Relationship between soil bacterial diversity and the fate of a specific microorganism

1.番茄青枯病病原菌的生长在抑制枯萎病的土壤中比在诱导枯萎病的土壤中更能抑制番茄根面以及根和茎内的生长。从番茄根际分离出需氧细菌。提取DNA，进行16S rDNA-PCR-RFLP分析。结果表明，抑制根的细菌群落结构比诱导根的细菌群落结构更加多样化。测定了番茄根部最重要的多糖之一果胶在果胶基质上的生长能力和果胶降解过程中果胶半乳糖苷酶的活性。抑制枯萎病的根部细菌在果胶基质上的生长能力和聚半乳糖醛酸酶活性均较高，表明其对病原菌的竞争能力较强。用少量抑制或诱导土壤熏蒸灭菌土壤作为土壤细菌接种剂的致病试验表明，该土壤对青枯病的抑制能力中包含了土壤生物因素。

1. The growth of the tomato bacterial wilt pathogen is repressed in the rhizoplane as well as inside of the tomato root and stem in the wilt-suppressive soil more than in the wilt-inducive soil.2. Aerobic bacteria were isolated from the rhizoplane of tomato. DNA was extracted from the isolates and was subjected to 16S rDNA-PCR-RFLP analysis. The result indicates that the bacterial community structure was more diversified in the suppressive root than in the inducive root.3. Growth ability on the pectin medium and poply-galactouronase activity, which is included in the degradation of pectin, one of the most important polysaccharides of tomato root, were examined. Bacteria in the wilt-suppressive root showed higher ability of both growth on the pectin medium and polygalacturonase activity, suggesting storonger competitive ability against pathogenic bacterium.4. Pathogen challenging experiment using fumigation-sterilized soils with small amount of suppressive or inducive soil as soil bacterial inoculum showed that soil biological factors are included in the suppression ability of bacterial wilt in this soil.