Institute for Limnology of the Austrian Academy of Sciences, Herzog Odilostraße.
Eur J Protistol. 2011 May;47(2):79-85. doi: 10.1016/j.ejop.2011.01.001. Epub 2011 Feb 21.
We investigated the effect of pH on the competition of two closely related chrysomonad species, Poterioochromonas malhamensis originating from circumneutral Lake Constance, and Ochromonas sp. isolated from a highly acidic mining lake in Austria (pH ∼2.6). We performed pairwise growth experiments between these two species at four different pH ranging from 2.5 to 7.0. Heterotrophic bacteria served as food for both flagellates. Results were compared to growth rates measured earlier in single species experiments over the same pH range. We tested the hypothesis that the acidotolerant species benefits from competitive release under conditions of acid stress. The neutrophilic strain numerically dominated over the acidotolerant strain at pH 7.0, but was the inferior competitor at pH 2.5. At pH 3.5 and 5.0 both strains coexisted. Surprisingly, P. malhamensis prevailed over Ochromonas sp. under moderately acidic conditions, i.e. at the pH where growth rates of the latter peaked when grown alone. Since bacterial food was not limiting, resource competition is improbable. It appears more likely that P. malhamensis ingested cells of its slightly smaller competitor. Adverse effects mediated via allelopathy, either directly on the competing flagellate or indirectly by affecting its bacterial food, might also have affected the outcome of competition.
我们研究了 pH 值对两种密切相关的金滴虫的竞争的影响，一种是源自中性湖泊康斯坦茨的 Poterioochromonas malhamensis，另一种是从奥地利高度酸性的采矿湖中分离出来的 Ochromonas sp.。我们在四个不同的 pH 值（2.5 到 7.0）下进行了这两种生物之间的成对生长实验。异养细菌作为两种鞭毛虫的食物。结果与在相同 pH 值范围内进行的单一物种实验中测量的生长速率进行了比较。我们检验了这样一个假设，即在酸性胁迫条件下，耐酸性物种通过竞争释放而受益。在 pH 值为 7.0 时，中性菌株在数量上超过了耐酸性菌株，但在 pH 值为 2.5 时，它是较差的竞争者。在 pH 值为 3.5 和 5.0 时，两种菌株共存。令人惊讶的是，P. malhamensis 在中度酸性条件下胜过 Ochromonas sp.，即在后者单独生长时生长速率达到峰值的 pH 值下。由于细菌食物不缺乏，资源竞争不太可能。更有可能的是，P. malhamensis 吞噬了其稍小的竞争对手的细胞。通过化感作用介导的不利影响，无论是直接对竞争的鞭毛虫，还是间接通过影响其细菌食物，也可能影响竞争的结果。
