Colonial variation and fimbriation of Actinobacillus actinomycetemcomitans

Three colonial variants of Actinobacillus actinomycetemcomitans, which formed transparent rough (TR)-, transparent smooth (TS)-, and opaque smooth (OS)-surfaced colonies, were described in relation to their fimbriation. TR- and TS-cells were adhesive to agar and glass surfaces but not the OS-cells. The examination by electron microscopy revealed that TR-cells were highly fimbriated but not TS- and OS-cells. Thus, TS-cells seemed to be an intermediate type. The fimbriae were isolated from TR-cells by suspending in 0.15 M ethanolamine-HCl buffer (pH 10.5) and purified by dissolving non-fimbrial components in 0.5% deoxycholate and 0.7% n-octyl-β-d-glucopyranoside. The relative molecular mass of the fimbrial subunit protein was 54 000.