Baker Dylan, Lauer James, Ortega Anna, Jackrel Sara L, Denef Vincent J
Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA.
Department of Ecology, Behavior and Evolution, University of California, San Diego, CA 92093, USA.
Microorganisms. 2022 Dec 25;11(1):62. doi: 10.3390/microorganisms11010062.
Phytoplankton is fundamental to life on Earth. Their productivity is influenced by the microbial communities residing in the phycosphere surrounding algal cells. Expanding our knowledge on how algal-bacterial interactions affect algal growth to more hosts and bacteria can help elucidate general principles of algal-host interactions. Here, we isolated 368 bacterial strains from phycosphere communities, right after phycosphere recruitment from pond water and after a month of lab cultivation and examined their impacts on growth of five green algal species. We isolated both abundant and rare phycosphere members, representing 18.4% of the source communities. Positive and neutral effects predominated over negative effects on host growth. The proportion of each effect type and whether the day of isolation mattered varied by host species. Bacteria affected algal carrying capacity more than growth rate, suggesting that nutrient remineralization and toxic byproduct metabolism may be a dominant mechanism. Across-host algal fitness assays indicated host-specific growth effects of our isolates. We observed no phylogenetic conservation of the effect on host growth among bacterial isolates. Even isolates with the same ASV had divergent effects on host growth. Our results emphasize highly specific host-bacterial interactions in the phycosphere and raise questions as to which mechanisms mediate these interactions.
浮游植物是地球上生命的基础。它们的生产力受到藻类细胞周围藻际中微生物群落的影响。将我们对藻菌相互作用如何影响藻类生长的认识扩展到更多宿主和细菌，有助于阐明藻宿主相互作用的一般原理。在这里，我们从池塘水中招募藻际群落并经过一个月的实验室培养后，从藻际群落中分离出368株细菌菌株，并研究了它们对五种绿藻物种生长的影响。我们分离出了丰富和稀有的藻际成员，占源群落的18.4%。对宿主生长的影响中，积极和中性效应占主导，超过了消极效应。每种效应类型的比例以及分离日是否重要因宿主物种而异。细菌对藻类承载能力的影响大于生长速率，这表明营养物质再矿化和有毒副产物代谢可能是主要机制。跨宿主藻类适应性测定表明我们分离出的菌株对宿主生长有特异性影响。我们观察到细菌分离株对宿主生长的影响不存在系统发育保守性。即使是具有相同ASV的分离株对宿主生长也有不同的影响。我们的结果强调了藻际中高度特异性的宿主-细菌相互作用，并提出了哪些机制介导这些相互作用的问题。
