Cyclic di-nucleotides – what is their role in biofilm formation and pathogenicity of Fusobacterium nucleatum?

Abstract

Introduction Cyclic di-nucleotides (CDNs) act as important second messengers in bacteria, regulating multiple cellular functions, including biofilm formation. Fusobacterium nucleatum is a key player in disease-associated biofilms in periodontitis (gum disease). Previous studies revealed the importance of CDNs in the virulence of other dental pathogens such as Porphyromonas gingivalis, but their function in F. nucleatum virulence remains elusive. Here, we aim to elucidate their importance in the pathogenicity of F. nucleatum. Methods Using bioinformatics, we identified a putative dual adenylyl/guanylyl cyclase in the genome of F. nucleatum ATCC 23726, the only currently genetically tractable strain. Consequently this target gene was deleted from the chromosome. Wild-type and mutant strains were grown in single- and multi-species biofilms, the amount of biomass quantified by crystal-violet assay and the biofilm topography analysed using scanning electron microscopy. Additionally, intracellular CDNs were quantified using LC-MS/MS. Results Differences in biofilm formation comparing wild-type, mutant and further F. nucleatum subspecies will be presented. Furthermore the level of CDN production of those strains will be shown. Conclusions Disease-associated biofilms in periodontitis affect over 50 % of the adult UK population. The disease can be debilitating, potentially leading to tooth loss and the bacteria involved have also been associated with systemic diseases such as cardiovascular disease, arthritis or certain types of cancer. Understanding the involvement of CDNs in the pathogenicity of F. nucleatum and its interaction with various periodontal pathogens might provide new insights into prevention and treatment of periodontitis and other conditions.