Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom.
Proc Natl Acad Sci U S A. 2011 Sep 6;108(36):14932-7. doi: 10.1073/pnas.1109169108. Epub 2011 Aug 22.
Gas vesicles are hollow intracellular proteinaceous organelles produced by aquatic Eubacteria and Archaea, including cyanobacteria and halobacteria. Gas vesicles increase buoyancy and allow taxis toward air-liquid interfaces, enabling subsequent niche colonization. Here we report a unique example of gas vesicle-mediated flotation in an enterobacterium; Serratia sp. strain ATCC39006. This strain is a member of the Enterobacteriaceae previously studied for its production of prodigiosin and carbapenem antibiotics. Genes required for gas vesicle synthesis mapped to a 16.6-kb gene cluster encoding three distinct homologs of the main structural protein, GvpA. Heterologous expression of this locus in Escherichia coli induced copious vesicle production and efficient cell buoyancy. Gas vesicle morphogenesis in Serratia enabled formation of a pellicle-like layer of highly vacuolated cells, which was dependent on oxygen limitation and the expression of ntrB/C and cheY-like regulatory genes within the gas-vesicle gene cluster. Gas vesicle biogenesis was strictly controlled by intercellular chemical signaling, through an N-acyl homoserine lactone, indicating that in this system the quorum-sensing molecule acts as a morphogen initiating organelle development. Flagella-based motility and gas vesicle morphogenesis were also oppositely regulated by the small RNA-binding protein, RsmA, suggesting environmental adaptation through physiological control of the choice between motility and flotation as alternative taxis modes. We propose that gas vesicle biogenesis in this strain represents a distinct mechanism of mobility, regulated by oxygen availability, nutritional status, the RsmA global regulatory system, and the quorum-sensing morphogen.
气室是水生真细菌和古细菌（包括蓝细菌和盐杆菌）产生的中空细胞内蛋白质细胞器。气室增加了浮力，并允许向气液界面进行趋化运动，从而能够进行后续小生境的殖民化。在这里，我们报告了一个独特的气室介导漂浮的例子，这个例子发生在肠杆菌中；即 Serratia sp. 菌株 ATCC39006。该菌株是肠杆菌科的成员，先前因其产生灵菌红素和碳青霉烯类抗生素而受到研究。气室合成所需的基因映射到一个 16.6kb 的基因簇，该基因簇编码主要结构蛋白 GvpA 的三个不同同源物。在大肠杆菌中异源表达该基因座诱导了大量囊泡的产生和有效的细胞浮力。Serratia 中气室的形态发生能够形成一层高度空泡化的细胞的类菌毛层，这依赖于氧气限制和气室基因簇内 ntrB/C 和 CheY 样调节基因的表达。气室生物发生受到严格的细胞间化学信号的控制，通过 N-酰基高丝氨酸内酯，表明在这个系统中，群体感应分子作为一种形态发生素，启动细胞器的发育。鞭毛运动和气室形态发生也受到小 RNA 结合蛋白 RsmA 的相反调节，表明通过运动和漂浮作为替代趋化运动模式的生理控制来适应环境。我们提出，该菌株中气室的生物发生代表了一种独特的运动机制，受氧气可用性、营养状况、RsmA 全局调节系统和群体感应形态发生素的调节。
