bluuebunny/crossref_metadata_2025_split huggingface dataset:
Secreted Euryarchaeal Microhalocins Kill Hyperthermophilic Crenarchaea
Authors: Haseltine Cynthia , Hill Tiffany , Montalvo-Rodriguez Rafael , Kemper Samantha K. , Shand Richard F. , Blum Paul 
Published: July 2002

ABSTRACT

Few antibiotics targeting members of the archaeal domain are currently available for genetic studies. Since bacterial antibiotics are frequently directed against competing and related organisms, archaea by analogy might produce effective antiarchaeal antibiotics. Peptide antibiotic (halocin) preparations from euryarchaeal halophilic strains S8a, GN101, and TuA4 were found to be toxic for members of the hyperthermophilic crenarchaeal genus
Sulfolobus
. No toxicity was evident against representative bacteria or eukarya. Halocin S8 (strain S8a) and halocin R1 (strain GN101) preparations were cytostatic, while halocin A4 (strain TuA4) preparations were cytocidal. Subsequent studies focused on the use of halocin A4 preparations and
Sulfolobus solfataricus
. Strain TuA4 cell lysates were not toxic for
S. solfataricus
, and protease (but not nuclease) treatment of the halocin A4 preparation inactivated toxicity, indicating that the A4 toxic factor must be a secreted protein. Potassium chloride supplementation of the
Sulfolobus
assay medium potentiated toxicity, implicating use of a salt-dependent mechanism. The utility of halocin A4 preparations for genetic manipulation of
S. solfataricus
was assessed through the isolation of UV-induced resistant mutants. The mutants exhibited stable phenotypes and were placed into distinct classes based on their levels of resistance.
The SHI-3 Iron Transport Island of
Shigella boydii
0-1392 Carries the Genes for Aerobactin Synthesis and Transport
Authors: Purdy Georgiana E. , Payne Shelley M. 
Published: July 2002

ABSTRACT

In
Shigella boydii
0-1392, genes encoding the synthesis and transport of the hydroxamate siderophore aerobactin are located within a 21-kb iron transport island between
lysU
and the
pheU
tRNA gene. DNA sequence analysis of the
S. boydii
0-1392 island, designated SHI-3 for
Shigella
island 3, revealed a conserved aerobactin operon associated with a P4 prophage-like integrase gene and numerous insertion sequences (IS). SHI-3 is present at the
pheU
tRNA locus in some
S. boydii
isolates but not in others. The map locations of the aerobactin genes vary among closely related species. The association of the aerobactin operon with phage genes and mobile elements and its presence at different locations within the genomes of enteric pathogens suggest that these virulence-enhancing genes may have been acquired by bacteriophage integration or IS element-mediated transposition. An
S. boydii
aerobactin synthesis mutant, 0-1392
iucB
, was constructed and was similar to the wild type in tissue culture assays of invasion and intercellular spread.
Analysis of Functional Domains of the
Enterococcus faecalis
Pheromone-Induced Surface Protein Aggregation Substance
Authors: Waters C. M. , Dunny G. M. 
Published: July 2002

ABSTRACT

Pheromone-inducible aggregation substance (AS) proteins of
Enterococcus faecalis
are essential for high-efficiency conjugation of the sex pheromone plasmids and also serve as virulence factors during host infection. A number of different functions have been attributed to AS in addition to bacterial cell aggregation, including adhesion to host cells, adhesion to fibrin, increased cell surface hydrophobicity, resistance to killing by polymorphonuclear leukocytes and macrophages, and increased vegetation size in an experimental endocarditis model. Relatively little information is available regarding the structure-activity relationship of AS. To identify functional domains, a library of 23 nonpolar 31-amino-acid insertions was constructed in Asc10, the AS encoded by the plasmid pCF10, using the transposons Tn
lacZ
/in and Tn
phoA
/in. Analysis of these insertions revealed a domain necessary for donor-recipient aggregation that extends further into the amino terminus of the protein than previously reported. In addition, insertions in the C terminus of the protein also reduced aggregation. As expected, the ability to aggregate correlates with efficient plasmid transfer. The results also indicated that an increase in cell surface hydrophobicity resulting from AS expression is not sufficient to mediate bacterial aggregation.
nag
Genes of
Ralstonia
(Formerly
Pseudomonas
) sp. Strain U2 Encoding Enzymes for Gentisate Catabolism
Authors: Zhou Ning-Yi , Fuenmayor Sergio L. , Williams Peter A. 
Published: July 2002

ABSTRACT

Ralstonia
sp. strain U2 metabolizes naphthalene via gentisate to central metabolites. We have cloned and sequenced a 21.6-kb region spanning the
nag
genes. Upstream of the pathway genes are
nagY,
homologous to chemotaxis proteins, and
nagR,
a regulatory gene of the LysR family. Divergently transcribed from
nagR
are the genes for conversion of naphthalene to gentisate (
nagAaGHAbAcAdBFCQED
) (S. L. Fuenmayor, M. Wild, A. L. Boyes, and P. A. Williams, J. Bacteriol. 180:2522–2530, 1998), which except for the insertion of
nagGH
, encoding the salicylate 5-hydroxylase, are homologous to and in the same order as the genes in the classical upper pathway operon described for conversion of naphthalene to salicylate found in the NAH7 plasmid of
Pseudomonas putida
PpG7. Downstream of
nahD
is a cluster of genes (
nagJIKLMN
) which are probably cotranscribed with
nagAaGHAbAcAdBFCQED
as a single large operon. By cloning into expression vectors and by biochemical assays, three of these genes (
nagIKL
) have been shown to encode the enzymes involved in the further catabolism of gentisate to fumarate and pyruvate. NagI is a gentisate 1,2-dioxygenase which converts gentisate to maleylpyruvate and is also able to catalyze the oxidation of some substituted gentisates. NagL is a reduced glutathione-dependent maleylpyruvate isomerase catalyzing the isomerization of maleylpyruvate to fumarylpyruvate. NagK is a fumarylpyruvate hydrolase which hydrolyzes fumarylpyruvate to fumarate and pyruvate. The three other genes (
nagJMN
) have also been cloned and overexpressed, but no biochemical activities have been attributed to them. NagJ is homologous to a glutathione
S
-transferase, and NagM and NagN are proteins homologous to each other and to other proteins of unknown function. Downstream of the operon is a partial sequence with homology to a transposase.
Regulation of
osmC
Gene Expression by the Two-Component System
rcsB-rcsC
in
Escherichia coli
Authors: Davalos-Garcia Marcela , Conter Annie , Toesca Isabelle , Gutierrez Claude , Cam Kaymeuang 
Published: July 2002

ABSTRACT

The
Escherichia coli osmC
gene encodes an envelope protein of unknown function whose expression depends on osmotic pressure and growth phase. The gene is transcribed from two overlapping promoters,
osmCp
1
and
osmCp
2
. Several factors regulating these promoters have been reported. The leucine-responsive protein Lrp represses
osmCp
1
and activates
osmCp
2
, the nucleoid-associated protein H-NS represses both promoters, and the stationary-phase sigma factor ς
s
specifically recognizes
osmCp
2
. This work reports the identification of an additional regulatory element, the two-component system
rcsB
-
rcsC
, affecting positively the distal promoter
osmCp
1
. The response regulator of the system, RcsB, does not affect expression of the proximal promoter
osmCp
2
. Deletion analysis located the site necessary for RcsB activation just upstream of
osmCp
1
. In vitro transcription experiments and gel mobility shift assays demonstrated that RcsB stimulates RNA polymerase binding at
osmCp
1
.
Anaerobic Metabolism of 3-Hydroxybenzoate by the Denitrifying Bacterium
Thauera aromatica
Authors: Laempe Diana , Jahn Martina , Breese Klaus , Schägger Hermann , Fuchs Georg 
Published: July 2002

ABSTRACT

The anaerobic metabolism of 3-hydroxybenzoate was studied in the denitrifying bacterium
Thauera aromatica
. Cells grown with this substrate were adapted to grow with benzoate but not with 4-hydroxybenzoate. Vice versa, 4-hydroxybenzoate-grown cells did not utilize 3-hydroxybenzoate. The first step in 3-hydroxybenzoate metabolism is a coenzyme A (CoA) thioester formation, which is catalyzed by an inducible 3-hydroxybenzoate–CoA ligase. The enzyme was purified and characterized. Further metabolism of 3-hydroxybenzoyl-CoA by cell extract required MgATP and was coupled to the oxidation of 2 mol of reduced viologen dyes per mol of substrate added. Purification of the 3-hydroxybenzoyl-CoA reducing enzyme revealed that this activity was due to benzoyl-CoA reductase, which reduced the 3-hydroxy analogue almost as efficiently as benzoyl-CoA. The further metabolism of the alicyclic dienoyl-CoA product containing the hydroxyl substitution obviously required additional specific enzymes. Comparison of the protein pattern of 3-hydroxybenzoate-grown cells with benzoate-grown cells revealed several 3-hydroxybenzoate-induced proteins; the N-terminal amino acid sequences of four induced proteins were determined and the corresponding genes were identified and sequenced. A cluster of six adjacent genes contained the genes for substrate-induced proteins 1 to 3; this cluster may not yet be complete. Protein 1 is a short-chain alcohol dehydrogenase. Protein 2 is a member of enoyl-CoA hydratase enzymes. Protein 3 was identified as 3-hydroxybenzoate–CoA ligase. Protein 4 is another member of the enoyl-CoA hydratases. In addition, three genes coding for enzymes of β-oxidation were present. The anaerobic 3-hydroxybenzoate metabolism here obviously combines an enzyme (benzoyl-CoA reductase) and electron carrier (ferredoxin) of the general benzoyl-CoA pathway with enzymes specific for the 3-hydroxybenzoate pathway. This raises some questions concerning the regulation of both pathways.
SigE Is a Chaperone for the
Salmonella enterica
Serovar Typhimurium Invasion Protein SigD
Authors: Darwin K. Heran , Robinson Lloyd S. , Miller Virginia L. 
Published: July 2002

ABSTRACT

SigD is translocated into eucaryotic cells by a type III secretion system. In this work, evidence that the putative chaperone SigE directly interacts with SigD is presented. A bacterial two-hybrid system demonstrated that SigE can interact with itself and SigD. In addition, SigD was specifically copurified with SigE-His
6
on a nickel column.
The Wide-Domain Carbon Catabolite Repressor CreA Indirectly Controls Expression of the
Aspergillus nidulans xlnB
Gene, Encoding the Acidic Endo-β-(1,4)-Xylanase X
24
Authors: Orejas Margarita , MacCabe Andrew P. , Pérez-González JoséAntonio , Kumar Sudeep , Ramón Daniel 
Published: July 2002

ABSTRACT

The
Aspergillus nidulans xlnB
gene, which encodes the acidic endo-β-(1,4)-xylanase X
24
, is expressed when xylose is present as the sole carbon source and repressed in the presence of glucose. That the mutation

creA
d
30

results in considerably elevated levels of
xlnB
mRNA indicates a role for the wide-domain repressor CreA in the repression of
xlnB
promoter (
xlnBp
) activity. Functional analyses of
xlnBp
::
goxC
reporter constructs show that none of the four CreA consensus target sites identified in
xlnBp
are functional in vivo. The CreA repressor is thus likely to exert carbon catabolite repression via an indirect mechanism rather than to influence
xlnB
expression by acting directly on
xlnB
.
The E1β and E2 Subunits of theBacillus subtilisPyruvate Dehydrogenase Complex Are Involved in Regulation of Sporulation
Authors: Gao Haichun , Jiang Xin , Pogliano Kit , Aronson Arthur I. 
Published: July 2002

ABSTRACTThepdhABCDoperon ofBacillus subtilisencodes the pyruvate decarboxylase (E1α and E1β), dihydrolipoamide acetyltransferase (E2), and dihydrolipoamide dehydrogenase (E3) subunits of the pyruvate dehydrogenase multienzyme complex (PDH). There are two promoters: one for the entire operon and an internal one in front of thepdhCgene. The latter may serve to ensure adequate quantities of the E2 and E3 subunits, which are needed in greater amounts than E1α and E1β. Disruptions of thepdhB,pdhC, andpdhDgenes were isolated, but attempts to construct apdhAmutant were unsuccessful, suggesting that E1α is essential. The three mutants lacked PDH activity, were unable to grow on glucose and grew poorly in an enriched medium. ThepdhBandpdhCmutants sporulated to only 5% of the wild-type level, whereas thepdhDmutant strain sporulated to 55% of the wild-type level. This difference indicated that the sporulation defect of thepdhBandpdhCmutant strains was due to a function(s) of these subunits independent of enzymatic activity. Growth, but not low sporulation, was enhanced by the addition of acetate, glutamate, succinate, and divalent cations. Results from the expression of variousspo-lacZfusions revealed that thepdhBmutant was defective in the late stages of engulfment or membrane fusion (stage II), whereas thepdhCmutant was blocked after the completion of engulfment (stage III). This analysis was confirmed by fluorescent membrane staining. The E1β and E2 subunits which are present in the soluble fraction of sporulating cells appear to function independently of enzymatic activity as checkpoints for stage II-III of sporulation.
ThePseudomonas aeruginosaQuorum-Sensing MoleculeN-(3-Oxododecanoyl)Homoserine Lactone Contributes to Virulence and Induces Inflammation In Vivo
Authors: Smith Roger S. , Harris Sarah G. , Phipps Richard , Iglewski Barbara 
Published: July 2002

ABSTRACTPseudomonas aeruginosahas two well-characterized quorum-sensing systems, Las and Rhl. These systems are composed of LuxR-type proteins, LasR and RhlR, and two acyl homoserine lactone (AHL) synthases, LasI and RhlI. LasI catalyzes the synthesis ofN-(3-oxododecanoyl)homoserine lactone (3O-C12-HSL), whereas RhlI catalyzes the synthesis ofN-butyryl-homoserine lactone. There is little known about the importance of AHLs in vivo and what effects these molecules have on eukaryotic cells. In order to understand the role of AHLs in vivo, we first tested the effects that deletions of the synthase genes inP. aeruginosahad on colonization of the lung. We demonstrate that in an adult mouse acute-pneumonia model, deletion of thelasIgene or both thelasIandrhlIgenes greatly diminished the ability ofP. aeruginosato colonize the lung. To determine whether AHLs have a direct effect on the host, we examined the effects of 3O-C12-HSL injected into the skin of mice. In this model, 3O-C12-HSL stimulated a significant induction of mRNAs for the cytokines interleukin-1α (IL-1α) and IL-6 and the chemokines macrophage inflammatory protein 2 (MIP-2), monocyte chemotactic protein 1, MIP-1β, inducible protein 10, and T-cell activation gene 3. Additionally, dermal injections of 3O-C12-HSL also induced cyclooxygenase 2 (Cox-2) expression. The Cox-2 enzyme is important for the conversion of arachidonic acid to prostaglandins and is associated with edema, inflammatory infiltrate, fever, and pain. We also demonstrate that 3O-C12-HSL activates T cells to produce the inflammatory cytokine gamma interferon and therefore potentially promotes a Th1 environment. Induction of these inflammatory mediators in vivo is potentially responsible for the significant influx of white blood cells and subsequent tissue destruction associated with 3O-C12-HSL dermal injections. Therefore, the quorum-sensing systems ofP. aeruginosacontribute to its pathogenesis both by regulating expression of virulence factors (exoenzymes and toxins) and by inducing inflammation.
The Global Regulatory
hns
Gene Negatively Affects Adhesion to Solid Surfaces by Anaerobically Grown
Escherichia coli
by Modulating Expression of Flagellar Genes and Lipopolysaccharide Production
Authors: Landini Paolo , Zehnder Alexander J. B. 
Published: July 2002

ABSTRACT

The initial binding of bacterial cells to a solid surface is a critical and essential step in biofilm formation. In this report we show that stationary-phase cultures of
Escherichia coli
W3100 (a K-12 strain) can efficiently attach to sand columns when they are grown in Luria broth medium at 28°C in fully aerobic conditions. In contrast, growth in oxygen-limited conditions results in a sharp decrease in adhesion to hydrophilic substrates. We show that the production of lipopolysaccharide (LPS) and of flagella, as well as the transcription of the
fliC
gene, encoding the major flagellar subunit, increases under oxygen-limited conditions. Inactivation of the global regulatory
hns
gene counteracts increased production of LPS and flagella in response to anoxia and allows
E. coli
W3100 to attach to sand columns even when it is grown under oxygen-limited conditions. We propose that increased production of the FliC protein and of LPS in response to oxygen limitation results in the loss of the ability of
E. coli
W3100 to adhere to hydrophilic surfaces. Indeed, overexpression of the
fliC
gene results in a decreased adhesion to sand even when W3100 is grown in fully aerobic conditions. Our observations strongly suggest that anoxia is a negative environmental signal for adhesion in
E. coli
.
Heat Shock Proteome of
Agrobacterium tumefaciens
: Evidence for New Control Systems
Authors: Rosen Ran , Büttner Knut , Becher Dörte , Nakahigashi Kenji , Yura Takashi , Hecker Michael , Ron Eliora Z. 
Published: July 2002

ABSTRACT

The regulation of
Agrobacterium tumefaciens
heat shock genes involves a transcriptional activator (RpoH) and repressor elements (HrcA-CIRCE). Using proteome analysis and mutants in these control elements, we show that the heat shock induction of 32 (out of 56) heat shock proteins is independent of RpoH and HrcA. These results indicate the existence of additional regulatory factors in the
A
.
tumefaciens
heat shock response.
Isolation and Characterization of cLV25, a
Bacteroides fragilis
Chromosomal Transfer Factor Resembling Multiple
Bacteroides
sp. Mobilizable Transposons
Authors: Bass Kathleen A. , Hecht David W. 
Published: July 2002

ABSTRACT

Horizontal DNA transfer contributes significantly to the dissemination of antibiotic resistance genes in
Bacteroides fragilis
. To further our understanding of DNA transfer in
B. fragilis
, we isolated and characterized a new transfer factor, cLV25. cLV25 was isolated from
B. fragilis
LV25 by its capture on the nonmobilizable
Escherichia coli-Bacteroides
shuttle vector pGAT400ΔBglII. Similar to other
Bacteroides
sp. transfer factors, cLV25 was mobilized in
E. coli
by the conjugative plasmid R751. Using Tn
1000
mutagenesis and deletion analysis of cLV25, two mobilization genes,
bmgA
and
bmgB
, were identified, whose predicted proteins have similarity to DNA relaxases and mobilization proteins, respectively. In particular, BmgA and BmgB were homologous to MocA and MocB, respectively, the two mobilization proteins of the
B. fragilis
mobilizable transposon Tn
4399
. A
cis
-acting origin of transfer (
oriT
) was localized to a 353-bp region that included nearly all of the intergenic region between
bmgB
and
orf22
and overlapped with the 3′ end of
orf22
. This
oriT
contained a putative
nic
site sequence but showed no significant similarity to the
oriT
regions of other transfer factors, including Tn
4399
. Despite the lack of sequence similarity between the
oriT
s of cLV25 and Tn
4399
, a mutation in the cLV25 putative DNA relaxase,
bmgA
, was partially complemented by Tn
4399
. In addition to the functional cross-reaction with Tn
4399
, a second distinguishing feature of cLV25 is that predicted proteins have similarity to proteins encoded not only by Tn
4399
but by several
Bacteroides
sp. transfer factors, including NBU1, NBU2, CTnDOT, Tn
4555
, and Tn
5520
.
Borrelia burgdorferiSensu Lato andEhrlichiaspp. inIxodesTicks from Southern Norway
Authors: Jenkins Andrew , Kristiansen Bjørn-Erik , Allum Anne-Gry , Aakre Randi Kersten , Strand Linda , Kleveland Ellen Johanne , van de Pol Ingrid , Schouls Leo 
Published: July 2002

ABSTRACTWe report the results of a study of the prevalence ofEhrlichiaandBorreliaspecies in 341 questingIxodes ricinusticks from two locations in southern Norway. The prevalences ofBorrelia burgdorferisensu lato andEhrlichiaspp. were, respectively, 16 and 11.5% at site 1 and 17 and 6% at site 2. Prevalence and species composition ofBorreliaandEhrlichiavaried with location and date of collection. The dominantBorreliaspecies at both sites wasBorrelia afzelii, followed byBorrelia burgdorferisensu stricto.Borrelia gariniiwas found in only a single tick. The dominant member of theEhrlichiagroup was a recently describedEhrlichia-like organism related to the monocytic ehrlichiae. Variants ofEhrlichia phagocytophilaand the agent of human granulocytic ehrlichiosis were also found. The highest prevalences forB. afzelii,B. burgdorferisensu stricto, and theEhrlichia-like organism were observed in May.B. afzeliiwas most prevalent in females, less prevalent in nymphs, and least prevalent in males, while the prevalence ofEhrlichiawas highest in nymphs, lower in females, and least in males. Double infections withB. afzeliiandB. burgdorferisensu stricto and withB. afzeliiand theEhrlichia-like organism were significantly overrepresented. Tick densities were highest in May, when densities of more than 200 ticks/100 m2were observed, and declined during the summer months to densities as low as 20 ticks/100 m2. We conclude that estimates of the prevalence of tick-borne bacteria are sensitive to the choice of date and site for collection of ticks. This is the first study of tick-borneBorreliaandEhrlichiain Norway and the lowest reportedB.gariniiprevalence in Northern Europe. The prevalence of theEhrlichia-like organism is described for the first time in questing ticks.
Rapid Differentiation of “
Mycobacterium canettii
” from Other
Mycobacterium tuberculosis
Complex Organisms by PCR-Restriction Analysis of the
hsp65
Gene
Authors: Goh Khye Seng , Legrand Eric , Sola Christophe , Rastogi Nalin 
Published: July 2002

ABSTRACT

A total of 102 isolates of the
Mycobacterium tuberculosis
complex, including available “
M. canettii
” isolates, were studied by PCR-restriction analysis of a 441-bp fragment of the
hsp65
gene. PRA upon
Hha
I enzyme digestion (GCGC) allowed easy differentiatiation of “
M. canettii
” from other members of the
M. tuberculosis
complex (three bands of 260, 105, and 60 bp for “
M. canetti
,” compared to four bands of 185, 105, 75, and 60 bp for other members of the
M. tuberculosis
complex). Sequencing of the 441-bp
hsp65
fragment of “
M. canettii
” isolates showed the disappearance of an
Hha
I site at position 235 due to a C-to-T transition that corresponded to position 631 of the homologous
hsp65
gene of
M. tuberculosis
H37Rv. Considering that “
M. canettii
” may also exist as a stable rough morphotype, we suggest that the true number of “
M. canettii
” isolates may be underestimated in clinical microbiology laboratories.