Studies On Soil Microorganism Molecular Ecology During Different Growing Period Of Cucumber

Use traditional methods and molecular method (DGGE) to research the change of microorganism, soil enzyme activity, community structure of microbe in root soil during different growing period of cucumber. PCR-DGGE revealed the change of community structure at molecular level , reflect the change of soil microorganism wholly.The change of the number of soil microorganism included bacterial, fungi, actinomyces and some bacterial with special physiological function such as azotobacter, cellulose discomposing bacterial, nitrobacter, P bacterial, K bacterial,etal. The number of bacterial in rhizosphere soil reached its peak at blossom stage , actinomyces and fungi reached its peak at fruit period. In rhizosphere soil, the number of these three microorganism was higer than non-rhizosphere soil , and began to decrease in later period.In non-rhizosphere soil , the number of K bacterial and nitrobacter reached maximum at blossom period , while in rhizosphere soil , they reached maximum at fruit stage. Cellulose discomposing and nitrobacter reached maximum at blossom and fruit stage respectively. Different from other bacterial , P bacterial in rhizosphere soil reached its peak at later stage.Soil enzyme including phosphatase , urease, proteinase, catalase were analysed.In seeding and blossom stage, urease activity was lower in non-rhizosphere than that in rhizosphere soil, but at fruit and later period , its activity was higher. In urease activity was higer than control, at blossom stage, urease activity reached its minimum and was lower than control, this showed that this period root of cucumber accumulated some amino to meet the need of growing.Phosphatase activity always decrease, it became zero after reaching 1.376 at stage in non-rhizosphere soil. In rhizosphere soil, the activity reached 1.990 at period and became zero at later period.Catalase activity reached its peak at seeding stage, but comparing with soil before planting, its activity was relatively lower. Catalase activity was lower in rhizosphere soil than control, while the activity was higer in non-rhizosphere than control.Proteinase activity in rhizosphere was higher than control , and it was true for non-rhizosphere except at later period.In rhizosphere soil, the number of azotobacter and nitrobacter was highly relative to urease activity, P bacterial was also highly relative to phosphatase. This suggested, these bacterial contributed enzyme activity.By using V3 region of 16SrDNA and space sequences of 18SrDNA and 5.8SrDNA, we studied the change of community structure of procaryotic and eucaryotic microorganism and found several characteristic bands which changed remarkably — their intensity become stronger. This indicated that mocroorganism corresponding to these bands were relative to the growing of cucumber.Analyze the similarity of V3 region of 16SrDNA, the result showed : the similarity of soil microorganism at blossom and fruit period was higher and reached 65%-75%. But it wasn't case for seeding and later period , the similarity is 60%. The similarity of space sequences of 18SrDNA and 5.8SrDNA was lower than that of V3 region and the kind of eucaryotic was fewer than procaryotic.Through analyzing traditional methods and DGGE profile , there are some relativities between them.