Effect of UV-B radiation on amino acids profile, antioxidant enzymes and lipid peroxidation of some cyanobacteria and green algae

UV radiation and its impact on living organisms became an essential concern over the past three decades and will be essential in the years to come. So, the present investigation was devoted to examining the impact of artificial UV-B radiation on the accumulation of amino acids and MDA contents as well as some antioxidant enzymes activities in three freshwater cyanobacterial species; <i>Planktothrix cryptovaginata, Nostoc carneum</i> and <i>Microcystis aeruginosa</i>, one freshwater green alga; <i>Scenedesmus acutus</i> and one marine cyanobacterium; <i>Microcystis</i>. The algal cultures were exposed directly to artificial UV-B radiation for 1, 3, 5, and 7 hours and amino acids, MDA contents, and the antioxidant enzyme activities; CAT, POD, APX, and SOD were analyzed. The data obtained indicated that alteration in MDA and antioxidant enzymes by UV stress depends on the algal species and the exposure time. The treatment of the investigated algae with different periods of UV-B exposure stimulated the biosynthesis of some individual amino acids and inhibited the accumulation of some others. In some cases, exposure to UV-B was accompanied by the disappearance of some amino acids. In addition, UV-B exposure for 3 hours stimulated the accumulation of total amino acids in <i>M. aeruginosa</i> and <i>S. acutus</i>, while 7 hours of UV-B enhanced the biosynthesis of total amino acids in <i>M. aeruginosa</i> only from the investigated algae. Exposure of some cyanobacteria and green algae to UV-B radiation stimulated the biosynthesis of some individual amino acids and inhibited the accumulation or accompanied by the disappearance of some others. However, the alteration in MDA and antioxidant enzymes by UV stress depends on the algal species and the exposure time.

紫外线辐射及其对生物体的影响在过去三十年间已成为学界高度关注的核心议题，且在未来仍将具有重要研究价值。为此，本研究聚焦于探究人工紫外线B（UV-B）辐射对以下物种的氨基酸积累、丙二醛（MDA）含量及部分抗氧化酶活性的影响：三种淡水蓝细菌——隐秘浮丝藻（Planktothrix cryptovaginata）、肉色念珠藻（Nostoc carneum）与铜绿微囊藻（Microcystis aeruginosa）；一种淡水绿藻——斜生栅藻（Scenedesmus acutus）；以及一种海洋蓝细菌——微囊藻属（Microcystis）物种。将各藻类培养物直接暴露于人工UV-B辐射下1、3、5及7小时，随后对其氨基酸含量、MDA含量以及过氧化氢酶（CAT）、过氧化物酶（POD）、抗坏血酸过氧化物酶（APX）与超氧化物歧化酶（SOD）的活性开展检测分析。检测结果显示，紫外胁迫下MDA与抗氧化酶的变化模式取决于藻类物种与辐照时长。不同时长的UV-B辐照处理可促进部分单体氨基酸的生物合成，同时抑制另一些氨基酸的积累。部分实验场景下，UV-B辐照还会导致部分氨基酸完全消失。此外，UV-B辐照3小时可促进铜绿微囊藻（M. aeruginosa）与斜生栅藻（S. acutus）的总氨基酸积累；而辐照7小时仅能提升本研究涉及的铜绿微囊藻的总氨基酸生物合成水平。部分蓝细菌与绿藻经UV-B辐照后，部分单体氨基酸的生物合成受到促进，而另一些氨基酸的积累则受到抑制，甚至出现消失现象。但需明确，紫外胁迫下MDA与抗氧化酶的变化仍取决于藻类物种与辐照时长。