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61.
Characterization of a Theta-Type Plasmid from Lactobacillus sakei: a Potential Basis for Low-Copy-Number Vectors in Lactobacilli 总被引:1,自引:0,他引:1 下载免费PDF全文
Carl-Alfred Alpert Anne-Marie Crutz-Le Coq Christine Malleret Monique Zagorec 《Applied microbiology》2003,69(9):5574-5584
The complete nucleotide sequence of the 13-kb plasmid pRV500, isolated from Lactobacillus sakei RV332, was determined. Sequence analysis enabled the identification of genes coding for a putative type I restriction-modification system, two genes coding for putative recombinases of the integrase family, and a region likely involved in replication. The structural features of this region, comprising a putative ori segment containing 11- and 22-bp repeats and a repA gene coding for a putative initiator protein, indicated that pRV500 belongs to the pUCL287 subfamily of theta-type replicons. A 3.7-kb fragment encompassing this region was fused to an Escherichia coli replicon to produce the shuttle vector pRV566 and was observed to be functional in L. sakei for plasmid replication. The L. sakei replicon alone could not support replication in E. coli. Plasmid pRV500 and its derivative pRV566 were determined to be at very low copy numbers in L. sakei. pRV566 was maintained at a reasonable rate over 20 generations in several lactobacilli, such as Lactobacillus curvatus, Lactobacillus casei, and Lactobacillus plantarum, in addition to L. sakei, making it an interesting basis for developing vectors. Sequence relationships with other plasmids are described and discussed. 相似文献
62.
Administration of IL-7 to normal mice stimulates B-lymphopoiesis and peripheral lymphadenopathy. 总被引:12,自引:0,他引:12
P J Morrissey P Conlon K Charrier S Braddy A Alpert D Williams A E Namen D Mochizuki 《Journal of immunology (Baltimore, Md. : 1950)》1991,147(2):561-568
Normal mice were injected with IL-7 (500 ng, twice daily) for various periods of time up to 6 days and the cellularity and phenotypic composition of the thymus, spleen, lymph node, and bone marrow was assessed. After 6 days of treatment, significant increases in the cellularity of the spleen, lymph node, and bone marrow were observed which returned to the normal range within 6 days after cessation of treatment. After 3 days of IL-7 treatment, increased numbers of B220+/surface(s) IgM- bone marrow cells were observed. After 6 days of treatment, these numbers were still further increased and a significant population of B220+/sIgM- cells were observed in the spleen. The numbers of c mu+/sIgM- cells were also increased in the IL-7-treated mice. Analysis of the expression of B220 and BP-1 on the sIgM- bone marrow cells revealed that the B220+/BP-1+ population was dramatically increased after IL-7 treatment and the size of the B220+/BP-1- population did not differ from control mice. The pre-B cell numbers declined rapidly after the cessation of IL-7 treatment. After 6 days of IL-7 treatment, a twofold increase in the number of B cells in the spleen and lymph node was observed. The B cell numbers declined to normal values within 6 days after the cessation of IL-7 administration. In the spleens of the IL-7-treated mice, there was a significant increase in the number of B cells with an immature phenotype (e.g., sIgMhi/sIgDlo, decreased levels of Ia and FcR expression). The numbers of CD8+ and CD4+ T cells were also increased in the lymph node and spleen of the IL-7-treated mice. These numbers declined to normal levels after the cessation of IL-7 treatment. 相似文献
63.
Myosin and subfragment-1 were prepared from rabbit hearts hypertrophied secondary to pulmonary artery constriction. The Ca2+ -stimulated ATPase activity was reduced while the potassium/EDTA-stimulated ATPase activity was unchanged in both the myosin and subfragment 1 (S-1) from hypertrophied hearts. When hypertrophy myosin was mixed with an equal quantity of control myosin, the ATPase activity of the mixed protein fell halfway between control and hypertrophy values. Similar results were obtained with control and hypertrophy S-1. The actin-stimulated ATPase activity of hypertrophy S-1 was slightly depressed but unlike hypertrophy myosin this depression was not significant when compared to normal S-1. This suggests that papain cleavage may have removed part of the conformational difference that exists between control and hypertrophy myosins. 相似文献
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Populations of carrot (Daucus carota) were raised over a widerange of densities (795763 plants m-2) to examine thedynamics of competition in terms of yielddensity relationshipsand size variability, and to investigate the effects of nutrientsupply on competition. While the relationship between shootyield and density was asymptotic, the relationship between rootand total yield and density tended to be parabolic. For a giventime and density series the relationship between yield per unitarea and density could best be described by the model: y=wmD(1+aD)b wherey is the yield per unit area,D is density,wm, a andb arefitted parameters. The parameterswm anda increased over timebut nutrient availability affected onlywm. An extension of thebasic yield-density model is proposed to describe the dynamicsof the yielddensity relationship over time: y=kD[1+cexp(-rt)]{1+ 相似文献
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Lactobacillus casei Is Able To Survive and Initiate Protein Synthesis during Its Transit in the Digestive Tract of Human Flora-Associated Mice 下载免费PDF全文
R. Oozeer N. Goupil-Feuillerat C. A. Alpert M. van de Guchte J. Anba J. Mengaud G. Corthier 《Applied microbiology》2002,68(7):3570-3574
Live Lactobacillus casei is present in fermented dairy products and has beneficial properties for human health. In the human digestive tract, the resident flora generally prevents the establishment of ingested lactic acid bacteria, the presence of which is therefore transient. The aim of this work was to determine if L. casei DN-114 001 survives during transit and how this bacterium behaves in the digestive environment. We used the human flora-associated (HFA) mouse model. L. casei DN-114 001 was genetically modified by the introduction of erm and lux genes, encoding erythromycin resistance and luciferase, respectively. For this modified strain (DN-240 041), light emission related to luciferase expression could easily be detected in the contents of the digestive tract. When inoculated into the digestive tract of HFA mice, L. casei (DN-240 041) survives but is eliminated with the same kinetics as an inert transit marker, indicating that it does not establish itself. In pure culture of L. casei, luciferase activities were high in the exponential and early stationary growth phases but decreased to become undetectable 1 day after inoculation. Viability was only slightly reduced even after more than 5 days. After transit in HFA mice, luciferase activity was detected even when 5-day-old L. casei cultures were given to the mice. In culture, the luciferase activity could be restored after 0.5 to 7 h of incubation in fresh medium or milk containing glucose, unless protein synthesis was inhibited by the addition of chloramphenicol or rifampin. These results suggest that in HFA mice L. casei DN-240 041, and thus probably L. casei DN-114 001, is able to initiate new protein synthesis during its transit with the diet. The beneficial properties of L. casei-fermented milk for human health might be related to this protein synthesis in the digestive tract. 相似文献
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基于高通量测序技术的微生物检测数据分析方法 总被引:1,自引:0,他引:1
高通量测序技术的发展正在逐渐改变诸多生物学领域的研究方法.为应对突发疫情以及新发未知微生物威胁的需求,微生物鉴定技术逐渐从传统的物理化学方法及核酸杂交等分子水平方法进一步走向利用无需培养的测序数据进行快速分析检测.随之而来的是对高通量数据分析在精度及速度的要求.基于高通量测序数据的微生物检测数据分析方法在近些年得到了快速的发展.本文分析了目前基于高通量测序数据的微生物检测数据分析方法,对其数据分析的处理流程和计算方法进行了研究,比较了各个微生物检测数据分析方法的特点及适用场景.最后结合本实验室工作总结微生物检测数据分析方法在实际应用中可能遇到的问题,希望对该应用领域的研究有一定的参考意义. 相似文献