Department of Medicine, University of Connecticut Health Center, Farmington, Connecticut, United States of America.
PLoS Pathog. 2012 Feb;8(2):e1002532. doi: 10.1371/journal.ppat.1002532. Epub 2012 Feb 16.
While the roles of rpoS(Bb) and RpoS-dependent genes have been studied extensively within the mammal, the contribution of the RpoS regulon to the tick-phase of the Borrelia burgdorferi enzootic cycle has not been examined. Herein, we demonstrate that RpoS-dependent gene expression is prerequisite for the transmission of spirochetes by feeding nymphs. RpoS-deficient organisms are confined to the midgut lumen where they transform into an unusual morphotype (round bodies) during the later stages of the blood meal. We show that round body formation is rapidly reversible, and in vitro appears to be attributable, in part, to reduced levels of Coenzyme A disulfide reductase, which among other functions, provides NAD+ for glycolysis. Our data suggest that spirochetes default to an RpoS-independent program for round body formation upon sensing that the energetics for transmission are unfavorable.
虽然 rpoS(Bb) 和依赖 RpoS 的基因的作用已在哺乳动物中得到广泛研究，但 RpoS 调控子对伯氏疏螺旋体的蜱传阶段的贡献尚未被研究。在此，我们证明了依赖 RpoS 的基因表达是通过喂食若虫传播螺旋体的前提。RpoS 缺陷型生物体被限制在中肠腔中，在血液餐的后期阶段它们转变为一种不寻常的形态（圆形体）。我们表明，圆形体的形成是快速可逆的，并且体外似乎部分归因于辅酶 A 二硫化物还原酶水平降低，除其他功能外，该酶还为糖酵解提供 NAD+。我们的数据表明，当螺旋体感觉到不利于传播的能量时，它们会默认采用一种不依赖 RpoS 的圆形体形成程序。
