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E W Nester

Publications and source records attributed to E W Nester.

172 records · Page 10Linked to original sources
PubMed1967

Macromolecular synthesis in newly transformed cells of Bacillus subtilis.

The capacity of newly transformed cells of Bacillus subtilis to synthesize deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and protein has been determined by following the kinetics of suicide after their exposure to tritiated precursors of each of these macromolecules. Competent cells, whether transformed or not, are heterogeneous with respect to DNA synthesis. About 40 to 50% are latent in DNA synthesis. This latency may persist for 2.5 to 3 hr since transformants are resistant to thymineless death for this period after DNA addition. The remainder of the transformants synthesize DNA at one-half the rate of the cells of the total population. Synthesis of stable RNA does not occur at an appreciable rate in newly transformed cells. Newly transformed cells, however, do synthesize protein extensively, as demonstrated by the lethality of incorporated tritiated amino acids. Either chloramphenicol or actinomycin D treatment during the time of exposure to the tritiated amino acid prevented the suicide of transformants.

Amino Acids↗
PubMed1967

Comparative control of a branch-point enzyme in microorganisms.

Thirty-two genera of microorganisms were identified with one of six distinctive control patterns for the enzyme 3-deoxy-d-arabino-heptulosonate-7-phosphate synthetase. These patterns included sequential feedback inhibition, isoenzyme feedback inhibition, cumulative feedback inhibition, and three (apparent) simple one-effector patterns. Documentation is provided of an overwhelming tendency for control patterns to be strongly conserved among the member species of the various genera that were examined.

Actinomycetales↗
PubMed1967

Aromatic amino acid biosynthesis: gene-enzyme relationships in Bacillus subtilis.

Single step mutants of Bacillus subtilis which required either one or all of the aromatic amino acids for growth were isolated. The relevant gene defect was determined for each mutant by enzyme assays in vitro. A mutant deficient in each enzyme step of aromatic amino acid biosynthesis was found with the exceptions of the shikimate kinase and the phenylalanine and tyrosine transaminases. Representative mutants carrying the defective genes were mapped by deoxyribonucleic acid mediated transformation by reference to the aromatic amino acid gene (aro) cluster and, alternately, to any of the other unlinked aro genes. The genes coding for dehydroquinate synthetase, 3-enol pyruvylshikimate 5-phosphate synthetase, one form of chorismate mutase, and prephenate dehydrogenase are linked to the aro cluster. Except for the previously identified linkage between the genes of 3-deoxy-d-arabino heptulosonic acid 7-phosphate synthetase and one species of chorismate mutase, the other genes involved in this pathway are neither linked to the aro cluster nor to each other.

Amino Acids↗
PubMed1966

Control of aromatic acid biosynthesis in Bacillus subtilis: sequenial feedback inhibition.

Nester, E. W. (University of Washington, Seattle), and R. A. Jensen. Control of aromatic acid biosynthesis in Bacillus subtilis: sequential feedback inhibition. J. Bacteriol. 91:1594-1598. 1966.-The three major end products of aromatic acid synthesis, tyrosine, phenylalanine, and tryptophan, were tested for their ability to inhibit the first enzymes of the three terminal branches of the pathway as well as the enzyme common to both tyrosine and phenylalanine synthesis. Tyrosine inhibits the activity of prephenate dehydrogenase and also prephenate dehydratase to a limited extent. Phenylalanine inhibits the activity of prephenate dehydratase and, at much higher concentrations, prephenate dehydrogenase. Tryptophan inhibits the activity of anthranilate synthetase and, to some extent, prephenate dehydrogenase and prephenate dehydratase. Chorismate mutase is not inhibited by either 1 mm tyrosine or 1 mm phenylalanine when these are present singly or together in the reaction mixture. The significance of the feedback control of the terminal branches to the feedback control of that part of the pathway common to the synthesis of all three amino acids is discussed.

Bacillus subtilis↗
PubMedDate not supplied

Mutants of the Agrobacterium tumefaciens virA gene exhibiting acetosyringone-independent expression of the vir regulon.

Hydroxylamine-induced mutations in the virA gene of Agrobacterium tumefaciens that do not require the plant phenolic-inducing compound acetosyringone for vir regulon induction were isolated. The isolation was based on the activation of both virB::lacZ and virE::cat fusions by mutant virA loci in the absence of acetosyringone. Three of these virA(Ais) (acetosyringone-independent signaling) mutants were characterized. All three mutants expressed a virB::lacZ fusion at high levels in the absence of acetosyringone. One virA (Ais) mutant, virA112, exhibited vir gene expression in the absence of inducing monosaccharides and acidic growth conditions, both of which are normally required for vir gene induction. The phenotype of the virA112 mutant resulted from a glycine to glutamic acid change near His-474, the site of VirA autophosphorylation.

Acetophenones↗
PubMedDate not supplied

T-DNA genes responsible for inducing a necrotic response on grape vines.

Agrobacterium tumefaciens supervirulent strain A281 induces a progressive necrotic response, rather than tumor formation, when inoculated on stems of several grape cultivars. The Ti plasmid, and specifically its T-DNA, is required for the process. In the present study, 40 T-DNA insertion mutants of A281 were generated via transposon mutagenesis and tested for their necrosis-inducing ability on grape stems in vitro. Ten mutants were attenuated in inducing necrogenesis. Restriction mapping and DNA sequencing revealed that at least two genes, tms1 and 6b, whose gene products are involved in the synthesis and activity modulation of auxin, are responsible for inducing necrogenesis. Double mutants of tms1 and 6b were totally non-necrogenic. The orientation of grapevine stem explants showed strong effects on the occurrence and progress of necrogenesis. Inoculation of Agrobacterium on physiological basal ends resulted in the greatest degree of necrogenesis. In addition, gene 5 of T-DNA, which modulates auxin responses in plants by the autoregulated synthesis of an auxin antagonist, was found to be separated from other TL-DNA genes by a novel insertion sequence, IS1312. Since a T-DNA borderlike sequence occurs in IS1312, gene 5 might not always be transferred into plants. Based on the accumulated data, we propose that the necrogenesis induced by Agrobacterium results from the sensitivity of grapevine cells to elevated levels of auxin or a precursor of auxin.

Agrobacterium tumefaciens↗