Pyrimidine Auxotrophs Research Articles

Pseudouridine kinase of [formula omitted]: A new enzyme

Pseudouridine kinase activity has been demonstrated in extracts of some pyrimidine auxotrophs of Escherichia coli . This enzyme has a pH optimum of 7, and requires ATP, Mg ++, and either K + or NH 4 +. Pseudouridine kinase is distinct from uridine kinase and deoxythymidine kinase. The presence of pseudouridine kinase and pseudouridylate synthetase activities in strains capable of growth on pseudouridine (Ψrd) as the sole pyrimidine source supports the following pathway for Ψrd utilization: ▪ ▪

Regulation of extracellular protease production in Bacillus cereus T: characterization of mutants producing altered amounts of protease.

Twenty-nine mutants of Bacillus cereus T were selected on casein agar for their inability to produce large amounts of extracellular protease. They all formed spores, and 27 were also auxotrophs for purines or pyrimidines. Upon reversion to prototrophy, a large fraction regained the capacity to produce protease. Conversely, reversion to normal protease production resulted in loss of the purine or pyrimidine requirement in a large fraction of the revertants. One spontaneous low-protease-producing pyrimidine auxotroph studied in detail grew as well as the wild type and produced spores which were identical to those produced by the wild type on the basis of heat resistance, dipicolinic acid content, density, and appearance in the electron microscope. The rate of protein turnover in the mutant was the same as the wild type. The mutant did grow poorly, however, when casein was the principal carbon source. A mutant excreting 5 to 10 times as much protease as the wild type was isolated as a secondary mutation from the hypoproducer discussed above. Loss of the pyrimidine requirement in this case did not alter the regulation of protease production. Although the secondary mutant grew somewhat faster in most media than the wild type, the final cell yield was lower. The spores of this mutant appeared to have excess coat on the basis of both electron microscopic and chemical studies. There appear to be closely related but distinct catabolic controls for both extracellular protease and spore formation. These controls can be dissociated as for the hypoproducers but can also appear integrated as for the hyperprotease producer.

Inhibitory effects and metabolism of 5-fluoropyrimidine derivatives in pneumococcus.

5-Fluorouracil (FU), 5-fluorocytosine, and the riboside and deoxyriboside derivatives of these fluoropyrimidines each exhibit a different spectrum of inhibitory effects in pneumococci. The biochemical basis of this finding seems to be the extremely low level of nucleoside phosphorylase (hydrolase) and N-trans-deoxyribosylase activity in pneumococcus and the consequent, relatively limited metabolic interconversion of the different fluoropyrimidines, which can therefore selectively affect one or the other of the several drug-sensitive biochemical reactions in this bacterium. Special attention was paid to the effect of fluoropyrimidines on the metabolism of cytosine and thymidine. In spite of the fact that FU is converted to both fluorouridine triphosphate and fluorocytidine triphosphate, only fluorouridylate but no fluorocytidylate can be detected in the ribonucleic acid Exogenous FU and fluorouridine also inhibit the synthesis of cytosine nucleotides from supplied uridine in a pyrimidine auxotroph. Thymidine was found to be a poor reversing agent for any of the fluoropyrimidine inhibitions. In both the wild type and in a thymidine-requiring (thymidylate-synthetase deficient) mutant, growing with supplied thymidine in the medium, fluorodeoxyuridine (FUdR) treatment caused cell death and inhibition of the incorporation of radioactive thymidine, adenosine, or uracil into deoxyribonucleic acid. It is suggested that FUdR (or a metabolic derivative) inhibits the transport of phosphorylation of thymidine in this microorganism.

Synthesis and assembly of ribosomal proteins at the onset of pyrimidine starvation

Ribosomal proteins from a pyrimidine auxotroph of Escherichia coli were pulse labelled with 14C-leucine prior to and following depletion of uridine. The incorporation of label into different 70S ribosomal protein bands decreased differentially at the onset of starvation. Readdition of uridine following the 14C-leucine pulse did not alter the labelling pattern. A sequential turn-off in the synthesis of different ribosomal proteins and a tight coupling between synthesis and assembly were indicated.

Pseudouridylate Synthetase of Escherichia coli : Correlation of Its Activity with Utilization of Pseudouridine for Growth

A direct correlation exists between the pseudouridylate synthetase activity and the ability of pyrimidine auxotrophs of Escherichia coli to grow on pseudouridine.

Significance of ribonucleotide reduction in the biosynthesis of deoxyribonucleotides in Escherichia coli.

A pyrimidine auxotroph of Escherichia coli, possessing decreased deaminase activities for cytidine and deoxycytidine, was grown with uniformly 14C‐labeled cytidine or uridine as sole pyrimidine source. The incorporation of radioactivity into the individual mononucleotides of DNA and RNA was determined. The pyrimidine nucleotides were degraded, and the distribution of isotope between their pentose and base moieties was analyzed.[14C]‐Cytidine was incorporated into RNA without loss of its isotope content. Furthermore, CMP of RNA and deoxyCMP of DNA had identical specific activities and pentose: base ratios. Therefore deoxyCMP of DNA was formed exclusively by reduction of a cytidine derivative.Only approximately 20% of the pentose isotope content of [14C]‐uridine was retained after incorporation into RNA. CMP, UMP, deoxyCMP, and deoxyTMP isolated from the nucleic acids had approximately equal specific activities and pentose: base ratios, indicating that both pyrimidine deoxyribonucleotides were formed by ribonucleotide reduction.[14C]‐Cytidine was converted to UMP of RNA with almost complete loss of isotope from the ribosyl moiety, but was converted to deoxyTMP of DNA with little loss of label. After estimation of different enzymatic activities in cell‐free extracts it was concluded that the major pathway yielding deoxyTMP of DNA did not involve deoxyTMP synthetase but rather proceeded directly from a deoxycytidine compound.

Growth and sporulation of a pyrimidine spore color mutant of Sordaria fimicola.

A nonautonomous spore color mutant of Sordaria fimicola is a pyrimidine auxotroph that produces hyaline nonviable ascospores. Uracil, uridine, and cytidine are more effective growth factors than cytosine and thymine and, in high concentrations, render the mutant self-fertile by inducing the ascospores to resume development and maturation. Crosses with the unlinked arginine non-autonomus spore color mutant st-59 yielded the double mutant st-59 pyr that requires both arginine and a pyrimidine for growth, which indicates a lack of suppression of the pyrimidine requirement by the arginine locus.

Regulation of extracellular protease production in Bacillus cereus.

Both sporulation and protease production can be inhibited by growing Bacillus cereus T in a medium containing a high concentration of a mixture of amino acids. Mutants selected for the ability to sporulate in this inhibitory medium were found to produce high levels of protease in the normal and inhibitory media. Comparison of the mutant and wild-type enzymes by gel electrophoresis and heat inactivation suggested that they were identical. One of the mutants proved to be a purine-requiring auxotroph. Reversion to prototrophy resulted in the loss of the capacity to sporulate in the inhibitory medium and loss of the ability to produce large amounts of protease. Mutants capable of producing high levels of protease and of sporulating in the inhibitory medium were also found when selecting for a purine, pyrimidine, or lysine requirement or for the capacity to sporulate in the presence of a high concentration of glucose. Protease production could be considerably delayed in the purine auxotrophs or completely inhibited in the pyrimidine auxotrophs by growing the cells in a medium containing the inhibitory mixture of amino acids plus hypoxanthine for the former or a pyrimidine for the latter. The fact that a variety of metabolic alterations could lead to excessive protease production suggested that a common catabolic or biosynthetic intermediate was involved in the control of the production of this enzyme(s).

Effects of auxotrophic mutations on the adaptation to inositol degradation in Aerobacter aerogenes.

SummaryThe ability of amino acid and of purine and pyrimidine auxotrophs of Aerobacter aerogenes to form adaptive enzymes for the degradation of myo-inositol has been investigated. It was found that adaptive enzyme synthesis by the amino acid auxotrophs could be stimulated in the absence of growth by addition of the required nutrilite, but not by addition of (NH4)2SO4. In contrast, adaptation in the guanine and pyramidine auxotrophs was enhanced by addition of (NH4)2SO4 alone. In all cases, dividing cells attained higher levels of adaptive enzyme than resting cells. The bearing of these results on the mechanism of adaptation is discussed. The poor utilization of histidine by strain 50 for growth on inositol does not seem to be due to the effect of histidine on adaptation,; but rather seems to suggest a metabolic relationship between inositol and histidine.

Proof that Bacteria are the Direct Cause of the Disease in Trees Known as Pear Blight

Previous articleNext article FreeProof that Bacteria are the Direct Cause of the Disease in Trees Known as Pear BlightJ. C. ArthurJ. C. Arthur Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Volume 10, Number 9/10Sep. - Oct., 1885 Article DOIhttps://doi.org/10.1086/325877 Views: 119Total views on this site Citations: 4Citations are reported from Crossref Journal History This article was published in the Botanical Gazette (1876-1991), which is continued by International Journal of Plant Sciences (1992-present). PDF download Crossref reports the following articles citing this article:L.S. Ramos, J.P. Sinn, B.L. Lehman, E.E. Pfeufer, K.A. Peter, T.W. McNellis Erwinia amylovora pyrC mutant causes fire blight despite pyrimidine auxotrophy, Letters in Applied Microbiology 60, no.66 (Apr 2015): 572–579.https://doi.org/10.1111/lam.12417Alfred Grafe 2000 Years Preceded the Emergence of Experimental Virology, (Jan 1991): 3–29.https://doi.org/10.1007/978-3-642-75250-6_2Kenneth F. Baker SEED PATHOLOGY, (Jan 1972): 317–416.https://doi.org/10.1016/B978-0-12-424303-3.50011-7G.W. KEITT History of Plant Pathology, (Jan 1959): 61–97.https://doi.org/10.1016/B978-0-12-395677-4.50009-5