背景:来自原氯球菌属的蓝细菌,Synechococcus,蓝藻是水生生态系统中最广泛的光合生物。然而,他们的淡水种群仍然缺乏勘探,由于不同内陆水体的采样不均匀和不足。
结果:在这项研究中,我们提供了来自中欧各地收集的非无菌培养物的170个优质淡水蓝细菌基因组。此外,我们回收了他们潜在的共生伙伴的33个基因组,它们有四个属,假单胞菌,中根瘤菌,Acidovorax,和Hydrogenophaga。共生相互作用的基因组基础涉及异养生物,这些生物受益于蓝藻细菌衍生的营养素,同时提供ROS的解毒作用。蓝细菌的全球丰度模式揭示了生态上重要的生态型,与营养状态有关,温度,和pH是关键的环境因素。(超)富营养化水体中的蓝细菌的适应可归因于其殖民地生活方式和CRISPR-Cas系统。绿藻中主要的CRISPR-Cas亚型为I-G和I-E,似乎是通过从其他细菌门的水平基因转移获得的。
结论:我们的发现为种群多样性提供了新的见解,生态学,和淡水生态系统中最广泛的光合自养生物的进化策略。视频摘要。
BACKGROUND: Picocyanobacteria from the genera Prochlorococcus, Synechococcus, and Cyanobium are the most widespread photosynthetic organisms in aquatic ecosystems. However, their freshwater populations remain poorly explored, due to uneven and insufficient sampling across diverse inland waterbodies.
RESULTS: In this study, we present 170 high-quality genomes of freshwater picocyanobacteria from non-axenic cultures collected across Central Europe. In addition, we recovered 33 genomes of their potential symbiotic partners affiliated with four genera, Pseudomonas, Mesorhizobium, Acidovorax, and Hydrogenophaga. The genomic basis of symbiotic interactions involved heterotrophs benefiting from picocyanobacteria-derived nutrients while providing detoxification of ROS. The global abundance patterns of picocyanobacteria revealed ecologically significant ecotypes, associated with trophic status, temperature, and pH as key environmental factors. The adaptation of picocyanobacteria in (hyper-)eutrophic waterbodies could be attributed to their colonial lifestyles and CRISPR-Cas systems. The prevailing CRISPR-Cas subtypes in picocyanobacteria were I-G and I-E, which appear to have been acquired through horizontal gene transfer from other bacterial phyla.
CONCLUSIONS: Our findings provide novel insights into the population diversity, ecology, and evolutionary strategies of the most widespread photoautotrophs within freshwater ecosystems. Video Abstract.