| 摘要: |
| 蓝细菌是具有产氧光合作用的自养型微生物，其个体微小，数量庞大，广泛分布在海洋和陆地环境中，同时部分蓝细菌又具有固氮作用，所以蓝细菌在全球碳循环和氮循环过程中都扮演重要角色。2-甲基藿烷类化合物（藿多醇和藿烷）是一类目前被广泛使用的蓝细菌生物标志物。2-甲基藿多醇被广泛用于估测近现代沉积物中蓝细菌的生物量和群落结构。而2-甲基霍烷则被应用于指示地质历史时期蓝细菌的生物量和重建古环境。本文总结了近年来2-甲基藿烷类化合物作为蓝细菌生物标志物的研究进展和具体的应用，并展望了未来关于此类化合物的研究方向。 |
| 关键词: 蓝细菌 生物标志物 2-甲基细菌藿多醇 2-甲基藿烷指数 |
| DOI：10.7515/JEE181005 |
| CSTR： |
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| 基金项目:国家自然科学基金项目（41476058）；国家重点研发计划项目（2016YFA0600904） |
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| Progress of research on the cyanobacterial biomarker—2-methylhopanoid and its application |
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ZHANG Junjie, XING Lei, HOU Di
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1. Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China
2. Institute of Marine Organic Geochemistry, Ocean University of China, Qingdao 266100, China
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| Abstract: |
| Background, aim, and scope Cyanobacteria are prokaryotic auxoautotrophs with small size and huge amount. Cyanobacteria exist widely in the ocean, lakes and soils, and some of them can fix nitrogen. Therefore, cyanobacteria play an important role in global carbon cycle and nitrogen cycle. It is important for understanding the evolution of earth environment to reconstruct the change in cyanobacteria. Owing to short lifetime of cyanobacteria, researchers used the biomarkers in sediments to reconstruct the interglacial and glacial evolution of cyanobacteria. In this paper, we summarize the study progress and the application of 2-methylhopanoids (2-methylbacteriohopanepolyols and 2-methylhopane) which are commonly used as biomarkers for cyanobacteria. Materials and methods Bacteriohopanepolyols (BHPs) are pentacyclic triterpenoids biosynthesised by many prokaryotes, the most well-known structural feature of BHPs associated with cyanobacteria is the presence of methylation at C-2. During the process of diagenesis, the branched chain of 2-methylbacteriohopanepolyols (2-MeBHPs) could be degraded, and they would be converted into the 2-methylhopane. Therefore, 2-MeBHPs are the precursor of 2-methyhopane. Results 2-Methylhopane and 2-MeBHPs are commonly used as biomarkers of cyanobacteria. 2-MeBHPs are usually used to estimate the biomass and community structure of cyanobacteria in recent and modern environments, while 2-methylhopane can trace the past change in cyanobacteria. Additionally, the relative abundance of 2-methylhopane (2-MeHI index) can indicate the cyanobacterial contribution to biological nitrogen fixation. Discussion Recently, the studies also indicated that there are some problems about 2-methyhopanoids as biomarkers of cyanobacteria to reconstruct the abundance of cyanobacteria and the past environmental change. (1) The sources of 2-methyhopanoids are still not unclear. 2-methyhopanoids are not only originated from cyanobacteria, and not all cyanobacteria can produce the 2-methyhopanoids. The studies have revealed that the hpnP gene is found not only in some cyanobacteria but also in α-proteobacteria and acidobacteria. (2) The content of the 2-methylhopane in marine sediments may be affected by terrestrial input. 2-MeBHPs can also be produced by terrestrial cyanobacteria and can be carried into the marginal sea by the river runoff. Consequently, there is a deviation using the 2-methylhopane index to reconstruct paleoenvironment in the marginal sea. Conclusions 2-Methylhopanoids have been widely used as cyanobacterial biomarkers to indicate the biomass and evolution of cyanobacteria. However, recent studied have revealed there are some problems about 2-methylhopanoids as cyanobacterial biomarker. Recommendations and perspectives In future, biological sources of 2-methylhopanoids need to be confirmed. The influence of terrestrial 2-methylhopanoids on environmental reconstruction needs to be evaluated in the marginal sea areas. Cyanobacteria culture and molecular biological methods can help to solve these problems. |
| Key words: cyanobacteria biomarker 2-methylbacteriohopanepolyol 2-methylhopanoid index |
