生物结皮胞外多糖理化特性及菌群结构的季节动态

doi:10.13287/j.1001-9332.202207.016

摘要/Abstract

摘要： 胞外多糖(EPS)是蓝藻重要抗逆物质,也是生物结皮中主要的碳储存形式,对结皮的物质循环、稳定度等具有重要作用。本研究以古尔班通古特沙漠不同季节(1月、4月、7月、10月)生物结皮为对象,对其EPS含量、组成、形貌特征及微生物群落结构进行了动态研究。结果表明: 1)EPS的分泌格局呈现明显的季节动态变化特征。1、4、7、10月EPS含量分别为81.72、52.46、76.77、70.54 μg·cm^-2,叶绿素a含量分别为2.7、4.94、4.2、5.98 μg·cm^-2,说明冬、夏两季蓝藻将固定的有机碳更多地分配给EPS,而春、秋两季则更多地用于自身生物量的积累。2)各个季节的EPS均由7种单糖组成,且葡萄糖和半乳糖的相对摩尔百分比之和为46%～56%,显著高于另外5种单糖;EPS的单糖组分与气温和降水之间具有显著的相关性;各季节EPS的傅里叶红外图谱无明显差别。3)原子力显微镜观测结果显示,7月、10月EPS具有更多的丝状及粗绳状结构,而1月、4月则呈块状结构。4)16S rDNA高通量测序结果表明,4个季节下蓝藻门和微鞘藻属始终为生物结皮优势细菌门和属,其相对丰度显著高于其他细菌门和属。变形菌门的相对丰度与岩藻糖和半乳糖的相对摩尔百分比呈显著正相关关系,说明单糖的百分比组成对结皮中异养细菌影响显著。在荒漠生境中,温度、水分等环境因子随季节变化显著,结皮胞外多糖理化特性及细菌群落的季节性变化受温度、水分、光照等气象因子的共同调控。

关键词: 生物结皮, 胞外多糖, 季节动态, 细菌群落, 原子力显微镜

Abstract: Exopolysaccharides (EPS), an important substance of cyanobacteria in resisting stresses, are the main form of carbon storage in biocrusts and play an important role in material cycling and stability of biocrusts. In this study, the biocrusts in different seasons (January, April, July, October) were collected from Gurbantunggut Desert, and the dynamics of EPS content, composition, morphological characteristics and microbial community structures were analyzed. The results showed that: 1) The excretion of EPS showed obvious seasonal dynamics. The EPS contents in January, April, July and October were 81.72, 52.46, 76.77, 70.54 μg·cm^-2, and the chlorophyll a contents were 2.7, 4.94, 4.2 and 5.98 μg·cm^-2, respectively. Cyanobacteria allocated more fixed organic carbon to EPS in winter and summer, and more to their own biomass accumulation in spring and autumn. 2) EPS in biocrusts of each season was composed of seven kinds of monosaccharides. The sum of relative mole percentages of glucose and galactose was 46%-56%, much higher than the other five monosaccharides. The monosaccharide compositions of EPS were significantly affected by temperature and precipitation. There was no significant difference in the Fourier infrared spectra of EPS in biocrusts across different seasons. 3) The observation results of atomic force microscope showed that more filamentous and thick rope-like structures occurred in EPS in July and October, while the EPS showed block-like morphology in January and April. 4) The results of 16S rDNA high-throughput sequencing showed that Cyanobacteria and Microcoleus were the dominant bacterial phyla and genus in biocrusts in all the four seasons, with significantly higher relative abundance than other bacterial phyla and genera. The relative abundance of Proteobacteria was significantly positively correlated with the relative mole percentages of fucose and galactose, indicating that the composition of monosaccharides affected heterotrophic bacteria in crusts. In deserts, environmental factors such as temperature and moisture changed significantly across seasons. The physicochemical properties of biocrust exopolysaccharides and the seasonal dynamics of bacterial communities were controlled by multiple factors, such as temperature, moisture, and light.

Key words: biological soil crust, exopolysaccharides, seasonal dynamic, bacterial community, atomic force microscopy

刘哲, 叶兴旺, 王吉平, 程永韬, 钱隆, 肖敬尚, 吴丽. 生物结皮胞外多糖理化特性及菌群结构的季节动态[J]. 应用生态学报, 2022, 33(7): 1801-1809.

LIU Zhe, YE Xing-wang, WANG Ji-ping, CHENG Yong-tao, QIAN Long, XIAO Jing-shang, WU Li. Seasonal dynamics of the physicochemical properties of biological crusts exopolysaccharides and the microbial community structure[J]. Chinese Journal of Applied Ecology, 2022, 33(7): 1801-1809.

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