Phototaxis in a wild isolate of the cyanobacterium Synechococcus elongatus
Phototaxis in a wild isolate of the cyanobacterium Synechococcus elongatus
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DOI：
10.1073/pnas.1812871115
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发表时间：
2018-12
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通讯作者：
Yiling Yang;Vinson Lam;M. Adomako;Ryan Simkovsky;A. Jakob;N. Rockwell;Susan E. Cohen;Susan E. Cohen;A. Taton;Jingtong Wang;J. Lagarias;A. Wilde;David Nobles;J. Brand;S. Golden
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作者：
Yiling Yang;Vinson Lam;M. Adomako;Ryan Simkovsky;A. Jakob;N. Rockwell;Susan E. Cohen;Susan E. Cohen;A. Taton;Jingtong Wang;J. Lagarias;A. Wilde;David Nobles;J. Brand;S. Golden
意义长聚球菌PCC 7942在基础研究和应用研究中得到了广泛的应用。然而，通过实验室驯化，这种模式生物似乎已经失去了在自然环境中重要的行为，如生物膜形成和趋光性。我们鉴定了长形葡萄球菌（S. elongatus）的野生分离株UTEX 3055，该菌株形成生物膜并具有趋光性，并研究了其趋光性调控机制。我们的研究结果表明，UTEX 3055的光致运动性设计比之前描述的蓝细菌的光致运动性设计更简单，因为单个5- gaf结构域的光感受器通过波长感应照明的方向，诱导积极和消极的反应。本研究扩展了我们对蓝藻中趋光机制的认识，并建立了一个趋光模式生物。许多蓝细菌通过光合作用将光作为能量来源，它们已经进化出了引导自己靠近或远离光源的能力。这个过程被称为“趋光性”，使生物体能够在最佳的光环境中定位，以改善生长和适应性。人们已经研究了球型蓝细菌聚囊藻（synechocytis sp.）菌株PCC 6803的趋光性机制，但杆状的长聚球菌（Synechococcus elongatus PCC 7942）在昼夜节律和代谢工程方面没有趋光性。在这项研究中，我们报道了一种新分离的S. elongatus菌株UTEX 3055，它的基因组与PCC 7942的基因组有98.5%的相同，但它具有运动和光致性。一个编码趋化样蛋白的六基因操纵子被证实参与趋光性。蓝藻色素PixJSe （Synpcc7942_0858）可以感知环境光信号，它携带5个响应蓝/绿光的GAF结构域，类似于Synechocystis的PixJ结构域。基于平板的趋光性实验表明，UTEX 3055使用PixJSe来感知蓝光和绿光。不同GAF结构域的保守功能半胱氨酸残基突变表明，PixJSe控制着正性和负性趋光性，而不是在聚囊藻中用于实现双向趋光性的多种蛋白质。
Significance The cyanobacterium Synechococcus elongatus PCC 7942 is widely used in basic and applied research. However, this model organism appears to have lost, through laboratory domestication, behaviors that are important in a natural environment, such as biofilm formation and phototaxis. We characterized a wild isolate of S. elongatus, UTEX 3055, that forms biofilms and is phototactic and investigated the mechanisms that regulate phototaxis. Our findings suggest a simpler design for phototactic motility in UTEX 3055 than that previously described for the cyanobacterium Synechocystis, because a single 5-GAF–domain photoreceptor senses the direction of illumination by wavelengths that induce both positive and negative responses. This study expands our knowledge of the mechanisms responsible for phototaxis in cyanobacteria and establishes a phototactic model organism. Many cyanobacteria, which use light as an energy source via photosynthesis, have evolved the ability to guide their movement toward or away from a light source. This process, termed “phototaxis,” enables organisms to localize in optimal light environments for improved growth and fitness. Mechanisms of phototaxis have been studied in the coccoid cyanobacterium Synechocystis sp. strain PCC 6803, but the rod-shaped Synechococcus elongatus PCC 7942, studied for circadian rhythms and metabolic engineering, has no phototactic motility. In this study we report a recent environmental isolate of S. elongatus, the strain UTEX 3055, whose genome is 98.5% identical to that of PCC 7942 but which is motile and phototactic. A six-gene operon encoding chemotaxis-like proteins was confirmed to be involved in phototaxis. Environmental light signals are perceived by a cyanobacteriochrome, PixJSe (Synpcc7942_0858), which carries five GAF domains that are responsive to blue/green light and resemble those of PixJ from Synechocystis. Plate-based phototaxis assays indicate that UTEX 3055 uses PixJSe to sense blue and green light. Mutation of conserved functional cysteine residues in different GAF domains indicates that PixJSe controls both positive and negative phototaxis, in contrast to the multiple proteins that are employed for implementing bidirectional phototaxis in Synechocystis.