Zhang Jessica, Takacs Constantin N, McCausland Joshua W, Mueller Elizabeth A, Buron Jeline, Thappeta Yashna, Wachter Jenny, Rosa Patricia A, Jacobs-Wagner Christine
Department of Biology, Stanford University, Stanford, CA 94305, USA.
Sarafan ChEM-H Institute, Stanford University, Stanford, CA 94305, USA.
bioRxiv. 2024 Oct 28:2024.10.28.620338. doi: 10.1101/2024.10.28.620338.
The Lyme disease agent is a polyploid bacterium with a segmented genome in which both the chromosome and over 20 distinct plasmids are present in multiple copies per cell. This pathogen can survive at least nine months in its tick vector in an apparent dormant state between blood meals, without losing cell proliferative capability when re-exposed to nutrients. Cultivated cells grown to stationary phase or resuspended in nutrient-limited media are often used to study the effects of nutrient deprivation. However, a thorough assessment of the spirochete's ability to recover from nutrient depletion has been lacking. Our study shows that starved cultures rapidly lose cell proliferative. Loss of genetic elements essential for cell proliferation contributes to the observed proliferative defect in stationary phase. The gradual decline in copies of genetic elements is not perfectly synchronized between chromosomes and plasmids, generating cells that harbor one or more copies of the essential chromosome but lack all copies of one or more non-essential plasmids. This phenomenon likely contributes to the well-documented issue of plasmid loss during in vitro cultivation of . In contrast, cells from ticks starved for 14 months showed no evidence of reduced cell proliferative ability or plasmid loss. Beyond their practical implications for studying , these findings suggest that the midgut of the tick vector offers a unique environment that supports the maintenance of 's segmented genome and cell proliferative potential during periods of tick fasting.
莱姆病病原体是一种多倍体细菌，具有分段基因组，其中染色体和20多种不同的质粒在每个细胞中都有多个拷贝。这种病原体可以在其蜱虫载体中以明显的休眠状态在血餐之间存活至少九个月，在重新接触营养物质时不会丧失细胞增殖能力。培养至稳定期或重悬于营养受限培养基中的细胞常用于研究营养剥夺的影响。然而，对于螺旋体从营养耗竭中恢复能力的全面评估一直缺乏。我们的研究表明，饥饿培养物会迅速丧失细胞增殖能力。细胞增殖所必需的遗传元件的丧失导致了在稳定期观察到的增殖缺陷。遗传元件拷贝数的逐渐下降在染色体和质粒之间并不完全同步，产生了含有一个或多个必需染色体拷贝但缺少一个或多个非必需质粒所有拷贝的细胞。这种现象可能导致了在体外培养过程中质粒丢失这一有充分记录的问题。相比之下，饥饿14个月的蜱虫中的细胞没有显示出细胞增殖能力降低或质粒丢失的迹象。除了对研究的实际意义之外，这些发现表明，蜱虫载体的中肠提供了一个独特的环境，在蜱虫禁食期间支持莱姆病病原体分段基因组的维持和细胞增殖潜力。
