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排序方式: 共有299条查询结果,搜索用时 218 毫秒
91.
Abdelaal Shamseldin Hassan Moawad Wafaa M. Abd El-Rahim Michael J. Sadowsky 《Systematic and applied microbiology》2014
Egyptian winter Berseem clover (EWBC) is one of the main important forage legume crops in Egypt that is used for animal feeding in winter and it occupies about 2.5 million feddans (Feddan = 4200 m2) in winter agricultural rotation systems. Forty-eight rhizobial isolates that nodulated this legume host from different geographical regions within Egypt were isolated. RFLP analyses of 16S rDNA (1.5 kb) and whole ribosomal DNA (5 kb), the sequencing of 16S rDNA, and the sequencing of nodC, nifH and house keeping genes were used to identify these isolates. The RFLP analysis of 16S rDNA (1.5 kb) among 15 representative strains with three enzymes generated two genotypes. The largest genotype was similar to Rhizobium etli CFN42T (93.33%) except for strain 902 that failed to re-nodulate EWBC. RFLP analysis of complete ribosomal DNA (5 kb) produced five genotypes. The majority of tested strains shared the genotype with R. etli CFN42T (53.33%). Only one strain (1002) shared the genotype with Rhizobium leguminosarum sv. trifolii 3023. The other four strains were comprised of two unique genotypes. Phylogenetic analysis of 16S rDNA sequences revealed that seven representative strains could be divided into two genetic clusters sharing the ancestral clad with R. etli CFN42T. A phylogenetic tree based on nodC gene sequence confirmed that all the examined strains shared the genetic lineage with R. leguminosarum sv. trifolii WSM1325. The phylogenetic trees of house keeping genes are supported strongly the identification of majority of strains as a novel symbiovar of R. etli with new lineages. 相似文献
92.
Shift of bacterial community structure in two Thai soil series affected by silver nanoparticles using ARISA 总被引:1,自引:0,他引:1
Wariya Chunjaturas John A. Ferguson Wutthida Rattanapichai Michael J. Sadowsky Kannika Sajjaphan 《World journal of microbiology & biotechnology》2014,30(7):2119-2124
In this study we examined the influence of silver nanoparticles (SNP) on the bacterial community and microbial processes in two soils from Thailand, a Ayutthaya (Ay) and Kamphaengsaen soil series (Ks). Results of this analysis revealed that SNP did not affect to pH, electrical conductivity, cation exchange capacity, and organic matter in both the Ay and Ks series. Automated ribosomal intergenic spacer analysis (ARISA) analysis profiles showed that bacterial community decreased with increasing SNP concentration. Pearson’s correlation coefficient and multidimensional scaling analyses indicated that the effects of SNP on the bacterial community structure depended more on soil types than SNP application rates and incubation periods. Additionally, the results showed that SNP application rates affected on amount of CO2 emissions, while SNP application rates had no effect on N mineralization in both soil types. This study is the first investigation of the effects of SNP on bacterial community using ARISA analysis. Our results might be useful to evaluate the risk associated with the applications of SNP for consumer products and agricultural practices. 相似文献
93.
David JJ Saliken Aillette Mulet-Sierra Nadr M Jomha Adetola B Adesida 《Arthritis research & therapy》2012,14(3):1-13
Introduction
The main objective of this study was to determine whether meniscus cells from the outer (MCO) and inner (MCI) regions of the meniscus interact similarly to or differently with mesenchymal stromal stem cells (MSCs). Previous study had shown that co-culture of meniscus cells with bone marrow-derived MSCs result in enhanced matrix formation relative to mono-cultures of meniscus cells and MSCs. However, the study did not examine if cells from the different regions of the meniscus interacted similarly to or differently with MSCs.Methods
Human menisci were harvested from four patients undergoing total knee replacements. Tissue from the outer and inner regions represented pieces taken from one third and two thirds of the radial distance of the meniscus, respectively. Meniscus cells were released from the menisci after collagenase treatment. Bone marrow MSCs were obtained from the iliac crest of two patients after plastic adherence and in vitro culture until passage 2. Primary meniscus cells from the outer (MCO) or inner (MCI) regions of the meniscus were co-cultured with MSCs in three-dimensional (3D) pellet cultures at 1:3 ratio, respectively, for 3 weeks in the presence of serum-free chondrogenic medium containing TGF-β1. Mono-cultures of MCO, MCI and MSCs served as experimental control groups. The tissue formed after 3 weeks was assessed biochemically, histochemically and by quantitative RT-PCR.Results
Co-culture of inner (MCI) or outer (MCO) meniscus cells with MSCs resulted in neo-tissue with increased (up to 2.2-fold) proteoglycan (GAG) matrix content relative to tissues formed from mono-cultures of MSCs, MCI and MCO. Co-cultures of MCI or MCO with MSCs produced the same amount of matrix in the tissue formed. However, the expression level of aggrecan was highest in mono-cultures of MSCs but similar in the other four groups. The DNA content of the tissues from co-cultured cells was not statistically different from tissues formed from mono-cultures of MSCs, MCI and MCO. The expression of collagen I (COL1A2) mRNA increased in co-cultured cells relative to mono-cultures of MCO and MCI but not compared to MSC mono-cultures. Collagen II (COL2A1) mRNA expression increased significantly in co-cultures of both MCO and MCI with MSCs compared to their own controls (mono-cultures of MCO and MCI respectively) but only the co-cultures of MCO:MSCs were significantly increased compared to MSC control mono-cultures. Increased collagen II protein expression was visible by collagen II immuno-histochemistry. The mRNA expression level of Sox9 was similar in all pellet cultures. The expression of collagen × (COL10A1) mRNA was 2-fold higher in co-cultures of MCI:MSCs relative to co-cultures of MCO:MSCs. Additionally, other hypertrophic genes, MMP-13 and Indian Hedgehog (IHh), were highly expressed by 4-fold and 18-fold, respectively, in co-cultures of MCI:MSCs relative to co-cultures of MCO:MSCs.Conclusions
Co-culture of primary MCI or MCO with MSCs resulted in enhanced matrix formation. MCI and MCO increased matrix formation similarly after co-culture with MSCs. However, MCO was more potent than MCI in suppressing hypertrophic differentiation of MSCs. These findings suggest that meniscus cells from the outer-vascular regions of the meniscus can be supplemented with MSCs in order to engineer functional grafts to reconstruct inner-avascular meniscus. 相似文献94.
Karl Rumbold Hugo JJ van Buijsen Karin M Overkamp Johan W van Groenestijn Peter J Punt J van der Mariët Werf 《Microbial cell factories》2009,8(1):1-11
Although many secondary metabolites with diverse biological activities have been isolated from myxobacteria, most strains
of these biotechnologically important gliding prokaryotes remain difficult to handle genetically. In this study we describe
the new fast growing myxobacterial thermophilic isolate GT-2 as a heterologous host for the expression of natural product
biosynthetic pathways isolated from other myxobacteria. According to the results of sequence analysis of the 16S rDNA, this
moderately thermophilic isolate is closely related to Corallococcus macrosporus and was therefore named C. macrosporus GT-2. Fast growth of moderately thermophilic strains results in shorter fermentation and generation times, aspects which are of
significant interest for molecular biological work as well as production of secondary metabolites. Development of a genetic
manipulation system allowed the introduction of the complete myxochromide biosynthetic gene cluster, located on a transposable
fragment, into the chromosome of GT-2. Genetic engineering of the biosynthetic gene cluster by promoter exchange leads to
much higher production of myxochromides in the heterologous host C. macrosporus GT-2 in comparison to the original producer Stigmatella aurantiaca and to the previously described heterologous host Pseudomonas putida (600 mg/L versus 8 mg/L and 40 mg/L, respectively). 相似文献
95.
Joseph P. Emerson Michelle L. Wagner Mark F. Reynolds Lawrence Que Jr Michael J. Sadowsky Lawrence P. Wackett 《Journal of biological inorganic chemistry》2005,10(7):751-760
The manganese-dependent 3,4-dihydroxyphenylacetate 2,3-dioxygenase (MndD) from Arthrobacter globiformis CM-2 is an extradiol-cleaving catechol dioxygenase that catalyzes aromatic ring cleavage of 3,4-dihydroxyphenylacetate (DHPA).
Based on the recent crystal structure of the MndD–DHPA complex, a series of site-directed mutations were made at a conserved
second-sphere residue, histidine 200, to gain insight into and clarify the role this residue plays in the Mn(II)-dependent
catalytic mechanism. In this study, we report the activities and spectroscopic data of these H200 variants and their DHPA
and 4-nitrocatechol (4-NC) complexes. The data collected from wild-type and mutant MndDs are consistent with a role for H200
interacting with a manganese-bound dioxygen moiety and are inconsistent with other previously proposed roles involving proton
transfer. Spectroscopic observations, including unique low-field EPR signals found when DHPA and 4-NC are bound to the Mn(II)
center of MndD, are discussed and their relationship to dioxygen activation catalyzed in MndD is explored.
Electronic Supplementary Material Supplementary material is available for this article at 相似文献
96.
The nodulation of Glycine max cv. Lambert and the nodulation-restricting plant introduction (PI) genotype PI 417566 by wild-type Bradyrhizobium japonicum USDA110 is regulated in a population-density-dependent manner. Nodulation on both plant genotypes was suppressed (inhibited) when plants received a high-density inoculum (10(9) cells/ml) of strain USDA110 grown in complex medium, and more nodules were produced on plants receiving a low-cell-density inoculum (10(5) cells/ml). Since cell-free supernatants from strain USDA110 grown to high cell density in complex medium decreased the expression of an nodY-lacZ fusion, this phenomenon was attributed to bradyoxetin-induced repression of nod gene expression. Inoculation of either the permissive soybean genotype (cv. Lambert) or PI 417566 with 10(9) cells/ml of the nodD2, nolA, nodW, and nwsB mutants of USDA110 enhanced nodulation (up to 24%) relative to that seen with inoculations done with 10(5) cells/ml of the mutants or the wild-type strain, indicating that these genes are involved in population-density-dependent nodulation of soybeans. In contrast, the number of nodules produced by an nodD1 mutant on either soybean genotype was less than those seen with the wild-type strain inoculated at a low inoculum density. The nodD2 mutant outcompeted B. japonicum strain USDA123 for nodulation of G. max cv. Lambert at a high or low inoculum density, and the results of root-tip-marking and time-to-nodulate studies indicated that the nolA and nodD2 mutants nodulated this soybean genotype faster than wild-type USDA110. Taken together, the results from these studies indicate that the nodD2 mutant of B. japonicum may be useful to enhance soybean nodulation at high inoculum densities and that NodD2 is a key repressor influencing host-controlled restriction of nodulation, density-dependent suppression of nodulation, perception of bradyoxetin, and competitiveness in the soybean-B. japonicum symbiosis. 相似文献
97.
Annette AM Gerritsen Rob JPM Scholten Willem JJ Assendelft Herman Kuiper Henrica CW de Vet Lex M Bouter 《BMC neurology》2001,1(1):8-7
Background
Carpal tunnel syndrome is a common disorder, which can be treated with surgery or conservative options. However, there is insufficient evidence and no consensus among physicians with regard to the preferred treatment for carpal tunnel syndrome. Therefore, a randomized controlled trial is conducted to compare the short- and long-term efficacy of surgery and splinting in patients with carpal tunnel syndrome. An attempt is also made to avoid the (methodological) limitations encountered in earlier trials on the efficacy of various treatment options for carpal tunnel syndrome. 相似文献98.
99.
Jennifer L. Seffernick Nir Shapir Michael Schoeb Gilbert Johnson Michael J. Sadowsky Lawrence P. Wackett 《Applied microbiology》2002,68(9):4672-4675
2-Chloro-4,6-diamino-s-triazine (CAAT) is a metabolite of atrazine biodegradation in soils. Atrazine chlorohydrolase (AtzA) catalyzes the dechlorination of atrazine but is unreactive with CAAT. In this study, melamine deaminase (TriA), which is 98% identical to AtzA, catalyzed deamination of CAAT to produce 2-chloro-4-amino-6-hydroxy-s-triazine (CAOT). CAOT underwent dechlorination via hydroxyatrazine ethylaminohydrolase (AtzB) to yield ammelide. This represents a newly discovered dechlorination reaction for AtzB. Ammelide was subsequently hydrolyzed by N-isopropylammelide isopropylaminohydrolase to produce cyanuric acid, a compound metabolized by a variety of soil bacteria. 相似文献
100.
JJ. ALDASORO C. AEDO F. MUÑOZ GARMENDIA 《Botanical journal of the Linnean Society. Linnean Society of London》1996,121(2):143-158
A multivariate morphometric study of the genus Pyrus in south-west Europe and North Africa shows that five species may be recognized in the area: P. bourgaeana Decne., P. communis L., P. cordata Dew., P. spinosa Forssk, and P. nivalis Jacq. Some valuable characters for identification of these species are proposed. In particular the width of fruit peduncle, petal size, leaf width and petiole length served to discriminate the taxa. Several names such as P. gharbiona Trab., P. cossonii Rehder (|M= P. longipes Balansa ex Coss. & Durieu) and P. boisseriana Buhse, are regarded as synonyms of P. cordata , while P. marnormis Trab. of P. bourgaeana. Consequently a check-list and a key to these species are provided. 相似文献