盐度对湛江等鞭金藻生长、脂肪酸及藻际菌群的影响

为探究盐度对湛江等鞭金藻(Isochrysis zhanjiangensis)生长、脂肪酸组成及藻际菌群的影响,本研究将湛江等鞭金藻置于4个盐度(12、18、24和30)下进行半连续培养,达到稳定生长状态后测定细胞密度(OD₇₅₀)、叶绿素荧光参数及脂肪酸组成,并分析藻际菌群组成。结果表明,湛江等鞭金藻在盐度18~24下有着较高的细胞密度、最大光化学效率(F_v/F_m)及有效光化学效率(F'_v/F'_m)。盐度12、18和24下脂肪酸组成无显著差异。盐度30下饱和脂肪酸显著高于其他三组,而不饱和脂肪酸显著低于其他三组。综合来看,盐度18~24是湛江等鞭金藻生长和不饱和脂肪酸积累的最适盐度范围。采用16S rDNA扩增子测序分析藻际菌群,从Chao1、ACE和Shannon指数推测盐度12下藻际菌群多样性显著高于其他三组。主坐标分析(PCoA)表明,盐度18、24和30组间藻际菌群组成相似,与盐度12组差异明显。藻际菌群组成分析显示盐度12下优势菌为变形菌门(Proteobacteria),占比为92.70%,其中占比最多的属为短波单胞菌属(Brevundimonas)。盐度18、24和30下优势菌为蓝菌门(Cyanobacteria),占比分别为97.63%、97.41%和93.51%,说明盐度12和盐度≥18对于湛江等鞭金藻是两个差异巨大的生长环境,会使其藻际菌群组成发生剧烈变化。本研究为湛江等鞭金藻培养方案优化提供了数据支持,同时为深入探究盐度对湛江等鞭金藻藻际菌群的影响奠定了基础。

Effects of Salinity on Growth,Fatty Acid,and Bacteria Community in Isochrysis zhanjiangensis

To explore the effect of salinity on the growth, fatty acid composition and bacteria community associated with Isochrysis zhanjiangensis, the algal cells were semi-continuously cultured with four salinities (12, 18, 24 and 30). After reaching the stable growth state, the cell density (OD₇₅₀), chlorophyll fluorescence parameters, fatty acid composition, and bacteria community were analyzed. The results indicated that the higher cell density, F_v/F_m, and F'_v/F'_m were obtained at salinity 18~24. There were no significant differences among the fatty acid compositions under salinity 12, 18 and 24. The saturated fatty acids under salinity 30 were significantly higher, while unsaturated fatty acids were significantly lower than that in other three groups. Overall, the salinity at 18~24 was more beneficial to its growth and UFA accumulation in I. zhanjiangensis. The bacteria community was analyzed by 16S rDNA amplification sequencing. It was speculated that the diversity of bacteria community at salinity 12 was significantly higher than others according to Chao1, ACE, and Shannon indexes. PCoA analysis indicated that the compositions of bacteria community were similar among groups with salinity 18, 24 and 30, significantly different from that with salinity 12. Further analysis showed that Proteobacteria (92.70%) was the dominant phylum at salinity 12, with the largest proportion of genus Brevundimonas. The dominant phylum at salinity 18, 24 and 30 were phylum Cyanobacteria, accounting for 97.63%, 97.41% and 93.51%, respectively, demonstrating that “salinity 12” and “salinity greater than or equal to 18” were two distinct environments for I. zhanjiangensis, which would drastically affect the composition of bacteria community. This study will provide data for optimizing the cultivation scheme of I. zhanjiangensis and lay the foundation for in-depth studies of the effect of salinity on the bacteria community.