Abstract
Filifactor alocis is a gram positive anaerobe that is emerging as an important periodontal pathogen. In the oral cavity F. alocis colonizes polymicrobial biofilm communities; however, little is known regarding the nature of the interactions between F. alocis and other oral biofilm bacteria. Here we investigate the community interactions of two strains of F. alocis with Streptococcus gordonii, Fusobacterium nucleatum, Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, organisms with differing pathogenic potential in the oral cavity. In an in vitro community development model, S. gordonii was antagonistic to the accumulation of F. alocis into a dual species community. In contrast, F. nucleatum and the type strain of F. alocis formed a synergistic partnership. Accumulation of a low passage isolate of F. alocis was also enhanced by F. nucleatum. In three species communities of S. gordonii, F. nucleatum and F. alocis, the antagonistic effects of S. gordonii superseded the synergistic effects of F. nucleatum toward F. alocis. The interaction between A. actinomycetemcomitans and F. alocis was strain specific and A. actinomycetemcomitans could either stimulate F. alocis accumulation or have no effect depending on the strain. P. gingivalis and F. alocis formed heterotypic communities with the amount of P. gingivalis greater than in the absence of F. alocis. However, while P. gingivalis benefited from the relationship, levels of F. alocis in the dual species community were lower compared to F. alocis alone. The inhibitory effect of P. gingivalis toward F. alocis was dependent, at least partially, on the presence of the Mfa1 fimbrial subunit. In addition, AI-2 production by P. gingivalis helped maintain levels of F. alocis. Collectively, these results show that the pattern of F. alocis colonization will be dictated by the spatial composition of microbial microenvironments, and that the organism may preferentially accumulate at sites rich in F. nucleatum.
Highlights
The dental plaque biofilm is comprised of complex communities of microorganisms embedded on tooth surfaces, and is a direct precursor of periodontal disease [1,2,3]
In vivo S. gordonii attaches to the salivary pellicle on enamel surfaces [3], and a saliva-coated glass surface was used for S. gordonii community formation
While the dental plaque biofilm develops on all subgingival tooth surfaces in the oral cavity, periodontal disease is more usually localized to specific sites
Summary
The dental plaque biofilm is comprised of complex communities of microorganisms embedded on tooth surfaces, and is a direct precursor of periodontal disease [1,2,3]. The microbial composition of periodontal disease lesions is much more varied than previously recognized and contains high levels of fastidious and as yet-to-be-cultivated taxons [6]. Organisms such as Selenomonas, Synergistes, Desulfobulbus, TM7 and Filifactor alocis have been identified as potential pathogens in a number of independent studies [6,7,8,9,10]. Study of the pathogenic properties of F. alocis is important to impute a causal association between F. alocis and periodontal disease. F. alocis has a number of characteristics consistent with that of a periodontal pathogen
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