The Spatial And Temporal Variations Of Cyanobacterial Community Structure In Paddy Fields In Northeast China And Its Response To Pyrazosulfuron-ethyl

Cyanobacteria is one of the main microbial groups in paddy field ecosystem. It playsimportant roles in increasing of soil fertility, promoting the soil structure and improving cropproduction. With the adjustment of planting structure, the northeast region has become one of theimportant rice production areas in China. And Pyrazosulfuron-ethyl is commonly herbicide in thenortheast paddy field. But there are rarely reports about cyanobacterial community structure andcyanobacterial community structure influenced on Pyrazosulfuron-ethyl. So this study aims toestimate the cyanobacterial community structure by PCR-DGGE method in paddy fields ofNortheast China and clarify the influence of different paddy environment factors oncyanobacterial community structure and its response mechanism of pyrazosulfuron-ethyl.Therefore, this study is of great significance in maintaining the paddy field ecosystemsustainable development and reasonable application of Pyrazosulfuron-ethyl. The results are asfollows:Diversity indices of DGGE fingerprint showed that the cyanobacterial communities in thepaddy soils are more abundant than those in the paddy floodwaters. The redundancy analysis(RDA) plots of DGGE fingerprint revealed that the cyanobacterial communities in different soilsamples were distinctly different among sampling locations, and soil C/N ratio was the majorfactor affecting the distribution of the cyanobacterial composition; whereas, no distinctdifference of the cyanobacterial communities was observed in the paddy floodwaters, and the pHof floodwater was determined as the major factor affecting the distribution of the cyanobacterialcommunities.Clone sequencing showed that filamentous cyanobacterial members belong toOscillatoriophycideae were dominated in the paddy fields, and several band sequences had thehighest similarity <97%to the known cyanobacteria. The sequences were submitted to GenBankand their accession numbers were from KM892885to KM892909.DGGE fingerprint showed that the number and distribution of cyanobacterial16S rDNA weredifferent in different concentrations of Pyrazosulfuron-ethyl. There were some public and specialbands in DGGE fingerprint. So cyanobacterial community structure was influenced byPyrazosulfuron-ethyl. Principal component analysis (PCA) of DGGE fingerprint showed that cyanobacterial community structure was easily influenced by Pyrazosulfuron-ethyl in the paddyfloodwaters and their community structure changed obviously. But cyanobacterial communitystructure changed irregularly in the paddy soils.DGGE band sequencing showed that several band sequences had the highest similarity <97%to the known cyanobacteria and they were divided into independent branch in phylogenetic tree.It showed that some new cyanobacterial groups were found under the stress ofPyrazosulfuron-ethyl. So the new cyanobacterial groups were belong to tolerance type ofPyrazosulfuron-ethyl.Cyanobacterial communities were very complexity and diversity, and several unknowncyanobacteria exist in the paddy fields of Northeast China. Cyanobacterial community structurewas influenced by Pyrazosulfuron-ethyl under laboratory conditions and the type ofcyanobacreria resistance of Pyrazosulfuron-ethyl was found. But those unknown cyanobacteriastill need to be researched and analysed.