The green alga Chlorella vulgaris has potential as a source of clean bioenergy with abundant metabolites and a high oil content, and antibiotics are often applied to remove bacteria from culture to obtain axenic algal strains. In this work, ceftazidime and gentamicin sulphate (GS) were added separately and in combination in the aseptic processing of C. vulgaris, and gene expression and metabolites were evaluated. The results showed that ceftazidime and GS effectively inhibited the proliferation of Cyanobacteria and Bacteroidetes, respectively. Overall, the effects of antibiotics on C. vulgaris differed: GS increased the algal concentration, whereas ceftazidime alone and in combination with GS treatment decreased the specific algal growth rate. Based on comparative transcription analysis, 5917 and 5899 differentially expressed genes (DEGs) were respectively upregulated and downregulated by ceftazidime, 963 and 3921 DEGs by GS, and 4532 and 1675 DEGs by the ceftazidime and GS combination. Pathway enrichment analysis showed that the downregulated DEGs in the ceftazidime groups were enriched in the fatty acid biosynthesis pathway but that the upregulated DEGs in the GS group were enriched in the fatty acid degradation pathway. Some pathways related to amino acid metabolism were markably influenced by antibiotic treatment. The results further indicated that antibiotics affected the intracellular concentration of fatty acids and amino acids in C. vulgaris. This study provides a new viewpoint regarding the response of C. vulgaris to antibiotics in the process of obtaining axenic algal strains. KEY POINTS: • Ceftazidime and gentamicin sulphate influenced bacterial proliferation. • Downregulated differentially expressed genes mapped to the fatty acid biosynthesis pathway. • Antibiotics affected intracellular concentrations of fatty acids and amino acids.

中文翻译：

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用抗生素培养的小球藻中脂肪酸和氨基酸代谢的基因表达。

绿藻小球藻有潜力作为清洁生物能源的来源，具有丰富的代谢产物和高油含量，因此经常使用抗生素从培养物中去除细菌，从而获得无菌藻类菌株。在这项工作中，头孢他啶和庆大霉素硫酸盐（GS）分别添加或组合添加到寻常梭状芽胞杆菌的无菌加工中，并评估了基因表达和代谢产物。结果表明，头孢他啶和GS分别有效抑制蓝细菌和拟杆菌的增殖。总体而言，抗生素对寻常念珠菌的作用不同：GS会增加藻类浓度，而单独使用头孢他啶以及与GS联合使用会降低特定的藻类生长速率。根据比较转录分析，头孢他啶分别上调和下调了5917和5899差异表达基因（DEG），GS分别上调和下调了差异表达基因（DEG），GS分别上调了963和3921 DEG，头孢他啶和GS组合分别上调了4532和1675 DEG。途径富集分析表明，头孢他啶组中的DEGs下调在脂肪酸生物合成途径中富集，而GS组中上调的DEGs在脂肪酸降解途径中富集。与氨基酸代谢有关的某些途径受到抗生素治疗的显着影响。结果还表明，抗生素影响寻常梭状芽胞杆菌中细胞内脂肪酸和氨基酸的浓度。这项研究提供了一个新的观点，即在获得轴生藻类菌株的过程中寻常梭状芽胞杆菌对抗生素的反应。关键点：•头孢他啶和硫酸庆大霉素影响细菌增殖。•下调差异表达基因，定位到脂肪酸生物合成途径。•抗生素影响细胞内脂肪酸和氨基酸的浓度。