Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.; Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China.
Department of Ocean Science and Engineering, Southern University of Science and Technology, Shenzhen, China.
Sci Total Environ. 2024 Feb 1;910:168702. doi: 10.1016/j.scitotenv.2023.168702. Epub 2023 Nov 20.
Cyanobacteria, the most abundant photosynthetic organisms in oceans, are tightly associated with diverse microbiota. However, the relationships between heterotrophic bacteria and cyanobacteria, particularly the diazotrophic group, are not fully understood. Here, we compared diel gene expressions of N fixing cyanobacteria Crocosphaera watsonii WH0003 and non-diazotrophic Synechococcus sp. RS9902 and their associated bacteria using metatranscriptomics approach. WH0003 showed significant up-regulation of O restriction and oxidative phosphorylation related genes at nighttime due to large carbon and energy investments for active N fixation. In contrast, RS9902 had higher expression for those genes at daytime. The two cyanobacteria hosted distinct bacterial communities with clear separate substrate utilization niches to reduce competition. Light-dark partitioning of nutrient acquisition among the dominant bacterial groups likely contributed to the dynamic balance for community coexistence. Moreover, particle-attached (PA) bacteria in RS9902 largely expressed glycoside hydrolases to hydrolyze complex carbohydrate compounds, while free-living (FL) bacteria priorly assimilated soluble, diffusible molecules. Spatial partitioning of nutrient acquisition between PA and FL bacteria implied that location initially influenced metabolic features of host associated bacteria. Our results advance knowledge on light-dark regulated metabolic activities of diazotrophic and non-diazotrophic cyanobacteria, and provide new insights into the coexisting strategies of different bacterial groups.
蓝藻是海洋中最丰富的光合生物，与多种微生物群紧密相关。然而，异养细菌与蓝藻（尤其是固氮组）之间的关系尚不完全清楚。在这里，我们使用宏转录组学方法比较了固氮蓝藻 Crocosphaera watsonii WH0003 和非固氮的 Synechococcus sp. RS9902 及其相关细菌的昼夜基因表达。由于主动固氮需要大量的碳和能量投入，WH0003 在夜间表现出 O 限制和氧化磷酸化相关基因的显著上调。相比之下，RS9902 在白天有更高的这些基因的表达。这两种蓝藻具有不同的细菌群落，具有明显的独立底物利用生态位，以减少竞争。在主要细菌群之间进行的营养获取的光暗分区可能有助于群落共存的动态平衡。此外，RS9902 中的颗粒附着（PA）细菌大量表达糖苷水解酶来水解复杂的碳水化合物化合物，而自由生活（FL）细菌优先同化可溶性、可扩散的分子。PA 和 FL 细菌之间营养获取的空间分区表明，位置最初影响了宿主相关细菌的代谢特征。我们的研究结果推进了对固氮和非固氮蓝藻昼夜调节代谢活动的认识，并为不同细菌群共存策略提供了新的见解。
