Institute for Inorganic and Analytical Chemistry, Friedrich Schiller University Jenagrid.9613.d, Jena, Germany.
Theoretical Microbial Ecology Group, Institute of Microbiology, Faculty of Biological Sciences, Friedrich Schiller University Jenagrid.9613.d, Jena, Germany.
Appl Environ Microbiol. 2022 Nov 22;88(22):e0161922. doi: 10.1128/aem.01619-22. Epub 2022 Oct 27.
Microalgae that form phytoplankton live and die in a complex microbial consortium in which they co-exist with bacteria and other microorganisms. The dynamics of species succession in the plankton depends on the interplay of these partners. Bacteria utilize substrates produced by the phototrophic algae, while algal growth can be supported by bacterial exudates. Bacteria might also use chemical mediators with algicidal properties to attack algae. To elucidate whether specific bacteria play universal or context-specific roles in the interaction with phytoplankton, we investigated the effect of cocultured bacteria on the growth of 8 microalgae. An interaction matrix revealed that the function of a given bacterium is highly dependent on the cocultured partner. We observed no universally algicidal or universally growth-promoting bacteria. The activity of bacteria can even change during the aging of an algal culture from inhibitory to stimulatory or vice versa. We further established a synthetic phytoplankton/bacteria community with the centric diatom, Coscinodiscus radiatus, and 4 phylogenetically distinctive bacterial isolates, Mameliella sp., Roseovarius sp., Croceibacter sp., and Marinobacter sp. Supported by a Lotka-Volterra model, we show that interactions within the consortium are specific and that the sum of the pairwise interactions can explain algal and bacterial growth in the community. No synergistic effects between bacteria in the presence of the diatom was observed. Our survey documents highly species-specific interactions that are dependent on algal fitness, bacterial metabolism, and community composition. This species specificity may underly the high complexity of the multi-species plankton communities observed in nature. The marine food web is fueled by phototrophic phytoplankton. These algae are central primary producers responsible for the fixation of ca. 40% of the global CO. Phytoplankton always co-occur with a diverse bacterial community in nature. This diversity suggests the existence of ecological niches for the associated bacteria. We show that the interaction between algae and bacteria is highly species-specific. Furthermore, both, the fitness stage of the algae and the community composition are relevant in determining the effect of bacteria on algal growth. We conclude that bacteria should not be sorted into algicidal or growth supporting categories; instead, a context-specific function of the bacteria in the plankton must be considered. This functional diversity of single players within a consortium may underly the observed diversity in the plankton.
形成浮游植物的微藻在一个复杂的微生物联合体中生活和死亡，其中它们与细菌和其他微生物共存。浮游生物中物种演替的动态取决于这些伙伴的相互作用。细菌利用光养藻类产生的底物，而藻类的生长可以得到细菌分泌物的支持。细菌还可以使用具有杀藻特性的化学介质来攻击藻类。为了阐明特定细菌在与浮游植物的相互作用中是发挥普遍作用还是特定环境作用，我们研究了共培养细菌对 8 种微藻生长的影响。相互作用矩阵表明，给定细菌的功能高度依赖于共培养的伙伴。我们没有观察到普遍的杀藻或普遍的促生长细菌。细菌的活性甚至可以在藻类培养物老化过程中从抑制变为刺激，反之亦然。我们进一步用中心硅藻 Coscinodiscus radiatus 和 4 种系统发育独特的细菌分离株 Mameliella sp.、Roseovarius sp.、Croceibacter sp. 和 Marinobacter sp. 建立了一个合成的浮游植物/细菌群落。在 Lotka-Volterra 模型的支持下，我们表明联合体中的相互作用是特定的，并且对相互作用的总和可以解释群落中藻类和细菌的生长。在硅藻存在的情况下，没有观察到细菌之间的协同作用。我们的调查记录了高度物种特异性的相互作用，这些相互作用依赖于藻类的适应性、细菌的新陈代谢和群落组成。这种物种特异性可能是自然界中观察到的多物种浮游生物群落高度复杂性的基础。海洋食物网由光养浮游植物提供燃料。这些藻类是负责固定全球约 40%CO 的中心初级生产者。浮游植物在自然界中总是与多样化的细菌群落共存。这种多样性表明相关细菌存在生态位。我们表明，藻类和细菌之间的相互作用具有高度的物种特异性。此外，藻类的适应性阶段和群落组成都是决定细菌对藻类生长影响的相关因素。我们得出结论，不应将细菌分为杀藻或促生长类别；相反，应考虑细菌在浮游生物中的特定环境功能。联合体中单种生物的这种功能多样性可能是观察到浮游生物多样性的基础。
