Interactions between bacteria and phytoplankton in the phycosphere facilitate and constrain biogeochemical cycling in aquatic ecosystems. Indole-3-acetic acid (IAA) is a bacterially produced chemical signal that promotes growth of phytoplankton and plants. Here, we explored the impact of IAA on bloom-forming cyanobacteria and their associated bacteria. Exposure to IAA and its precursor, tryptophan, resulted in a strong growth response in a bloom of the freshwater cyanobacterium, . Metatranscriptome analysis revealed the induction of an antioxidant response in upon exposure to IAA, potentially allowing populations to increase photosynthetic rate and overcome internally generated reactive oxygen. Our data reveal that co-occurring bacteria within the phycosphere microbiome exhibit a division of labor for supportive functions, such as nutrient mineralization and transport, vitamin synthesis, and reactive oxygen neutralization. These complex dynamics within the phycosphere microbiome are an example of interactions within a microenvironment that can have ecosystem-scale consequences.

中文翻译：

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3-吲哚乙酸通过抗氧化反应促进水华形成微囊藻的生长

藻圈中细菌和浮游植物之间的相互作用促进和限制水生生态系统中的生物地球化学循环。3-吲哚乙酸 (IAA) 是细菌产生的化学信号，可促进浮游植物和植物的生长。在这里，我们探讨了 IAA 对水华形成蓝藻及其相关细菌的影响。接触 IAA 及其前体色氨酸会导致淡水蓝细菌大量生长。宏转录组分析揭示了暴露于 IAA 后会诱导抗氧化反应，可能使种群提高光合作用速率并克服内部产生的活性氧。我们的数据显示，藻圈微生物组内共存的细菌表现出支持功能的分工，例如营养物矿化和运输、维生素合成和活性氧中和。藻圈微生物组内的这些复杂动态是微环境内相互作用的一个例子，可能会产生生态系统规模的后果。