Growth of Thalassiosira gravida and Thalassiosira rotula across different levels of temperature, photoperiod, and microbiome presence

The provided data represent maximum growth rates of the temperate diatom Thalassiosira rotula obtained from the Harder Lab (University of Bremen; strain T. rotula_S16) and the polar diatom Thalassiosira gravida was obtained from the Norwegian culture collection of algae (NORCCA strain number UIO 478). Data were assessed in a nanocosm (microtiter-plate) 7-day multi-stressor laboratory experiment conducted in November 2022. The experimental design includes different combinations of temperature (4°C; 9°C; 13.5°C), photoperiod (4:20; 16:8; 24:0) and microbiome presence (xenic; axenic) at which growth was assessed to evaluate interactive effects of abiotic factors (temperature & photoperiod) and biotic facors (interactions with microbiome bacteria). Moreover, the code to process the data for statistical analysis is provided.

Methods
Diatom cultures were pre-acclimatized to experimental conditions for 7 days by inoculating 40 ml batch cultures with 500 cells ml-1 (2000 cells ml-1 for treatments with 4h photoperiod to obtain sufficient biomass) which were grown at each of the nine treatment conditions to allow acclimatization of fluorophores. The actual subsequent multifactorial experiment was conducted in white 96-well plates (Greiner, Germany) with 300 µl experimental units and 48 replicates per treatment. After chlorophyll-a fluorescence of the acclimatized stock cultures was measured with a photo-spectrometric plate reader (ClarioStar Plus BMG Labtech, excitation 440 nm, emission 680 nm) plates were inoculated at twice the initial fluorescence units of the blank values measured in the growth medium. To maintain sterile conditions, the 96-well plates were sealed with a gas-permeable membrane (Breathe-Easy, Sigma-Aldrich, United States). Plates were incubated in climate cabinets at the respective experimental temperature and were placed onto LED tables emitting 50 µmol m-2 s-1 under the photoperiod settings above. Fluorescence intensity was measured daily at the same time after 5 minutes of dark acclimation and the experiment was terminated after seven days. After blank values of fluorescence in the growth medium were subtracted from the experimental fluorescence data, maximum growth rates (µmax) were calculated for each experimental unit by fitting non-linear models to the data using the “growthrates” package (Petzoldt, 2020).

本数据集收录了温带硅藻旋链角毛藻（Thalassiosira rotula）与极地硅藻厚链角毛藻（Thalassiosira gravida）的最大生长速率数据：其中旋链角毛藻菌株T. rotula_S16由不来梅大学Harder实验室提供，厚链角毛藻菌株UIO 478则来源于挪威藻类培养保藏中心（Norwegian Culture Collection of Algae, NORCCA）。数据来源于2022年11月开展的7天多胁迫微孔板型微宇宙实验室实验。实验设计涵盖温度（4°C、9°C、13.5°C）、光周期（4:20、16:8、24:0）以及微生物组存在状态（有菌体系、无菌体系）的不同组合，通过测定生长情况以解析非生物因子（温度与光周期）和生物因子（与菌群细菌的互作）的交互效应。此外，本数据集还附带用于统计分析的数据处理代码。

方法
硅藻培养物先经7天的实验条件预驯化：将初始密度为500 cells·ml⁻¹的批量培养物（光周期4h的处理组初始密度调整为2000 cells·ml⁻¹以获得足够生物量），按9种处理条件分别接种至40ml培养液中，使荧光基团完成驯化。
后续正式多因素实验采用德国Greiner公司生产的白色96孔板开展，每孔培养液体积为300μl，每个处理设置48次生物学重复。使用分光光度酶标仪（ClarioStar Plus BMG Labtech，激发波长440nm，发射波长680nm）测定预驯化储备培养物的叶绿素a荧光后，将接种至96孔板的初始荧光值设定为空白培养液荧光值的2倍。为维持无菌环境，96孔板使用透气膜（Breathe-Easy, Sigma-Aldrich, 美国）进行密封。
实验板置于对应实验温度的气候箱中培养，并放置在光强为50μmol·m⁻²·s⁻¹的LED光照平台上，按前述光周期设置运行。每日于固定时间点进行荧光强度测定，测定前先进行5分钟暗适应。实验持续7天后终止。
将实验荧光数据扣除培养液空白荧光值后，使用「growthrates」R包（Petzoldt, 2020）拟合非线性模型，为每个实验单元计算最大生长速率（μ_max）。