Discovery and Characterization of New Hydroxamate Siderophores, Baumannoferrin A and B, produced byAcinetobacter baumannii

ChemBioChem ◽  
2015 ◽  
Vol 16 (13) ◽  
pp. 1896-1904 ◽  
Author(s):  
William F. Penwell ◽  
Nancy DeGrace ◽  
Sharon Tentarelli ◽  
Lise Gauthier ◽  
Catherine M. Gilbert ◽  
...  
Keyword(s):  
Hydroxamate Siderophores

scholarly journals Identification and characterization of an iron-regulated gene, chtA, required for the utilization of the xenosiderophores aerobactin, rhizobactin 1021 and schizokinen by Pseudomonas aeruginosa

Microbiology ◽  
2006 ◽  
Vol 152 (4) ◽  
pp. 945-954 ◽  
Author(s):  
Páraic Ó Cuív ◽  
Paul Clarke ◽  
Michael O'Connell
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Outer Membrane ◽  
Membrane Receptor ◽  
Outer Membrane Receptor ◽  
Significant Similarity ◽  
Hydroxamate Siderophores ◽  
Insertional Inactivation ◽  
Titration Assay

Pseudomonas aeruginosa utilizes several xenosiderophores under conditions of iron limitation, including the citrate hydroxamate siderophore aerobactin. Analysis of the P. aeruginosa genome sequence revealed the presence of two genes, chtA (PA4675) and PA1365, encoding proteins displaying significant similarity to the aerobactin outer-membrane receptor, IutA, of Escherichia coli. The chtA and PA1365 genes were mutated by insertional inactivation and it was demonstrated that ChtA is the outer-membrane receptor for aerobactin. ChtA also mediated the utilization of rhizobactin 1021 and schizokinen, which are structurally similar to aerobactin. In contrast to the utilization of other xenosiderophores by P. aeruginosa, there was no apparent redundancy in the utilization of aerobactin, rhizobactin 1021 and schizokinen. The utilization of citrate hydroxamate siderophores by P. aeruginosa was demonstrated to be TonB1 dependent. A Fur box was identified in the region directly upstream of chtA and it was demonstrated by the in vivo Fur titration assay that this region is capable of binding Fur and accordingly that expression of chtA is iron regulated. The PA1365 mutant was unaffected in the utilization of citrate hydroxamate siderophores.

Characterization of the promiscuous N-acyl CoA transferase, LgoC, in legonoxamine biosynthesis

2020 ◽  
Vol 18 (12) ◽  
pp. 2219-2222 ◽  
Author(s):  
Fleurdeliz Maglangit ◽  
Saad Alrashdi ◽  
Justine Renault ◽  
Laurent Trembleau ◽  
Catherine Victoria ◽  
...  
Keyword(s):  
Micrococcus Luteus ◽  
Coa Transferase ◽  
Hydroxamate Siderophores

More than 500 siderophores are known to date, but only three were identified to be aryl-containing hydroxamate siderophores, legonoxamines A and B from Streptomyces sp. MA37, and aryl ferrioxamine 2 from Micrococcus luteus KLE1011.

scholarly journals Characterization of a broadly specific cadaverine N-hydroxylase involved in desferrioxamine B biosynthesis in Streptomyces sviceus

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0248385
Author(s):  
Lesley-Ann Giddings ◽  
George T. Lountos ◽  
Kang Woo Kim ◽  
Matthew Brockley ◽  
Danielle Needle ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Substrate Inhibition ◽  
Product Formation ◽  
Desferrioxamine B ◽  
Hydroxamate Siderophores ◽  
Nadph Oxidation ◽  
High Concentrations ◽  
The Individual ◽  
Clinical Drug

N-hydroxylating flavin-dependent monooxygenases (FMOs) are involved in the biosynthesis of hydroxamate siderophores, playing a key role in microbial virulence. Herein, we report the first structural and kinetic characterization of a novel alkyl diamine N-hydroxylase DesB from Streptomyces sviceus (SsDesB). This enzyme catalyzes the first committed step in the biosynthesis of desferrioxamine B, a clinical drug used to treat iron overload disorders. X-ray crystal structures of the SsDesB holoenzyme with FAD and the ternary complex with bound NADP+ were solved at 2.86 Å and 2.37 Å resolution, respectively, providing a structural view of the active site environment. SsDesB crystallized as a tetramer and the structure of the individual protomers closely resembles the structures of homologous N-hydroxylating FMOs from Erwinia amylovora (DfoA), Pseudomonas aeruginosa (PvdA), and Aspergillus fumigatus (SidA). Using NADPH oxidation, oxygen consumption, and product formation assays, kinetic parameters were determined for various substrates with SsDesB. SsDesB exhibited typical saturation kinetics with substrate inhibition at high concentrations of NAD(P)H as well as cadaverine. The apparent kcat values for NADPH in steady-state NADPH oxidation and oxygen consumption assays were 0.28 ± 0.01 s-1 and 0.24 ± 0.01 s-1, respectively. However, in product formation assays used to measure the rate of N-hydroxylation, the apparent kcat for NADPH (0.034 ± 0.008 s-1) was almost 10-fold lower under saturating FAD and cadaverine concentrations, reflecting an uncoupled reaction, and the apparent NADPH KM was 33 ± 24 μM. Under saturating FAD and NADPH concentrations, the apparent kcat and KM for cadaverine in Csaky assays were 0.048 ± 0.004 s-1 and 19 ± 9 μM, respectively. SsDesB also N-hydroxylated putrescine, spermidine, and L-lysine substrates but not alkyl (di)amines that were branched or had fewer than four methylene units in an alkyl chain. These data demonstrate that SsDesB has wider substrate scope compared to other well-studied ornithine and lysine N-hydroxylases, making it an amenable biocatalyst for the production of desferrioxamine B, derivatives, and other N-substituted products.

Morphological Characterization of Mycobacteriophage R1

1974 ◽  
Vol 32 ◽  
pp. 254-255
Author(s):  
B. L. Soloff ◽  
T. A. Rado
Keyword(s):  
Carbon Source ◽  
Stationary Phase ◽  
Growth Phase ◽  
Minimal Medium ◽  
Morphological Characterization ◽  
Logarithmic Growth Phase ◽  
Complete Lysis ◽  
Lysogenic Culture ◽  
Logarithmic Growth

Mycobacteriophage R1 was originally isolated from a lysogenic culture of M. butyricum. The virus was propagated on a leucine-requiring derivative of M. smegmatis, 607 leu−, isolated by nitrosoguanidine mutagenesis of typestrain ATCC 607. Growth was accomplished in a minimal medium containing glycerol and glucose as carbon source and enriched by the addition of 80 μg/ ml L-leucine. Bacteria in early logarithmic growth phase were infected with virus at a multiplicity of 5, and incubated with aeration for 8 hours. The partially lysed suspension was diluted 1:10 in growth medium and incubated for a further 8 hours. This permitted stationary phase cells to re-enter logarithmic growth and resulted in complete lysis of the culture.

AEM analysis of crystallization in Ti-based amorphous alloys

1983 ◽  
Vol 41 ◽  
pp. 270-271
Author(s):  
A.R. Pelton ◽  
A.F. Marshall ◽  
Y.S. Lee
Keyword(s):  
Magnetic Properties ◽  
Amorphous Alloys ◽  
Amorphous Materials ◽  
Isothermal Annealing ◽  
Amorphous Matrix ◽  
Nucleation And Growth ◽  
Current Interest ◽  
Amorphous Films ◽  
Electrical And Magnetic Properties

Amorphous materials are of current interest due to their desirable mechanical, electrical and magnetic properties. Furthermore, crystallizing amorphous alloys provides an avenue for discerning sequential and competitive phases thus allowing access to otherwise inaccessible crystalline structures. Previous studies have shown the benefits of using AEM to determine crystal structures and compositions of partially crystallized alloys. The present paper will discuss the AEM characterization of crystallized Cu-Ti and Ni-Ti amorphous films.Cu60Ti40: The amorphous alloy Cu60Ti40, when continuously heated, forms a simple intermediate, macrocrystalline phase which then transforms to the ordered, equilibrium Cu3Ti2 phase. However, contrary to what one would expect from kinetic considerations, isothermal annealing below the isochronal crystallization temperature results in direct nucleation and growth of Cu3Ti2 from the amorphous matrix.

Characterization of Coherent, Ordered Precipitates in Nickel-Base Alloys

1973 ◽  
Vol 31 ◽  
pp. 144-145
Author(s):  
B. H. Kear ◽  
J. M. Oblak
Keyword(s):  
Stable Phase ◽  
Nickel Base Superalloy ◽  
Alloy 718 ◽  
Commercial Alloy ◽  
Precipitate Morphology ◽  
Continuous Precipitation ◽  
Nickel Base ◽  
Base Superalloy ◽  
Strengthening Precipitate

A nickel-base superalloy is essentially a Ni/Cr solid solution hardened by additions of Al (Ti, Nb, etc.) to precipitate a coherent, ordered phase. In most commercial alloy systems, e.g. B-1900, IN-100 and Mar-M200, the stable precipitate is Ni3 (Al,Ti) γ′, with an LI2structure. In A lloy 901 the normal precipitate is metastable Nis Ti3 γ′ ; the stable phase is a hexagonal Do2 4 structure. In Alloy 718 the strengthening precipitate is metastable γ″, which has a body-centered tetragonal D022 structure.Precipitate MorphologyIn most systems the ordered γ′ phase forms by a continuous precipitation re-action, which gives rise to a uniform intragranular dispersion of precipitate particles. For zero γ/γ′ misfit, the γ′ precipitates assume a spheroidal.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

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