Transcriptional and Translational Analysis of Biofilm Determinants of Aggregatibacter actinomycetemcomitans in Response to Environmental Perturbation. Infection and immunity [Infect Immun] Journal article

Fimbriae, lipopolysaccharide (LPS) and extracellular polymeric substance (EPS) all contribute to biofilm formation by the periodontopathogen Aggregatibacter actinomycetemcomitans. To understand how individual biofilm determinants respond to changing environmental conditions, the transcription of genes responsible for fimbriae, LPS and EPS production, as well as the translation of these components were determined in rough (Rv) and isogenic smooth (Sv) variants of A. actinomycetemcomitans cultured in half-strength and full-strength culture medium under anaerobic or aerobic conditions, and in iron-supplemented and iron-chelated medium. The transcription of tadV (fimbrial assembly), pgaC (extracellular polysaccharide synthesis), and orf8 or rmlB (lipopolysaccharide synthesis) was measured by real-time PCR. The amounts of fimbriae, LPS and EPS were also estimated from stained SDS-PAGE gels, and verified by Western blot and ELISA using specific antibodies. Each gene was significantly up-regulated in the Rv as compared to Sv. The transcription of fimbrial, LPS and EPS genes in the Rv was increased approximately two-fold in cells cultured in full-strength medium under anaerobic conditions when compared to cells cultured under aerobic conditions. Under anaerobic conditions, the transcription of fimbriae and EPS enzymes was elevated in both Rv and Sv cells cultured in half-compared to full-strength medium. Iron-chelation also increased the transcription and translation of all biofilm determinants compared to their expression with iron supplementation. Yet the quantity of biofilm was not significantly changed by any environmental perturbation except iron limitation. Thus, anaerobic conditions, nutrient stress and iron limitation each up-regulate known biofilm determinants of A. actinomycetemcomitans to contribute to biofilm formation.

Infection and immunity [Infect Immun]