Watt James M, Swiatlo Ed, Wade Mary M, Champlin Franklin R
Department of Biological Sciences, Mississippi State University, Starkville, MS 39762, USA.
FEMS Microbiol Lett. 2003 Aug 8;225(1):9-14. doi: 10.1016/S0378-1097(03)00437-3.
The capsule of Pasteurella multocida serotype A strain ATCC 11039 is composed of hyaluronic acid and is an important virulence factor. Repeated subculturing of certain capsular serotype A strains results in dissociation from a capsulated to a noncapsulated phenotype with a concomitant loss of virulence. Although noncapsulated variants have been thought to arise as a result of mutation, the molecular mechanisms underlying this event are unknown. In this study, we demonstrate that restoration of the capsulated phenotype occurs in vivo subsequent to intraperitoneal inoculation of BALB/c mice with a noncapsulated variant. Moreover, reverse transcription polymerase chain reaction analysis revealed the capsule locus to be under transcriptional control. Cloning and sequencing of a 290-bp fragment within the promoter containing intergenic region of the capsule locus of 11039/iso revealed no significant alterations occurred subsequent to subculturing. These results demonstrate that serotype A P. multocida strain ATCC 11039 regulates capsule expression in response to an unidentified environmental factor(s), thereby providing insights into the molecular mechanisms underlying colonial dissociation.
多杀性巴氏杆菌A血清型菌株ATCC 11039的荚膜由透明质酸组成，是一种重要的毒力因子。某些荚膜A血清型菌株的反复传代培养会导致从有荚膜表型转变为无荚膜表型，同时毒力丧失。尽管一直认为无荚膜变体是由突变产生的，但这一事件背后的分子机制尚不清楚。在本研究中，我们证明在用无荚膜变体腹腔接种BALB/c小鼠后，体内会出现有荚膜表型的恢复。此外，逆转录聚合酶链反应分析表明荚膜基因座受转录控制。对11039/iso荚膜基因座启动子含基因间区域内一个290 bp片段的克隆和测序显示，传代培养后未发生显著改变。这些结果表明，A血清型多杀性巴氏杆菌菌株ATCC 11039会根据未知的环境因子调节荚膜表达，从而为菌落解离背后的分子机制提供了见解。
