UPMC Univ Paris 06, UMR 7621, LOMIC, Observatoire Océanologique, 66650 Banyuls/mer, France.
Microb Ecol. 2012 Feb;63(2):324-33. doi: 10.1007/s00248-011-9915-7. Epub 2011 Sep 2.
We investigated the abundance and activity of SAR11 on a monthly time scale between January 2008 and October 2008 in the oligotrophic NW Mediterranean Sea. Applying MICRO-CARD-FISH, we observed that SAR11 had a large contribution to bulk abundance (37 ± 6% of DAPI-stained cells) and to bulk bacterial heterotrophic production (BHP), as estimated from leucine incorporation (55 ± 15% of DAPI-cells assimilating leucine) in surface waters (5 m) throughout the study period. SAR11 contributed also substantially to the assimilation of glucose, ATP, and a combination of amino acids (44 ± 17%, 37 ± 14%, and 43 ± 12% of DAPI cells assimilating these compounds, respectively), organic compounds that provide either single or combined sources of C, P, and N. Temporal changes in the abundance of SAR11 cells that assimilated leucine, glucose, amino acids, and ATP revealed a pattern consistent with that of substrate-active DAPI cells, suggesting that the activity of SAR11 can explain to a large extent the variability in total cells contributing to the utilization of these compounds. Short-term nutrient enrichment experiments performed on each sampling date revealed a strong co-limitation of at least two of the three elements analyzed (C, N, P), in particular, during summer and early autumn. The in situ abundance of SAR11 cells assimilating leucine appeared to increase with P limitation as determined in the nutrient enrichment experiments (r = 0.81, p = 0.015). Our results demonstrate that SAR11 is an important component of the active bacterial community in the NW Mediterranean Sea. Our observations further indicate that the activity of the bulk bacterial community is linked to the activity of SAR11, possibly due to its adaptation to nutrient limitation.
我们在 2008 年 1 月至 2008 年 10 月的每月时间尺度上调查了寡营养的西北地中海中 SAR11 的丰度和活性。应用 MICRO-CARD-FISH，我们观察到 SAR11 对总丰度（DAPI 染色细胞的 37±6%）和通过亮氨酸掺入（DAPI 细胞吸收亮氨酸的 55±15%）估计的总细菌异养生产（BHP）有很大的贡献，在整个研究期间在表面水中（5 米）。SAR11 还大量参与了葡萄糖、ATP 和氨基酸的同化（分别为 DAPI 细胞同化这些化合物的 44±17%、37±14%和 43±12%），这些有机化合物提供了单一或组合的 C、P 和 N 来源。吸收亮氨酸、葡萄糖、氨基酸和 ATP 的 SAR11 细胞丰度的时间变化与底物活性 DAPI 细胞的模式一致，表明 SAR11 的活性在很大程度上可以解释对这些化合物的利用的总细胞变化。在每个采样日期进行的短期营养强化实验表明，至少有三种分析元素（C、N、P）中的两种受到强烈的共同限制，特别是在夏季和初秋。在营养强化实验中确定的，吸收亮氨酸的 SAR11 细胞的原位丰度似乎随着磷限制的增加而增加（r=0.81，p=0.015）。我们的结果表明，SAR11 是西北地中海活跃细菌群落的重要组成部分。我们的观察结果进一步表明，总细菌群落的活性与 SAR11 的活性有关，可能是由于其对营养限制的适应。
