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At least 577 records · Page 32Linked to original sources
PubMed1971

Extent of host deletions associated with bacteriophage P2-mediated eduction.

A series of independent Escherichia coli K eductants has been isolated and tested to determine the extent of their deletions. The deletions cover the P2 prophage in location H, the his operon, a suppressor of the recBC phenotype (sbcB), the gene for gluconate-6-phosphate dehydrogenase (gnd), a locus involved in cell wall synthesis (rfb), and in some cases all or part of genes involved in methylgalactoside uptake (mglP). One end of the deletion, the P2 prophage end, appears to be the same for all eductants. The other end, however, can be located before, within, and after the mglP locus.

Carbon Isotopes↗
PubMed1974

Sugar metabolism in transketolase mutants of Escherichia coli.

This paper continues the description of transketolase mutants of Escherichia coli; they are absolutely unable to grow on pentoses, but slightly "leaky" with respect to their aromatic requirement (B. L. Josephson and D. G. Fraenkel, 1969). Several experiments have explored the degree of leakiness and shown it to be low. There is little conversion of radioactive xylose to carbon dioxide. The labeling of ribose in cells grown on [1-(14)C]glucose and [2-(14)C]glucose accords with its origin being chiefly by the oxidative pathway. A mutant lacking both transketolase and gluconate-6-phosphate dehydrogenase has been constructed; it requires supplementation with pentose. Pentoses are inhibitory to growth of transketolase mutants, but high levels of pentose phosphates do not accumulate in this situation. Several experimental results are suggestive of regulation of metabolic flow in the oxidative branch of the hexose monophosphate shunt.

Aerobiosis↗
PubMed1976

Isolation and description of a menaquinone mutant from Bacillus licheniformis.

A menaquinone mutant (SG1) of Bacillus licheniformis has been isolated by selecting for colonies that are resistant to low levels of kanamycin (1.5 mug/ml) but sensitive to the same concentration of kanamycin in the presence of shikimate (25 mug/ml). The wild type (IU1) contained 0.38 +/- 0.02 nmol of menaquinone-7 (MK-7) per mg (dry weight) of cells when grown +/- shikimate, whereas SG1 had less than 0.01 nmol of MK-7 per mg (dry weight) of cells when grown in the presence of shikimate. SG1 had a generation time of 85 min, as compared to 24 min for IU1 grown +/- shikimate. SG1 doubled with a generation time of 28 min when grown in the presence of shikimate. IU1 consumed O2 at various rates depending on the stage of growth. A triphasic O2 consumption curve with maxima at mid-exponential phase, the transition from exponential to stationary phase, and early stationary phase was found for IU1 +/- shikimate and SG1 + shikimate. SG1 grown without shikimate consumed O2 at a low level (10 to 20% of IU1). Normal respiration could be restored to SG1 8.5 min after shikimate addition, whereas normal growth was not restored until 40 min after shikimate addition. Electron microscopic studies of SG1 and IU1 have indicated a morphological alteration in the mutant. SG1 is a dwarf cell as compared to IU1, when grown without shikimate. However, SG1 grown with shikimate became morphologically indistinguishable from IU1.

Bacillus↗
PubMed2024

Genetic modification of the shikimate pathway to reduce lignin content in switchgrass (Panicum virgatum L.) significantly impacts plant microbiomes.

UNLABELLED: Switchgrass (Panicum virgatum L.) is considered a sustainable biofuel feedstock, given its fast-impact growth, low input requirements, and high biomass yields. Improvements in bioenergy conversion efficiency of switchgrass could be made by reducing its lignin content. Engineered switchgrass that expresses a bacterial 3-dehydroshikimate dehydratase (QsuB) has reduced lignin content and improved biomass saccharification due to the rerouting of the shikimate pathway towards the simple aromatic protocatechuate at the expense of lignin biosynthesis. However, the impacts of this QsuB trait on switchgrass microbiome structure and function remain unclear. To address this, wild-type and QsuB-engineered switchgrass were grown in switchgrass field soils, and samples were collected from inflorescences, leaves, roots, rhizospheres, and bulk soils for microbiome analysis. We investigated how QsuB expression influenced switchgrass-associated fungal and bacterial communities using high-throughput Illumina MiSeq amplicon sequencing of ITS and 16S rDNA. Compared to wild-type, QsuB-engineered switchgrass hosted different microbial communities in roots, rhizosphere, and leaves. Specifically, QsuB-engineered plants had a lower relative abundance of arbuscular mycorrhizal fungi (AMF). Additionally, QsuB-engineered plants had fewer Actinobacteriota in root and rhizosphere samples. These findings may indicate that changes in the plant metabolism impact both AMF and Actinobacteriota similarly or potential interactions between AMF and the bacterial community. This study enhances understanding of plant-microbiome interactions by providing baseline microbial data for developing beneficial bioengineering strategies and by assessing nontarget impacts of engineered plant traits on the plant microbiome. IMPORTANCE: Bioenergy crops provide an important strategy for mitigating climate change. Reducing the lignin in bioenergy crops could improve fermentable sugar yields for more efficient conversion into bioenergy and bioproducts. In this study, we assessed how switchgrass engineered for low lignin impacted aboveground and belowground switchgrass microbiome. Our results show unexpected reductions in mycorrhizas and actinobacteria in belowground tissues, raising questions on the resilience and function of genetically engineered plants in agricultural systems.

Panicum↗
PubMed1996

Biosynthesis of the acetylenic compounds in cultured cells of Asparagus officinalis from D- and 13C-labelled phenylalanines.

Studies on the biosynthetic pathway of acetylenic compounds, 4-[5-(4-methoxyphenoxy)-3-penten-1-ynyl]phenol and its related compounds, in cultured cells of Asparagus officinalis L. (Liliaceae) revealed that all of the 17 carbon atoms in their skeletons are supplied by phenylalanine. It is also concluded that p-substituted phenylacetylenic moieties (the C6-C2 unit) in these compounds are derived from C6-C3 shikimate pathway metabolites via phenylalanine. As a working hypothesis concerning the C6-O-C3 unit formation, a spirotetrahydrofuran type intermediate is predicted.

Acetylene↗
PubMed2006

Purification and properties of NADP-dependent shikimate dehydrogenase from Gluconobacter oxydans IFO 3244 and its application to enzymatic shikimate production.

NADP-Dependent shikimate dehydrogenae (SKDH, EC 1.1.1.25) was purified from Gluconobacter oxydans IFO 3244. SKDH showed a single protein band on native-PAGE accompanying enzyme activity. It required NADP exclusively and catalyzed only the shuttle reaction between shikimate and 3-dehydroshikimate. The optimum pH for shikimate oxidation and 3-dehydroshikimate reduction was found at pH 10 and 7 respectively. SKDH proved to be a useful catalyst for shikimate production from 3-dehydroshikimate.

Alcohol Oxidoreductases↗
PubMed2000

The kinetic mechanism of 5-enolpyruvylshikimate-3-phosphate synthase from a gram-positive pathogen Streptococcus pneumoniae.

The Streptococcus pneumoniae 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase is a potential novel antibacterial target. The enzyme catalyzes a reversible transfer of an enolpyruvyl group from phospho(enol)pyruvate (PEP) to shikimate 3-phosphate (S3P) to give EPSP with the release of inorganic phosphate (Pi). Understanding the kinetic mechanism of this enzyme is crucial to the design of novel inhibitors of this enzyme that may have potential as antibacterial agents. Steady-state kinetic studies of product inhibition and inhibition by glyphosate (GLP) have demonstrated diverse inhibition patterns of the enzyme. In the forward reaction, GLP is a competitive inhibitor with respect to PEP, but an uncompetitive inhibitor relative to S3P. Product inhibition shows that EPSP is a competitive inhibitor versus both PEP and S3P, suggesting that the forward reaction follows a random sequential mechanism. In the reverse reaction, GLP is an uncompetitive inhibitor versus EPSP, but a noncompetitive inhibitor versus Pi. This indicates that a non-productive quaternary complex might be formed between the enzyme, EPSP, GLP and Pi. Product inhibition in the reverse reaction has also been investigated. The inhibition patterns of the S. pneumoniae EPSP synthase are not entirely consistent with those of EPSP synthases from other species, indicating that EPSP synthases from different organisms may adopt unique mechanisms to catalyze the same reactions.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗
PubMed2003

Determination of enzymatic activity of 5-enolpyruvylshikimate-3-phosphate synthase by LC/MS.

A liquid chromatography-mass spectrometry (LC/MS) method for determining the enzymatic activity of 5-enolpyruvylshikimate-3-phosphate synthase (EPSP synthase), an enzyme of the shikimate pathway, was developed. EPSP synthase catalyzes the formation of 5-enolpyruvylshikimate-3-phosphate (EPSP) from shikimate-3-phosphate (S-3-P) and phosphoenolpyruvate (PEP) in microorganisms and plants. The enzymatic activity of EPSP synthase was assessed by the determination of EPSP after a 30-min incubation with S-3-P and PEP using the LC/MS system. EPSP synthase activity is given in terms of the produced EPSP (pmol/min/mg protein). Glyphosate (N-phosphonomethyl glycine)-tolerant EPSP synthase from the Agrobacterium sp. strain CP4 (CP4-EPSP synthase) in genetically modified soybeans (GM-soybeans) was found to have an enzymatic activity of 736 EPSP pmol/min/mg protein in the presence of 3 nmol of S-3-P. In contrast, the enzyme activity of non-GM-soybeans was 21 EPSP pmol/min/mg protein. The EPSP synthase activity was markedly decreased in the non-GM-soybeans by the addition of glyphosate, but the enzyme activity of the GM-soybeans was only slightly decreased with this treatment. This LC/MS system could also be applicable to the measurement of EPSP synthase activity in different plant species and the detection of herbicide-tolerant EPSP synthase in GM foods.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗