characterize putative novel Campylobacter taxa and the C. fetus group.
• To conduct a comparative genomic analysis of the C. fetus group.

Main Methods:

• Sequencing of 76 Campylobacter genomes (26 C. lanienae strains and 50 strains of novel taxa).
• Comparative genomic analysis, including average nucleotide identity (ANI) analysis.
• Analysis of genome size, CRISPR/Cas systems, flagellin genes, and selenium metabolism genes.

Main Results:

• Genomic analysis supports the identification of three novel Campylobacter species.
• C. lanienae and the three novel species form a distinct clade, termed the C. lanienae clade.
• The C. lanienae clade exhibits reduced genome size, distinct CRISPR/Cas systems, multiple flagellin genes, and lacks selenium metabolism genes.

Conclusions:

• The study defines the C. lanienae clade within the C. fetus group.
• The identified genomic features provide clear distinctions for the C. lanienae clade and its constituent species.
• This research enhances the understanding of Campylobacter diversity and evolution.