Increased production of outer membrane vesicles by cultured freshwater bacteria in response to ultraviolet radiation
Increased production of outer membrane vesicles by cultured freshwater bacteria in response to ultraviolet radiation
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DOI：
10.1016/j.micres.2016.08.002
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发表时间：
2017-01-01
影响因子：
6.7
通讯作者：
Melo, Rossana C. N.
中科院分区：
文献类型：
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作者：
Gamalier, Juliana P.;Silva, Thiago P.;Melo, Rossana C. N.
膜囊泡的分泌是真核细胞和原核细胞的重要生物学过程。这一过程已在致病菌中得到表征，但在水生生态系统中的非致病菌中尚不清楚。在此，我们首次研究了革兰氏阴性菌的外膜囊泡（OMVs）的形成过程，从革兰氏阴性菌的外膜（OM）中挤出纳米级囊泡，在淡水细菌培养中暴露于或不暴露于紫外线辐射（UVR）作为环境应激源后。将从巴西水生生态系统（Funil水库）分离的淡水细菌非无菌培养物暴露于UVA + UVB （UVA + UVB）下3 h，分析细胞密度、活力和超微结构。首先，我们发现紫外线可诱导细菌死亡。UVR处理3 h后对细胞密度有显著的负影响。这种减少与细胞死亡直接相关，正如细胞活力荧光探针所揭示的那样，它可以区分活/死细菌。透射电子显微镜（TEM）显示，在UVR暴露3小时后，细胞死亡的变化表明，与对照组相比，受损细胞显著增加。其次，我们证明革兰氏阴性菌在正常生长和UVR暴露后释放omv。omv被清楚地识别为从细菌OM中出芽的圆形膜结合囊泡，作为分离的或聚集的囊泡或游离在细胞外培养基中。值得注意的是，定量TEM分析显示，细菌对UVR的反应是增加omv的形成。此外，尽管未治疗组中每个完整或受损细胞的omv数量没有差异，但UVR导致细菌在死亡过程中产生更高的囊泡。这意味着退化细菌在裂解前释放omv，这种分泌可能是对环境条件（如紫外线辐射）快速变化的适应性/保护性反应。(C) 2016 Elsevier GmbH版权所有。
Secretion of membrane vesicles is an important biological process of both eukaryotic and prokaryotic cells. This process has been characterized in pathogenic bacteria, but is less clear in non-pathogenic bacteria from aquatic ecosystems. Here, we investigated, for the first time, the process of formation of outer membranes vesicles (OMVs), nanoscale vesicles extruded from the outer membrane (OM) of gram negative bacteria, in cultures of freshwater bacteria after exposure or not to ultraviolet radiation (UVR) as an environmental stressor. Non-axenic cultures of freshwater bacteria isolated from a Brazilian aquatic ecosystem (Funil reservoir) were exposed or not to UVR (UVA + UVB) over a 3 h period, during which cell density, viability and ultrastructure were analyzed. First, we showed that UVR induce bacterial death. UVR triggered significant negative effect on cell density after 3 h of UVR treatment. This decrease was directly associated with cell death as revealed by a cell viability fluorescent probe that enables the distinction of live/dead bacteria. Transmission electron microscopy (TEM) revealed changes indicative of cell death after 3 h of UVR exposure, with significant increase of damaged cells compared to the control group. Second, we demonstrated that gram-negative bacteria release OMVs during normal growth and after UVR exposure. OMVs were clearly identified as round, membrane-bound vesicles budding off from the bacterial OM as isolated or clustered vesicles or free in the extracellular medium. Remarkably, quantitative TEM analyses showed that bacteria respond to UVR with increased formation of OMVs. Moreover, while OMVs numbers per intact or damaged cell did not differ in the untreated group, UVR led to a higher vesiculation by bacteria in process of death. This means that degenerating bacteria release OMVs before lysis and that this secretion might be an adaptive/protective response to rapid changes in environmental conditions such as UV radiation. (C) 2016 Elsevier GmbH. All rights reserved.