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S F Stoddard

Publications and source records attributed to S F Stoddard.

9 recordsLinked to original sources
PubMed2001

Taxonomic characterization of Ketogulonigenium vulgare gen. nov., sp. nov. and Ketogulonigenium robustum sp. nov., which oxidize L-sorbose to 2-keto-L-gulonic acid.

Four bacterial strains that oxidize L-sorbose to 2-keto-L-gulonic acid, a key intermediate in the synthesis of vitamin C, were isolated from soils of geographically distinct locations. All were Gram-negative, facultatively anaerobic, chemoheterotrophic rods. Comparative analysis revealed nearly identical 16S rDNA sequences amongst them (99.7-100% identical) and identified them as members of the alpha-subclass of the Proteobacteria. Phylogenetic analysis identified the closest taxonomically defined genus as Roseobacter (92.1-92.8% identical). On the basis of phylogenetic, phenotypic and genotypic analyses, a new genus is proposed, Ketogulonigenium gen. nov. Based upon these analyses, we also propose the reclassification of strain DSM 4025TP, originally identified as Gluconobacter oxydans, to the genus Ketogulonigenium. Two species are proposed: the type species Ketogulonigenium vulgare gen. nov., sp. nov., consisting of strains 62A-12APP, 266-13BPP and the type strain K. vulgare DSM 4025TP, and Ketogulonigenium robustum gen. nov., sp. nov., consisting of the type strain K. robustum X6LTP (= NRRL B-21627 = KCTC 0858BP). The species affiliation of the fifth strain (291-19PP) remains unresolved.

Base Sequence↗
PubMed1998

Purification, regulation, and molecular and biochemical characterization of pyruvate carboxylase from Methanobacterium thermoautotrophicum strain deltaH.

We discovered that Methanobacterium thermoautotrophicum strain DeltaH possessed pyruvate carboxylase (PYC), and this biotin prototroph required exogenously supplied biotin to exhibit detectable amounts of PYC activity. The enzyme was highly labile and was stabilized by 10% inositol in buffers to an extent that allowed purification to homogeneity and characterization. The purified enzyme was absolutely dependent on ATP, Mg2+ (or Mn2+ or Co2+), pyruvate, and bicarbonate for activity; phosphoenolpyruvate could not replace pyruvate, and acetyl-CoA was not required. The enzyme was inhibited by ADP and alpha-ketoglutarate but not by aspartate or glutamate. ATP was inhibitory at high concentrations. The enzyme, unlike other PYCs, exhibited nonlinear kinetics with respect to bicarbonate and was inhibited by excess Mg2+, Mn2+, or Co2+. The 540-kDa enzyme of A4B4 composition contained a non-biotinylated 52-kDa subunit (PYCA) and a 75-kDa biotinylated subunit (PYCB). The pycB gene was probably monocistronic and followed by a putative gene of a DNA-binding protein on the opposite strand. The pycA was about 727 kilobase pairs away from pycB on the chromosome and was probably co-transcribed with the biotin ligase gene (birA). PYCA and PYCB showed substantial sequence identities (33-62%) to, respectively, the biotin carboxylase and biotin carboxyl carrier + carboxyltransferase domains or subunits of known biotin-dependent carboxylases/decarboxylases. We discovered that PYCB and probably the equivalent domains or subunits of all biotin-dependent carboxylases harbored the serine/threonine dehydratase types of pyridoxal-phosphate attachment site. Our results and the existence of an alternative oxaloacetate synthesizing enzyme phosphoenolpyruvate carboxylase in M. thermoautotrophicum strain DeltaH (Kenealy, W. R., and Zeikus, J. G. (1982) FEMS Microbiol. Lett. 14, 7-10) raise several questions for future investigations.

Amino Acid Sequence↗
PubMed1990

Characterization of the C operon transcript of bacteriophage Mu.

Mu transcription occurs in three phases: early, middle, and late. Middle transcription occurs in the region of the C gene, which encodes the transactivator for late transcription. A middle promoter, Pm, was previously localized between 0.28 and 1.2 kilobase pairs upstream of C. We used S1 nuclease mapping with both unlabeled and radiolabeled capped RNAs from induced lysogens to characterize C transcription and identify its promoter. The C transcription initiation site was localized to a 4-base-pair region, approximately 740 base pairs upstream of C within the region containing Pm. Transcription of C was activated between 4 and 8 min after induction of cts and Cam lysogens and increased throughout the lytic cycle. Significant C transcription did not occur in replication-defective Aam lysogens. These kinetic and regulatory characteristics identify the C transcript as a middle RNA species and demonstrate that Pm is the C promoter. DNA sequence analysis of the Pm region showed a good -10, but poor -35, site homology to the Escherichia coli RNA polymerase consensus sequence. In addition, the sequence demonstrated that C is the distal gene in a middle operon containing several open reading frames. S1 mapping also showed an upstream transcript with a 3' end in the Pm region at a sequence strongly resembling a Rho-independent terminator. The regulatory characteristics of this RNA are consistent with this terminator, t9.2, being the early operon terminator.

Bacteriophage mu↗
PubMed1989

Localization and regulation of bacteriophage Mu promoters.

Mu promoters active during the lytic cycle were located by isolating RNA at various times after induction of Mu prophages, radiolabeling it by capping in vitro, and hybridizing it to Mu DNA fragments on Southern blots. Signals were detected from four new promoters in addition to the previously characterized Pe (early), PcM (repressor), and Pmom (late) promoters. A major signal upstream of C was first observed at 12 min and intensified thereafter with RNA from cts and C amber but not replication-defective prophages; these characteristics indicate that this signal arises from a middle promoter, which we designate Pm. With 20- and 40-min RNA, four additional major signals originated in the C-lys, F-G-I, N-P, and com-mom regions. These signals were missing with RNA from C amber and replication-defective prophages and therefore reflected the activity of late promoters, one of which we presume was Pmom. Uninduced lysogens showed weak signals from five regions, one from the early regulatory region, three between genes B and lys, and one near the late genes K, L, and M. The first of these probably resulted from PcM activity; the others remain to be identified.

Bacteriophage mu↗
PubMed1980

Selective deficiency in collagen-induced platelet aggregation during L-asparaginase therapy.

Platelet aggregation studies were performed on 10 pediatric patients with acute lymphoblastic leukemia (ALL) receiving induction therapy with vincristine, prednisone, and L-asparaginase. An isolated abnormality in platelet aggregation in response to collagen was found in all patients during the course of therapy. Platelet aggregation in response to collagen normalized following the discontinuation of L-asparaginase, while patients were still on vincristine and prednisone. In contrast to the abnormal collagen response, platelet aggregation induced by epinephrine, arachidonic acid, adenosine diphosphate (ADP), and thrombin were normal both during and following therapy. In the one patient with a normal platelet count before therapy, aggregation induced by all agents was normal. This selective abnormality in collagen aggregation therefore appears to result from therapy, with the use of L-asparaginase in particular being implicated.

Asparaginase↗
PubMed1979

Vitamin E inhibits the release of calcium from a platelet fraction in vitro.

Vitamin E, an inhibitor of platelet aggregation, was evaluated for its effects on platelet intracellular calcium flux. These studies used a platelet membrane fraction containing membranes of the dense tubular system which actively sequesters calcium in the presence of ATP and magnesium. After these membrane vesicles have accumulated calcium, the cation can be released by addition of the calcium ionophore A23187. Vitamin E had no effect on uptake of calcium by the membrane vesicles, but showed a concentration dependent inhibition of the release of calcium induced by A23187. In similar or slightly higher concentrations than inhibited calcium release, vitamin E also inhibited platelet aggregation, internal contraction and secretion, but had no effect on prostaglandin and thromboxane synthesis and potentiated phospholipase A2 activity. It is suggested that vitamin E acts to inhibit platelet internal contraction and secretion by preventing efflux of calcium from the dense tubular system. The potentiation of phospholiplase A2 by vitamin E could be explained by a localized increase of calcium at the site of the phospholipase A2 on the inner side of the dense tubular system membrane proximal to the vitamin E block.

Arachidonic Acids↗
PubMed1978

Prostaglandin endoperoxides promote calcium release from a platelet membrane fraction in vitro.

A calcium sequestering platelet membrane fraction was prepared and the effect of arachidonic acid, PGG2 and PGH2 on calcium content evaluated. At 4 degrees C, 6.7--16.7 micrometers arachidonic acid caused significant release of calcium from preloaded vesicles. Such release was completely inhibited by aspirin pretreating the platelets from which the membrane fraction was prepared. Gamma-linolenic acid, not a substrate for prostaglandin synthesis, did not cause calcium release. At 37 degrees C, after a 5 minute calcium loading of the membrane vesicles, arachidonic acid, PGG2, and PGH2 caused release of calcium. Calcium release by the PGG2 and PGH2 was only slightly inhibited by aspirin. Imidazole, which prevented conversion of the prostaglandin endoperoxides to thromboxanes, also only slightly inhibited calcium release. Other prostaglandins including PGD2, PGE1, PGE2 and PGD2 had no effect on the calcium content of the vesicles. These studies suggest that PGG2 and PGH2 may exert their effects on platelets by mobilizing calcium from an internal membrane store to make it available to promote platelet activation.

Arachidonic Acids↗
PubMed1978

Platelet storage pool deficiency and prostaglandin synthesis in chronic granulocytic leukaemia.

Platelet function was evaluated in eight patients with chronic granulocytic leukaemia (CGL), seven Ph1 positive and one Ph1 negative. Seven of the eight patients' platelets had an absence of the second wave of adrenaline induced aggregation on at least one occasion, while five had impaired collagen aggregation. The platelets of all seven patients with abnormal responses to adrenaline, aggregated with arachidonic acid, thus ruling out a cyclo-oxygenase deficiency. A marked decrease in the ADP, serotonin, and dense body content of platelets was found in all five patients evaluated. Mixtures of CGL patient platelets with platelets from normal donors who had ingested aspirin gave a normal biphasic response to adrenaline. Normal release of the storage pool contents from aspirin treated platelets was shown by stirring a mixture of CGL platelets and 14C-serotonin labelled aspirin treated platelets with adrenaline. The CGL platelets alone or in the mixture produced malondialdehyde in response to adrenaline. These experimental results suggest that CGL platelets have a storage pool deficiency but can synthesize prostaglandins and thromboxanes in response to arachidonic acid and adrenaline.

Adenosine Diphosphate↗