In this study, we tested the hypothesis that the growth efficiency of freshwater bacteria is differentially affected by ultraviolet radiation (UVR, 280–400 nm) as mediated through changes in their production and respiration rates. Five bacterial strains affiliated to Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Actinobacteria were isolated from different freshwater habitats and exposed in the laboratory to photosynthetically active radiation (PAR) and PAR + UVR, or kept in the dark for 4 h. Afterward, bacterial carbon production and respiration were assessed by measuring leucine incorporation and oxygen consumption rates, respectively. Ultraviolet radiation decreased significantly the bacterial production of Acidovorax sp., Pseudomonas sp. and Actinobacterium MHWTa3, and the respiration rate of Acidovorax sp. and Acinetobacter lwoffii. Measurements of respiration of a natural bacterial community collected from the same lake where A. lwoffii was isolated resulted in significantly higher rates after exposure to PAR + UVR than in the dark. In the presence of UVR, bacterial growth efficiency significantly decreased in Acidovorax sp., Pseudomonas sp., and Actinobacterium MHWTa3, but it increased in A. lwoffii or it remained unchanged in Sphingomonas sp. Our results indicate that although the outcome was strain-specific, UVR has the potential to alter the efficiency by which dissolved organic matter is transformed into bacterial biomass and thus to affect the biogeochemical carbon cycle.

中文翻译：

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对比紫外线辐射对淡水细菌生长效率的影响。

在这项研究中，我们检验了淡水细菌的生长效率受紫外线辐射（UVR，280-400 nm）的不同影响的假设，这是通过其生产和呼吸速率的变化介导的。从不同的淡水栖息地中分离出隶属于Alphaproteobacteria、Betaproteobacteria、Gammaproteobacteria和Actinobacteria 的五种细菌菌株，并在实验室中暴露于光合有效辐射 (PAR) 和 PAR + UVR，或在黑暗中保持 4 h。然后，分别通过测量亮氨酸掺入和耗氧率来评估细菌碳产生和呼吸作用。紫外线辐射显着降低了细菌的产生嗜酸菌属，假单胞菌属。和放线菌MHWTa3，以及Acidovorax sp.的呼吸速率。和lwoffii 不动杆菌。从分离A. lwoffii的同一湖收集的天然细菌群落的呼吸测量结果在暴露于 PAR + UVR 后比在黑暗中显着更高。在 UVR 存在下，Acidovorax sp.、Pseudomonas sp. 和Actinobacterium MHWTa3 的细菌生长效率显着降低，但在A. lwoffii 中增加或在鞘氨醇单胞菌中保持不变sp. 我们的结果表明，虽然结果是菌株特异性的，但 UVR 有可能改变溶解有机物转化为细菌生物量的效率，从而影响生物地球化学碳循环。