Isolation of a biofilm-defective mutant of Actinomyces from a patient with gingivitis

Abstract

Although oral biofilms play an important role in chronic bacterial infections including periodontitis, the genetic mechanisms contributing to their development are poorly understood. To unravel the nature of the oral biofilm, we tried to identify genes responsible for biofilm formation in Actinomyces, which forms an adhesive platform to promote further attachment of the late colonizers of the oral biofilm. Using a random mutagenesis and biofilm assay for A. oris MG-1, a reference strain of Actinomyces isolated from a patient with gingivitis, we tentatively identified a mutant, AOM0010, with reduced biofilm phenotype. However, from the observations of growth rates, we conclude that AOM0010 is not so much the biofilm-defective mutant but the mutant with defects in growth. The transposon in AOM0010 was inserted into the ANA2550 encoding 2-C-methyl-D-erythritol 4-phosphate (MEP) cytidylyltransferase, suggesting that the function of this gene is required for cell growth in A. oris. Unfortunately, this study could not enhance our understanding of Actinomyces biofilm formation, whereas the strategy of transposon mutagenesis was applicable to A. oris MG-1. Therefore, further isolation and characterization of Tn 5 insertion mutants of A. oris MG-1 would lead to better understanding of molecular mechanisms underlying oral biofilm development.