伴放线放线杆菌菌落生长形态变化的观察

目的：观察伴放线放线杆菌（Actinobacillus actinomycetemcomitans,Aa)从粗糙型到光滑型的转变过程，认别Aa在实验室传代过程中出现的不同生长形态。方法：从牙周炎患者龈下菌班中分离出的原代菌株8株，应用固体及液体培养基连续传代，液体培养每次传代的同时接种固体培养基观察相应的菌落形态。结果：液体培养获得3株光滑型转变株。菌落的变化从粘附的小菌落到沉淀的大菌落到完全的均匀生长，转化过程大约需要7－8代。在这一过程中相应传至固体培养基上生长的Aa从粘附的半透明的小菌落变大、不透明并失去粘附的特性，又随着边缘的扩散变为扁平，透明度也增加；与此同进内部的星形结构逐渐变简单、变小，最后消失。固体培养未获得典型的转变株。结论：Aa从粗糙型到光滑型的转变是一个菌落湿度逐渐增加，体积逐渐增大，并逐渐失去内部结构的过程。这一过程至少可以看到半透明突起的粗糙型，不透明突起的光滑型和近乎透明的扁平光滑型3种菌落形态。

Phenotypic variation in Actinobacillus actinomycetemcomitans

OBJECTIVE: To investigate the colony variation in Actinobacillus actinomycetemcomitans (Aa) from rough to smooth and recognize its different morphology during laboratory translations. METHODS: Primary strains isolated from subgingival plaque of two juvenile periodontitis patients were repeatedly subcultured on agar plates and broth; for broth culture, every generation was translated in broth and on solid medium separately to observe the corresponding morphologies of Aa grow in broth. RESULTS: Three smooth strains of Aa from the broth culture were obtained. The process was about 7-8 generations: colonies changed from a small and adherence phenotype to a bigger and sediment ones and finally the culture supernatant became turbid; the corresponding morphologies grow on agar exhibiting an adherent, small rough colony phenotype which had a star-shaped internal structure converted gradually to a kind of bigger, opaque, nonadherent, smooth phenotype, then the colony extended out from the margin of the colony and finally converted to a flat, almost parent morphology and the same time the star-like inner structure converted to a simpler and smaller type and finally disappeared. We could not get completely smooth variants of Aa from agar. CONCLUSIONS: The variation in colony morphology of Aa from rough to smooth is a process, in which the colony was gradually wetter and bigger and at the same time gradually lost the inner structure. During this process three colony morphologies at least can be seen, including rough, opaque smooth and almost translucent smooth.