Pérez Germán, Doldán Soledad, Scavone Paola, Borsani Omar, Irisarri Pilar
Laboratorio de Microbiología, Depto. Biología Vegetal, Facultad de Agronomía, Avda. Garzón 908, Montevideo, Uruguay.
Laboratorio de Bioquímica, Depto. Biología Vegetal, Facultad de Agronomía, Avda. Garzón 908, Montevideo, Uruguay.
Plant Physiol Biochem. 2016 Nov;108:231-240. doi: 10.1016/j.plaphy.2016.07.014. Epub 2016 Jul 21.
Cyanobacteria are successful in diverse habitats due to their adaptation strategies. Their mechanisms to cope with individual stresses have been studied. However, the response to combined stress conditions as found in nature remains unclear. With this aim, we studied the dual effect of 24h-osmotic and 3h-UV irradiation on the cyanobacterium Calothrix BI22. Our approach included the study of redox homeostasis, oxidative damage, reactive oxygen species production-consumption processes and photosynthetic activity. Superoxide in vivo determination with confocal image processing showed the highest accumulation under UV. However, no lipoperoxidation occurred due to a high SOD activity. This cyanobacterium was less prepared to cope with the osmotic stress assayed. Under this condition, O photoevolution decreased abruptly and oxidative damage was produced by reactive species other than superoxide. In this situation the cellular control of the amount of ROS failed to prevent oxidative damage and photosynthesis was seriously disturbed in spite of maximum quantum photosynthetic efficiency remained unchanged. Calothrix BI22 presented the more severe oxidative damage when both stressors were applied. The osmotic stress disentangled the mechanisms developed by this cyanobacterium to deal with 3h-UV irradiation alone.
蓝细菌因其适应策略而能在多样的生境中成功生存。它们应对单一胁迫的机制已得到研究。然而，对于自然界中存在的复合胁迫条件的响应仍不清楚。基于此目的，我们研究了24小时渗透胁迫和3小时紫外线照射对蓝细菌眉藻Calothrix BI22的双重影响。我们的研究方法包括对氧化还原稳态、氧化损伤、活性氧产生 - 消耗过程以及光合活性的研究。通过共聚焦图像处理对体内超氧化物的测定表明，紫外线照射下超氧化物积累最多。然而，由于超氧化物歧化酶（SOD）活性高，未发生脂质过氧化。这种蓝细菌应对所测定的渗透胁迫的准备不足。在此条件下，光放氧突然下降，除超氧化物外的其他活性物质产生了氧化损伤。在这种情况下，尽管最大光合量子效率保持不变，但细胞对活性氧含量控制未能防止氧化损伤，光合作用受到严重干扰。当同时施加两种胁迫因素时，眉藻Calothrix BI22表现出更严重的氧化损伤。渗透胁迫扰乱了这种蓝细菌单独应对3小时紫外线照射所形成的机制。
