Gene expression and phenotypic traits of Aggregatibacter actinomycetemcomitans in response to environmental changes

Background and Objective Periodontopathogens experience several challenges in the oral cavity that may influence their transcription profile and resulting phenotype. This study evaluated the effect of environmental changes on phenotype and gene expression in a serotype b A ggregatibacter actinomycetemcomitans isolate. Material and Methods Cultures in early exponential phase and at the start of stationary growth phase in microaerophilic and anaerobic atmospheres were evaluated. Cell hydrophobic properties were measured by adherence to n‐hexadecane; in addition, adhesion to, and the ability to invade, KB cells was evaluated. Relative transcription of 12 virulence‐associated genes was determined by real‐time reverse transcritption quantitative PCR. Results The culture conditions tested in this study were found to influence the phenotypic and genotypic traits of A . actinomycetemcomitans . Cells cultured in microaerophilic conditions were the most hydrophobic, reached the highest adhesion efficiency and showed up‐regulation of omp100 (which encodes an adhesion) and pga (related to polysaccharide synthesis). Cells grown anaerobically were more invasive to epithelial cells and showed up‐regulation of genes involved in host‐cell invasion or apoptosis induction (such as apa H , omp29, cag E and cdt B ) and in adhesion to extracellular matrix protein ( ema A ) . Conclusion Environmental conditions of different oral habitats may influence the expression of factors involved in the binding of A . actinomycetemcomitans to host tissues and the damage resulting thereby, and thus should be considered in in‐vitro studies assessing its pathogenic potential.