McKee A S, McDermid A S, Wait R, Baskerville A, Marsh P D
Pathology Division, PHLS Centre for Applied Microbiology and Research, Salisbury, Wiltshire.
J Med Microbiol. 1988 Sep;27(1):59-64. doi: 10.1099/00222615-27-1-59.
The spontaneous appearance of unusual colony forms was observed during prolonged growth of Bacteroides gingivalis W50 in a chemostat. Two variants were selected for further study which could be distinguished from the parent strain by the rate and intensity of pigmentation of their colonies. For example, after anaerobic incubation for 14 days, variant W50/BR1 produced brown colonies whereas those of the parent strain were black; in contrast, variant W50/BE1 did not show signs of pigmentation until incubation had continued for 21 days. In subsequent studies in the chemostat, variant W50/BE1 bred true even after prolonged growth whereas other colony forms appeared after incubation of variant W50/BR1 for 14 days. The relatedness of W50/BR1 and W50/BE1 to the parent strain was confirmed by comparisons of the whole-cell fatty-acid profiles, the patterns of pre-formed enzymes and by the metabolic end products after growth. However, the variants did differ from the parent strain in their virulence in a mouse pathogenicity model. The parent strain killed all mice given infective doses greater than 5 x 10(8) cfu whereas W50/BR1 was much less virulent (2 out of 10 mice killed and higher infective doses needed for higher mortality rates) and W50/BE1 was avirulent at all infective doses tested.
在牙龈拟杆菌W50在恒化器中长时间培养期间，观察到异常菌落形态的自发出现。选择了两个变体进行进一步研究，它们可以通过菌落色素沉着的速率和强度与亲本菌株区分开来。例如，厌氧培养14天后，变体W50/BR1产生棕色菌落，而亲本菌株的菌落为黑色；相比之下，变体W50/BE1直到培养持续21天才出现色素沉着迹象。在随后的恒化器研究中，变体W50/BE1即使在长时间生长后仍能稳定遗传，而变体W50/BR1培养14天后出现了其他菌落形态。通过比较全细胞脂肪酸谱、预制酶的模式以及生长后的代谢终产物，证实了W50/BR1和W50/BE1与亲本菌株的相关性。然而，在小鼠致病性模型中，这些变体与亲本菌株在毒力方面存在差异。亲本菌株杀死了所有给予大于5×10⁸ cfu感染剂量的小鼠，而W50/BR1的毒力要低得多（10只小鼠中有2只死亡，且死亡率越高所需的感染剂量越高），并且W50/BE1在所有测试的感染剂量下均无致病性。
