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E C Niederhoffer

Publications and source records attributed to E C Niederhoffer.

8 recordsLinked to original sources
PubMed1996

Production of superoxide dismutases from Proteus mirabilis and Proteus vulgaris.

Proteus mirabilis and Proteus vulgaris expressed a combination of superoxide dismutase (Sod) activities, which was assigned to FeSod1, FeSod2 and MnSod for P. mirabilis, and FeSod, MnSod and CuZnSod for P. vulgaris. Production of the Sod proteins was dependent on the availability of iron, whether cells were grown under anaerobiosis or aerobiosis and growth phase. Nalidixic acid and chloramphenicol inhibited cell growth and the iron- and dioxygen-dependent production of Sod. These results support the involvement of metal ions and redox status in the production of Proteus Sods.

Aerobiosis↗
PubMed1995

Heavy metal effects on Proteus mirabilis superoxide dismutase production.

Proteus mirabilis expressed three superoxide dismutase activities, which depended on the level of soluble iron and dioxygen in the culture medium. Cadmium and lead decreased production of super oxide dismutase in liquid culture and on solid medium. A fourth super oxide dismutase activity appeared in extracts from cells grown in the presence of cadmium. These results support the idea of an interaction between toxic metal ions and putative iron- and redox-dependent regulatory systems.

Cadmium↗
PubMed1994

Phenylalanine- and tyrosine-dependent production of enterobactin in Escherichia coli.

Under low-iron conditions, Escherichia coli synthesizes the siderophore enterobactin. When compared to wild-type cells grown in iron sufficient medium, cells grown under iron limitation, in the absence of tyrosine and phenylalanine or the presence of both, increased catechol production (a measure of enterobactin and its degradation product 2,3-dihydroxybenzoic acid) 5- to 9-fold while cells supplemented with tyrosine alone produced a 10- to 20-fold increase. Mutations in fur, tyrA, pheA, or pheU generally resulted in increased enterobactin production, while a tyrR mutant was unaffected by combinations of tyrosine and phenylalanine.

Catechols↗
PubMed1993

Improved methods for the cultivation of strictly anaerobic, extremely thermophilic methanogens.

The strictly anaerobic, extremely thermophilic methanogens, Methanobacterium thermoautotrophicum Marburg and M. thermoautotrophicum delta H, have been cultivated in liquid culture and on solid medium in screw-top bottles, which permit continuous monitoring of the growth of the microorganisms. We have been able to routinely grow methanogens in medium containing bicarbonate, TRIS or 4-morpholinepropanesulfonic acid (MOPS) buffers and three different sulfur sources (sulfide, sulfite and thiosulfate) at temperatures up to 70 degrees C and at pressures up to 35 psi while monitoring cell density or colony formation.

Anaerobiosis↗
PubMed1990

Novel effect of aromatic compounds on the iron-dependent expression of the Escherichia coli K12 manganese superoxide dismutase (sodA) gene.

In Escherichia coli, the superoxide dismutase genes (sodA and sodB) sense the availability of Fe through the action of the fur locus [E. C. Niederhoffer, C. M. Naranjo, K. L. Bradley, J. A. Fee (1990) Control of Escherichia coli superoxide dismutases (sodA and sodB) genes by the ferric uptake regulation (fur) locus, J. Bacteriol. 172, 1930-1938]. Previous work from other laboratories has shown that a variety of metal chelators and of redox-active aromatic compounds can dramatically induce expression of sodA. Here we show that non-redox-active, non-metal-chelating aromatic compounds also enhance expression of a chromosomal sodA gene fusion and that these effects are strongly modulated by the Fur phenotype (Fur +/-) and by the availability of iron in the culture medium. The compounds studied were ethidium bromide, hemin, 2,2'-bipyridine, 1,10-phenantroline, 4,7-phenantroline, rhodamine B1, rhodamine 6G, and, for comparison to previous studies, Paraquat.

Ethidium↗
PubMed1990

Control of Escherichia coli superoxide dismutase (sodA and sodB) genes by the ferric uptake regulation (fur) locus.

The ferric uptake regulation (fur) gene product participates in regulating expression of the manganese- and iron-containing superoxide dismutase genes of Escherichia coli. Examination of beta-galactosidase activity coded from a chromosomal phi(sodA'-'lacZ) fusion suggests that metallated Fur protein acts as a transcriptional repressor of sodA (manganese superoxide dismutase [MnSOD]). Gel retardation assays demonstrate high-affinity binding of pure, Mn2(+)-Fur protein to DNA fragments containing the sodA promoter. These data and the presence of an iron box sequence in its promoter strongly suggest that sodA is part of the iron uptake regulon. An sodB'-'lacZ fusion gene borne on either a low- or high-copy plasmid yielded approximately two- to threefold more beta-galactosidase activity in Fur+ compared with Fur- cells; the levels of activity depended only weakly on the growth phase and did not change during an extended stationary phase. Measurement of FeSOD activity in logarithmic growth phase and in overnight cultures of sodA and fur sodA backgrounds revealed that almost no FeSOD activity was expressed in Fur- strains, whereas wild-type levels were expressed in Fur+ cells. Fur+ and Fur- cells bearing the multicopy plasmid pHS1-4 (sodB+) expressed approximately sevenfold less FeSOD activity in the fur background, and staining of nondenaturing electrophoretic gels indicates that synthesis of FeSOD protein was greatly reduced in Fur- cells. Gel retardation assays show that Mn2(+)-Fur had a significantly higher affinity for the promoter fragment of sodB compared with that of random DNA sequences but significantly lower than for the promoter fragment of sodA. These observations suggest that the apparent positive regulation of sodB does not result exclusively from a direct interaction of holo (metallated) Fur itself with the sodB promoter. Nevertheless, the sodB gene also appears to be part of the iron uptake regulon but not in the classical manner of Fe-dependent repression.

Chromosomes, Bacterial↗