bluuebunny/crossref_metadata_2025_split huggingface dataset:
Signal Transduction Cascade for Regulation of RpoS: Temperature Regulation of DsrA
Authors: Repoila F. , Gottesman S. 
Published: July 2002

ABSTRACT

Many environmental parameters modulate the amount of the RpoS sigma factor in
Escherichia coli
. Temperature control of RpoS depends on the untranslated RNA DsrA. DsrA activates RpoS translation by pairing with the leader of the mRNA. We find that temperature affects both the rate of transcription initiation of the
dsrA
gene and the stability of DsrA RNA. Both are increased at low temperature (25°C) compared to 37 or 42°C. The combination of these results is 25-fold-less DsrA at 37°C and 30-fold less at 42°C than at 25°C. Using an adapted
lacZ
-based reporter system, we show that temperature control of transcription initiation of
dsrA
requires only the minimal promoter of 36 bp. Overall, transcription responses to temperature lead to a sixfold increase in DsrA synthesis at 25°C over that at 42°C. Furthermore, two activating regions and a site for LeuO negative regulation were identified in the
dsrA
promoter. The activating regions also activate transcription in vitro. DsrA decays with a half-life of 23 min at 25°C and 4 min at 37 and 42°C. These results demonstrate that the
dsrA
promoter and the stability of DsrA RNA are the thermometers for RpoS temperature sensing. Multiple inputs to DsrA accumulation allow sensitive modulation of changes in the synthesis of the downstream targets of DsrA such as RpoS.
Energy-Dependent Conformational Change in the TolA Protein ofEscherichia coliInvolves Its N-Terminal Domain, TolQ, and TolR
Authors: Germon Pierre , Ray Marie-Céline , Vianney Anne , Lazzaroni Jean Claude 
Published: July 2002

ABSTRACTTolQ, TolR, and TolA inner membrane proteins ofEscherichia coliare involved in maintaining the stability of the outer membrane. They share homology with the ExbB, ExbD, and TonB proteins, respectively. The last is involved in energy transduction between the inner and the outer membrane, and its conformation has been shown to depend on the presence of the proton motive force (PMF), ExbB, and ExbD. Using limited proteolysis experiments, we investigated whether the conformation of TolA was also affected by the PMF. We found that dissipation of the PMF by uncouplers led to the formation of a proteinase K digestion fragment of TolA not seen when uncouplers are omitted. This fragment was also detected in ΔtolQ, ΔtolR,andtolA(H22P) mutants but, in contrast to the parental strain, was also seen in the absence of uncouplers. We repeated those experiments in outer membrane mutants such aslpp,pal,and Δrfamutants: the behavior of TolA inlppmutants was similar to that observed with the parental strain. However, the proteinase K-resistant fragment was never detected in the Δrfamutant. Altogether, these results suggest that TolA is able to undergo a PMF-dependent change of conformation. This change requires TolQ, TolR, and a functional TolA N-terminal domain. The potential role of this energy-dependent process in the stability of the outer membrane is discussed.
A Program of
Yersinia enterocolitica
Type III Secretion Reactions Is Activated by Specific Signals
Authors: Lee Vincent T. , Mazmanian Sarkis K. , Schneewind Olaf 
Published: July 2002

ABSTRACT

Successful establishment of
Yersinia
infections requires the type III machinery, a protein transporter that injects virulence factors (Yops) into macrophages. It is reported here that the
Yersinia
type III pathway responds to environmental signals by transporting proteins to distinct locations.
Yersinia enterocolitica
cells sense an increase in extracellular amino acids (glutamate, glutamine, aspartate, and asparagine) that results in the activation of the type III pathway. Another signal, provided by serum proteins such as albumin, triggers the secretion of YopD into the extracellular medium. The third signal, a decrease in calcium concentration, appears to be provided by host cells and causes
Y. enterocolitica
to transport YopE and presumably other virulence factors across the eukaryotic plasma membrane. Mutations in several genes encoding regulatory molecules (
lcrG
,
lcrH
,
tyeA
,
yopD
,
yopN
,
yscM1
, and
yscM2
) bypass the signal requirement of the type III pathway. Together these results suggest that yersiniae may have evolved distinct secretion reactions in response to environmental signals.
Killing Effect and Antitoxic Activity of the
Leptospira interrogans
Toxin-Antitoxin System in
Escherichia coli
Authors: Picardeau Mathieu , Ren Shuangxi , Saint Girons Isabelle 
Published: July 2002

ABSTRACT

We report the first evidence of a chromosome-encoded toxin-antitoxin locus in spirochetes. This locus has been found in the pathogenic spirochete
Leptospira interrogans
and exhibits homologies with the
pem
/
chp
loci. The
L. interrogans chp
locus consists of two genes:
chpK
(for “killer protein”) and its upstream partner
chpI
(for “inhibitory protein”). Expression of ChpK in
Escherichia coli
results in the inhibition of bacterial growth. The coexpression of ChpI neutralizes ChpK toxicity. By Southern blot analysis,
chp
homologs were found in all representative pathogenic strains of
L. interrogans
.
IS
186
Insertion at a Hot Spot in the
lon
Promoter as a Basis for Lon Protease Deficiency of
Escherichia coli
B: Identification of a Consensus Target Sequence for IS
186
Transposition
Authors: SaiSree L. , Reddy Manjula , Gowrishankar J. 
Published: July 2002

ABSTRACT

The radiation sensitivity of
Escherichia coli
B was first described more than 50 years ago, and the genetic locus responsible for the trait was subsequently identified as
lon
(encoding Lon protease). We now show that both
E. coli
B and the first reported
E. coli
K-12
lon
mutant, AB1899, carry IS
186
insertions in opposite orientations at a single site in the
lon
promoter region and that this site represents a natural hot spot for transposition of the insertion sequence (IS) element. Our analysis of deposited sequence data for a number of other IS
186
insertion sites permitted the deductions that (i) the consensus target site sequence for IS
186
transposition is 5′-(G)
≥4
(N)
3–6
(C)
≥4
-3′, (ii) the associated host sequence duplication varies within the range of 6 to 12 bp and encompasses the N
(3–6)
sequence, and (iii) in a majority of instances, at least one end of the duplication is at the G-N (or N-C) junction. IS
186
-related sequences were absent in closely related bacterium
Salmonella enterica
serovar Typhimurium, indicating that this IS element is a recent acquisition in the evolutionary history of
E. coli.
Effects Exerted by Transcriptional Regulator PcaU from
Acinetobacter
sp. Strain ADP1
Authors: Trautwein Gaby , Gerischer Ulrike 
Published: July 2002

ABSTRACT

Protocatechuate degradation is accomplished in a multistep inducible catabolic pathway in
Acinetobacter
sp. strain ADP1. The induction is brought about by the transcriptional regulator PcaU in concert with the inducer protocatechuate. PcaU, a member of the new IclR family of transcriptional regulators, was shown to play a role in the activation of transcription at the promoter for the structural
pca
genes, leaving open the participation of additional activators. In this work we show that there is no PcaU-independent transcriptional activation at the
pca
gene promoter. The minimal inducer concentration leading to an induction response is 10
−5
M protocatechuate. The extent of expression of the
pca
genes was observed to depend on the nature of the inducing carbon source, and this is assumed to be caused by different internal levels of protocatechuate in the cells. The basal level of expression was shown to be comparatively high and to vary depending on the noninducing carbon source independent of PcaU. In addition to the activating function, in vivo results suggest a repressing function for PcaU at the
pca
gene promoter in the absence of an elevated inducer concentration. Expression at the
pcaU
gene promoter is independent of the growth condition but is subject to strong negative autoregulation. We propose a model in which PcaU exerts a repressor function both at its own promoter and at the structural gene promoter and in addition functions as an activator of transcription at the structural gene promoter at elevated inducer concentration.
Intergenic Suppression between the Flagellar MS Ring Protein FliF of
Salmonella
and FlhA, a Membrane Component of Its Export Apparatus
Authors: Kihara May , Minamino Tohru , Yamaguchi Shigeru , Macnab Robert M. 
Published: July 2002

ABSTRACT

The MS ring of the flagellar basal body of
Salmonella
is an integral membrane structure consisting of about 26 subunits of a 61-kDa protein, FliF. Out of many nonflagellate
fliF
mutants tested, three gave rise to intergenic suppressors in flagellar region II. The pseudorevertants swarmed, though poorly; this partial recovery of motile function was shown to be due to partial recovery of export function and flagellar assembly. The three parental mutants were all found to carry the same mutation, a six-base deletion corresponding to loss of Ala-174 and Ser-175 in the predicted periplasmic domain of the FliF protein. The 19 intergenic suppressors identified all lay in
flhA
, and they consisted of 10 independent examples at the nucleotide level or 9 at the amino acid level. Since two of the nine corresponded to different substitutions at the same amino acid position, only eight positions in the FlhA protein have given rise to suppressors. Thus, FliF-FlhA intergenic suppression is a fairly rare event. FlhA is a component of the flagellar protein export apparatus, with an integral membrane domain encompassing the N-terminal half of the sequence and a cytoplasmic C-terminal domain. All of the suppressing mutations lay within the integral membrane domain. These mutations, when placed in a wild-type
fliF
background, had no mutant phenotype. In the
fliF
mutant background, mutant FlhA was dominant, yielding a pseudorevertant phenotype. Wild-type FlhA did not exert significant negative dominance in the pseudorevertant background, indicating that it does not compete effectively with mutant FlhA for interaction with mutant FliF. Mutant FliF was partially dominant over wild-type FliF in both the wild-type and second-site FlhA backgrounds. Membrane fractionation experiments indicated that the
fliF
mutation, though preventing export, was mild enough to permit assembly of the MS ring itself, and also assembly of the cytoplasmic C ring onto the MS ring. The data from this study provide genetic support for a model in which at least the FlhA component of the export apparatus physically interacts with the MS ring within which it is housed.
Growth-Phase-Dependent Expression of the Cyclopeptide Antibiotic Microcin J25
Authors: Chiuchiolo Marı́a J. , Delgado Mónica A. , Farı́as Ricardo N. , Salomón Raúl A. 
Published: July 2002

ABSTRACT

Microcin J25 is a 2,107-Da, plasmid-encoded, cyclopeptide antibiotic produced by
Escherichia coli.
We have isolated
lacZ
fusions to
mcjA
(encoding the 58-amino-acid microcin precursor) and
mcjB
and
mcjC
(which are required for microcin maturation), and the regulation of these fusions was used to identify factors that control the expression of these genes. The
mcjA
gene was found to be dramatically induced as cells entered the stationary phase. Expression of
mcjA
could be induced by resuspending uninduced exponential-phase cells in spent supernatant obtained from an early-stationary-phase culture. Induction of
mcjA
expression was not dependent on high cell density, pH changes, anaerobiosis, or the buildup of some inducer. A starvation for carbon and inorganic phosphate induced
mcjA
expression, while under nitrogen limitation there was no induction at all. These results taken together suggest that stationary-phase induction of
mcjA
is triggered by nutrient depletion. The
mcjB
and
mcjC
genes were also regulated by the growth phase of the culture, but in contrast to
mcjA
, they showed substantial expression already during exponential growth. Induction of the microcin genes was demonstrated to be independent of RpoS, the cyclic AMP-Crp complex, OmpR, and H-NS. Instead, we found that the growth-phase-dependent expression of
mcjA
,
mcjB
, and
mcjC
may be explained by the concerted action of the positively acting transition state regulators ppGpp, Lrp, and integration host factor. Measurements of microcin J25 production by strains defective in these global regulators showed a good correlation with the reduced expression of the fusions in such mutant backgrounds.
Involvement of Domain 3 in Oligomerization by the Protective Antigen Moiety of Anthrax Toxin
Authors: Mogridge Jeremy , Mourez Michael , Collier R. John 
Published: July 2002

ABSTRACT

Protective antigen (PA), a component of anthrax toxin, binds receptors on mammalian cells and is activated by a cell surface protease. The resulting active fragment, PA
63
, forms ring-shaped heptamers, binds the enzymic moieties of the toxin, and translocates them to the cytosol. Of the four crystallographic domains of PA, domain 1 has been implicated in binding the enzymic moieties; domain 2 is involved in membrane insertion and oligomerization; and domain 4 binds receptor. To determine the function of domain 3, we developed a screen that allowed us to isolate random mutations that cause defects in the activity of PA. We identified several mutations in domain 3 that affect monomer-monomer interactions in the PA
63
heptamer, indicating that this may be the primary function of this domain.
Genes Involved in Copper Homeostasis in
Escherichia coli
Authors: Grass Gregor , Rensing Christopher 
Published: July 2002

ABSTRACT

Recently, genes for two copper-responsive regulatory systems were identified in the
Escherichia coli
chromosome. In this report, data are presented that support a hypothesis that the putative multicopper oxidase CueO and the transenvelope transporter CusCFBA are involved in copper tolerance in
E. coli
.
An α/β-Type, Small, Acid-Soluble Spore Protein Which Has Very High Affinity for DNA Prevents Outgrowth of
Bacillus subtilis
Spores
Authors: Hayes Christopher S. , Setlow Peter 
Published: July 2002

ABSTRACT

A derivative of SspC, a minor α/β-type, small, acid-soluble spore protein (SASP) from
Bacillus subtilis
, was generated that has a very high affinity for DNA. This protein (SspC
Δ11-D13K
) was able to confer UV resistance on spores lacking α/β-type SASP, and spores with SspC
Δ11-D13K
triggered germination normally. However, SspC
Δ11-D13K
blocked outgrowth of ≥90% of germinated spores, and SspC
Δ11-D13K
persisted in these germinated spores, whereas wild-type SspC was almost completely degraded. The outgrowth phenotype of spores with SspC
Δ11-D13K
is proposed to be due to the high stability of the SspC
Δ11-D13K
-DNA complex, which prevents rapid degradation of this α/β-type SASP early in germination. The persistence of this protein on spore DNA then interferes with transcription during spore outgrowth.
Specific Binding of Integrase to the Origin of Transfer (
oriT
) of the Conjugative Transposon Tn
916
Authors: Hinerfeld Douglas , Churchward Gordon 
Published: July 2002

ABSTRACT

Purified integrase protein (Int) of the conjugative transposon Tn
916
was shown, using nuclease protection experiments, to bind specifically to a site within the origin of conjugal transfer of the transposon,
oriT
. A sequence similar to the ends of the transposon that are bound by the C-terminal DNA-binding domain of Int was present in the protected region. However, Int binding to
oriT
required both the N- and C-terminal DNA-binding domains of Int, and the pattern of nuclease protection differed from that observed when Int binds to the transposon ends and flanking DNA. Binding of Int to
oriT
may be part of a mechanism to prevent premature conjugal transfer of Tn
916
prior to excision from the donor DNA.
Overexpression of the PepF Oligopeptidase Inhibits Sporulation Initiation inBacillus subtilis
Authors: Kanamaru Kyoko , Stephenson Sophie , Perego Marta 
Published: July 2002

ABSTRACTTheyjbGgene encoding the homologue of the PepF1 and PepF2 oligoendopeptidases ofLactococcus lactis(Monnet et al., J. Biol. Chem. 269:32070–32076, 1994; Nardi et al., J. Bacteriol. 179:4164–4171, 1997) has been identified inBacillus subtilisas an inhibitor of sporulation initiation when present in the cells on a multicopy plasmid. Genetic analysis suggested that the inhibitory effect is due to hydrolysis of the PhrA peptide in a form as small as the pentapeptide (ARNQT). Inactivation of PhrA results in deregulation of the RapA phosphatase and thus dephosphorylation of the Spo0F∼∼P response regulator component of the phosphorelay for sporulation initiation. When overexpressed, theB. subtilisPepF is most likely hydrolyzing additional peptides of the Phr family, as is the case for PhrC involved in control of competence development. Chromosomal inactivation of theyjbG/pepFgene did not give rise to any detectable phenotype. The function of PepF inB. subtilisremains unknown. Limited experiments with ayjbGparalogue calledyusXindicated that a frameshift is present, making the corresponding gene product inactive.
BetS Is a Major Glycine Betaine/Proline Betaine Transporter Required for Early Osmotic Adjustment in
Sinorhizobium meliloti
Authors: Boscari Alexandre , Mandon Karine , Dupont Laurence , Poggi Marie-Christine , Le Rudulier Daniel 
Published: July 2002

ABSTRACT

Hybridization to a PCR product derived from conserved betaine choline carnitine transporter (BCCT) sequences led to the identification of a 3.4-kb
Sinorhizobium meliloti
DNA segment encoding a protein (BetS) that displays significant sequence identities to the choline transporter BetT of
Escherichia coli
(34%) and to the glycine betaine transporter OpuD of
Bacillus subtilis
(30%). Although the BetS protein shows a common structure with BCCT systems, it possesses an unusually long hydrophilic C-terminal extension (169 amino acids). After heterologous expression of
betS
in
E. coli
mutant strain MKH13, which lacks choline, glycine betaine, and proline transport systems, both glycine betaine and proline betaine uptake were restored, but only in cells grown at high osmolarity or subjected to a sudden osmotic upshock. Competition experiments demonstrated that choline, ectoine, carnitine, and proline were not effective competitors for BetS-mediated betaine transport. Kinetic analysis revealed that BetS has a high affinity for betaines, with

K
m

s of 16 ± 2 μM and 56 ± 6 μM for glycine betaine and proline betaine, respectively, in cells grown in minimal medium with 0.3 M NaCl. BetS activity appears to be Na
+
driven. In an
S. meliloti betS
mutant, glycine betaine and proline betaine uptake was reduced by about 60%, suggesting that BetS represents a major component of the overall betaine uptake activities in response to salt stress. β-Galactosidase activities of a
betS-lacZ
strain grown in various conditions showed that
betS
is constitutively expressed. Osmotic upshock experiments performed with wild-type and
betS
mutant cells, treated or not with chloramphenicol, indicated that BetS-mediated betaine uptake is the consequence of immediate activation of existing proteins by high osmolarity, most likely through posttranslational activation. Growth experiments underscored the crucial role of BetS as an emerging system involved in the rapid acquisition of betaines by
S. meliloti
subjected to osmotic upshock.
The PtlE Protein of
Bordetella pertussis
Has Peptidoglycanase Activity Required for Ptl-Mediated Pertussis Toxin Secretion
Authors: Rambow-Larsen Amy A. , Weiss Alison A. 
Published: July 2002

ABSTRACT

Pertussis toxin of
Bordetella pertussis
is secreted by a type IV secretion system comprised of the products of the nine
ptl
(pertussis toxin liberation) genes. These proteins are believed to form a complex spanning both the inner and outer membranes and passing through the peptidoglycan layer. Peptidoglycan acts as a barrier for transport through the periplasm of large folded molecules. Assembled pertussis toxin and the secretion component proteins PtlC through PtlH are too large to diffuse through intact peptidoglycan. Therefore, we hypothesized that the Ptl system contains a peptidoglycanase activity. The PtlE protein was found to exhibit a sequence match to the active site of glycohydrolase enzymes. An N-terminally polyhistidine-tagged PtlE fusion protein, constructed and expressed in
Escherichia coli
and in
B. pertussis
, exhibited peptidoglycanase activity on activity gels. A fusion protein with alanine substitutions at the putative active site residues (aspartic acid at position 53 and glutamic acid at position 62) lacked peptidoglycanase activity.
B. pertussis
strains with the amino acid substitutions were deficient for pertussis toxin secretion. Based on these results, we concluded that PtlE is a peptidoglycanase responsible for the local removal or rearrangement of the peptidoglycan layer during Ptl secretion complex assembly.
High Frequency of Mutator Strains among Human Uropathogenic
Escherichia coli
Isolates
Authors: Denamur Erick , Bonacorsi Stéphane , Giraud Antoine , Duriez Patrick , Hilali Farida , Amorin Christine , Bingen Edouard , Andremont Antoine , Picard Bertrand , Taddei François , Matic Ivan 
Published: July 2002

ABSTRACT

By using a panel of 603 commensal and pathogenic
Escherichia coli
and
Shigella
isolates, we showed that mutation rates of strains vary considerably among different ecotypes. Uropathogenic strains had the highest frequency of mutators, while strains from patients with bacteremia had the lowest mutation rates. No correlation between the mutation rates and antibiotic resistance was observed among the studied strains.
Laribacter
hongkongensis
gen. nov., sp. nov., a Novel Gram-Negative Bacterium Isolated from a Cirrhotic Patient with Bacteremia and Empyema
Authors: Yuen Kwok-Yung , Woo Patrick C. Y. , Teng Jade L. L. , Leung Kit-Wah , Wong Michelle K. M. , Lau Susanna K. P. 
Published: July 2002

ABSTRACT

A bacterium was isolated from the blood and empyema of a cirrhotic patient. The cells were facultatively anaerobic, nonsporulating, gram-negative, seagull shaped or spiral rods. The bacterium grows on sheep blood agar as nonhemolytic, gray colonies 1 mm in diameter after 24 h of incubation at 37°C in ambient air. Growth also occurs on MacConkey agar and at 25 and 42°C but not at 4, 44, and 50°C. The bacterium can grow in 1 or 2% but not 3, 4, or 5% NaCl. No enhancement of growth is observed with 5% CO
2
. The organism is aflagellated and nonmotile at both 25 and 37°C. It is oxidase, catalase, urease, and arginine dihydrolase positive, and it reduces nitrate. It does not ferment, oxidize, or assimilate any sugar tested. 16S rRNA gene sequencing showed that there are 91 base differences (6.2%), 112 base differences (7.7%), and 116 base differences (8.2%) between the bacterium and
Microvirgula
aerodenitrificans
,
Vogesella
indigofera
, and
Chromobacterium
species, respectively. The G+C content (mean and standard deviation) is 68.0% ± 2.43%, and the genomic size is about 3 Mb. Based on phylogenetic affiliation, the bacterium belongs to the
Neisseriaceae
family of the β-subclass of
Proteobacteria
. For these reasons, a new genus and species,
Laribacter
hongkongensis
gen. nov., sp. nov., is proposed, for which HKU1 is the type strain. Further studies should be performed to ascertain the potential of this bacterium to become an emerging pathogen.