Noonan B, Trust T J
Department of Biochemistry and Microbiology, University of Victoria, British Columbia, Canada.
Mol Microbiol. 1995 Jan;15(1):65-75. doi: 10.1111/j.1365-2958.1995.tb02221.x.
The asoA gene of Aeromonas salmonicida is located approximately 7 kb downstream of the A-layer structural gene, vapA. A 6 kb BamHI fragment containing asoA was cloned and marker-exchange mutagenesis using a kanamycin-resistance cassette was performed to generate an asoA mutation in the low-virulence strain A449L. When analysed by electron microscopy, the mutant A449L-MB exhibited an altered surface morphology. Strands and blebs of membranous material were observed protruding from the disorganized cell surface. This material was shown to contain lipopolysaccharide and A-layer subunit protein. The disorganization of the surface of A449L-MB had no apparent effect on virulence when the bacteria were administered to rainbow trout (Oncorhynchus mykiss) by bath immersion. However, when administered by intraperitoneal injection, the mutant A449L-MB was found to exhibit significantly increased virulence. The predicted amino acid sequence of AsoA shows homology to a number of polytopic membrane proteins involved in translocation across the cytoplasmic membrane.
杀鲑气单胞菌的asoA基因位于A层结构基因vapA下游约7 kb处。克隆了一个包含asoA的6 kb BamHI片段，并使用卡那霉素抗性盒进行标记交换诱变，以在低毒力菌株A449L中产生asoA突变。通过电子显微镜分析时，突变体A449L-MB表现出改变的表面形态。观察到膜状物质的条带和泡从杂乱的细胞表面突出。该物质显示含有脂多糖和A层亚基蛋白。当通过浸浴将细菌施用于虹鳟（Oncorhynchus mykiss）时，A449L-MB表面的紊乱对毒力没有明显影响。然而，当通过腹腔注射给药时，发现突变体A449L-MB表现出显著增加的毒力。AsoA的预测氨基酸序列与许多参与跨细胞质膜转运的多跨膜蛋白具有同源性。
