Matthias Jens Keller

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Proteins directing the biosynthesis of galactoglucan (exopolysaccharide II) in Rhizobium meliloti Rm2011 are encoded by the exp genes. Sequence analysis of a 32-kb DNA fragment of megaplasmid 2 containing the exp gene cluster identified previously (J. Glazebrook and G. C. Walker, Cell 56:661-672, 1989) revealed the presence of 25 open reading frames.(More)
Employing the biparental exogenous plasmid isolation method, conjugative plasmids conferring mercury resistance were isolated from the microbial community of the rhizosphere of field grown alfalfa plants. Five different plasmids were identified, designated pSB101-pSB105. One of the plasmids, pSB102, displayed broad host range (bhr) properties for plasmid(More)
The genome of Sinorhizobium meliloti type strain Rm1021 consists of three replicons: the chromosome and two megaplasmids, pSymA and pSymB. Additionally, many indigenous S. meliloti strains possess one or more smaller plasmids, which represent the accessory genome of this species. Here we describe the complete nucleotide sequence of an accessory plasmid,(More)
The Rhizobium meliloti Tn5 mutant Rm3131, producing galactoglucan (EPS II) instead of succinoglycan (EPS I), was complemented by a 3.6-kb EcoRI-fragment of the Rhizobium meliloti genome. Sequencing of this fragment revealed six open reading frames (ORFs). The ORF found to be affected in the mutant Rm3131 codes for a putative protein of 15.7 kDa and forms a(More)
The nucleotide sequence of a 4.8-kb ClaI-EcoRI DNA fragment of megaplasmid 2 of Rhizobium meliloti Rm2011 involved in succinoglucan (EPS I) synthesis and nodule infection was determined. Four open reading frames (ORFs) were identified on this fragment. A mutational analysis revealed that these ORFs represent genes that were termed exoX, exoY, exoF, and(More)
The detection superoxide production in vascular cells is usually limited by a low sensitivity of available assays. We tested the applicability of the luminol derivate L-012 ¿8-amino-5-chloro-7-phenylpyridol¿3,4-dpyridazine-1,4(2H,3H)dione to measure superoxide production in cultured endothelial cells (human umbilical vein endothelial cells) and rat aortic(More)
Osteointegration of metal implants into aged organisms can be severely compromised due to reduced healing capacity of bone, lack of precursor cells for new bone formation, or osteoporosis. Here, we report on successful implant healing in a novel model of aged sheep in the presence of nonglycosylated bone morphogenetic protein 2 (BMP-2). Ewes of 8 to 12(More)
Brain lesions induced in newborn mice or rats by the glutamatergic agonists ibotenate (acting on NMDA and metabotropic receptors) or S-bromowillardiine (acting on AMPA-kainate receptors) mimic some aspects of white matter cysts and transcortical necrosis observed in human perinatal brain damage associated with cerebral palsy. Exogenous and endogenous(More)
BACKGROUND Propofol is commonly used as sedative in newborns and children. Recent experimental studies led to contradictory results, revealing neurodegenerative or neuroprotective properties of propofol on the developing brain. We investigated neurodevelopmental short- and long-term effects of neonatal propofol treatment. METHODS 6-day-old Wistar rats(More)
BACKGROUND Currently, a limited range of biochemical tests for hypoxia are in clinical use. Early diagnostic and functional biomarkers that mirror cellular metabolism and recovery during resuscitation are lacking. We hypothesized that the quantification of metabolites after hypoxia and resuscitation would enable the detection of markers of hypoxia as well(More)