Application Of The PCR-DGGE To Analyze The Community Biodiversity Of Soil Bacteria In Intensive Cropping System

The winter wheat-summer maize farming system is the typical farming pattern in Henan district. We chose the soil sample of this farming system as our study object, with the PCR-DGGE method, avoiding of the traditional pure culture methods, we analysis the bacterial community changes at different growing period and depths.In our study, the effective of three soil DNA extraction methods which based on different lytic principles for isolation of the total farmland microbial DNA were compared. The results showed that the chemical-enzymatic method could obtain the best DNA with the highest molecular weight and purity, is more propitious to molecular ecology study. And then we optimize the PCR method, as there are "GC clamp" with the primer, so we compared the traditional and Touchdown strategy. The result shown that with the Touchdown strategy, the aim gene fragment was best amplified. It is more suitable for our study.At last, the target gene was separated by DGGE, and the cluster analysis was carried. From the result we can see that there are abundant bacterial communities at the different growing period and depths of wheat and maize farm soil. The comparability of the community structure in different samples was weak, but the diversity was high. This suggested that the bacteria were continuous change with the growing of the crop and the depth increase. The mutual benefit communities were developed and others were restrained or disappeared. From the result we also can got the conclusion that the influence of the crop growing to the bacterial communities is more obvious than the depth change.