Laboratory of Molecular Environmental Microbiology, Department of Environmental Science and Ecological Engineering, Korea University, Seoul 02841, Republic of Korea.
Laboratory of Molecular Environmental Microbiology, Department of Environmental Science and Ecological Engineering, Korea University, Seoul 02841, Republic of Korea.
J Hazard Mater. 2023 Apr 15;448:130932. doi: 10.1016/j.jhazmat.2023.130932. Epub 2023 Feb 2.
Lysine toxicity on certain groups of bacterial cells has been recognized for many years, but the detailed molecular mechanisms that drive this phenomenon have not been elucidated. Many cyanobacteria including Microcystis aeruginosa cannot efficiently export and degrade lysine, although they have evolved to maintain a single copy of the lysine uptake system through which arginine or ornithine can also be transported into the cytoplasm. Autoradiographic analysis using C-l-lysine confirmed that lysine was competitively uptaken into cells with arginine or ornithine, which explained the arginine or ornithine-mediated alleviation of lysine toxicity in M. aeruginosa. A relatively non-specific MurE amino acid ligase could incorporate l-lysine into the 3rd position of UDP-N-acetylmuramyl-tripeptide by replacing meso-diaminopimelic acid during the stepwise addition of amino acids on peptidoglycan (PG) biosynthesis. However, further transpeptidation was blocked because lysine substitution at the pentapeptide of the cell wall inhibited the activity of transpeptidases. The leaky PG structure caused irreversible damage to the photosynthetic system and membrane integrity. Collectively, our results suggest that a lysine-mediated coarse-grained PG network and the absence of concrete septal PG lead to the death of slow-growing cyanobacteria.
赖氨酸毒性对某些细菌细胞已经被认识了很多年，但驱动这一现象的详细分子机制尚未阐明。许多蓝藻，包括铜绿微囊藻，不能有效地将赖氨酸输出和降解，尽管它们已经进化到通过单一拷贝的赖氨酸摄取系统来维持，该系统也可以运输精氨酸或鸟氨酸进入细胞质。使用 C-l-赖氨酸的放射自显影分析证实，赖氨酸与精氨酸或鸟氨酸竞争进入细胞，这解释了精氨酸或鸟氨酸在铜绿微囊藻中缓解赖氨酸毒性的作用。一种相对非特异性的 MurE 氨基酸连接酶可以通过在肽聚糖（PG）生物合成中逐步添加氨基酸时取代间二氨基庚二酸，将 l-赖氨酸掺入 UDP-N-乙酰胞壁酰三肽的第 3 位。然而，由于细胞壁五肽中的赖氨酸取代抑制了转肽酶的活性，进一步的转肽反应被阻断。有缺陷的 PG 结构对光合作用系统和膜完整性造成不可逆的损害。总的来说，我们的结果表明，赖氨酸介导的粗粒 PG 网络和缺乏具体的隔膜 PG 导致生长缓慢的蓝藻死亡。
