Adaptation of Mycobacterium smegmatis to stationary phase
Adaptation of Mycobacterium smegmatis to stationary phase
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DOI：
10.1128/jb.181.1.270-283.1999
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发表时间：
1999-01-01
影响因子：
3.2
通讯作者：
Williams, HD
中科院分区：
文献类型：
--
作者：
Smeulders, MJ;Keer, J;Williams, HD
结核分枝杆菌可在宿主肺组织内存留多年而不引起临床疾病。人们对杆菌的生存状态知之甚少，尽管它经常被称为休眠。一些证据表明，细胞在营养缺乏的静止期存活。因此，我们正在研究作为分枝杆菌持久性模型的耻垢分枝杆菌的稳定期存活。M.在碳、氮或磷饥饿的情况下，包皮垢病培养物可以存活650天。在碳限制培养基中，细胞在碳源（甘油）完全耗尽之前进入稳定期，并且在稳定期的早期阶段继续从培养基中吸收甘油。这些结果表明，当甘油接近极限浓度时，细胞能够感知并启动进入稳定期的关闭，这涉及从培养基中摄取剩余的甘油。在稳定期早期，细胞进行还原性细胞分裂，变得更耐渗透和酸胁迫和池mRNA稳定。静止期细胞也更耐氧化应激，但这种电阻诱导在指数期后期的细胞密度依赖性的方式。在新鲜培养基中恢复后，稳定期培养物显示蛋白质合成立即增加，而与培养时间无关。在75%的长期稳定期培养物中观察到扁平菌落变体，并且经常占据整个群体。冷冻扫描电子显微镜显示，扁平菌落菌株的殖民地组织不同，扁平菌落的组织似乎不如野生型菌落。与指数相适应的野生型菌株的竞争实验表明，平坦的菌株在稳定期具有竞争优势，以及提供证据表明，生长和细胞分裂发生在稳定期培养的耻垢病。这些结果反对静止相M。包皮垢细胞培养物进入类似于休眠的静止状态，但支持它们是动态细胞群的观点。
Mycobacterium tuberculosis can persist for many years within host lung tissue without causing clinical disease. Little is known about the state in which the bacilli survive, although it is frequently referred to as dormancy. Some evidence suggests that cells survive in nutrient-deprived stationary phase. Therefore, we are studying stationary-phase survival of Mycobacterium smegmatis as a model for mycobacterial persistence. M. smegmatis cultures could survive 650 days of either carbon, nitrogen, or phosphorus starvation. In carbon-limited medium, cells entered stationary phase before the carbon source (glycerol) had been completely depleted and glycerol uptake from the medium continued during the early stages of stationary phase. These results suggest that the cells are able to sense when the glycerol is approaching limiting concentrations and initiate a shutdown into stationary phase, which involves the uptake of the remaining glycerol from the medium. During early stationary phase, cells underwent reductive cell division and became more resistant to osmotic and acid stress and pool mRNA stabilized. Stationary-phase cells were also more resistant to oxidative stress, but this resistance was induced during late exponential phase in a cell-density-dependent manner. Upon recovery in fresh medium, stationary-phase cultures showed an immediate increase in protein synthesis irrespective of culture age, Colony morphology variants accumulated in stationary-phase cultures. A flat colony variant was seen in 75% of all long-term-stationary-phase cultures and frequently took over the whole population Cryo scanning electron microscopy showed that the colony organization was different in flat colony strains, flat colonies appearing less well organized than wild-type colonies. Competition experiments with an exponential-phase-adapted wild-type strain showed that the flat strain had a competitive advantage in stationary phase, as well a providing evidence that growth and cell division occur in stationary-phase cultures of nit smegmatis. These results argue against stationary-phase M. smegmatis cultures entering a quiescent state akin to dormancy but support the idea that they are a dynamic population of cells.