Analysis of the effect of changing environmental conditions on the expression patterns of exported surface-associated proteins of the oral pathogen Actinobacillus actinomycetemcomitans

Actinobacillus actinomycetemcomitans has been specifically implicated in the aetiology of one or more of the periodontal diseases, conditions in which inflammation of the gums is associated with destruction of the alveolar bone supporting the teeth. In these diseases there is loss of attachment of the gums (gingivae) to the teeth forming a periodontal pocket. The microenvironment of this pocket is extremely complex and it is likely that there will be substantial variation in the environmental conditions operating in this habitat. The aim of the current investigation was to study the effect of disease-relevant environmental factors on the production and release of secreted surface-associated proteins of A. actinomycetemcomitans. These secreted proteins contain many of the virulence determinants of this organism. A range of environmental conditions were investigated: growth in a CO2-enriched aerobic atmosphere vs anaerobic growth, presence of serum or blood, biofilm vs planktonic mode of growth and iron depletion. Differential expression of a number of the secreted surface-associated proteins was observed under different growth conditions and these included the glycolytic enzyme triose phosphate isomerase. An ability to adapt to prevailing environmental conditions may facilitate the survival of the organism in the changing microenvironment of the periodontal pocket. (C) 2001 Academic Press.