The spatiotemporal distributions of microbes in soil by different methods could affect the efficacy of the microbes to reduce the soil hydraulic conductivity.In this study,the specimens of bio-mediated sands were prep...The spatiotemporal distributions of microbes in soil by different methods could affect the efficacy of the microbes to reduce the soil hydraulic conductivity.In this study,the specimens of bio-mediated sands were prepared using three different methods,i.e.injecting,mixing,and pouring a given microbial so-lution onto compacted sand specimens.The hydraulic conductivity was measured by constant-head tests,while any soil microstructural changes due to addition of the microbes were observed by scan-ning electron microscope(SEM)and mercury intrusion porosimetry(MIP)tests.The amount of dextran concentration produced by microbes in each type of specimen was quantified by a refractometer.Results show that dextran production increased exponentially after 5-7 d of microbial settling with the supply of culture medium.The injection and mixing methods resulted in a similar amount and uniform dis-tribution of dextran in the specimens.The pouring method,however,produced a nonuniform distri-bution,with a higher concentration near the specimen surface.As the supply of culture medium discontinued,the dextran content near the surface produced by the pouring method decreased dramatically due to high competition for nutrients with foreign colonies.Average dextran concentration was negatively and correlated with hydraulic conductivity of bio-mediated soils exponentially,due to the clogging of large soil pores by dextran.The hydraulic conductivity of the injection and mixing cases did not change significantly when the supply of culture medium was absent.展开更多
比较16S r RNA基因、dna A、rpoB部分基因序列对Leuconostoc mesenteroides（Leu.mesenteroides）及其近缘种的分辨力,为肠膜明串珠菌提供快速准确的鉴定方法。以分离自自然发酵乳制品中的8株Leu.mesenteroides为研究对象,以其看家基因d...比较16S r RNA基因、dna A、rpoB部分基因序列对Leuconostoc mesenteroides（Leu.mesenteroides）及其近缘种的分辨力,为肠膜明串珠菌提供快速准确的鉴定方法。以分离自自然发酵乳制品中的8株Leu.mesenteroides为研究对象,以其看家基因dnaA、rpoB部分基因序列作为分子标记,结合Gene Bank数据库中的近缘种及亚种的相应序列构建系统发育树,并与16S r RNA基因的系统发育树进行比较。研究发现,基于Leu.mesenteroides及其近缘种的dna A和rpo B部分基因序列构建的系统发育树的拓扑结构与16S r RNA基因基本一致,但分辨率高于16S r RNA基因;种间的dna A和rpo B部分基因序列相似性分别为81.7~84.8%和85.5、87.4%,而种间16S r RNA基因相似性为98.1%~99.5%。相较于16S r RNA基因,dna A和rpo B基因更容易鉴定肠膜明串珠菌及其近缘种,其中rpo B可明晰区分试验菌株与肠膜明串珠菌亚种间的系统发育关系,因此rpo B基因可作为16S r RNA基因的辅助工具用于Leu.mesenteroides及其近缘种的快速鉴定。展开更多
基金The first author(V.Kamchoom)acknowledges the grant(Grant No.FRB66065/0258-RE-KRIS/FF66/53)from King Mongkut’s Insti-tute of Technology Ladkrabang(KMITL)and National Science,Research and Innovation Fund(NSRF)the grant under Climate Change and Climate Variability Research in Monsoon Asia(CMON3)from the National Research Council of Thailand(NRCT)(Grant No.N10A650844)the National Natural Science Foundation of China(NSFC).
文摘The spatiotemporal distributions of microbes in soil by different methods could affect the efficacy of the microbes to reduce the soil hydraulic conductivity.In this study,the specimens of bio-mediated sands were prepared using three different methods,i.e.injecting,mixing,and pouring a given microbial so-lution onto compacted sand specimens.The hydraulic conductivity was measured by constant-head tests,while any soil microstructural changes due to addition of the microbes were observed by scan-ning electron microscope(SEM)and mercury intrusion porosimetry(MIP)tests.The amount of dextran concentration produced by microbes in each type of specimen was quantified by a refractometer.Results show that dextran production increased exponentially after 5-7 d of microbial settling with the supply of culture medium.The injection and mixing methods resulted in a similar amount and uniform dis-tribution of dextran in the specimens.The pouring method,however,produced a nonuniform distri-bution,with a higher concentration near the specimen surface.As the supply of culture medium discontinued,the dextran content near the surface produced by the pouring method decreased dramatically due to high competition for nutrients with foreign colonies.Average dextran concentration was negatively and correlated with hydraulic conductivity of bio-mediated soils exponentially,due to the clogging of large soil pores by dextran.The hydraulic conductivity of the injection and mixing cases did not change significantly when the supply of culture medium was absent.
文摘比较16S r RNA基因、dna A、rpoB部分基因序列对Leuconostoc mesenteroides（Leu.mesenteroides）及其近缘种的分辨力,为肠膜明串珠菌提供快速准确的鉴定方法。以分离自自然发酵乳制品中的8株Leu.mesenteroides为研究对象,以其看家基因dnaA、rpoB部分基因序列作为分子标记,结合Gene Bank数据库中的近缘种及亚种的相应序列构建系统发育树,并与16S r RNA基因的系统发育树进行比较。研究发现,基于Leu.mesenteroides及其近缘种的dna A和rpo B部分基因序列构建的系统发育树的拓扑结构与16S r RNA基因基本一致,但分辨率高于16S r RNA基因;种间的dna A和rpo B部分基因序列相似性分别为81.7~84.8%和85.5、87.4%,而种间16S r RNA基因相似性为98.1%~99.5%。相较于16S r RNA基因,dna A和rpo B基因更容易鉴定肠膜明串珠菌及其近缘种,其中rpo B可明晰区分试验菌株与肠膜明串珠菌亚种间的系统发育关系,因此rpo B基因可作为16S r RNA基因的辅助工具用于Leu.mesenteroides及其近缘种的快速鉴定。
