淹水时间对水稻土中地杆菌科群落结构及丰度的影响

摘要

[目的]通过模拟水稻土淹水过程,探讨地杆菌科(Geobacteraceae)群落结构和相对丰度随淹水时间的动态变化特征,揭示其群落结构和相对丰度变化与微生物Fe(Ⅲ)还原的内在联系.[方法]提取水稻土淹水培养1 h、1 d、5 d、10 d、20 d和30 d后的微生物总DNA,构建地杆菌科16S rDNA克隆文库,采用PCR-RFLP 方法分析地杆菌科的群落结构和多样性变化特征,通过Real-time PCR技术测定地杆菌科相对丰度的动态变化.采用厌氧泥浆培养方法,测定水稻土中Fe(Ⅱ)产生量变化.[结果]供试水稻土中,微生物Fe(Ⅲ)还原过程在淹水培养初期变化明显,培养20 d后达到稳定期,最大铁还原潜势为10.16 mg/g,最大反应速率为1.064 mg/(g·d),最大反应速率对应的时间为4.84 d.(A)多样性指数显示,水稻土中地杆菌科的多样性随淹水时间延长呈现波动性变化,淹水5 d和20 d处理出现2个峰值,而淹水10 d和30 d处理的多样性明显减小.β多样性指数表明淹水过程中群落结构存在明显差异.不同淹水时间共产生了10种地杆菌科优势类型,分别属于Clade 1和Clade 2.Real-time PCR结果表明,地杆菌科与总细菌16S rDNA丰度的比值在淹水培养1d时最小(1.20%),而20d时达到最大值(4.54%).[结论]淹水培养的水稻土中,地杆菌科微生物的多样性和相对丰度的动态变化与微生物Fe(Ⅲ)还原过程密切相关.%[Objective]The dynamic characteristics of community structure and relative abundance of Geobacteraceae were investigated to understand their response to microbial iron ( Ⅲ ) reducing in flooded paddy soil.[Methods]The paddy soil was incubated anaerobically and the amount of Fe(Ⅱ) was determined during the flooding incubation.We retrieved Geobacteraceae sequences from clone libraries constructed for different time points ( 1 h and day 1 , 5, 10, 20 and 30) after flooding of the paddy soil.The diversity and community structure were analyzed by using RFLP method, and the relative abundance of Geobacteraceae was detected by real-time PCR.[Results]Microbial reduction of iron ( Ⅲ ) changed greatly in early time and was stable after incubated for 20 d in paddy soil.The largest iron reduction potential was 10.16 mg/g with a Vmax of 1.064 mg/(g.d) at the time of 4.84 d whereas this process achieved plateau after 20 days flooding.Diversity of Geobacteraceae, given by alpha indices, fluctuated during the flooding incubation.Two peaks of diversity were observed in treatments of 5 d and 20 d respectively, while significant low diversity appeared in samples of 10 d and 30 d.Beta indices described the differences between community structures of Geobacteraceae and hence reflected the variation of the flooding situation over time.In all samples, 10 RFLP-based preponderant types were found, which fell into clade 1 and clade 2 of Geobacteraceae.The relative abundance of Geobacteraceae was the lowest in 1 d (1.20％ ) and the highest in 20 d (4.54％ ).[Conclusion]The dynamic variation of Geobacteraceae diversity, community structure and abundance are closely related to microbial iron( Ⅲ ) reducing in flooding paddy soil.