Department of Medical Microbiology and Immunology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA.
mBio. 2012 Jan 10;3(1). doi: 10.1128/mBio.00285-11. Print 2012.
Vibrio fischeri, the bacterial symbiont of the Hawaiian bobtail squid, Euprymna scolopes, uses quorum sensing to control genes involved in bioluminescence, host colonization, and other biological processes. Previous work has shown that AinS/R-directed quorum sensing also regulates the expression of rpoQ (VF_A1015), a gene annotated as an RpoS-like sigma factor. In this study, we demonstrate using phylogenetics that RpoQ is related to, but distinct from, the stationary-phase sigma factor RpoS. Overexpression of rpoQ results in elevated chitinase activity but decreased motility and luminescence, three activities associated with symbiosis. The reduction in bacterial luminescence associated with the overexpression of rpoQ occurs both in culture and within the light-emitting organ of the squid host. This suppression of bioluminescence is due to the repression of the luxICDABEG promoter. Our results highlight RpoQ as a novel regulatory component, embedded in the quorum-signaling network that controls several biological processes in V. fischeri.
Quorum signaling is a widely occurring phenomenon that functions in diverse bacterial taxa. It is most often found associated with species that interact with animal or plant hosts, either as mutualists or pathogens, and controls the expression of genes critical to tissue colonization. We present the discovery of rpoQ, which encodes a new regulatory component in the quorum-signaling pathway of Vibrio fischeri. RpoQ is a novel protein in the RpoS family of stationary-phase sigma factors. Unlike many other regulatory proteins involved in the quorum-signaling pathways of the Vibrionaceae, the distribution of RpoQ appears to be restricted to only two closely related species. The role of this regulator is to enhance some quorum-signaling outputs (motility) while suppressing others (luminescence). We propose that RpoQ may be a recently evolved or acquired component in V. fischeri that provides this organism with an additional level of regulation to modulate its existing quorum-signaling pathway.
发光杆菌，夏威夷短尾乌贼的细菌共生体，Euprymna scolopes，使用群体感应来控制与生物发光、宿主定殖和其他生物过程相关的基因。以前的工作表明，AinS/R 定向群体感应也调节 rpoQ（VF_A1015）的表达，该基因注释为 RpoS 样 sigma 因子。在这项研究中，我们通过系统发育学证明，RpoQ 与但不同于停滞期 sigma 因子 RpoS。rpoQ 的过表达导致几丁质酶活性升高，但运动性和发光性降低，这三种活性与共生有关。rpoQ 过表达与细菌发光相关的降低既发生在培养物中，也发生在鱿鱼宿主的发光器官中。这种生物发光的抑制是由于 luxICDABEG 启动子的抑制。我们的结果强调了 RpoQ 作为一个新的调节成分，嵌入在控制发光杆菌中几种生物学过程的群体信号网络中。
群体感应是一种广泛存在的现象，存在于不同的细菌分类群中。它最常与与动物或植物宿主相互作用的物种相关联，无论是作为共生体还是病原体，并且控制对组织定殖至关重要的基因的表达。我们发现了 rpoQ，它编码了 Vibrio fischeri 群体信号通路中的一个新的调节成分。RpoQ 是 RpoS 家族中停滞期 sigma 因子的一种新型蛋白质。与参与 Vibrionaceae 群体信号通路的许多其他调节蛋白不同，RpoQ 的分布似乎仅限于两个密切相关的物种。该调节剂的作用是增强一些群体信号输出（运动性），同时抑制其他输出（发光性）。我们提出，RpoQ 可能是 V. fischeri 中最近进化或获得的成分，为该生物体提供了额外的调节水平，以调节其现有的群体信号通路。
