bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transcription of the Gene Mediating Methicillin Resistance in
Staphylococcus aureus
(
mecA
) Is Corepressed but Not Coinduced by Cognate
mecA
and β-Lactamase Regulators
Authors: McKinney Tanya K. , Sharma Vijay K. , Craig William A. , Archer Gordon L. 
Published: July 2002

ABSTRACT

Resistance to β-lactam antibiotics in staphylococci is mediated by
mecA
and
blaZ
, genes encoding a penicillin-binding protein (PBP2a) with low β-lactam affinity and β-lactamase, respectively. The
mec
and
bla
regulators,
mecR1-mecI
and
blaR1-blaI
, respectively, encode inducer-repressors with sufficient amino acid homology to suggest that they could coregulate PBP2a production. In order to test this hypothesis, plasmids containing
mec
and
bla
regulatory sequences were introduced into
Staphylococcus aureus
containing a chromosomal
mecA-lacZ
transcriptional fusion. Corepression was confirmed by demonstrating a gene dosage-dependent reduction in β-galactosidase activity by either MecI or BlaI and additive repression when both were present. Both MecI-MecI and BlaI-BlaI homodimer and MecI-BlaI heterodimer interactions were demonstrated in the yeast two-hybrid assay, and purified MecI and BlaI protected the same
mec
promoter-operator sequences. However, MecI was approximately threefold more effective at
mecA-lacZ
transcriptional repression than was BlaI. While MecI and BlaI displayed similar activity as repressors of
mecA
transcription, there was a marked difference between MecR1 and BlaR1 in the rate and specificity of induction. Induction through BlaR1 by a β-lactam was 10-fold greater than through MecR1 at 60 min and was 81% of maximal by 2 h, while induction through MecR1 never exceeded 20% of maximal. Furthermore, complementation studies showed that MecI- or BlaI-mediated
mecA
transcriptional repression could be relieved by induction through homologous but not heterologous sensor-inducer proteins, demonstrating the repressor specificity of induction.
Direct Ring Fission of Salicylate by a Salicylate 1,2-Dioxygenase Activity from
Pseudaminobacter salicylatoxidans
Authors: Hintner Jan-Peter , Lechner Christa , Riegert Ulrich , Kuhm Andrea Elisabeth , Storm Thomas , Reemtsma Thorsten , Stolz Andreas 
Published: July 2002

ABSTRACT

In cell extracts of
Pseudaminobacter salicylatoxidans
strain BN12, an enzymatic activity was detected which converted salicylate in an oxygen-dependent but NAD(P)H-independent reaction to a product with an absorbance maximum at 283 nm. This metabolite was isolated, purified, and identified by mass spectrometry and
1
H and
13
C nuclear magnetic resonance spectroscopy as 2-oxohepta-3,5-dienedioic acid. This metabolite could be formed only by direct ring fission of salicylate by a 1,2-dioxygenase reaction. Cell extracts from
P. salicylatoxidans
also oxidized 5-aminosalicylate, 3-, 4-, and 5-chlorosalicylate, 3-, 4-, and 5-methylsalicylate, 3- and 5-hydroxysalicylate (gentisate), and 1-hydroxy-2-naphthoate. The dioxygenase was purified and shown to consist of four identical subunits with a molecular weight of about 45,000. The purified enzyme showed higher catalytic constants with gentisate or 1-hydroxy-2-naphthoate than with salicylate. It was therefore concluded that
P. salicylatoxidans
synthesized a gentisate 1,2-dioxygenase with an extraordinary substrate range, which also allowed the oxidation of salicylate.
Involvement of
hyp
Gene Products in Maturation of the H
2
-Sensing [NiFe] Hydrogenase of
Ralstonia eutropha
Authors: Buhrke Thorsten , Bleijlevens Boris , Albracht Simon P. J. , Friedrich Bärbel 
Published: July 2002

ABSTRACT

The biosynthesis of [NiFe] hydrogenases is a complex process that requires the function of the Hyp proteins HypA, HypB, HypC, HypD, HypE, HypF, and HypX for assembly of the H
2
-activating [NiFe] site. In this study we examined the maturation of the regulatory hydrogenase (RH) of
Ralstonia eutropha
. The RH is a H
2
-sensing [NiFe] hydrogenase and is required as a constituent of a signal transduction chain for the expression of two energy-linked [NiFe] hydrogenases. Here we demonstrate that the RH regulatory activity was barely affected by mutations in
hypA
,
hypB
,
hypC
, and
hypX
and was not substantially diminished in
hypD
- and
hypE
-deficient strains. The lack of HypF, however, resulted in a 90% decrease of the RH regulatory activity. Fourier transform infrared spectroscopy and the incorporation of
63
Ni into the RH from overproducing cells revealed that the assembly of the [NiFe] active site is dependent on all Hyp functions, with the exception of HypX. We conclude that the entire Hyp apparatus (HypA, HypB, HypC, HypD, HypE, and HypF) is involved in an efficient incorporation of the [NiFe] center into the RH.
Size Comparisons among Integral Membrane Transport Protein Homologues in
Bacteria
,
Archaea
, and
Eucarya
Authors: Chung Yong Joon , Krueger Christel , Metzgar David , Saier Milton H. 
Published: July 2002

ABSTRACT

Integral membrane proteins from over 20 ubiquitous families of channels, secondary carriers, and primary active transporters were analyzed for average size differences between homologues from the three domains of life:
Bacteria
,
Archaea
, and
Eucarya
. The results showed that while eucaryotic homologues are consistently larger than their bacterial counterparts, archaeal homologues are significantly smaller. These size differences proved to be due primarily to variations in the sizes of hydrophilic domains localized to the N termini, the C termini, or specific loops between transmembrane α-helical spanners, depending on the family. Within the
Eucarya
domain, plant homologues proved to be substantially smaller than their animal and fungal counterparts. By contrast, extracytoplasmic receptors of ABC-type uptake systems in
Archaea
proved to be larger on average than those of their bacterial homologues, while cytoplasmic enzymes from different organisms exhibited little or no significant size differences. These observations presumably reflect evolutionary pressure and molecular mechanisms that must have been operative since these groups of organisms diverged from each other.
Characterization of the Catalytic Activities of the PhoQ Histidine Protein Kinase of
Salmonella enterica
Serovar Typhimurium
Authors: Montagne Martin , Martel Alexandre , Le Moual Hervé 
Published: July 2002

ABSTRACT

Studies of
Escherichia coli
membranes that were highly enriched in the
Salmonella enterica
serovar Typhimurium PhoQ protein showed that the presence of ATP and divalent cations such as Mg
2+
, Mn
2+
, Ca
2+
, or Ba
2+
resulted in PhoQ autophosphorylation. However, when Mg
2+
or Mn
2+
was present at concentrations higher than 0.1 mM, the kinetics of PhoQ autophosphorylation were strongly biphasic, with a rapid autophosphorylation phase followed by a slower dephosphorylation phase. A fusion protein lacking the sensory and transmembrane domains retained the autokinase activity but could not be dephosphosphorylated when Mg
2+
or Mn
2+
was present at high concentrations. The instability of purified [
32
P]phospho-PhoP in the presence of PhoQ-containing membranes indicated that PhoQ also possesses a phosphatase activity. The PhoQ phosphatase activity was stimulated by increasing the Mg
2+
concentration. These data are consistent with a model in which Mg
2+
binding to the sensory domain of PhoQ coordinately regulates autokinase and phosphatase activities.
ς
B
Activity Depends on RsbU in
Staphylococcus aureus
Authors: Giachino P. , Engelmann S. , Bischoff M. 
Published: July 2002

ABSTRACT

Derivatives of the widely used laboratory strain
Staphylococcus aureus
NCTC8325, which are natural
rsbU
mutants, were shown to be unable to produce RsbU, a positive regulator of the alternative sigma factor ς
B
. The lack of RsbU prevented the heat-dependent production of ς
B
-controlled transcripts and resulted in reduced H
2
O
2
and UV tolerance, enhanced alpha-hemolysin activity, and the inability to produce the alkaline shock protein Asp23. After 48 h of growth,
rsbU
mutant strains failed to accumulate staphyloxanthin, the major stationary-phase carotenoid. Transcription of Asp23 was found to be exclusively controlled by ς
B
, making it an excellent target for the study of ς
B
activity in
S. aureus
. Reporter gene experiments, using the firefly luciferase gene (
luc
+) fused to the ς
B
-dependent promoter(s) of
asp23
, revealed that ς
B
is almost inactive in 8325 derivatives.
cis
complementation of the 8325 derivative BB255 with the wild-type
rsbU
gene from strain COL produced the
rsbU
+
derivative GP268, a strain possessing a ς
B
activity profile comparable to that of the
rsbU
+
wild-type strain Newman. In GP268, the heat inducibility of ς
B
-dependent genes, Asp23 production, alpha-hemolysin activity, pigmentation, and susceptibility to H
2
O
2
were restored to the levels observed in strain Newman, clearly demonstrating that RsbU is needed for activation of ς
B
in
S. aureus
.
The ATP-Dependent Lon Protease ofSalmonella entericaSerovar Typhimurium Regulates Invasion and Expression of Genes Carried onSalmonellaPathogenicity Island 1
Authors: Takaya Akiko , Tomoyasu Toshifumi , Tokumitsu Akane , Morioka Mizue , Yamamoto Tomoko 
Published: July 2002

ABSTRACTAn early step in the pathogenesis ofSalmonella entericaserovar Typhimurium infection is bacterial penetration of the intestinal epithelium. Penetration requires the expression of invasion genes found inSalmonellapathogenicity island 1 (SPI1). These genes are controlled in a complex manner by regulators in SPI1, including HilA and InvF, and those outside SPI1, such as two-component regulatory systems and small DNA-binding proteins. We report here that the expression of invasion genes and the invasive phenotype ofS. entericaserovar Typhimurium are negatively regulated by the ATP-dependent Lon protease, which is known to be a major contributor to proteolysis inEscherichia coli. A disrupted mutant oflonwas able to efficiently invade cultured epithelial cells and showed increased production and secretion of three identified SPI1 proteins, SipA, SipC, and SipD. Thelonmutant also showed a dramatic enhancement in transcription of the SPI1 geneshilA,invF,sipA, andsipC. The increases ranged from 10-fold to almost 40-fold. It is well known that the expression of SPI1 genes is also regulated in response to several environmental conditions. We found that the disruption oflondoes not abolish the repression ofhilAandsipCexpression by high-oxygen or low-osmolarity conditions, suggesting that Lon represses SPI1 gene expression by a regulatory pathway independent of these environmental signals. Since HilA is thought to function as a central regulator of SPI1 gene expression, it is speculated that Lon may regulate SPI1 gene expression by proteolysis of putative factors required for activation ofhilAexpression.
Phylogenetic Analysis Reveals Multiple Lateral Transfers of Adenosine-5′-Phosphosulfate Reductase Genes among Sulfate-Reducing Microorganisms
Authors: Friedrich Michael W. 
Published: July 2002

ABSTRACT

Lateral gene transfer affects the evolutionary path of key genes involved in ancient metabolic traits, such as sulfate respiration, even more than previously expected. In this study, the phylogeny of the adenosine-5′-phosphosulfate (APS) reductase was analyzed. APS reductase is a key enzyme in sulfate respiration present in all sulfate-respiring prokaryotes. A newly developed PCR assay was used to amplify and sequence a fragment (∼900 bp) of the APS reductase gene,
apsA
, from a taxonomically wide range of sulfate-reducing prokaryotes (
n
= 60). Comparative phylogenetic analysis of all obtained and available ApsA sequences indicated a high degree of sequence conservation in the region analyzed. However, a comparison of ApsA- and 16S rRNA-based phylogenetic trees revealed topological incongruences affecting seven members of the
Syntrophobacteraceae
and three members of the
Nitrospinaceae
, which were clearly monophyletic with gram-positive sulfate-reducing bacteria (SRB). In addition,
Thermodesulfovibrio islandicus
and
Thermodesulfobacterium thermophilum
,
Thermodesulfobacterium commune
, and
Thermodesulfobacterium hveragerdense
clearly branched off between the radiation of the δ-proteobacterial gram-negative SRB and the gram-positive SRB and not close to the root of the tree as expected from 16S rRNA phylogeny. The most parsimonious explanation for these discrepancies in tree topologies is lateral transfer of
apsA
genes across bacterial divisions. Similar patterns of insertions and deletions in ApsA sequences of donor and recipient lineages provide additional evidence for lateral gene transfer. From a subset of reference strains (
n
= 25), a fragment of the dissimilatory sulfite reductase genes (
dsrAB
), which have recently been proposed to have undergone multiple lateral gene transfers (M. Klein et al., J. Bacteriol. 183:6028–6035, 2001), was also amplified and sequenced. Phylogenetic comparison of DsrAB- and ApsA-based trees suggests a frequent involvement of gram-positive and thermophilic SRB in lateral gene transfer events among SRB.
Energetics of
Helicobacter pylori
and Its Implications for the Mechanism of Urease-Dependent Acid Tolerance at pH 1
Authors: Stingl Kerstin , Uhlemann Eva-Maria , Schmid Roland , Altendorf Karlheinz , Bakker Evert P. 
Published: July 2002

ABSTRACT

In the presence of urea the neutrophilic human pathogen
Helicobacter pylori
survives for several hours at pH 1 with concomitant cytoplasmic pH homeostasis. To study this effect in detail, the transmembrane proton motive force and cytoplasmic urease activity of
H. pylori
were determined at various pH values. In the absence of urea, the organism maintained a close-to-neutral cytoplasm and an internally negative membrane potential at external pH values greater than 4 to 5. In the presence of urea,
H. pylori
accomplished cytoplasmic pH homeostasis down to an external pH of 1.2. At this external pH, the cytoplasmic pH was 4.9 and the membrane potential was slightly negative inside. The latter finding is in contrast to the situation in acidophiles, which develop inside-positive membrane potentials under similar conditions. Measurements of the time course of the membrane potential confirmed that addition of urea to the cells led to hyperpolarization. Most likely, this effect was due to electrogenic export of ammonium cations from the cytoplasm. The urease activity of intact cells increased nearly exponentially with decreasing external pH. This activation was not due to enhanced gene expression at low external pH values. In cell extracts the pH optimum of urease activity was dependent on the buffer system and was about pH 5 in sodium citrate buffer. Since this is the cytoplasmic pH of the cells at pH 1 to 2, we propose that cytoplasmic pH is a factor in the in vivo activation of the urease at low external pH values. The mechanism by which urease activity leads to cytoplasmic pH homeostasis in
H. pylori
is discussed.
Identification of Two Quorum-Sensing Systems in
Sinorhizobium meliloti
Authors: Marketon Melanie M. , González Juan E. 
Published: July 2002

ABSTRACT

Sinorhizobium meliloti
is a free-living soil bacterium which is capable of establishing a symbiotic relationship with the alfalfa plant (
Medicago sativa
). This symbiosis involves a network of bacterium-host signaling, as well as the potential for bacterium-bacterium communication, such as quorum sensing. In this study, we characterized the production of
N
-acyl homoserine lactones (AHLs) by two commonly used
S. meliloti
strains, AK631 and Rm1021. We found that AK631 produces at least nine different AHLs, while Rm1021 produces only a subset of these molecules. To address the difference in AHL patterns between the strains, we developed a novel screening method to identify the genes affecting AHL synthesis. With this screening method, chromosomal
groEL
(
groELc
) was shown to be required for synthesis of the AHLs that are unique to AK631 but not for synthesis of the AHLs that are made by both AK631 and Rm1021. We then used the screening procedure to identify a mutation in a gene homologous to
traM
of
Agrobacterium tumefaciens
, which was able to suppress the phenotype of the
groELc
mutation. A
traR
homolog was identified immediately upstream of
traM
, and we propose that its gene product requires a functional
groELc
for activity and is also responsible for inducing the synthesis of the AHLs that are unique to AK631. We show that the
traR
/
traM
locus is part of a quorum-sensing system unique to AK631 and propose that this locus is involved in regulating conjugal plasmid transfer. We also present evidence for the existence of a second quorum-sensing system,
sinR
/
sinI
, which is present in both AK631 and Rm1021.
Genetic Evidence that the
uvsE
Gene Product of
Deinococcus radiodurans
R1 Is a UV Damage Endonuclease
Authors: Earl Ashlee M. , Rankin Sara K. , Kim Kwang-Pyo , Lamendola Oleana N. , Battista John R. 
Published: July 2002

ABSTRACT

An in vitro transposition system, developed to facilitate gene disruption in
Deinococcus radiodurans
R1, has been used to inactivate the gene designated
dr1819
in

uvrA-1
+

and
uvrA-1
backgrounds.
dr1819
encodes a protein with homology to a UV DNA damage endonuclease expressed by
Schizosaccharomyces pombe
. Interruption of
dr1819
greatly sensitizes the
uvrA-1
strain but not the

uvrA-1
+

strain to UV light, indicating that the
dr1819
gene product is a component in a DNA repair pathway that can compensate for the loss of nucleotide excision repair in this species. Clones of
dr1819
will restore UV resistance to UVS78, a
uvrA-1 uvsE
strain, indicating that
dr1819
and
uvsE
are the same locus.
Whole-Genome Analysis of Genes Regulated by theBacillus subtilisCompetence Transcription Factor ComK
Authors: Ogura Mitsuo , Yamaguchi Hirotake , Kobayashi Kazuo , Ogasawara Naotake , Fujita Yasutaro , Tanaka Teruo 
Published: July 2002

ABSTRACTTheBacillus subtiliscompetence transcription factor ComK is required for establishment of competence for genetic transformation. In an attempt to study the ComK factor further, we explored the genes regulated by ComK using the DNA microarray technique. In addition to the genes known to be dependent on ComK for expression, we found many genes or operons whose ComK dependence was not known previously. Among these genes, we confirmed the ComK dependence of 16 genes by usinglacZfusions, and three genes were partially dependent on ComK. Transformation efficiency was significantly reduced in ansmfdisruption mutant, although disruption of the other ComK-dependent genes did not result in significant decreases in transformation efficiency. Nucleotide sequences similar to that of the ComK box were found for most of the newly discovered genes regulated by ComK.
GranulicatellaandAbiotrophiaSpecies from Human Clinical Specimens
Authors: Christensen Jens Jørgen , Facklam Richard R. 
Published: July 2002

ABSTRACTOne hundred one isolates of nutritionally variant streptococci from 97 patients were phenotypically characterized and compared with the type strains ofGranulicatella adiacens(formerlyAbiotrophia adiacens) (ATCC 49175T)Abiotrophia defectiva(ATCC 49176T), andGranulicatella elegans(formerlyAbiotrophia elegans) (DSM 11693T). Of the isolates, 55 and 43 resembledG.adiacensandA.defectiva, respectively, while 3 strains resembledG.elegans. Phenotypic characteristics useful in differentiating between species within the generaGranulicatellaandAbiotrophia(G.adiacens,G.elegans,Granulicatella balaenopterae, andA.defectiva) were production of α- and β-galactosidase; production of β-glucuronidase; hippurate hydrolysis; arginine dihydrolase activity; and acid production from trehalose, sucrose, pullulan, and tagatose. From the reports submitted with the specimens, the clinical diagnosis was endocarditis in 58% of patients and septicemia or bacteremia in 26% of patients.
Evaluation of ColorPAC
Giardia/Cryptosporidium
Rapid Assay and ProSpecT
Giardia/Cryptosporidium
Microplate Assay for Detection of
Giardia
and
Cryptosporidium
in Fecal Specimens
Authors: Katanik M. T. , Schneider S. K. , Rosenblatt J. E. , Hall G. S. , Procop G. W. 
Published: July 2002

ABSTRACT

Detection of
Giardia
and
Cryptosporidium
in clinical stool specimens using the ColorPAC and ProSpecT enzyme immunoassays revealed 98.7% agreement for
Giardia
detection and 98.1% agreement for
Cryptosporidium
detection. Sensitivities were uniformly 100%. The specificities of the ColorPAC immunoassay for
Giardia
and
Cryptosporidium
detection were 100 and 99.5%, respectively, and those for the ProSpecT assay were 98.4 and 98.6%, respectively. The false-positive reactions with the ProSpecT assay occurred with specimens that were grossly bloody.
Relatedness of
Streptococcus suis
Isolates of Various Serotypes and Clinical Backgrounds as Evaluated by Macrorestriction Analysis and Expression of Potential Virulence Traits
Authors: Allgaier Achim , Goethe Ralph , Wisselink Henk J. , Smith Hilde E. , Valentin-Weigand Peter 
Published: July 2002

ABSTRACT

We evaluated the genetic diversity of
Streptococcus suis
isolates of different serotypes by macrorestriction analysis and elucidated possible relationships between the genetic background, expression of potential virulence traits, and source of isolation. Virulence traits included expression of serotype-specific polysaccharides, muramidase-released protein (MRP), extracellular protein factor (EF), hemolysin activity, and adherence to epithelial cells. Macrorestriction analysis of streptococcal DNA digested with restriction enzymes
Sma
I and
Apa
I allowed differentiation of single isolates that could be assigned to four major clusters, named A1, A2, B1, and B2. Comparison of the genotypic and phenotypic features of the isolates with their source of isolation showed that (i) the
S. suis
population examined, which originated mainly from German pigs, exhibited a genetic diversity and phenotypic patterns comparable to those found for isolates from other European countries; (ii) certain phenotypic features, such as the presence of capsular antigens of serotypes 2, 1, and 9, expression of MRP and EF, and hemolysin activity (and in particular, combinations of these features), were strongly associated with the clinical background of meningitis and septicemia; and (iii) isolates from pigs with meningitis and septicemia showed a significantly higher degree of genetic homogeneity compared to that for isolates from pigs with pneumonia and healthy pigs. Since the former isolates are considered highly virulent, this supports the theory of a clonal relationship among highly virulent strains.
Detection and Heterogeneity of Herpesviruses Causing Pacheco's Disease in Parrots
Authors: Tomaszewski Elizabeth , Wilson Van G. , Wigle William L. , Phalen David N. 
Published: July 2002

ABSTRACT
Pacheco's disease (PD) is a common, often fatal, disease of parrots. We cloned a virus isolate from a parrot that had characteristic lesions of PD. Three viral clones were partially sequenced, demonstrating that this virus was an alphaherpesvirus most closely related to the gallid herpesvirus 1. Five primer sets were developed from these sequences. The primer sets were used with PCR to screen tissues or tissue culture media suspected to contain viruses from 54 outbreaks of PD. The primer sets amplified DNA from all but one sample. Ten amplification patterns were detected, indicating that PD is caused by a genetically heterogeneous population of viruses. A single genetic variant (psittacid herpesvirus variant 1) amplified with all primer sets and was the most common virus variant (62.7%). A single primer set (23F) amplified DNA from all of the positive samples, suggesting that PCR could be used as a rapid postmortem assay for these viruses. PCR was found to be significantly more sensitive than tissue culture for the detection of psittacid herpesviruses.