The microbial population dynamics in bulk and developing cucumber rhizospheres were studiedby cultivation and cultivation-independent approach based on directly extracted DNA toprovide baseline data. Soil and rhizosph...The microbial population dynamics in bulk and developing cucumber rhizospheres were studiedby cultivation and cultivation-independent approach based on directly extracted DNA toprovide baseline data. Soil and rhizosphere samples were taken from tested field 2, 4, 7 and10 weeks after the seeds were planted, which was positively related to the corresponding dateof cucumber growth stages. The plate culture amount showed that total number of bacteria,fungi and actinomyces began to rise when cucumber planted and quickly reached peak at seedlingor blossom period, but decreased slightly later. Bacterial population in rhizosphere washigher by comparison with that of counterpart except for seedling and flowering stages, butthe shift trend of them were quite similar all the time. Nitrogen fixating, nitrobacter andammonifying bacteria showed the same change tendency in population as bacteria and actinomycesdid, however, cellulose-decomposing bacteria had the contrary rhizosphere effect as cucumberdeveloped. Data revealed that positive relevance existed between the dominant rhizospheremicrobe population and cucumber development. PCR was employed to amplify the V3 region of 16SrDNA, then the products were subjected to denaturing gradient gel electrophoresis(DGGE). DGGEprofile indicated that a few microbe species lived stable in farmland soil, but some wereinfluenced by population due to cucumber roots growth. Significant difference was observed inbulk and rhizosphere soils especially for the seedling and flowering samples. Few prominentbands in DGGE patterns, which displayed stronger or less illumination, means the representativebacteria had great population variation in that period. These phenomena indicated thatflowering cucumber heavily affected rhizosphere bacteria, or the bacteria, most probably theuncultured bacteria, functioned specially to cucumber blossom. Most detected bands with noillumination change in DGGE quite possibly represent the indigenous microbes that wereessential for constructing and stabilizing farmland microecological environment.展开更多
Toxoplasmosis, caused by Toxoplasma gondii ( T. gondii ), an obligate intracellular parasite, is a globally distributed zoonosis. It is estimated that one third of population has been infected by this parasite world...Toxoplasmosis, caused by Toxoplasma gondii ( T. gondii ), an obligate intracellular parasite, is a globally distributed zoonosis. It is estimated that one third of population has been infected by this parasite worldwide. In some regions of Europe, the serum antibodies against T. gondii were detected in more than 80% of the examined population. In China, T. gondii was isolated for the first time from a rabbit in Fujian Province in 1954, 1 and the first case of human toxoplasmosis was reported in Jiangxi Province in 1964. 2 Later, in 1978, the first epidemic survey on toxoplasmosis was carried out in Guangxi Province. In 1982, the first national survey on toxoplasmosis supported by the National Natural Sciences Foundation of China was carried out and the result was published in 1988. Since that, many surveys on toxoplasmosis were reported in China. These results indicated that T. gondii infection in this country is very common and in some circumstances, the infection causes serious disease. For instance, T. gondii infection in pregnant women causes abortion, stillbirth, abnormal embryo and thus, it has been considered as the most commonly infectious agent of “TORCH syndrome” (TORCH syndrome refers to infection of a developing fetus or newborn by any of a group of infectious agents. “TORCH” is an acronym meaning toxoplasmosis, other agents, rubella, cytomegalovirus, and herpes simples). In immunocompromised patients, toxoplasmosis is also one of the most frequent complications. Because of the medical importance of T. gondii , more and more Chinese researchers are interested in this parasite. Aetiology Infected animals are the most important source for T. gondii infection, although humans can also be taken as the infective source for this disease particularly the vertical transmission from pregnant woman to fetus through the placenta. T. gondii widely distributes in variant animals from mammals to birds. At least 190 species of animals displayed serologically positive to T. gondii and 141 species of these animals pathogenically infected by T. gondii have been confirmed in China. 3展开更多
文摘The microbial population dynamics in bulk and developing cucumber rhizospheres were studiedby cultivation and cultivation-independent approach based on directly extracted DNA toprovide baseline data. Soil and rhizosphere samples were taken from tested field 2, 4, 7 and10 weeks after the seeds were planted, which was positively related to the corresponding dateof cucumber growth stages. The plate culture amount showed that total number of bacteria,fungi and actinomyces began to rise when cucumber planted and quickly reached peak at seedlingor blossom period, but decreased slightly later. Bacterial population in rhizosphere washigher by comparison with that of counterpart except for seedling and flowering stages, butthe shift trend of them were quite similar all the time. Nitrogen fixating, nitrobacter andammonifying bacteria showed the same change tendency in population as bacteria and actinomycesdid, however, cellulose-decomposing bacteria had the contrary rhizosphere effect as cucumberdeveloped. Data revealed that positive relevance existed between the dominant rhizospheremicrobe population and cucumber development. PCR was employed to amplify the V3 region of 16SrDNA, then the products were subjected to denaturing gradient gel electrophoresis(DGGE). DGGEprofile indicated that a few microbe species lived stable in farmland soil, but some wereinfluenced by population due to cucumber roots growth. Significant difference was observed inbulk and rhizosphere soils especially for the seedling and flowering samples. Few prominentbands in DGGE patterns, which displayed stronger or less illumination, means the representativebacteria had great population variation in that period. These phenomena indicated thatflowering cucumber heavily affected rhizosphere bacteria, or the bacteria, most probably theuncultured bacteria, functioned specially to cucumber blossom. Most detected bands with noillumination change in DGGE quite possibly represent the indigenous microbes that wereessential for constructing and stabilizing farmland microecological environment.
文摘Toxoplasmosis, caused by Toxoplasma gondii ( T. gondii ), an obligate intracellular parasite, is a globally distributed zoonosis. It is estimated that one third of population has been infected by this parasite worldwide. In some regions of Europe, the serum antibodies against T. gondii were detected in more than 80% of the examined population. In China, T. gondii was isolated for the first time from a rabbit in Fujian Province in 1954, 1 and the first case of human toxoplasmosis was reported in Jiangxi Province in 1964. 2 Later, in 1978, the first epidemic survey on toxoplasmosis was carried out in Guangxi Province. In 1982, the first national survey on toxoplasmosis supported by the National Natural Sciences Foundation of China was carried out and the result was published in 1988. Since that, many surveys on toxoplasmosis were reported in China. These results indicated that T. gondii infection in this country is very common and in some circumstances, the infection causes serious disease. For instance, T. gondii infection in pregnant women causes abortion, stillbirth, abnormal embryo and thus, it has been considered as the most commonly infectious agent of “TORCH syndrome” (TORCH syndrome refers to infection of a developing fetus or newborn by any of a group of infectious agents. “TORCH” is an acronym meaning toxoplasmosis, other agents, rubella, cytomegalovirus, and herpes simples). In immunocompromised patients, toxoplasmosis is also one of the most frequent complications. Because of the medical importance of T. gondii , more and more Chinese researchers are interested in this parasite. Aetiology Infected animals are the most important source for T. gondii infection, although humans can also be taken as the infective source for this disease particularly the vertical transmission from pregnant woman to fetus through the placenta. T. gondii widely distributes in variant animals from mammals to birds. At least 190 species of animals displayed serologically positive to T. gondii and 141 species of these animals pathogenically infected by T. gondii have been confirmed in China. 3
