Limnological Station, Institute of Plant Biology, University of Zürich, Kilchberg, Switzerland.
FEMS Microbiol Ecol. 2010 Feb;71(2):281-90. doi: 10.1111/j.1574-6941.2009.00800.x. Epub 2009 Oct 23.
We investigated the antibiotic effects of extracts of freeze-dried biomass and culture supernatants from the mixotrophic chrysophyte species Ochromonas danica, Poterioochromonas sp. strain DS, and Poterioochromonas malhamensis on bacterial strains isolated from lake water. Methanolic biomass extracts inhibited the growth of all tested strains, albeit to a different extent, whereas aqueous biomass extracts only affected bacteria of the genus Flectobacillus. The antibiotic action of supernatants from flagellate cultures could be mostly attributed to lipophilic substances, but the growth of bacteria affiliated with Flectobacillus and Sphingobium was also affected by hydrophilic compounds. A comparison of biomass extracts from light- and dark-adapted cultures of Poterioochromonas sp. strain DS showed that the growth-inhibiting factor was unrelated to chlorophyll derivatives. Supernatants from a dark-adapted, phagotrophically grown flagellate culture had stronger antibiotic effects and affected more bacterial strains than the supernatant from a light-adapted culture. Significant growth reduction of a Flectobacillus isolate was already induced by extremely low concentrations of lipophilic extracts from these supernatants. Our results show that metabolites of the studied flagellates - either released actively or during cell lysis - may selectively affect the growth of some aquatic bacteria even in very small doses and thus potentially affect microbial community composition. Moreover, the antibiotic potential of mixotrophic chrysophytes may change with their nutritional mode.
我们研究了混养性金藻物种 Ochromonas danica、Pterioochromonas sp. strain DS 和 Pterioochromonas malhamensis 的冻干生物量提取物和培养上清液对从湖水分离的细菌菌株的抗生素作用。甲醇生物量提取物抑制了所有测试菌株的生长，但抑制程度不同，而水生物量提取物仅影响 Flectobacillus 属的细菌。鞭毛藻培养物上清液的抗生素作用主要归因于亲脂性物质，但 Flectobacillus 和 Sphingobium 属细菌的生长也受到亲水性化合物的影响。比较 Poterioochromonas sp. strain DS 的光适应和暗适应培养物的生物量提取物表明，生长抑制因子与叶绿素衍生物无关。与光适应培养物的上清液相比，暗适应、吞噬生长的鞭毛藻培养物的上清液具有更强的抗生素作用，并影响更多的细菌菌株。这些上清液中的低浓度亲脂性提取物就能显著降低 Flectobacillus 分离株的生长。我们的研究结果表明，研究鞭毛藻的代谢产物 - 无论是主动释放还是在细胞裂解时释放 - 即使在非常低的剂量下也可能选择性地影响一些水生细菌的生长，从而可能影响微生物群落组成。此外，混养性金藻的抗生素潜力可能会随着它们的营养方式而变化。
