Variations in the surface proteins and restriction enzyme systems of Mycoplasma pulmonis in the respiratory tract of infected rats
Variations in the surface proteins and restriction enzyme systems of Mycoplasma pulmonis in the respiratory tract of infected rats
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DOI：
10.1046/j.1365-2958.2001.02464.x
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发表时间：
2001-05-01
影响因子：
3.6
通讯作者：
Dybvig, K
中科院分区：
文献类型：
--
作者：
Gumulak-Smith, J;Teachman, A;Dybvig, K
限制和修饰(R-nn)系统通常被认为可以保护细菌免受外来DNA的入侵。本文提出了由肺支原体hsd基因座编码的相变R-M系统存在替代作用，比较了在不同环境中生长的肺支原体细胞群体的R-M活性和表面抗原的产生。肺支原体X1048菌株在实验室培养基中增殖时，>；95%的菌落形成单位(CFU)缺乏R-M活性而产生可变的表面蛋白VsaA，实验感染大鼠鼻部的支原体也缺乏R-M活性而产生VsaA。相比之下，从感染大鼠下呼吸道分离的支原体的细胞群更为复杂，从气管分离的支原体的结果最为显著。在感染后14天，38%的支原体分离株产生VsaA以外的VSA蛋白，34%的分离株具有活跃的限制性内切酶系统。这些数据表明，动物组织中不同的选择压力影响支原体细胞群的表面蛋白和R-M活性。我们认为，R-M活性和细胞表面蛋白的产生的变化对于支原体在宿主内的生存是重要的。
Restriction and modification (R-nn) systems are generally thought to protect bacteria from invasion by foreign DNA. This paper proposes the existence of an alternative role for the phase-variable R-M systems encoded by the hsd loci of Mycoplasma pulmonis, Populations of M. pulmonis cells that arose during growth in different environments were compared with respect to R-M activity and surface antigen production. When M. pulmonis strain X1048 was propagated in laboratory culture medium, > 95% of colony-forming units (cfu) lacked R-M activity and produced the variable surface protein VsaA, Mycoplasmas isolated from the nose of experimentally infected rats also lacked R-M activity and produced VsaA, In contrast, the cell population of mycoplasmas isolated from the lower respiratory tract of the infected rats was more complex, The most dramatic results were obtained for mycoplasmas isolated from the trachea, At 14 days postinfection, 38% of mycoplasma isolates produced a Vsa protein other than VsaA, and 34% of isolates had active restriction systems, These data suggest that differences in selection pressures in animal tissues affect the surface proteins and the R-M activity of the mycoplasmal cell population, We propose that variations in the production of R-M activity and cell surface proteins are important for the survival of the mycoplasma within the host.