Sharbati Soroush, Schramm Kira, Rempel Sonja, Wang Hwa, Andrich Ronny, Tykiel Verena, Kunisch Ralph, Lewin Astrid
Freie Universität Berlin, Institute of Veterinary Biochemistry, Berlin, Germany.
BMC Microbiol. 2009 Feb 9;9:31. doi: 10.1186/1471-2180-9-31.
Highly pathogenic mycobacteria like Mycobacterium tuberculosis are characterised by their slow growth and their ability to reside and multiply in the very hostile phagosomal environment and a correlation between the growth rate of mycobacteria and their pathogenicity has been hypothesised. Here, porin genes from M. fortuitum were cloned and characterised to address their impact on the growth rate of fast-growing and pathogenic mycobacteria.
Two genes encoding porins orthologous to MspA from M. smegmatis, porM1 and porM2, were cloned from M. fortuitum strains, which were originally isolated from human patients. Both porin genes were at least partially able to complement the mutations of a M. smegmatis mutant strain lacking the genes mspA and mspC with respect to the growth rate. PorM1 and porM2 were present in different strains of M. fortuitum including the type strain. Comparative expression analysis of porM genes revealed divergent porin expression among analysed M. fortuitum strains. Repression of the expression of porins by antisense technique decreased the growth rates of different M. fortuitum. The effects of over-expression of porM1 as well as porM2 varied depending on the strain and the concentration of antibiotic added to the medium and indicated that PorM1 and PorM2 enhance the growth of M. fortuitum strains, but also the diffusion of the antibiotic kanamycin into the cells.
This study demonstrates the important role of porin expression in growth as well as antibiotic susceptibility of the opportunistic bacterium M. fortuitum.
高致病性分枝杆菌，如结核分枝杆菌，其特点是生长缓慢，能够在极具敌意的吞噬体环境中生存和繁殖，并且有人推测分枝杆菌的生长速率与其致病性之间存在相关性。在此，对偶然分枝杆菌的孔蛋白基因进行克隆和表征，以研究它们对快速生长和致病性分枝杆菌生长速率的影响。
从最初从人类患者分离出的偶然分枝杆菌菌株中克隆出两个与耻垢分枝杆菌的MspA直系同源的孔蛋白编码基因porM1和porM2。就生长速率而言，这两个孔蛋白基因至少部分能够弥补耻垢分枝杆菌一个缺乏mspA和mspC基因的突变菌株的突变。PorM1和PorM2存在于偶然分枝杆菌的不同菌株中，包括模式菌株。对porM基因的比较表达分析显示，在所分析的偶然分枝杆菌菌株中孔蛋白表达存在差异。通过反义技术抑制孔蛋白的表达降低了不同偶然分枝杆菌的生长速率。PorM1和PorM2过表达的影响因菌株和添加到培养基中的抗生素浓度而异，表明PorM1和PorM2既能促进偶然分枝杆菌菌株的生长，也能促进抗生素卡那霉素向细胞内的扩散。
本研究证明了孔蛋白表达在机会致病菌偶然分枝杆菌的生长以及抗生素敏感性方面的重要作用。
