Department of Microbiology, Morrill Science Center IVN, University of Massachusetts Amherst, Amherst, MA 01003, USA.
ISME J. 2013 Jul;7(7):1286-98. doi: 10.1038/ismej.2013.20. Epub 2013 Feb 28.
The importance of bacteria in the anaerobic bioremediation of groundwater polluted with organic and/or metal contaminants is well recognized and in some instances so well understood that modeling of the in situ metabolic activity of the relevant subsurface microorganisms in response to changes in subsurface geochemistry is feasible. However, a potentially significant factor influencing bacterial growth and activity in the subsurface that has not been adequately addressed is protozoan predation of the microorganisms responsible for bioremediation. In field experiments at a uranium-contaminated aquifer located in Rifle, CO, USA, acetate amendments initially promoted the growth of metal-reducing Geobacter species, followed by the growth of sulfate reducers, as observed previously. Analysis of 18S rRNA gene sequences revealed a broad diversity of sequences closely related to known bacteriovorous protozoa in the groundwater before the addition of acetate. The bloom of Geobacter species was accompanied by a specific enrichment of sequences most closely related to the ameboid flagellate, Breviata anathema, which at their peak accounted for over 80% of the sequences recovered. The abundance of Geobacter species declined following the rapid emergence of B. anathema. The subsequent growth of sulfate-reducing Peptococcaceae was accompanied by another specific enrichment of protozoa, but with sequences most similar to diplomonadid flagellates from the family Hexamitidae, which accounted for up to 100% of the sequences recovered during this phase of the bioremediation. These results suggest a prey-predator response with specific protozoa responding to increased availability of preferred prey bacteria. Thus, quantifying the influence of protozoan predation on the growth, activity and composition of the subsurface bacterial community is essential for predictive modeling of in situ uranium bioremediation strategies.
细菌在受有机和/或金属污染物污染的地下水的厌氧生物修复中的重要性已得到充分认识，在某些情况下，对相关地下微生物在地下地球化学变化下的原位代谢活性进行建模是可行的。然而，一个潜在的重要因素影响着地下细菌的生长和活性，但尚未得到充分解决，那就是原生动物对负责生物修复的微生物的捕食。在美国科罗拉多州里弗尔铀污染含水层的现场实验中，最初添加乙酸盐促进了金属还原菌 Geobacter 物种的生长，随后是硫酸盐还原菌的生长，这与之前的观察结果一致。18S rRNA 基因序列分析表明，在添加乙酸盐之前，地下水中存在与已知食细菌原生动物密切相关的广泛多样性序列。Geobacter 物种的大量繁殖伴随着与阿米巴鞭毛虫 Breviata anathema 最密切相关的序列的特定富集，其峰值时占回收序列的 80%以上。Geobacter 物种的丰度在 Breviata anathema 的快速出现后下降。随后硫酸盐还原菌 Peptococcaceae 的生长伴随着另一种原生动物的特定富集，但与六鞭毛虫Hexamitidae 家族的双鞭毛原生动物的序列最相似，在生物修复的这一阶段，它们占回收序列的 100%。这些结果表明存在一种猎物-捕食者的反应，特定的原生动物对增加的首选猎物细菌的可用性作出反应。因此，量化原生动物捕食对地下细菌群落生长、活性和组成的影响，对于原位铀生物修复策略的预测建模至关重要。
