Dichelobacter nodosus VCS1703A

Dichelobacter nodosus (strain VCS1703A) is an aerotolerant anaerobe that is the principal causative agent of footrot in ruminants, a disease that leads to severe economic losses in the wool and meat industries. This Gram-negative bacterium is phylogenetically associated with the gamma subdivision of the Proteobacteria. The small size of the D. nodosus genome makes it the smallest anaerobic bacterium sequenced to date and places it among the smallest non-intracellular bacterial pathogens yet characterized. It differs markedly from small genomes of intracellular bacteria, retaining greater biosynthetic capabilities and lacking any evidence of extensive ongoing genome reduction (only six pseudogenes have been identified in D. nodosus). Almost 20% of the genome is derived from lateral gene transfer. Most of these regions seem to be associated with virulence. Though compact, its genome shows intergenic spacing that, in average, is closer to the median observed in prokaryotic genomes. D. nodosus lacks various metabolic pathways related to amino acid biosynthesis and is capable only of weak short-term, but not sustained, growth under microaerophilic conditions. The analysis of its metabolic pathways showed unsuspected capabilities, including carbohydrate utilization, electron transfer and several aerobic pathways. Once aerotolerant Dichelobacter nodosus infects the host, which it does through the production of a number of fimbrial adhesins, it secretes both extracellular proteases and toxins resulting in damage to the soft tissue underneath the horn of the hoof. Infection with D. nodosus requires climatic conditions of warm weather and moist pastures. D. nodosus can undergo serogroup conversion, and reservoirs of serogroups are found in infected hooves. This limits the value of available vaccines. The analysis of its genome revealed several immunogenic proteins that are candidate antigens for a cross-protective vaccine. Strain VCS1703A is virulent and naturally transformable. (EBI Integr8)