中科院亚热带生态所揭示固碳细菌和藻类丰度对亚热带红壤不同
中国科学院亚热带农业生态研究所研究员吴金水领衔的农业生态过程方向研究团队近日在亚热带红壤不同土地利用方式的土壤固碳微生物(细菌和藻类)丰度和多样性研究方面取得了新进展。
土壤微生物数量、群落结构及其多样性受植被类型、土壤类型、土地利用方式等多种因素的影响而发生演变。特别是不同土地利用方式会对土壤的物质组成和营养平衡等产生一系列的作用，进而导致土壤微生物群落结构和功能发生改变。土壤微生物在推动土壤碳循环过程方面发挥着重要作用，因此，研究不同土地利用方式下土壤固碳微生物(细菌和藻类)的数量、群落结构及其多样性对认识土壤固碳能力及碳汇效应、促进土地资源可持续利用具有重要意义。
基于此，该团队选取亚热带丘陵区四种典型不同土地利用方式的土壤(森林、稻田、玉米旱地和茶园土壤)，通过末端限制性片段长度多肽性分析(T-RFLP)与定量PCR等分子生物学技术，探讨了其固碳关键功能微生物(细菌和藻类)的种群结构、数量与多样性，同时还量化了卡尔文循环关键酶RubisCO酶编码的固碳功能基因(cbbL)的数量特征及其对不同土地利用方式的响应与反馈机制。结果表明，不同土地利用方式显著影响固碳微生物(细菌和藻类)功能基因cbbL的丰度，稻田土壤的cbbL的丰度最高，可达到4.33×108 copies g-1，而茶园土壤的最低，其细菌和藻类的cbbL数量分别为0.98×108和0.23×106 copies g-1。T-RFLP分析表明，不同土地利用方式下，细菌cbbL的优势种群有T-RFs 60 b.p.(相对丰度12%―35%)和128 b.p.(相对丰度23%―29%)。不同土地利用方式下的固碳细菌主要为兼性自养菌，包括分枝杆菌、沼泽红假单胞菌、慢生根瘤菌产碱杆菌等。然而一些丰度较小的片段在不同土地利用方式下的土壤中的分布也不均衡，差异有的达到极显著水平，如T-RF 23 b.p.，28 b.p.，40 b.p.，51 b.p. 等在茶园土壤中并未出现。而藻类cbbL的优势种群则主要集中在T-RFs 123 b.p.，132 b.p.，148 b.p. 和 382 b.p.。这些片段与已知种属藻类末端片段吻合，它们分别为黄藻、硅藻和红藻等。而且，主成分分析(PCA)表明土壤有机碳和全氮是影响土壤细菌cbbL的种群结构、丰度及其多样性的决定性因素，而土壤全磷含量则是影响藻类cbbL的主要因素。该研究深化了研究人员对不同土地利用方式下红壤微生物固碳的生物学机制的认识。
上述研究成果以Abundance and diversity of CO2-assimilating bacteria and algae within red agricultural soils are modulated by changing management practice为题发表在Microbial Ecology(DOI: 10.1007/s00248-015-0621-8。审稿人和编辑认为“该研究利用T-RFLP与定量PCR技术，是一项加深农业土壤碳固定微生物机制的创新性工作，……结果非常有趣和有用”。该研究得到了中国科学院、国家自然科学基金委等项目的资助。
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原文摘要：
Elucidating the biodiversity of CO2-assimilating bacterial and algal communities in soils is important for obtaining a mechanistic view of terrestrial carbon sinks operating at global scales. “Red” acidic soils (Orthic Acrisols) cover large geographic areas and are subject to a range of management practices, which may alter the balance between carbon dioxide production and assimilation through changes in microbial CO2-assimilating populations. Here, we determined the abundance and diversity of CO2-assimilating bacteria and algae in acidic soils using quantitative PCR and terminal restriction fragment length polymorphism (T-RFLP) of the cbbL gene, which encodes the key CO2assimilation enzyme (ribulose-1,5-bisphosphate carboxylase/oxygenase) in the Calvin cycle. Within the framework of a long-term experiment (Taoyuan Agro-ecosystem, subtropical China), paddy rice fields were converted in 1995 to four alternative land management regimes: natural forest (NF), paddy rice (PR), maize crops (CL), and tea plantations (TP). In 2012 (17 years after land use transformation), we collected and analyzed the soils from fields under the original and converted land management regimes. Our results indicated that fields under the PR soil management system harbored the greatest abundance of cbbL copies (4.33 × 108 copies g−1 soil). More than a decade after converting PR soils to natural, rotation, and perennial management systems, a decline in both the diversity and abundance of cbbL-harboring bacteria and algae was recorded. The lowest abundance of bacteria (0.98 × 108 copies g−1 soil) and algae (0.23 × 106 copies g−1 soil) was observed for TP soils. When converting PR soil management to alternative management systems (i.e., NF, CL, and TP), soil edaphic factors (soil organic carbon and total nitrogen content) were the major determinants of bacterial autotrophic cbbL gene diversity. In contrast, soil phosphorus concentration was the major regulator of algal cbbL community composition. Our results provide new insights into the diversity, abundance, and modulation of organisms responsible for microbial autotrophic CO2 fixation in red acidic soils subjected to changing management regimes.
作者：生物帮
