bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of the 13-Kilobase
ermF
Region of the
Bacteroides
Conjugative Transposon CTnDOT
Authors: Whittle Gabrielle , Hund Bonnie D. , Shoemaker Nadja B. , Salyers Abigail A. 
Published: July 2002

ABSTRACT

The conjugative transposon CTnDOT is virtually identical over most of its length to another conjugative transposon, CTnERL, except that CTnDOT carries an
ermF
gene that is not found on CTnERL. In this report, we show that the region containing
ermF
appears to consist of a 13-kb chimera composed of at least one class I composite transposon and a mobilizable transposon (MTn). Although the
ermF
region contains genes also carried on
Bacteroides
transposons Tn
4351
and Tn
4551
, it does not contain the IS
4351
element which is found on these transposons. In CTnDOT, insertion of the
ermF
region occurred near a stem-loop structure at the end of
orf2
, an open reading frame located immediately downstream of the integrase (
int
) gene of CTnDOT, and in a region known to be important for excision of CTnERL and CTnDOT. The chimera that comprises the
ermF
region can apparently no longer excise and circularize, but it contains a functional mobilization region related to that described for the
Bacteroides
MTn Tn
4399
. Analysis of 19 independent
Bacteroides
isolates showed that the
ermF
region is located in the same position in all of the strains analyzed and that the compositions of the
ermF
region are almost identical in these strains. Therefore, it appears that CTnDOT-like elements present in community and clinical isolates of
Bacteroides
were derived from a common ancestor and proliferated in the diverse
Bacteroides
population.
The Phosphinomethylmalate Isomerase Gene
pmi,
Encoding an Aconitase-Like Enzyme, Is Involved in the Synthesis of Phosphinothricin Tripeptide in
Streptomyces viridochromogenes
Authors: Heinzelmann E. , Kienzlen G. , Kaspar S. , Recktenwald J. , Wohlleben W. , Schwartz D. 
Published: July 2002

ABSTRACT

Streptomyces viridochromogenes
Tü494 produces the antibiotic phosphinothricin tripeptide (PTT). In the postulated biosynthetic pathway, one reaction, the isomerization of phosphinomethylmalate, resembles the aconitase reaction of the tricarboxylic acid (TCA) cycle. It was speculated that this reaction is carried out by the corresponding enzyme of the primary metabolism (C. J. Thompson and H. Seto, p. 197–222,
in
L. C. Vining and C. Stuttard, ed.,
Genetics and Biochemistry of Antibiotic Production,
1995). However, in addition to the TCA cycle aconitase gene, a gene encoding an aconitase-like protein (the phosphinomethylmalate isomerase gene,
pmi
) was identified in the PTT biosynthetic gene cluster by Southern hybridization experiments, using oligonucleotides which were derived from conserved amino acid sequences of aconitases. The deduced protein revealed high similarity to aconitases from plants, bacteria, and fungi and to iron regulatory proteins from eucaryotes. Pmi and the
S. viridochromogenes
TCA cycle aconitase, AcnA, have 52% identity. By gene insertion mutagenesis, a
pmi
mutant (Mapra1) was generated. The mutant failed to produce PTT, indicating the inability of AcnA to carry out the secondary-metabolism reaction. A His-tagged protein (Hispmi*) was heterologously produced in
Streptomyces lividans
. The purified protein showed no standard aconitase activity with citrate as a substrate, and the corresponding gene was not able to complement an
acnA
mutant. This indicates that Pmi and AcnA are highly specific for their respective enzymatic reactions.
Role of the Single Regulator MrsR1 and the Two-Component System MrsR2/K2 in the Regulation of Mersacidin Production and Immunity
Authors: Guder André , Schmitter Tim , Wiedemann Imke , Sahl Hans-Georg , Bierbaum Gabriele 
Published: July 2002

ABSTRACT

The lantibiotic mersacidin is an antimicrobial peptide of 20 amino acids which inhibits bacterial cell wall biosynthesis by binding to the precursor molecule lipid II and which is produced by
Bacillus
sp. strain HIL Y-85,54728. The structural gene of mersacidin as well as accessory genes is organized in a biosynthetic gene cluster which is located on the chromosome and contains three open reading frames with similarities to regulatory proteins:
mrsR2
and
mrsK2
encode two proteins with homology to bacterial two-component systems, and
mrsR1
shows similarity to a response regulator. Both
mrsR2/K2
and
mrsR1
were inactivated by insertion of an antibiotic resistance marker. Disruption of
mrsR1
resulted in loss of mersacidin production; however, producer self-protection was not impaired. In contrast, inactivation of
mrsR2/K2
led to an increased susceptibility to mersacidin whereas biosynthesis of the lantibiotic remained unaffected. Binding of mersacidin to intact cells was significantly enhanced in the
mrsR2/K2
knockout mutant. Reverse transcription-PCR analysis from total RNA preparations showed that in contrast to the wild-type strain, the structural genes of the ABC transporter MrsFGE were not transcribed in the knockout mutant. It was therefore concluded that producer self-protection against mersacidin is conferred by the ABC transporter MrsFGE and that the transcription of
mrsFGE
is regulated by MrsR2/K2, whereas production of the antibacterial peptide is solely activated by MrsR1.
Engineering of a
Bacillus subtilis
Strain with Adjustable Levels of Intracellular Biotin for Secretory Production of Functional Streptavidin
Authors: Wu Sau-Ching , Wong Sui-Lam 
Published: July 2002

ABSTRACT

Streptavidin is a biotin-binding protein which has been widely used in many in vitro and in vivo applications. Because of the ease of protein recovery and availability of protease-deficient strains, the
Bacillus subtilis
expression-secretion system is an attractive system for streptavidin production. However, attempts to produce streptavidin using
B. subtilis
face the problem that cells overproducing large amounts of streptavidin suffer poor growth, presumably because of biotin deficiency. This problem cannot be solved by supplementing biotin to the culture medium, as this will saturate the biotin binding sites in streptavidin. We addressed this dilemma by engineering a
B. subtilis
strain (WB800BIO) which overproduces intracellular biotin. The strategy involves replacing the natural regulatory region of the
B. subtilis
chromosomal biotin biosynthetic operon (
bioWAFDBIorf2
) with an engineered one consisting of the
B. subtilis groE
promoter and gluconate operator. Biotin production in WB800BIO is induced by gluconate, and the level of biotin produced can be adjusted by varying the gluconate dosage. A level of gluconate was selected to allow enhanced intracellular production of biotin without getting it released into the culture medium. WB800BIO, when used as a host for streptavidin production, grows healthily in a biotin-limited medium and produces large amounts (35 to 50 mg/liter) of streptavidin, with over 80% of its biotin binding sites available for future applications.
Shedding ofEscherichia coliO157:H7 in Dairy Cattle Housed in a Confined Environment following Waterborne Inoculation
Authors: Shere J. A. , Kaspar C. W. , Bartlett K. J. , Linden S. E. , Norell B. , Francey S. , Schaefer D. M. 
Published: July 2002

ABSTRACTA study ofEscherichia coliO157:H7 transmission and shedding was conducted with bull calves housed in individual pens within a confined environment. For comparative purposes, the numbers and duration ofE. coliO157:H7 shedding in naturally infected calves were monitored after a single purchased calf (calf 156) tested positive prior to inoculation. During the next 8 days, the calves in adjacent pens and a pen directly across a walkway from calf 156 began to shed this serotype O157:H7 strain. Five of the eight calves in this room shed this O157:H7 strain at some time during the following 8 weeks. The numbers ofE. coliO157:H7 isolates shed in these calves varied from 60 to 105CFU/g of feces, and the duration of shedding ranged from 17 to >31 days. The genomic DNAs from isolates recovered from these calves were indistinguishable when compared by usingXbaI digestion and pulsed-field gel electrophoresis. Inoculation of calves with 1 liter of water containing ca. 103to 104CFU ofE. coliO157:H7/ml resulted in shedding in 10 of 12 calves (trial 1, 4 of 4 calves; trial 2, 6 of 8 calves). The inoculated calves shed the inoculation strain (FRIK 1275) as early as 24 h after administration. The duration of shedding varied from 18 to >43 days at levels from 102to 106CFU/g of feces. The numbers of doses necessary to initiate shedding varied among calves, and two calves in trial 2 never shed FRIK 1275 after four doses (ca. 106CFU per dose). Results from this study confirm previous reports of animal-to-animal and waterborne dissemination ofE. coliO157:H7 and highlight the need for an effective water treatment to reduce the spread of this pathogen in cattle.
Enrichment of Members of the Family
Geobacteraceae
Associated with Stimulation of Dissimilatory Metal Reduction in Uranium-Contaminated Aquifer Sediments
Authors: Holmes Dawn E. , Finneran Kevin T. , O'Neil Regina A. , Lovley Derek R. 
Published: July 2002

ABSTRACT

Stimulating microbial reduction of soluble U(VI) to insoluble U(IV) shows promise as a strategy for immobilizing uranium in uranium-contaminated subsurface environments. In order to learn more about which microorganisms might be involved in U(VI) reduction in situ, the changes in the microbial community when U(VI) reduction was stimulated with the addition of acetate were monitored in sediments from three different uranium-contaminated sites in the floodplain of the San Juan River in Shiprock, N.Mex. In all three sediments U(VI) reduction was accompanied by concurrent Fe(III) reduction and a dramatic enrichment of microorganisms in the family
Geobacteraceae
, which are known U(VI)- and Fe(III)-reducing microorganisms. At the point when U(VI) reduction and Fe(III) reduction were nearing completion,
Geobacteraceae
accounted for ca. 40% of the 16S ribosomal DNA (rDNA) sequences recovered from the sediments with bacterial PCR primers, whereas
Geobacteraceae
accounted for fewer than 5% of the 16S rDNA sequences in control sediments that were not amended with acetate and in which U(VI) and Fe(III) reduction were not stimulated. Between 55 and 65% of these
Geobacteraceae
sequences were most similar to sequences from
Desulfuromonas
species, with the remainder being most closely related to
Geobacter
species. Quantitative analysis of
Geobacteraceae
sequences with most-probable-number PCR and TaqMan analyses indicated that the number of
Geobacteraceae
sequences increased from 2 to 4 orders of magnitude over the course of U(VI) and Fe(III) reduction in the acetate-amended sediments from the three sites. No increase in
Geobacteraceae
sequences was observed in control sediments. In contrast to the predominance of
Geobacteraceae
sequences, no sequences related to other known Fe(III)-reducing microorganisms were detected in sediments. These results compare favorably with an increasing number of studies which have demonstrated that
Geobacteraceae
are important components of the microbial community in a diversity of subsurface environments in which Fe(III) reduction is an important process. The combination of these results with the finding that U(VI) reduction takes place during Fe(III) reduction and prior to sulfate reduction suggests that
Geobacteraceae
will be responsible for much of the Fe(III) and U(VI) reduction during uranium bioremediation in these sediments.
Biodegradation of Methyl
tert
-Butyl Ether and Other Fuel Oxygenates by a New Strain,
Mycobacterium austroafricanum
IFP 2012
Authors: François Alan , Mathis Hugues , Godefroy Davy , Piveteau Pascal , Fayolle Françoise , Monot Frédéric 
Published: July 2002

ABSTRACT

A strain that efficiently degraded methyl
tert
-butyl ether (MTBE) was obtained by initial selection on the recalcitrant compound
tert
-butyl alcohol (TBA). This strain, a gram-positive methylotrophic bacterium identified as
Mycobacterium austroafricanum
IFP 2012, was also able to degrade
tert
-amyl methyl ether and
tert
-amyl alcohol. Ethyl
tert
-butyl ether was weakly degraded.
tert
-Butyl formate and 2-hydroxy isobutyrate (HIBA), two intermediates in the MTBE catabolism pathway, were detected during growth on MTBE. A positive effect of Co
2+
during growth of
M. austroafricanum
IFP 2012 on HIBA was demonstrated. The specific rate of MTBE degradation was 0.6 mmol/h/g (dry weight) of cells, and the biomass yield on MTBE was 0.44 g (dry weight) per g of MTBE. MTBE, TBA, and HIBA degradation activities were induced by MTBE and TBA, and TBA was a good inducer. Involvement of at least one monooxygenase during degradation of MTBE and TBA was shown by (i) the requirement for oxygen, (ii) the production of propylene epoxide from propylene by MTBE- or TBA- grown cells, and (iii) the inhibition of MTBE or TBA degradation and of propylene epoxide production by acetylene. No cytochrome P-450 was detected in MTBE- or TBA-grown cells. Similar protein profiles were obtained after sodium dodecyl sulfate-polyacrylamide gel electrophoresis of crude extracts from MTBE- and TBA-grown cells. Among the polypeptides induced by these substrates, two polypeptides (66 and 27 kDa) exhibited strong similarities with known oxidoreductases.
A Strain ofBacillus sphaericusCauses Slower Development of Resistance inCulex quinquefasciatus
Authors: Pei Guofeng , Oliveira Cláudia M. F. , Yuan Zhiming , Nielsen-LeRoux Christina , Silva-Filha Maria Helena , Yan Jianpin , Regis Lêda 
Published: July 2002

ABSTRACTTwo field-collectedCulex quinquefasciatuscolonies were subjected to selection pressure by three strains ofBacillus sphaericus, C3-41, 2362, and IAB59, under laboratory conditions. After 13 and 18 generations of exposure to high concentrations of C3-41 and IAB59, a field-collected low-level-resistant colony developed >144,000- and 46.3-fold resistance to strains C3-41 and IAB59, respectively. A field-collected susceptible colony was selected with 2362 and IAB59 for 46 and 12 generations and attained >162,000- and 5.7-fold resistance to the two agents, respectively. The pattern of resistance evolution in mosquitoes depended on continuous selection pressure, and the stronger the selection pressure, the more quickly resistance developed. The resistant colonies obtained after selection withB. sphaericusC3-41 and 2362 showed very high levels of cross-resistance toB. sphaericus2362 and C3-41, respectively, but they displayed only low-level cross-resistance to IAB59. On the other hand, the IAB59-selected colonies had high cross-resistance to both strains C3-41 and 2362. Additionally, the slower evolution of resistance against strain IAB59 may be explained by the presence of another larvicidal factor. This is in agreement with the nontoxicity of the cloned and purified binary toxin (Bin1) of IAB59 for 2362-resistant larvae. We also verified that all theB. sphaericus-selected colonies showed no cross-resistance toBacillus thuringiensissubsp.israelensis, suggesting that it would be a promising alternative in managing resistance toB. sphaericusinC. quinquefasciatuslarvae.
Ageing Is Associated with a Prolonged Fever Response in Human Endotoxemia
Authors: Krabbe Karen Suárez , Bruunsgaard Helle , Hansen Christian Muff , Møller Kirsten , Fonsmark Lise , Qvist Jesper , Madsen Per Lav , Kronborg Gitte , Andersen Henrik Ørbaek , Skinhøj Peter , Pedersen Bente Klarlund 
Published: July 2002

ABSTRACTThe purpose of this study was to investigate whether an age-associated impaired acute-phase response exists. Nine healthy elderly volunteers (median, 66 years; range, 61 to 69 years) and eight young controls (median, 24 years; range, 20 to 27 years) were given an intravenous bolus of endotoxin (2 ng/kg). The rectal temperature was monitored continuously, and blood samples for cytokine measurements were obtained before endotoxin administration as well as 0.5, 1, 1.5, 2, 3, 4, 8, 12, and 24 h after the injection. The elderly subjects showed a more prolonged fever response compared to the young controls. Levels of tumor necrosis factor alpha (TNF-α), soluble TNF receptors (sTNFR-I), interleukin-6 (IL-6), IL-8, IL-10, and IL-1 receptor antagonist (IL-1ra) in plasma increased markedly following endotoxin administration in both groups. The elderly group showed larger initial increases in TNF-α and sTNFR-I levels and prolonged increased levels of sTNFR-I. Monocyte concentrations decreased in both groups, with the elderly group showing a more rapid decrease and a slower subsequent increase than did the young group. Furthermore, the elderly group had a more rapid increase in C-reactive protein levels than did the young group. In conclusion, ageing is associated with an altered acute-phase response including initial hyperreactivity, prolonged inflammatory activity, and prolonged fever response.
Treatment with Neurokinin-1 Receptor Antagonist Reduces Severity of Inflammatory Bowel Disease Induced byCryptosporidium parvum
Authors: Sonea Ioana M. , Palmer Mitchell V. , Akili Dhuha , Harp James A. 
Published: July 2002

ABSTRACTInflammatory bowel disease (IBD) is a chronic, debilitating disorder of uncertain and perhaps multiple etiologies. It is believed to be due in part to disregulation of the immune system. Neuroimmune interactions may be involved in induction or maintenance of IBD. In the present study, we examined the potential role of a neurotransmitter, substance P, in a mouse model of IBD. We found that binding sites for substance P, and more specifically, neurokinin-1 receptors, were upregulated in intestinal tissue of mice with IBD-like syndrome. Dosing of mice with LY303870, a neurokinin-1 receptor antagonist, reduced the severity of IBD, and treatment of mice with preexisting IBD allowed partial healing of lesions. We hypothesize that blocking the binding of substance P to the neurokinin-1 receptor interrupts the inflammatory cascade that triggers and maintains intestinal lesions of IBD.
Drug Targets and Mechanisms of Resistance in the Anaerobic Protozoa
Authors: Upcroft Peter , Upcroft Jacqueline A. 
Published: July 2002

SUMMARYThe anaerobic protozoa Giardia duodenalis, Trichomonas vaginalis, and Entamoeba histolytica infect up to a billion people each year. G. duodenalis and E. histolytica are primarily pathogens of the intestinal tract, although E. histolytica can form abscesses and invade other organs, where it can be fatal if left untreated. T. vaginalis infection is a sexually transmitted infection causing vaginitis and acute inflammatory disease of the genital mucosa. T. vaginalis has also been reported in the urinary tract, fallopian tubes, and pelvis and can cause pneumonia, bronchitis, and oral lesions. Respiratory infections can be acquired perinatally. T. vaginalis infections have been associated with preterm delivery, low birth weight, and increased mortality as well as predisposing to human immunodeficiency virus infection, AIDS, and cervical cancer. All three organisms lack mitochondria and are susceptible to the nitroimidazole metronidazole because of similar low-redox-potential anaerobic metabolic pathways. Resistance to metronidazole and other drugs has been observed clinically and in the laboratory. Laboratory studies have identified the enzyme that activates metronidazole, pyruvate:ferredoxin oxidoreductase, to its nitroso form and distinct mechanisms of decreasing drug susceptibility that are induced in each organism. Although the nitroimidazoles have been the drug family of choice for treating the anaerobic protozoa, G. duodenalis is less susceptible to other antiparasitic drugs, such as furazolidone, albendazole, and quinacrine. Resistance has been demonstrated for each agent, and the mechanism of resistance has been investigated. Metronidazole resistance in T. vaginalis is well documented, and the principal mechanisms have been defined. Bypass metabolism, such as alternative oxidoreductases, have been discovered in both organisms. Aerobic versus anaerobic resistance in T. vaginalis is discussed. Mechanisms of metronidazole resistance in E. histolytica have recently been investigated using laboratory-induced resistant isolates. Instead of downregulation of the pyruvate:ferredoxin oxidoreductase and ferredoxin pathway as seen in G. duodenalis and T. vaginalis, E. histolytica induces oxidative stress mechanisms, including superoxide dismutase and peroxiredoxin. The review examines the value of investigating both clinical and laboratory-induced syngeneic drug-resistant isolates and dissection of the complementary data obtained. Comparison of resistance mechanisms in anaerobic bacteria and the parasitic protozoa is discussed as well as the value of studies of the epidemiology of resistance.
Gallium Disrupts Iron Metabolism of Mycobacteria Residing within Human Macrophages
Authors: Olakanmi Oyebode , Britigan Bradley E. , Schlesinger Larry S. 
Published: July 2002

ABSTRACTMycobacterium tuberculosisandM. aviumcomplex (MAC) enter and multiply within monocytes and macrophages in phagosomes. In vitro growth studies using standard culture media indicate that siderophore-mediated iron (Fe) acquisition plays a critical role in the growth and metabolism of bothM. tuberculosisand MAC. However, the applicability of such studies to conditions within the macrophage phagosome is unclear, due in part to the absence of experimental means to inhibit such a process. Based on the ability of gallium (Ga3+) to concentrate within mononuclear phagocytes and on evidence that Ga disrupts cellular Fe-dependent metabolic pathways by substituting for Fe3+and failing to undergo redox cycling, we hypothesized that Ga could disrupt Fe acquisition and Fe-dependent metabolic pathways of mycobacteria. We find that Ga(NO3)3and Ga-transferrin produce an Fe-reversible concentration-dependent growth inhibition ofM. tuberculosisstrains and MAC grown extracellularly and within human macrophages. Ga is bactericidal forM. tuberculosisgrowing extracellularly and within macrophages. Finally, we provide evidence that exogenously added Fe is acquired by intraphagosomalM. tuberculosisand that Ga inhibits this Fe acquisition. Thus, Ga(NO3)3disruption of mycobacterial Fe metabolism may serve as an experimental means to study the mechanism of Fe acquisition by intracellular mycobacteria and the role of Fe in intracellular survival. Furthermore, given the inability of biological systems to discriminate between Ga and Fe, this approach could have broad applicability to the study of Fe metabolism of other intracellular pathogens.