bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Mutant Form of the
Neisseria gonorrhoeae
Pilus Secretin Protein PilQ Allows Increased Entry of Heme and Antimicrobial Compounds
Authors: Chen Ching-ju , Tobiason Deborah M. , Thomas Christopher E. , Shafer William M. , Seifert H. Steven , Sparling P. Frederick 
Published: January 2004

ABSTRACT

A spontaneous point mutation in
pilQ
(
pilQ1
) resulted in phenotypic suppression of a hemoglobin (Hb) receptor mutant (
hpuAB
mutant), allowing gonococci to grow on Hb as the sole source of iron. PilQ, formerly designated OMP-MC, is a member of the secretin family of proteins located in the outer membrane and is required for pilus biogenesis. The
pilQ1
mutant also showed decreased piliation and transformation efficiency. Insertional inactivation of
pilQ1
resulted in the loss of the Hb utilization phenotype and decreased entry of free heme. Despite the ability of the
pilQ1
mutant to use Hb for iron acquisition and porphyrin, there was no demonstrable binding of Hb to the cell surface. The
pilQ1
mutant was more sensitive to the toxic effect of free heme in growth medium and hypersensitive to the detergent Triton X-100 and multiple antibiotics. Double mutation in
pilQ1
and
tonB
had no effect on these phenotypes, but a double
pilQ1 pilT
mutant showed a reduction in Hb-dependent growth and decreased sensitivity to heme and various antimicrobial agents. Insertional inactivation of wild-type
pilQ
also resulted in reduced entry of heme, Triton X-100, and some antibiotics. These results show that PilQ forms a channel that allows entry of heme and certain antimicrobial compounds and that a gain-of function point mutation in
pilQ
results in TonB-independent, PilT-dependent increase of entry.
Rhodobacter capsulatus nifA1
Promoter: High-GC −10 Regions in High-GC Bacteria and the Basis for Their Transcription
Authors: Richard Cynthia L. , Tandon Animesh , Kranz Robert G. 
Published: January 2004

ABSTRACT

It was previously shown that the
Rhodobacter capsulatus
NtrC enhancer-binding protein activates the
R. capsulatus
housekeeping RNA polymerase but not the
Escherichia coli
RNA polymerase at the
nifA1
promoter. We have tested the hypothesis that this activity is due to the high G+C content of the −10 sequence. A comparative analysis of
R. capsulatus
and other α-proteobacterial promoters with known transcription start sites suggests that the G+C content of the −10 region is higher than that for
E. coli
. Both in vivo and in vitro results obtained with
nifA1
promoters with −10 and/or −35 variations are reported here. A major conclusion of this study is that α-proteobacteria have evolved a promiscuous sigma factor and core RNA polymerase that can transcribe promoters with high-GC −10 regions in addition to the classic
E. coli
Pribnow box. To facilitate studies of
R. capsulatus
transcription, we cloned and overexpressed all of the RNA polymerase subunits in
E. coli
, and these were reconstituted in vitro to form an active, recombinant
R. capsulatus
RNA polymerase with properties mimicking those of the natural polymerase. Thus, no additional factors from
R. capsulatus
are necessary for the recognition of high-GC promoters or for activation by
R. capsulatus
NtrC. The addition of
R. capsulatus
σ
70
to the
E. coli
core RNA polymerase or the use of −10 promoter mutants did not facilitate
R. capsulatus
NtrC activation of the
nifA1
promoter by the
E. coli
RNA polymerase. Thus, an additional barrier to activation by
R. capsulatus
NtrC exists, probably a lack of the proper
R. capsulatus
NtrC-
E. coli
RNA polymerase (protein-protein) interaction(s).
The RecA Protein ofHelicobacter pyloriRequires a Posttranslational Modification for Full Activity
Authors: Fischer Wolfgang , Haas Rainer 
Published: January 2004

ABSTRACTThe RecA protein is a central component of the homologous recombination machinery and of the SOS system in most bacteria. In performing these functions, it is involved in DNA repair processes and plays an important role in natural transformation competence. This may be especially important inHelicobacter pylori, where an unusually high degree of microdiversity among strains is generated by homologous recombination. We have suggested previously that theH. pyloriRecA protein is subject to posttranslational modifications that result in a slight shift in its electrophoretic mobility. Here we show that at least two genes downstream ofrecAare involved in this modification and that this process is dependent on genes involved in glycosylation and lipopolysaccharide biosynthesis. Site-directed mutagenesis of a putative glycosylation site results in production of an unmodified RecA protein. This posttranslational modification is not involved in membrane targeting or cell division functions but is necessary for the full function of RecA in DNA repair. Thus, it might be an adaptation to the specific requirements ofH. pyloriin its natural environment.
A Predicted ABC Transporter, FtsEX, Is Needed for Cell Division in
Escherichia coli
Authors: Schmidt Kari L. , Peterson Nicholas D. , Kustusch Ryan J. , Wissel Mark C. , Graham Becky , Phillips Gregory J. , Weiss David S. 
Published: January 2004

ABSTRACT

FtsE and FtsX have homology to the ABC transporter superfamily of proteins and appear to be widely conserved among bacteria. Early work implicated FtsEX in cell division in
Escherichia coli
, but this was subsequently challenged, in part because the division defects in
ftsEX
mutants are often salt remedial. Strain RG60 has an
ftsE
::
kan
null mutation that is polar onto
ftsX
. RG60 is mildly filamentous when grown in standard Luria-Bertani medium (LB), which contains 1% NaCl, but upon shift to LB with no NaCl growth and division stop. We found that FtsN localizes to potential division sites, albeit poorly, in RG60 grown in LB with 1% NaCl. We also found that in wild-type
E. coli
both FtsE and FtsX localize to the division site. Localization of FtsX was studied in detail and appeared to require FtsZ, FtsA, and ZipA, but not the downstream division proteins FtsK, FtsQ, FtsL, and FtsI. Consistent with this, in media lacking salt, FtsA and ZipA localized independently of FtsEX, but the downstream proteins did not. Finally, in the absence of salt, cells depleted of FtsEX stopped dividing before any change in growth rate (mass increase) was apparent. We conclude that FtsEX participates directly in the process of cell division and is important for assembly or stability of the septal ring, especially in salt-free media.
Reduced Transaminase B (IlvE) Activity Caused by the Lack ofyjgFIs Dependent on the Status of Threonine Deaminase (IlvA) inSalmonella entericaSerovar Typhimurium
Authors: Schmitz George , Downs Diana M. 
Published: January 2004

ABSTRACTThe YjgF/YER057c/UK114 family is a highly conserved class of proteins that is represented in the three domains of life. Thus far, a biochemical function demonstrated for these proteins in vivo or in vitro has yet to be defined. In several organisms, strains lacking a YjgF homolog have a defect in branched-chain amino acid biosynthesis. This study probes the connection betweenyjgFand isoleucine biosynthesis inSalmonella enterica.In strains lackingyjgFthe specific activity of transaminase B, catalyzing the last step in the synthesis of isoleucine, was reduced. In the absence ofyjgF, transaminase B activity could be restored by inhibiting threonine deaminase, the first enzymatic step in isoleucine biosynthesis. Strains lackingyjgFshowed an increased sensitivity to sulfometruron methyl, a potent inhibitor of acetolactate synthase. Based on work described here and structural reports in the literature, we suggest a working model in which YjgF has a role in protecting the cell from toxic effects of imbalanced ketoacid pools.
The
trans
-Acting Protein Interacting with the DNA Motif Proximal to the Transcriptional Start Site of Plant
l
-Asparaginase Is Bacterial Sarcosine Oxidase
Authors: Jones William T. , Al-Samarrai Taha , Reeves Janice M. , Ryan Gordon B. , Kirk Christopher A. , Vincze Eva , Harvey Dawn , McCambridge Marie , Greenwood David , Reynolds Paul H. S. 
Published: January 2004

ABSTRACT

A
trans
-acting protein interacting with a specific sequence motif proximal to the transcriptional start site of the
l
-asparaginase promoter has been observed previously (E. Vincze, J. M. Reeves, E. Lamping, K. J. F. Farnden, and P. H. S. Reynolds, Plant Mol. Biol. 26:303-311, 1994). Gel retardation experiments in which protein extracts of
Mesorhizobium loti
and developing nodules were used suggested a bacterial origin for the repressor binding protein (
rep2037
). Nodulation tests were performed by using different Fix
−
Tn
5
mutants of
M. loti.
Analyses of these mutants revealed a correlation between the presence of
Mesorhizobium
in the nodule-like structures and the ability of nodule protein extracts to bind the repressor binding domain (RBD). Through the use of mutated RBD sequences, the RBD sequence was identified as CTAAAAT. The repressor protein was isolated from
M. loti
NZP2037 by multiple chromatographic procedures and affinity separation by using concatemers of RBD attached to magnetic beads. Sequencing of the recovered protein resulted in identification of the repressor protein as the sarcosine oxidase α subunit. This was confirmed by expression of the gene encoding the
M. loti
α subunit of sarcosine oxidase in
Escherichia coli.
When the expressed peptide was bound to RBD, the gel retardation result was identical to the result obtained with
rep2037
from
M. loti
strain NZP2037.
Regulation of the Tryptophan Biosynthetic Genes in
Bacillus halodurans
: Common Elements but Different Strategies than Those Used by
Bacillus subtilis
Authors: Szigeti Reka , Milescu Mirela , Gollnick Paul 
Published: January 2004

ABSTRACT

In
Bacillus subtilis
, an RNA binding protein called TRAP regulates both transcription and translation of the tryptophan biosynthetic genes.
Bacillus halodurans
is an alkaliphilic
Bacillus
species that grows at high pHs. Previous studies of this bacterium have focused on mechanisms of adaptation for growth in alkaline environments. We have characterized the regulation of the tryptophan biosynthetic genes in
B. halodurans
and compared it to that in
B. subtilis. B. halodurans
encodes a TRAP protein with 71% sequence identity to the
B. subtilis
protein. Expression of anthranilate synthetase, the first enzyme in the pathway to tryptophan, is regulated significantly less in
B. halodurans
than in
B. subtilis
. Examination of the control of the
B. halodurans trpEDCFBA
operon both in vivo and in vitro shows that only transcription is regulated, whereas in
B. subtilis
both transcription of the operon and translation of
trpE
are controlled. The attenuation mechanism that controls transcription in
B. halodurans
is similar to that in
B. subtilis
, but there are some differences in the predicted RNA secondary structures in the
B. halodurans trp
leader region, including the presence of a potential anti-antiterminator structure. Translation of
trpG
, which is within the folate operon in both bacilli, is regulated similarly in the two species.
Binding of SycH Chaperone to YscM1 and YscM2 Activates Effector
yop
Expression in
Yersinia enterocolitica
Authors: Cambronne Eric D. , Sorg Joseph A. , Schneewind Olaf 
Published: January 2004

ABSTRACT

Yersinia enterocolitica
transports YscM1 and YscM2 via the type III pathway, a mechanism that is required for the establishment of bacterial infections. Prior to host cell contact, YscM1 and YscM2 exert posttranscriptional regulation to inhibit expression of effector
yop
genes, which encode virulence factors that travel the type III pathway into the cytoplasm of macrophages. Relief from repression has been predicted to occur via the type III secretion of YscM1 and YscM2 into the extracellular medium, resulting in the depletion of regulatory molecules from the bacterial cytoplasm. Using digitonin fractionation and fluorescence microscopy of FlAsH-labeled polypeptides in
Yersinia
-infected cells, we have localized YscM1 and YscM2 within the host cell cytoplasm. Type III injection of YscM1 and YscM2 required the SycH chaperone. Expression of C-terminal fusions of YscM1 and YscM2 to the neomycin phosphotransferase reporter revealed sequences required for regulatory activity and for secretion in the absence of SycH. Coexpression of SycH and glutathione
S
-transferase (GST)-YscM1 or GST-YscM2, hybrid GST variants that cannot be transported by the type III apparatus, also relieved repression of Yop synthesis. GST-SycH bound to YscM1 and YscM2 and activated effector
yop
expression without initiation of the bound regulatory molecules into the type III pathway. Further, regulation of
yop
expression by YscM1, YscM2, and SycH is shown to act independently of factors that regulate secretion, and gel filtration chromotography revealed populations of YscM1 and YscM2 that are not bound to SycH under conditions where Yop synthesis is repressed. Taken together, these results suggest that YscM1- and YscM2-mediated repression may be relieved through binding to the cytoplasmic chaperone SycH prior to their type III injection into host cells.
Regulation ofl-Alanine Dehydrogenase inRhizobium leguminosarumbv.viciaeand Its Role in Pea Nodules
Authors: Lodwig Emma , Kumar Shalini , Allaway David , Bourdes Alex , Prell Jürgen , Priefer Ursula , Poole Philip 
Published: January 2004

ABSTRACTAlanine dehydrogenase (AldA) is the principal enzyme with which pea bacteroids synthesize alanine de novo. In free-living culture, AldA activity is induced by carboxylic acids (succinate, malate, and pyruvate), although the best inducer is alanine. Measurement of the intracellular concentration of alanine showed that AldA contributes to net alanine synthesis in laboratory cultures. Divergently transcribed fromaldAis an AsnC type regulator,aldR.Mutation ofaldRprevents induction of AldA activity. Plasmid-bornegusAfusions showed thataldRis required for transcription of bothaldAandaldR; hence, AldR is autoregulatory. However, plasmid fusions containing thealdA-aldRintergenic region could apparently titrate out AldR, sometimes resulting in a complete loss of AldA enzyme activity. Therefore, integratedaldR::gusAandaldA::gusAfusions, as well as Northern blotting, were used to confirm the induction ofaldAactivity. BothaldAandaldRwere expressed in the II/III interzone and zone III of pea nodules. Overexpression ofaldAin bacteroids did not alter the ability of pea plants to fix nitrogen, as measured by acetylene reduction, but caused a large reduction in the size and dry weight of plants. This suggests that overexpression ofaldAimpairs the ability of bacteroids to donate fixed nitrogen that the plant can productively assimilate. We propose that the role of AldA may be to balance the alanine level for optimal functioning of bacteroid metabolism rather than to synthesize alanine as the sole product of N2reduction.
The Left End of IS
2
: a Compromise between Transpositional Activity and an Essential Promoter Function That Regulates the Transposition Pathway
Authors: Lewis Leslie A. , Cylin Edruge , Lee Ho Kyung , Saby Robert , Wong Wilson , Grindley Nigel D. F. 
Published: January 2004

ABSTRACT

Cut-and-paste (simple insertion) and replicative transposition pathways are the two classical paradigms by which transposable elements are mobilized. A novel variation of cut and paste, a two-step transposition cycle, has recently been proposed for insertion sequences of the IS
3
family. In IS
2
this variation involves the formation of a circular, putative transposition intermediate (the minicircle) in the first step. Two aspects of the minicircle may involve its proposed role in the second step (integration into the target). The first is the presence of a highly reactive junction formed by the two abutted ends of the element. The second is the assembly at the minicircle junction of a strong hybrid promoter which generates higher levels of transposase. In this report we show that IS
2
possesses a highly reactive minicircle junction at which a strong promoter is assembled and that the promoter is needed for the efficient completion of the pathway. We show that the sequence diversions which characterize the imperfect inverted repeats or ends of this element have evolved specifically to permit the formation and optimal function of this promoter. While these sequence diversions eliminate catalytic activity of the left end (IRL) in the linear element, sufficient sequence information essential for catalysis is retained by the IRL in the context of the minicircle junction. These data confirm that the minicircle is an essential intermediate in the two-step transposition pathway of IS
2
.
Transcriptional Profiling of Colicin-Induced Cell Death ofEscherichia coliMG1655 Identifies Potential Mechanisms by Which Bacteriocins Promote Bacterial Diversity
Authors: Walker Daniel , Rolfe Matthew , Thompson Arthur , Moore Geoffrey R. , James Richard , Hinton Jay C. D. , Kleanthous Colin 
Published: January 2004

ABSTRACTWe report the transcriptional response ofEscherichia coliMG1655 to damage induced by colicins E3 and E9, bacteriocins that kill cells through inactivation of the ribosome and degradation of chromosomal DNA, respectively. Colicin E9 strongly induced the LexA-regulated SOS response, while colicin E3 elicited a broad response that included the induction of cold shock genes, symptomatic of translational arrest. Colicin E3 also increased the transcription of cryptic prophage genes and other laterally acquired mobile elements. The transcriptional responses to both these toxins suggest mechanisms that may promote genetic diversity inE. colipopulations, pointing to a more general role for colicins in adaptive bacterial physiology than has hitherto been realized.
DNA Binding by the Meningococcal RdgC Protein, Associated with Pilin Antigenic Variation
Authors: Moore Timothy , Sharples Gary J. , Lloyd Robert G. 
Published: January 2004

ABSTRACT

The RdgC protein of
Neisseria gonorrhoeae
is required for efficient pilin antigenic variation, although its precise role has yet to be established. We demonstrate that the nearly identical RdgC from
Neisseria meningitidis
binds DNA with little specificity for sequence or structure, like the
Escherichia coli
protein. We also show that neither protein is able to constrain torsional tension in relaxed DNA. These data exclude several possible roles for RdgC in pilin antigenic variation and suggest that RdgC performs a similar function in both
E. coli
and the
Neisseria
spp.
Inhibiting Cell Division in
Escherichia coli
Has Little If Any Effect on Gene Expression
Authors: Arends S. J. Ryan , Weiss David S. 
Published: January 2004

ABSTRACT

DNA microarrays were used to compare gene expression in dividing and nondividing (filamentous) cultures of
Escherichia coli
. Although cells from these cultures differed profoundly in morphology, their gene expression profiles were nearly identical. These results extend previous evidence that there is no division checkpoint in
E. coli
, and progression through the cell cycle is not regulated by the transcription of different genes during different parts of the cell cycle.
Expression of
Vibrio vulnificus
Capsular Polysaccharide Inhibits Biofilm Formation
Authors: Joseph Lavin A. , Wright Anita C. 
Published: January 2004

ABSTRACT

Vibrio vulnificus
is a human pathogen that produces lethal septicemia in susceptible persons, and the primary virulence factor for this organism is capsular polysaccharide (CPS). The role of the capsule in
V. vulnificus
biofilms was examined under a variety of conditions, by using either defined CPS mutants or spontaneous CPS expression phase variants derived from multiple strains. CPS expression was shown to inhibit attachment and biofilm formation, which contrasted with other studies describing polysaccharides as integral to biofilms in related species.
New directions for flashbulb memories: comments on the ACP Special Issue
Authors: Neisser Ulric 
Published: January 2004

AbstractThis commentary briefly addresses each of the ten papers in the special issue. The commentator's assessment is mixed: some of the papers seem to represent little or no advance, while others open up whole new areas of research. A number of concepts new to this area are introduced, including event memory (which was probably biased by extensive media coverage), expressive writing (which may have helped at least some participants deal with the stresses of 9/11), and the subjective probabilities of success and failure (which may have been temporarily shifted across whole populations). Copyright © 2003 John Wiley & Sons, Ltd.
Evidence for the differential impact of time and emotion on personal and event memories for September 11, 2001
Authors: Smith Marilyn C. , Bibi Uri , Sheard D. Erin 
Published: January 2004

AbstractOne week and six months following 9/11, University of Toronto students completed a questionnaire that assessed memory for that day's events. Questions assessed personal autobiographical information and event‐related information. Recently, Pezdek (2003) reported that ‘flash‐bulb memories’ for event and autobiographical information varied with the extent of participant involvement: as emotional involvement increased, event memory improved whereas autobiographical memory declined. This dichotomy was further explored in this study with a Canadian sample, a group expected to be less personally involved in the events. In accordance with Pezdek's hypothesis, the consistency of recall was better for autobiographical information than for event information. The two types of memories were also differentially affected by (1) emotion: event memory was better for those who experienced higher levels of emotion, whereas autobiographical memory was unaffected by emotion; and (2) the passage of time: over the six‐month interval, the accuracy of event memory declined, whereas the number of personal information details actually increased. Copyright © 2003 John Wiley & Sons, Ltd.
Delay related changes in personal memories for September 11, 2001
Authors: Lee Peter James , Brown Norman R. 
Published: January 2004

AbstractThis study examined delay related changes of people's recollections for 11th September 2001. 1481 participants were surveyed 4–24 hours or 10 days after the event. 142 participants were re‐tested in April, 2002. Test‐retest consistency was low after seven months (66.5%). Word counts for open ended descriptions revealed that people wrote significantly more contextual information 10 days after the event than respondents had on 11th or 12th September although no difference was found for retest participants 7 months later. Ratings for emotional reaction decreased monotonically over time. These results suggest early indexing may be a critical factor if the amount of information reported, type of information reported, or level of affect is a research issue. However, test‐retest consistency was not influenced by the ten day delay in indexing. Copyright © 2003 John Wiley & Sons, Ltd.