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Objective: To detect the presence of Porphyromonas gingivalis (Pg) and Actinobacillus actinomycetemcomitans (Aa) using polymerase chain reaction (PCR) in the oral plaque samples from children and investigate the relationship between bacteria and clinical parameters., Methods: A total of 151 children aged 7 to 12 years were selected from Changchun Ziqiang primary school. The supragingival plaque sample was collected from the mesiobuccal and labial surfaces of the right maxillary central incisor and the right maxillary first molar. Extracted DNA from plaque samples was used for PCR analysis. Intraoral examination, probing depth (PD) and bleeding on probing (BOP) were performed and recorded., Results: The detection rate for Pg was 27.6% and Aa 54.3% in supragingival plaque. The detection rates for Pg in molars were much higher than those in incisors (P < 0.01). The detection rate of Pg was positively related to BOP+ and PD. The detection rate for Pg increased gradually with aging, and the detection rate for Aa was highest in the group aged 11 to 12 and the detection rates for Pg and Aa were higher in the gingiva with BOP+ than that with BOP- (P < 0.05). The detection rates for Pg increased remarkably with BOP+ and especially when PD was greater than 4 mm., Conclusions: Detection rates of putative periodontal pathogens from healthy children of 7 to 12 years of age were high. The detection rates for Pg in molars were much higher than those in incisors,and the presence of Pg and Aa in supragingival plaque was related to periodontal parameters.

With cucumber (Cucumis sativus L.) variety Jinyou 1 as test material, a greenhouse experiment was conducted to study the effects of different water and fertilizer supply on the cucumber soil nutrient content, enzyme activity, and microbial diversity. Three water regimes (50%-60%, 70%-80%, and 90%-100% soil relative moisture content) and two fertilization practices (600 kg N x hm(-2) + 420 kg P2O5 x hm(-2) and 420 kg N x hm(-2) + 294 kg P2O5 x hm(-2)) were designed. The increase of water and fertilizer supply benefited the increase of soil available P content and sucrase activity. Increasing fertilization rate increased soil NH(4+)-N content but decreased soil protease activity, and increasing soil relative moisture content decreased the soil NH(4+)-N content and urease activity. Soil microbial diversity had no significant correlations with soil nutrient contents, but significantly positively correlated with soil urease activity and negatively correlated with soil sucrase activity. Among the treatments, the treatment 70%-80% soil relative moisture content + 600 kg N x hm(-2) and 420 kg P2O5 x hm(-2) had the highest soil nutrient contents, soil urease, sucrase, and phosphatase activities, and soil microbial diversity and evenness, being the best in soil potential productivity.