An Investigaton Of The Relationship And Effects Between Phosphine Distribution And Bacterial Communities In Typical Paddy Soil Of South China

Phosphorus (P), which plays an important role in the biogeochemical cycle, is a limiting and important nutrient in soils. The distribution and the availability of phosphorus significantly influence the sustainable development of agriculture. Phosphine, which exists in paddy soils and atmosphere upon the paddy, is a gas carrier of phosphorus in the natural environment. Lots of investigations indicated that the poorly soluble phosphorus in the soil could be converted to phosphine by the microbial and non-microbal mechanism. At the same time, phosphine in the paddy soils could be oxidised to phosphorus, which could be absorbed by crops, but phosphine could damage organisms for its toxicity effect. The distribution and relationship between phosphine and bacterial community and the phosphine effect of bacterial community are still unclear, which could enrich the theory of phosphine biogeochemical and improve the soil phosphorus availability.In the present study, typical paddy fields in South China were taken as the research object, and the relationship among the phosphine distribution, environmental variables and bacterial community was systematically studied. And the bacterial diversity of soils which was influenced by phosphine was investigated. The phosphine influence mechanism for bacterial was studied by a long time cultivation of phosphine influenced paddy soil. The main results of the present work are as follows:(1) MBP concentration distribution in different regions and various depths were investigated, and the results indicated that the concentration of MBP (matrix bound phosphine) in the topsoil layer (0-20 cm)>moderate soil layer(20-40cm)> underlying layer (40-60 cm); and the content of pH, phosphatase and organic matter in the soil significantly affected the MBP concentration by correlation and multiple linear regression analysis;(2) The principal component analysis (PCA) and redundancy analysis (RDA) which oriented from polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) indicated that the environmental variables(pH, phosphatase and organic matter) significantly related to MBP content could explain the 38.2%(p<0.05) of the bacterial community change and MBP well explained the 9.6%(p<0.05) bacterial community change alone. The results combined discriminant analysis (DA) and sequencing of cluster analysis indicated that the bacterial distribution had a direct relationship with the concentration of MBP derived from molecular fingerprint technology.(3) A significant linear relationship between the concentration of phosphine and microbial diversity was observed in the phosphine influence experiment and the significant level was as follows:the surface soil layer(0-20 cm)>moderate soil layer (20-40 cm)>subsoil layer(40-60 cm). Under the influence of phosphine, the abundant bacterial community changed significantly and bacterial diversity and community structure changed similar trends regardless of different sampling sites in different soil layers. Analysis results based on PCA and PL curve indicated that changes in soil at different depths were more significant in 0-10 days, and stabilized after 10 days. In the end, microbial community structure layered obviously.(4) The RDA analysis combined environmental variable (Fe, Fe+, Mn+, organic phosphorus, inorganic phosphorus and total phosphorus) change and community microorganisms succession which were influenced by phosphine indicated that the bacterial community structure stabilized after 10 days, and the concentration of inorganic phosphorus increased significantly, and Fe2+ and Mn2+ contents increased continuously. Meanwhile, the selected environmental factors well explained the changes in the environment microbial community structure, and the explained relationship of Hunan, Guangzhou, Guangxi, Jiangxi sampling points were 95.4%(p<0.05),89.5%(p<0.05),93.7%(p<0.05) and 92.4%(p<0.05) separately.(5) The disappeared DGGE bands were sequenced, and sequencing analysis showed that the phosphine widespread affect soil bacteria, and the disappeared bacteria mainly originated from Deltaproteobacteria, Gammaproteobacteria, Alphaproteobacteria and Bacillus etc. Phosphine may be a strong reducing agent and a nucleophilic reagent, resulting in the DNA oxidative or DNA alkylation, followed by DNA damage and distortion.(6) Phosphine lead microbial communities to decrease and caused permanent damage to paddy soil microbial communities. After 7.0 mg/m3 phosphine processing, inoculum of paddy soil was not beneficial to enrich phosphine production bacteria.Under continuous cultivation of anaerobic conditions, Fresh paddy soils could form a stable anaerobic phosphine production system, with the increase of phosphine emissions.