Pérez María Teresa, Sommaruga Ruben
Laboratory of Aquatic Photobiology and Plankton Ecology, Institute of Ecology, University of Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria.
Environ Microbiol. 2007 Sep;9(9):2200-10. doi: 10.1111/j.1462-2920.2007.01334.x.
We studied the interactive effects of dissolved organic matter (DOM) and solar radiation on the activity and community structure of bacteria from an alpine lake. Activity was assessed both at the community level as leucine incorporation rates and at the single-cell level by microautoradiography. Fluorescent in situ hybridization and signal amplification by catalysed reporter deposition (CARD-FISH) was used to track changes in the bacterial community composition. Bacteria-free filtrates of different DOM sources (lake, algae or soil) were incubated either in the dark or exposed to solar radiation. Afterwards, the natural bacterial assemblage was inoculated and the cultures incubated in the dark for 24-48 h. Bacterial activity was enhanced in the first 24 h in the soil and algal DOM amendments kept in the dark. After 48 h, the enhancement effect was greatly reduced. The initial bacterial community was dominated by Betaproteobacteria followed by Actinobacteria. The relative abundance (expressed as a percentage of DAPI-stained cells) of Betaproteobacteria increased first in dark incubated DOM amendments, but after 48 h no significant differences were detected among treatments. In contrast, the relative abundance of Actinobacteria increased in pre-irradiated DOM treatments. Although Betaproteobacteria dominated at the end of the experiment, the relative abundance of their R-BT subgroup differed among treatments. Changes in bacterial community activity were significantly correlated with those of the relative abundance and activity of Betaproteobacteria, whereas the contribution of Actinobacteria to the bulk activity was very modest. Our results indicate a negative effect of DOM photoalteration on the bulk bacterial activity. The magnitude of this effect was time-dependent and related to rapid changes in the bacterial assemblage composition.
我们研究了溶解有机物（DOM）和太阳辐射对高山湖泊细菌活性及群落结构的交互作用。活性评估在群落水平上通过亮氨酸掺入率进行，在单细胞水平上通过微放射自显影进行。采用荧光原位杂交和催化报告沉积信号放大技术（CARD-FISH）来追踪细菌群落组成的变化。将不同DOM来源（湖泊、藻类或土壤）的无菌滤液分别在黑暗中培养或暴露于太阳辐射下。之后，接种天然细菌群落，并将培养物在黑暗中培养24 - 48小时。在黑暗中保存的土壤和藻类DOM添加物中，细菌活性在最初24小时内增强。48小时后，增强效果大幅降低。初始细菌群落以β-变形菌为主，其次是放线菌。β-变形菌的相对丰度（以DAPI染色细胞的百分比表示）在黑暗培养的DOM添加物中首先增加，但48小时后各处理间未检测到显著差异。相比之下，放线菌的相对丰度在预辐照的DOM处理中增加。尽管在实验结束时β-变形菌占主导，但它们的R-BT亚群的相对丰度在各处理间有所不同。细菌群落活性的变化与β-变形菌的相对丰度和活性的变化显著相关，而放线菌对总体活性的贡献非常小。我们的结果表明DOM光化学改变对总体细菌活性有负面影响。这种影响的程度与时间有关，并且与细菌群落组成的快速变化有关。
