Institute of Green Environmental Research Center, University of Incheon, Incheon, Republic of Korea.
Aquat Toxicol. 2012 Oct 15;122-123:206-13. doi: 10.1016/j.aquatox.2012.06.002. Epub 2012 Jun 29.
The effects of ultraviolet B (UV-B; 295-320 nm) radiation on certain vital physiological (photosynthesis), biochemical (production of reactive oxygen species - ROS) and behavioral (motility and orientation) characteristics were investigated in the unicellular photoautotroph, Euglena agilis Carter. The photosynthetic performance of E. agilis was recorded after exposure of between 15 and 60 min followed by a period of recovery lasting 6-24h under dim light (5-10 μmol photons m(-2) s(-1)). The maximum quantum yield of PS II (F(v)/F(m)) was reduced to 65% and 14% of initial values immediately following 15 and 30 min UV-B exposure, but recovered to 100 and 86% of the initials, respectively. Values of rETR(max) in E. agilis exposed to 15 min UV-B were similar to those of the initials, but a 30 min UV exposure resulted in 75% reduction of rETR(max) with only a 43% recovery as compared with the initial after 24h recovery. After a 60 min UV-B exposure, there were no Chl a fluorescence signals, and hence no F(v)/F(m) or rETR(max). A UV dose-dependent increase in DCFH-DA fluorescence was found in E. agilis cells, reflecting an increase in ROS production. After exposures to UV-B for between 15 and 60 min, the percentages of motile cells in the population decreased to 76, 39 and 15%, respectively. Following 24h in dim light, the percentage of motile cells increased to between 66% and 95% of the initial value. The velocity of non-irradiated cells was 60 μm s(-1), which decreased to 16-35 μm s(-1) immediately following exposure for 15-60 min. After periods of time in dim light (6, 12 and 24h) velocities had recovered to between 44 and 81% of the initial value. In untreated controls, the r-value was 0.23, indicating random movement of E. agilis, but it increased to 0.35 and 0.72 after exposure to UV-B for 30 and 60 min, respectively. There was a tendency towards vertical downward movement of cells proportional to the duration of exposure. The compactness of E. agilis decreased from 2.9 in controls to 1.8-2.3 in cells treated with UV-B although significant recovery followed. UV-B dose-dependent interaction between photosynthetic activity, ROS production and movement is discussed in terms of a UV-protective mechanism in E. agilis.
研究了紫外线 B（UV-B；295-320nm）辐射对单细胞光自养生物衣藻 Euglena agilis Carter 的某些重要生理（光合作用）、生化（活性氧物种 - ROS 产生）和行为（运动和定向）特性的影响。在弱光（5-10 μmol 光子 m(-2) s(-1)）下，在 15 至 60 分钟的暴露后记录衣藻的光合作用性能，然后进行持续 6-24 小时的恢复。PS II 的最大量子产率（F(v)/F(m)）在 15 和 30 分钟的 UV-B 暴露后立即降低至初始值的 65%和 14%，但分别恢复至初始值的 100%和 86%。在暴露于 15 分钟 UV-B 的衣藻中，rETR(max)的值与初始值相似，但 30 分钟的 UV 暴露导致 rETR(max)减少 75%，而在 24 小时恢复后仅恢复 43%。在 60 分钟的 UV-B 暴露后，没有叶绿素 a 荧光信号，因此没有 F(v)/F(m)或 rETR(max)。衣藻细胞中的 DCFH-DA 荧光呈 UV 剂量依赖性增加，反映出 ROS 产生增加。在 15 至 60 分钟的 UV-B 暴露后，群体中运动细胞的百分比分别下降至 76%、39%和 15%。在弱光下 24 小时后，运动细胞的百分比增加到初始值的 66%至 95%之间。未经辐照的细胞的速度为 60 μm s(-1)，在 15-60 分钟的暴露后立即降低至 16-35 μm s(-1)。在弱光（6、12 和 24 小时）的一段时间后，速度恢复到初始值的 44%至 81%之间。在未处理的对照中，r 值为 0.23，表明衣藻的随机运动，但在暴露于 UV-B 30 和 60 分钟后，r 值分别增加到 0.35 和 0.72。细胞有向垂直向下运动的趋势，与暴露时间成正比。尽管随后有显著恢复，但衣藻的紧凑度从对照中的 2.9 降低至用 UV-B 处理的细胞中的 1.8-2.3。根据衣藻中的 UV 保护机制，讨论了光合作用、ROS 产生和运动之间的紫外线剂量依赖性相互作用。
