一株从家蚕体内分离获得的微孢子虫GXM_2的生物学特性

Biological characteristics of a strain of microsporidia GXM_2 isolated from silkworm

【目的】研究一株从家蚕体内分离获得的新微孢子虫（GXM2）的致病性和生物学特征,为全面防控家蚕微粒子病提供参考依据。【方法】观察GXM2添食感染家蚕的病症,以半数感染浓度（IC50）法测定GXM2对家蚕的食下感染力,镜检调查GXM2的胚种传染率,并利用光学显微镜、透射电子显微镜观察GXM2孢子的形态、血清学反应、生活史及内部结构。【结果】GXM2感染蚕体病症为：发病急,病程短（6～9d）,出现不蜕皮或半蜕皮症状,类似生理性病害。GXM2对家蚕（蚁蚕）的IC50为2.76×105个孢子/mL,是家蚕微孢子虫（N.b）的4.8倍;对家蚕的胚种传染率为1.19%。GXM2呈卵圆形,大小为（2.49±0.10）μm×（4.19±0.15）μm。GXM2孢子在N.b免疫抗体血清中未能发生凝聚反应,其生活史中发现单核和双核并存,均以二分裂方式增殖,最后形成单核、双核两种成熟孢子;GXM2孢子的极丝有9~11圈,与N.b孢子内部结构有明显差异。【结论】GXM2对家蚕具有较强的致病性和危害性,与N.b异属异种,即要求进行蚕种母蛾微粒子病检疫时应采取分类检验处理技术,进一步完善广西家蚕微粒子病防治技术体系。

[Objective]The present study was conducted to investigate the pathogenicity and classification features of a strain of microspofidia （GXM2） isolated from silkworm in order to provide basis for comprehensively controlling silkworm pebrine. [Method]GXM2 infected symptom of silkworm was observed, the ingestive infectivity of GXM2 to silkworm was determined by use of 50% infectious concentration （IC50） and the semen infection rate of GXM2 was investigated under microscope, spore morphology, serological reaction, life cycle and internal structure were observed under optical microscope and transmission electron microscope. [Result]GXM2 infected symptom of silkworm was in acute morbidity, short course of disease（6-9 days）, and no ecdysis or half ecdysis, which was similar to physiological diseases. IC50 of GXM2 was 2.76×105 spores/mL, 4.8 times of that of N.b. The semen infection rate of GXM2 was 1.19%. GXM2 spore was oval in shape and （2.49±0.10） cm×（4.19±0.15） μm in size, and did not condense in serum of N.b immune antibody. During the life cycle of GXM2, uninuclear and binuclear coexisted, propagated in binary fission, then formed two kinds （uninuclear and binuclear） of mature spores. Innerstructure of GXM2 was quite different from N.b, with 9 to 11 coils of polar filament in spores. [Conclusion]GXM2 was strongly infective and harmful to Bombyx mori. GXM2 and Nosema bombycis （N.b） were different species and different genus. Classified inspection and processing technologies should be adopted to further improve the technology system of silkworm pebrine control.