Hasman H, Chakraborty T, Klemm P
Department of Microbiology, Technical University of Denmark, DK-2800 Lyngby, Denmark.
J Bacteriol. 1999 Aug;181(16):4834-41. doi: 10.1128/JB.181.16.4834-4841.1999.
Antigen 43 (Ag43), the product of the flu gene, is a surface-displayed autotransporter protein of Escherichia coli. Ag43 is responsible for the autoaggregation and flocculation of static liquid cultures of many E. coli strains. The expression of Ag43 has been reported to be phase variable and controlled by the product of the oxyR gene. Type 1 fimbriae are thin adhesive thread-like surface organelles responsible for bacterial receptor recognition and tissue colonization. Like that of Ag43, the expression of type 1 fimbriae is phase variable. Interestingly, previous results have suggested that the expression of type 1 fimbriae and the expression of Ag43 are mutually exclusive. In the present report, we show, by use of well-defined mutants, that fimbriation abolishes Ag43-mediated autoaggregation but does not affect Ag43 expression. Autoaggregation is shown to require an intercellular Ag43-Ag43 interaction, and the physical presence of fimbriae on the cells seems to abrogate this interaction. The Ag43 or OxyR status does not appear to influence fimbria expression, and our results suggest that the expression of Ag43 and the expression of fimbriae are independent processes.
抗原43（Ag43）是流感基因的产物，是大肠杆菌的一种表面展示自转运蛋白。Ag43负责许多大肠杆菌菌株静态液体培养物的自聚集和絮凝。据报道，Ag43的表达呈相变，受oxyR基因产物的控制。1型菌毛是纤细的、类似粘性丝线的表面细胞器，负责细菌受体识别和组织定植。与Ag43一样，1型菌毛的表达也是相变的。有趣的是，先前的结果表明，1型菌毛的表达与Ag43的表达相互排斥。在本报告中，我们通过使用明确的突变体表明，菌毛形成消除了Ag43介导的自聚集，但不影响Ag43的表达。自聚集被证明需要细胞间的Ag43-Ag43相互作用，而细胞上菌毛的物理存在似乎消除了这种相互作用。Ag43或OxyR状态似乎不影响菌毛表达，我们的结果表明，Ag43的表达和菌毛的表达是独立的过程。
