AN Bach Institute of Biochemistry, Russian Academy of Sciences, Leninsky pr 33, Moscow 119071, Russia.
Tuberculosis (Edinb). 2011 Mar;91(2):146-54. doi: 10.1016/j.tube.2010.12.006. Epub 2011 Jan 22.
It is believed that latent tuberculosis is associated with the persistence of Mycobacterium tuberculosis (MTB) in a dormant-like state. Dormant cells of MTB with coccoid morphology were produced in some in vivo studies, but similar forms were not produced in the known in vitro models in sufficient amounts to permit their characterization. This work demonstrates the efficient formation of phase-dark ovoid cells in MTB cultures within 150 days after the onset of stationary phase. During this time the medium underwent gradual acidification (pH 8.5 → 4.7) as a result of cellular metabolism. A rapid change in the external pH resulted in cell degradation and death. In common with the dormant forms found in other organisms, the ovoid cells had thickened cell walls, a low metabolic activity and elevated resistance to antibiotics and heating. The ovoid cells had lost the ability to form colonies on solid medium and were thus regarded as operationally «non-culturable». At an early stage in the acidification process (about 40 days post inoculation), the ovoid cells self-resuscitated when placed in fresh liquid medium. However, ovoid cells, stored for a prolonged time, required supernatant from active MTB cells, or externally added recombinant form of resuscitation promoting factor (Rpf) for successful resuscitation. It is suggested that the adaptation of cellular metabolism leading to gradual acidification of the external medium results in the formation of morphologically distinct dormant MTB cells in vitro. The model of MTB dormancy developed here could be a useful tool for the development of new drugs against latent TB.
据信,潜伏性结核病与分枝杆菌(MTB)在休眠状态下的持续存在有关。一些体内研究产生了具有球菌形态的 MTB 休眠细胞,但在已知的体外模型中没有产生足够数量的类似形式,无法对其进行表征。这项工作表明,在静止期开始后 150 天内,MTB 培养物中能够高效形成相暗的椭圆形细胞。在此期间,由于细胞代谢,培养基逐渐酸化(pH8.5→4.7)。外部 pH 的快速变化导致细胞降解和死亡。与在其他生物体中发现的休眠形式一样,椭圆形细胞具有增厚的细胞壁、低代谢活性和对抗生素和加热的高抗性。椭圆形细胞失去了在固体培养基上形成菌落的能力,因此被视为操作上的“不可培养”。在酸化过程的早期(接种后约 40 天),当将椭圆形细胞放入新鲜液体培养基中时,它们会自我复苏。然而,长时间储存的椭圆形细胞需要来自活性 MTB 细胞的上清液或外部添加重组形式的复苏促进因子(Rpf)才能成功复苏。据推测,导致外部介质逐渐酸化的细胞代谢适应导致体外形成形态上明显不同的休眠 MTB 细胞。这里开发的 MTB 休眠模型可能是开发针对潜伏性结核病的新药的有用工具。