| Summary: | 碩士 === 國立陽明大學 === 微生物及免疫學研究所 === 98 === Mycobacterium abscessus is an opportunistic pathogen which often infects immunodeficient patients in skin, lung or soft tissue. Previous studies showed that M. abscessus possesses spontaneous morphotype switching ability; changing between rough and smooth. This morphotype switching ability affects the pathogenicity of M. abscessus in human. In this study, we used transposon mutagenesis technique to generate insertion mutants of M. abscessus derived from the clinical isolate cs1c strain for analyzing the factors involved in the spontaneous morphotype switch. We generated 20 mutants with morphological change. Of these mutants, a defective mab_1974 gene was identified after sequencing and alignment. The protein product of mab_1974 gene was predicted to contain an Nlpc/p60 domain. The proteins with the Nlpc/p60 domain have shown to have bacterial cell wall hydrolyzing activity. To characterize the function of mab_1974 protein in M. abscessus, we tested several phenotypical differences between M. abscessus wild type and mab_1974::Tn mutant. The results showed that mab_1974::Tn mutant strain displayed slower growth rate, weaker lysozyme resistance and intracellular survivability than that of the wild type strain. In addition to analyze the enzyme activity of mab_1974 protein in the future, we successfully expressed His-tagged mab_1974 protein in E. coli XL-1 blue strain and this may facilitate the protein purification procedure and characterization.
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