Table_1_RNA-seq Insights Into the Impact of Alteromonas macleodii on Isochrysis galbana.XLS

Phycospheric bacteria may be the key biological factors affecting the growth of algae. However, the studies about interaction between Isochrysis galbana and its phycospheric bacteria are limited. Here, we show that a marine heterotrophic bacterium, Alteromonas macleodii, enhanced the growth of I. galbana, and inhibited non-photochemical quenching (NPQ) and superoxide dismutase (SOD) activities of this microalgae. Further, we explored this phenomenon via examining how the entire transcriptomes of I. galbana changed when it was co-cultured with A. macleodii. Notable increase was observed in transcripts related to photosynthesis, carbon fixation, oxidative phosphorylation, ribosomal proteins, biosynthetic enzymes, and transport processes of I. galbana in the presence of A. macleodii, suggesting the introduction of the bacterium might have introduced increased production and transport of carbon compounds and other types of biomolecules. Besides, the transcriptome changed largely corresponded to reduced stress conditions for I. galbana, as inferred from the depletion of transcripts encoding DNA repair enzymes, superoxide dismutase (SOD) and other stress-response proteins. Taken together, the presence of A. macleodii mainly enhanced photosynthesis and biosynthesis of I. galbana and protected it from stress, especially oxidative stress. Transfer of fixed organic carbon, but perhaps other types of biomolecules, between the autotroph and the heterotroph might happen in I. galbana-A. macleodii co-culture. The present work provides novel insights into the transcriptional consequences of I. galbana of mutualism with its heterotrophic bacterial partner, and mutually beneficial associations existing in I. galbana-A. macleodii might be explored to improve productivity and sustainability of aquaculture algal rearing systems.

浮游细菌可能是影响藻类生长的关键生物因素。然而，关于金藻（Isochrysis galbana）与其浮游细菌之间相互作用的深入研究尚显不足。本研究揭示了海洋异养细菌Alteromonas macleodii能够促进金藻的生长，并抑制该微藻的非光合猝灭（NPQ）和超氧化物歧化酶（SOD）活性。进一步地，我们通过观察金藻与A. macleodii共培养时整个转录组的变化，探讨了这一现象。在A. macleodii存在的情况下，金藻与光合作用、碳固定、氧化磷酸化、核糖体蛋白、生物合成酶以及运输过程相关的转录本显著增加，这表明该细菌的引入可能促进了碳化合物及其他生物分子的生产与运输。此外，转录组的变化在很大程度上与金藻减轻压力状态相对应，这一推断源于编码DNA修复酶、超氧化物歧化酶（SOD）及其他压力反应蛋白的转录本耗竭。综上所述，A. macleodii的存在主要增强了金藻的光合作用和生物合成，并保护其免受压力，尤其是氧化压力的侵害。在金藻-A. macleodii共培养体系中，可能发生了自养生物与异养生物之间固定有机碳的转移，或许还有其他类型的生物分子。本研究为揭示金藻与其异养细菌合作伙伴互利共生关系的转录后果提供了新的见解，且金藻-A. macleodii之间的互利共生关系或许可用于提高水产养殖藻类养殖系统的生产力和可持续性。