부산대학교 도서관

Summary: In Chapter 3, I show that both a rough-colony (Tad+) natural isolate and its smooth-colony (Tad-) laboratory variant adhere and produce a biofilm. Adherence by the Tad+ strain is considerably stronger than that by the isogenic Tad- strain; and the structure of the biofilm from the Tad+ strain is very different from the biofilm of the Tad- strain, with the latter having the properties of a "classic" biofilm. I chose several regulators that I thought might affect expression of the tad locus in A. actinomycetemcomitans. Deletion of their genes and the resulting strain phenotypes led to cpxR, whose deletion affected phenotypes of both the Tad+ and Tad- strains. The adherence of the smooth (Tad-) strain was complemented by cpxR in trans, whereas the adherence of the rough (Tad+) strain required the presence of the next downstream gene, cpxA, for complementation to occur. These studies identified trans-acting regulatory genes for the tad locus. Furthermore, they show significant differences between rough-colony forming (Tad+) and smooth-colony forming (Tad -) strains of A. actinomycetemcomitans.