Structural studies of a novel exopolysaccharide produced by a mutant of Rhizobium meliloti strain Rm1021

Her, Guor‐Rong; Glazebrook, Jane; Walker, Graham C.; Reinhold, Vernon N.

doi:10.1016/0008-6215(90)84300-j

Cited by 82 publications

(48 citation statements)

References 15 publications

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“…EPS II, a second class of exopolysaccharide synthesized by some S. meliloti strains, consists of repeating galactose-glucose disaccharide subunits with acetyl and pyruvyl side groups (76,96). EPS II is normally not present at detectable levels in the S. meliloti wild-type strain Rm1021 because of an insertion into expR, a luxR-type transcriptional activator that is required for EPS II synthesis.…”

Section: Bacterial Contributions To Infection Threadsmentioning

confidence: 99%

Infection and Invasion of Roots by Symbiotic, Nitrogen-Fixing Rhizobia during Nodulation of Temperate Legumes

Gage

2004

Microbiol Mol Biol Rev

775

532

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Bacteria belonging to the genera Rhizobium, Mesorhizobium, Sinorhizobium, Bradyrhizobium, and Azorhizobium (collectively referred to as rhizobia) grow in the soil as free-living organisms but can also live as nitrogen-fixing symbionts inside root nodule cells of legume plants. The interactions between several rhizobial species and their host plants have become models for this type of nitrogen-fixing symbiosis. Temperate legumes such as alfalfa, pea, and vetch form indeterminate nodules that arise from root inner and middle cortical cells and grow out from the root via a persistent meristem. During the formation of functional indeterminate nodules, symbiotic bacteria must gain access to the interior of the host root. To get from the outside to the inside, rhizobia grow and divide in tubules called infection threads, which are composite structures derived from the two symbiotic partners. This review focuses on symbiotic infection and invasion during the formation of indeterminate nodules. It summarizes root hair growth, how root hair growth is influenced by rhizobial signaling molecules, infection of root hairs, infection thread extension down root hairs, infection thread growth into root tissue, and the plant and bacterial contributions necessary for infection thread formation and growth. The review also summarizes recent advances concerning the growth dynamics of rhizobial populations in infection threads

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Section: Bacterial Contributions To Infection Threadsmentioning

confidence: 99%

Infection and Invasion of Roots by Symbiotic, Nitrogen-Fixing Rhizobia during Nodulation of Temperate Legumes

Gage

2004

Microbiol Mol Biol Rev

775

532

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“…EPS I is required for invasion of Medicago sativa root nodules by S. meliloti, but can be replaced by EPS II (Glazebrook and Walker, 1989;Gonzalez et al, 1996;Wang et al, 1999). EPS II consists of alternating glucose and galactose residues which are decorated by acetyl and pyruvyl groups (Her et al, 1990). Biosynthesis of EPS II is directed by the 30 kb exp gene cluster that comprises 22 genes organized in four operons R€ u uberg et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

Specific binding of the regulatory protein ExpG to promoter regions of the galactoglucan biosynthesis gene cluster of Sinorhizobium meliloti - a combined molecular biology and force spectroscopy investigation

Bartels

Baumgarth

Anselmetti

et al. 2003

Journal of Structural Biology

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Specific protein-DNA interaction is fundamental for all aspects of gene transcription. We focus on a regulatory DNA-binding protein in the Gram-negative soil bacterium Sinorhizobium meliloti 2011, which is capable of fixing molecular nitrogen in a symbiotic interaction with alfalfa plants. The ExpG protein plays a central role in regulation of the biosynthesis of the exopolysaccharide galactoglucan, which promotes the establishment of symbiosis. ExpG is a transcriptional activator of exp gene expression. We investigated the molecular mechanism of binding of ExpG to three associated target sequences in the exp gene cluster with standard biochemical methods and single molecule force spectroscopy based on the atomic force microscope (AFM). Binding of ExpG to expA1, expG-expD1, and expE1 promoter fragments in a sequence specific manner was demonstrated, and a 28 bp conserved region was found. AFM force spectroscopy experiments confirmed the specific binding of ExpG to the promoter regions, with unbinding forces ranging from 50 to 165 pN in a logarithmic dependence from the loading rates of 70-79 000 pN/s. Two different regimes of loading rate-dependent behaviour were identified. Thermal off-rates in the range of k off ¼ ð1:2 AE 1:0Þ Â 10 À3 s À1 were derived from the lower loading rate regime for all promoter regions. In the upper loading rate regime, however, these fragments exhibited distinct differences which are attributed to the molecular binding mechanism.

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“…In rhizobia, the mucoid phenotype is often related to the production of exopolysaccharides (EPS). In the case of S. meliloti, two types of EPS are produced: succinoglycan (EPS I) and galactoglucan (EPS II) (128,129). Their production is under control of a number of environmental signals, including phosphate concentrations and quorum sensing, and EPS play an important role in the establishment of an efficient symbiotic interaction with host plants as well (90,(130)(131)(132).…”

Section: Regulation Of Mucoidy and Cell Densitymentioning

confidence: 99%

Developmental and environmental regulatory pathways in alpha-proteobacteria

Ardissone

Viollier²

2012

Front Biosci

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Spatial and temporal control of cell differentiation and morphogenesis plays a key role in prokaryotes as well as eukaryotes. This is particularly important for bacteria that divide asymmetrically, as they generate two morphologically and functionally distinct daughter cells. Several alpha-proteobacteria, including the aquatic, free-living Caulobacter crescentus, the symbiotic rhizobia and the plant and animal pathogens Agrobacterium and Brucella, have been shown to undergo asymmetrical division. C. crescentus has become a model system for the study of the regulatory networks, in particular the control of the cell cycle, the cytokinetic machinery, the cytoskeleton and the functions required for duplication and differentiation in general. As the bulk of these regulatory networks and functions is conserved in most alpha-proteobacteria, we recapitulate the recent advances in understanding these spatially and temporally controlled processes, focusing on cell cycle progression, DNA replication and partitioning, cell division and regulation of specific phenotypes that vary during the cell cycle or in the case of different lifestyles (like extracellular polysaccharide production) in C. crescentus and other alpha-proteobacteria

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Structural studies of a novel exopolysaccharide produced by a mutant of Rhizobium meliloti strain Rm1021

Cited by 82 publications

References 15 publications

Infection and Invasion of Roots by Symbiotic, Nitrogen-Fixing Rhizobia during Nodulation of Temperate Legumes

Infection and Invasion of Roots by Symbiotic, Nitrogen-Fixing Rhizobia during Nodulation of Temperate Legumes

Specific binding of the regulatory protein ExpG to promoter regions of the galactoglucan biosynthesis gene cluster of Sinorhizobium meliloti - a combined molecular biology and force spectroscopy investigation

Developmental and environmental regulatory pathways in alpha-proteobacteria

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