Department of Ecology, Environment and Plant Sciences, Stockholm University, 106 91 Stockholm, Sweden; email:
Department of Ocean Sciences, University of California, Santa Cruz, California 95064, USA; email:
Annu Rev Microbiol. 2019 Sep 8;73:435-456. doi: 10.1146/annurev-micro-090817-062650.
Cyanobacteria are common in symbiotic relationships with diverse multicellular organisms (animals, plants, fungi) in terrestrial environments and with single-celled heterotrophic, mixotrophic, and autotrophic protists in aquatic environments. In the sunlit zones of aquatic environments, diverse cyanobacterial symbioses exist with autotrophic taxa in phytoplankton, including dinoflagellates, diatoms, and haptophytes (prymnesiophytes). Phototrophic unicellular cyanobacteria related to and are associated with a number of groups. N-fixing cyanobacteria are symbiotic with diatoms and haptophytes. Extensive genome reduction is involved in the N-fixing endosymbionts, most dramatically in the unicellular cyanobacteria associated with haptophytes, which have lost most of the photosynthetic apparatus, the ability to fix C, and the tricarboxylic acid cycle. The mechanisms involved in N-fixing symbioses may involve more interactions beyond simple exchange of fixed C for N. N-fixing cyanobacterial symbioses are widespread in the oceans, even more widely distributed than the best-known free-living N-fixing cyanobacteria, suggesting they may be equally or more important in the global ocean biogeochemical cycle of N.Despite their ubiquitous nature and significance in biogeochemical cycles, cyanobacterium-phytoplankton symbioses remain understudied and poorly understood.
蓝细菌与陆地环境中多样的多细胞生物（动物、植物、真菌）以及水生环境中单细胞异养、混合营养和自养原生生物存在共生关系。在水生环境的光照区，与浮游植物中的自养分类群（包括甲藻、硅藻和甲藻）存在多样的蓝细菌共生关系。与 和 相关的光合单细胞蓝细菌与许多群体相关。固氮蓝细菌与硅藻和甲藻共生。固氮内共生体涉及广泛的基因组减少，最显著的是与甲藻相关的单细胞蓝细菌，它们失去了大部分光合作用装置、固定 C 的能力和三羧酸循环。固氮共生的机制可能涉及超出简单固定 C 与 N 交换的更多相互作用。固氮蓝细菌共生在海洋中广泛存在，甚至比最著名的自由生活固氮蓝细菌分布更广，这表明它们在全球海洋氮的生物地球化学循环中可能同样重要或更重要。尽管它们在生物地球化学循环中具有普遍存在的性质和重要性，但蓝细菌-浮游植物共生关系仍然研究不足，了解甚少。
