Verónica Rojas M, Olivares P Jorge, del Río Rodrigo, Marshall Sergio H
Laboratorio de Genética e Inmunología Molecular, Instituto de Biología, Pontificia Universidad Católica de Valparaíso, Avenida Brasil 2950, Valparaíso, Chile.
Microb Pathog. 2008 May;44(5):370-8. doi: 10.1016/j.micpath.2007.10.012. Epub 2007 Nov 5.
We report a novel genetically different small infective variant of the fish pathogen Piscirickettsia salmonis (sP.s). sP.s variants were recovered both from ageing post-infected CHSE-214 culture cells as well as from naturally infected fish. The ITS region of sP.s variants, although sharing a common core sequence, is different from the ITS of the prototype strain LF-89 from which they originate. Thus, sP.s can be selectively amplified with sequence-specific discriminatory set of PCR primers. Transcriptionally, sP.s are fully active as shown by reverse transcription PCR analysis. Immunologically, sP.s is specifically recognized by antibodies against standard P. salmonis. Structurally, atomic force microscopy shows that sP.s. is well below (<0.2microm) the standard range size described for this pathogen (0.5-1.5microm). Functionally, although sP.s is infective their in vitro progeny is a hundred percent identical to the LF-89 prototype strain. In summary sP.s, represent selectable infective variants of the LF-89 strain and not new strains, probably resulting from a survival strategy of the bacteria in response to limiting growth conditions. In this frame, sP.s could be responsible of horizontal infection of fish in the field.
我们报告了鱼类病原体鲑鱼立克次氏体（sP.s）一种新的基因不同的小感染性变体。sP.s变体既从感染后老化的CHSE - 214培养细胞中分离得到，也从自然感染的鱼类中分离得到。sP.s变体的ITS区域，尽管共享一个共同的核心序列，但与它们起源的原型菌株LF - 89的ITS不同。因此，sP.s可以用序列特异性的鉴别性PCR引物组进行选择性扩增。转录方面，逆转录PCR分析表明sP.s具有完全活性。免疫方面，sP.s能被抗标准鲑鱼立克次氏体的抗体特异性识别。结构上，原子力显微镜显示sP.s远低于（<0.2微米）该病原体描述的标准范围大小（0.5 - 1.5微米）。功能上，尽管sP.s具有感染性，但其体外后代与LF - 89原型菌株百分之百相同。总之，sP.s代表LF - 89菌株的可选择感染性变体而非新菌株，可能是细菌为应对有限生长条件而采取的一种生存策略的结果。在此框架下，sP.s可能是野外鱼类水平感染的原因。
