BACKGROUND Fluorescence microscopy is a powerful tool in cell biology, especially for the study of dynamic processes. Intensive irradiation of bacteria with UV, blue and violet light has been shown to be able to kill cells, but very little information is available on the effect of blue or violet light during live-cell imaging. RESULTS We show here that in the model bacterium Bacillus subtilis chromosome segregation and cell growth are rapidly halted by standard violet (405 nm) and blue light (CFP) (445-457 nm) excitation, whereas they are largely unaffected by green light (YFP). The stress sigma factor σB and the blue-light receptor YtvA are not involved in growth arrest. Using synchronized B. subtilis cells, we show that the use of blue light for fluorescence microscopy likely induces non-specific toxic effects, rather than a specific cell cycle arrest. Escherichia coli and Caulobacter crescentus cells also stop to grow after 15 one-second exposures to blue light (CFP), but continue growth when imaged under similar conditions in the YFP channel. In the case of E. coli, YFP excitation slows growth relative to white light excitation, whereas CFP excitation leads to cell death in a majority of cells. Thus, even mild violet/blue light excitation interferes with bacterial growth. Analyzing the dose-dependent effects of violet light in B. subtilis, we show that short exposures to low-intensity violet light allow for continued cell growth, while longer exposures do not. CONCLUSIONS Our experiments show that care must be taken in the design of live-cell imaging experiments in that violet or blue excitation effects must be closely controlled during and after imaging. Violet excitation during sptPALM or other imaging studies involving photoactivation has a threshold, below which little effects can be seen, but above which a sharp transition into cell death occurs. YFP imaging proves to be better suited for time-lapse studies, especially when cell cycle or cell growth parameters are to be examined.

中文翻译：

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细菌细胞的生长在荧光显微镜下被紫色和蓝色阻止，但不被黄光激发。

背景技术荧光显微镜术是细胞生物学中的强大工具，特别是对于动态过程的研究。紫外线，蓝光和紫光对细菌的密集照射已显示能够杀死细胞，但是在活细胞成像期间，关于蓝光或紫光的作用的信息很少。结果我们在这里显示，在标准细菌中，枯草芽孢杆菌的染色体分离和细胞生长被标准紫光（405 nm）和蓝光（CFP）（445-457 nm）激发迅速停止，而它们基本上不受绿光（YFP）的影响。 ）。应力σ因子σB和蓝光受体YtvA不参与生长停滞。使用同步化的枯草芽孢杆菌细胞，我们证明了使用蓝光进行荧光显微镜检查可能会诱导非特异性毒性作用，而不是特定的细胞周期停滞。在暴露于蓝光（CFP）15一秒钟后，大肠杆菌和新月形杆菌细胞也停止生长，但是当在YFP通道中以类似条件成像时，它们继续生长。对于大肠杆菌，YFP激发相对于白光激发减慢了生长，而CFP激发导致大多数细胞死亡。因此，即使是轻微的紫/蓝光激发也会干扰细菌的生长。分析枯草芽孢杆菌中紫光的剂量依赖性效应，我们发现短时间暴露于低强度紫光可以使细胞持续生长，而长时间暴露则不然。结论我们的实验表明，在活细胞成像实验的设计中必须注意，在成像期间和成像后必须严格控制紫罗兰色或蓝色激发效应。sptPALM或其他涉及光激活的成像研究中的紫光激发有一个阈值，低于该阈值几乎看不到任何影响，但高于此阈值则会发生急剧转变为细胞死亡。YFP成像被证明更适合于延时研究，尤其是在要检查细胞周期或细胞生长参数时。