Microbial Flora And Molecular Ecological Research In Paddy Soil Of Tai Lake Region

Paddy soil is a very important type of soil for agricultural cultivation. Soil microorganisms are not only an important composition of soil ecologyical system, but also an important index of soil fertileity. They take part in the process of soil structure formation and improvement and carbon transformation. In general, soil microorganisms have often been studied by conventional methods based either on cultivation techniques or on metabolic activities. However, for the moment, it is well known that about 90%~99% of the microorganisms existing in nature are uncultured. To overcome this drawback, molecular biological techniques especially the method of 16S rDNA analysis are increasingly employed in the analysis of microorganisms in their natural habitats.This research has been studied the paddy soil in Tai Lake region. The methods of colony counting in dilution culture, soil enzyme activity measurement and amplified ribosomal DNA restriction analysis (ARDRA) were synthetically used to investigate the microbial activities and the bacterial community in paddy soil.To investigate the different microbial floras between paddy soils and other soils, the method of colony counting in dilution culture was used to take count of the quantity of bacteria, facultative anaerobes, actinomyces and fungi in four paddy soils and control soils around Tai Lake. The result is indicated that, for the two soil types, the number of all kinds of microorganisms decreased with the increase in soil depth. Compared with control soils, when paddy soils are flooded, the number of anaerobes especially facultative anaerobes increased, and the number of actinomyces and fungi decreased. To investigate the different microbial activities between paddy soils and other soils, catalase activities and cellulase activities in the two soil types are measured. The result is that, for the two soil types, catalase activities increased with the increase in soil depth, but the trend of cellulase activities is opposite. And the two soil enzyme activities in paddy soils are both higher than that in control soils. After correlation analysis, it is found that the two enzyme activities in the two soil types are related to soil moisture content and pH value. In paddy soils, catalase activities are related to the number of actinomyces and fungi, and cellulase activities are related to the number of facultative anaerobes. In control soils, catalase activities are related...