bluuebunny/crossref_metadata_2025_split huggingface dataset:
Apoptosis-Inducing Factor Participation in Bovine MacrophageMycobacterium bovis-Induced Caspase-Independent Cell Death
Authors: Vega-Manriquez X. , López-Vidal Y. , Moran J. , Adams L. G. , Gutiérrez-Pabello J. A. 
Published: December 2006

ABSTRACTMycobacterium tuberculosiscomplex species survive and replicate in phagosomes of the host cell. Cell death (CD) has been highlighted as one of the probable outcomes in this host-pathogen interaction. Previously, our group demonstrated macrophage apoptosis as a consequence ofMycobacterium bovisinfection. In this study, we aimed to identify the contribution of apoptotic effector elements inM. bovis-induced CD. Bovine macrophages were either infected withM. bovis(multiplicity of infection, 10:1) or treated with anM. boviscell extract (CFE). Structural changes compatible with CD were evaluated. Chromatin condensation was increased three times by the CFE. On the other hand, a terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) assay demonstrated that levels of DNA fragmentation induced byM. bovisand CFE were 53.7% ± 24% and 38.9% ± 14%, respectively, whereas control cells had a basal proportion of 8.9% ± 4.1%. Rates of DNA fragmentation were unaffected by the presence of the pan-caspase inhibitorN-benzyloxycarbonyl-Val-Ala-Asp (z-VAD). Cells treated with 100 μg of CFE for 12 h had a fivefold decrease in the level of mitochondrial outer membrane permeabilization compared to that of untreated cells. NeitherM. bovisinfection nor CFE treatment induced activation of caspase 3, 8, or 9. Translocation of apoptosis-inducing factor (AIF) to the nucleus was identified in 32% ± 3.5% and 26.3% ± 4.9% ofM. bovis-infected and CFE-treated cells, respectively. Incubation of macrophages with z-VAD prior to infection did not alter the percentage of cells showing AIF translocation. Our data suggest thatM. bovis-induced CD in bovine macrophages is caspase independent with AIF participation.
Isolation and Characterization of Biofilm Formation-Defective Mutants of
Staphylococcus aureus
Authors: Tu Quoc Patrick H. , Genevaux Pierre , Pajunen Maria , Savilahti Harri , Georgopoulos Costa , Schrenzel Jacques , Kelley William L. 
Published: December 2006

ABSTRACT

Staphylococcus aureus
produces biofilm and this mode of colonization facilitates infections that are often difficult to treat and engender high morbidity and mortality. We have exploited bacteriophage Mu transposition methods to create an insertional mutant library in a highly biofilm-forming
S. aureus
clinical isolate. Our screen identified 38 insertions in 23 distinct genes together with one intergenic region that significantly reduced biofilm formation. Nineteen insertions were mapped in loci not previously known to affect biofilm in this organism. These include insertions in
codY
,
srrA
,
mgrA
, and
fmtA
, a putative DEAD-box helicase, two members of the zinc-metallo-β lactamase/β-CASP family, and a hypothetical protein with a GGDEF motif. Fifteen insertions occurred in the
icaADBC
operon, which produces intercellular adhesion antigen (PIA) and is important for biofilm formation in many strains of
S. aureus
and
Staphylococcus epidermidis
. Obtaining a high proportion of independent Em-Mu disruptions in
icaADBC
demonstrated both the importance of PIA for biofilm formation in this clinical strain and the strong validation of the screening procedure that concomitantly uncovered additional mutants. All non-
ica
mutants were further analyzed by immunoblotting and biochemical fractionation for perturbation of PIA and wall teichoic acid. PIA levels were diminished in the majority of non-
ica
insertional mutants. Three mutant strains were chosen and were functionally complemented for restored biofilm formation by transformation with plasmids carrying the cloned wild-type gene under the control of a xylose-inducible promoter. This is a comprehensive collection of biofilm-defective mutants that underscores the multifactorial genetic program underlying the establishment of biofilm in this insidious pathogen.
Toll-Like Receptor-2-Mediated C-C Chemokine Receptor 3 and Eotaxin-Driven Eosinophil Influx Induced by
Mycobacterium bovis
BCG Pleurisy
Authors: D'Ávila Heloisa , Almeida Patrícia E. , Roque Natália R. , Castro-Faria-Neto Hugo C. , Bozza Patrícia T. 
Published: December 2006

ABSTRACT

An acute and persistent eosinophil infiltration is observed during
Mycobacterium bovis
BCG pleural infection in mice. Eosinophil accumulation, lipid body formation, and eotaxin production were significantly reduced in BCG-infected Toll-like receptor-2 (TLR2)-deficient mice compared to wild-type mice. Neutralization of eotaxin or CCR3 drastically inhibited BCG-induced eosinophil accumulation and lipid body formation, indicating that BCG-induced eosinophil recruitment and activation is largely dependent of TLR2-mediated eotaxin generation.
Lactate Acquisition Promotes Successful Colonization of the Murine Genital Tract byNeisseria gonorrhoeae
Authors: Exley Rachel M. , Wu Hong , Shaw Jonathan , Schneider Muriel C. , Smith Harry , Jerse Ann E. , Tang Christoph M. 
Published: December 2006

ABSTRACTPrevious studies onNeisseria gonorrhoeaehave demonstrated that metabolism of lactate in the presence of glucose increases the growth rate of the bacterium and enhances its resistance to complement-mediated killing. Although these findings in vitro suggest that the acquisition of lactate promotes gonococcal colonization, the significance of this carbon source to the survival of the gonococcus in vivo remains unknown. To investigate the importance of lactate utilization duringNeisseria gonorrhoeaegenital tract infection, we identified the genelctP, which encodes the gonococcal lactate permease. A mutant that lacks a functional copy oflctPwas unable to take up exogenous lactate and did not grow in defined medium with lactate as the sole carbon source, in contrast to the wild-type and complemented strains; the mutant strain exhibited no growth defect in defined medium containing glucose. In defined medium containing physiological concentrations of lactate and glucose, thelctPmutant demonstrated reduced early growth and increased sensitivity to complement-mediated killing compared with the wild-type strain; the enhanced susceptibility to complement was associated with a reduction in lipopolysaccharide sialylation of thelctPmutant. The importance of lactate utilization during colonization was evaluated in the murine model of lower genital tract infection. ThelctPmutant was significantly attenuated in its ability to colonize and survive in the genital tract, while the complemented mutant exhibited no defect for colonization. Lactate is a micronutrient in the genital tract that contributes to the survival of the gonococcus.
PduL Is an Evolutionarily Distinct Phosphotransacylase Involved in B
12
-Dependent 1,2-Propanediol Degradation by
Salmonella enterica
Serovar Typhimurium LT2
Authors: Liu Yu , Leal Nicole A. , Sampson Edith M. , Johnson Celeste L. V. , Havemann Gregory D. , Bobik Thomas A. 
Published: December 2006

ABSTRACT

Salmonella enterica
degrades 1,2-propanediol (1,2-PD) in a coenzyme B
12
-dependent manner. Previous enzymatic assays of crude cell extracts indicated that a phosphotransacylase (PTAC) was needed for this process, but the enzyme involved was not identified. Here, we show that the
pduL
gene encodes an evolutionarily distinct PTAC used for 1,2-PD degradation. Growth tests showed that
pduL
mutants were unable to ferment 1,2-PD and were also impaired for aerobic growth on this compound. Enzyme assays showed that cell extracts from a
pduL
mutant lacked measurable PTAC activity in a background that also carried a
pta
mutation (the
pta
gene was previously shown to encode a PTAC enzyme). Ectopic expression of
pduL
corrected the growth defects of a
pta
mutant. PduL fused to eight C-terminal histidine residues (PduL-His
8
) was purified, and its kinetic constants were determined: the
V
max
was 51.7 ± 7.6 μmol min
−1
mg
−1
, and the

K
m

values for propionyl-PO
4
2−
and acetyl-PO
4
2−
were 0.61 and 0.97 mM, respectively. Sequence analyses showed that PduL is unrelated in amino acid sequence to known PTAC enzymes and that PduL homologues are distributed among at least 49 bacterial species but are absent from the
Archaea
and
Eukarya
.
Detection of a Group II Intron without an Open Reading Frame in the Alpha-Toxin Gene ofClostridium perfringensIsolated from a Broiler Chicken
Authors: Ma Menglin , Ohtani Kaori , Shimizu Tohru , Misawa Naoaki 
Published: December 2006

ABSTRACTA DNA insertion of 834 bp, designated CPF-G2Im, was identified within the alpha toxin gene (cpa) ofClostridium perfringensstrain CPBC16ML, isolated from a broiler chicken. Sequence analysis of CPF-G2Im indicated that it was integrated 340 nucleotides downstream of the start codon ofcpa. However, the insertion did not abolish the phospholipase C and hemolytic activities of CPBC16ML. To investigate the expression of its alpha toxin, the intact copy ofcpawas cloned into an expression vector and transformed intoEscherichia coliM15 cells. Immunoblotting analysis showed that the protein expressed from the transformant as well as in the culture supernatant ofC. perfringensstrain CPBC16ML had the expected molecular weight detected in reference strains ofC. perfringens. Northern hybridization and reverse transcriptase PCR (RT-PCR) analysis revealed that the entire CPF-G2Im insertion was completely spliced from thecpaprecursor mRNA transcripts. The sequence of the insertion fragment has 95% and 97% identity to two noncoding regions corresponding to sequences that flank a predicted group II RT gene present in the pCPF4969 plasmid ofC. perfringens. However, an RT was not encoded by the CPF-G2Im fragment. Based on the secondary structure prediction analysis, CPF-G2Im revealed typical features of group II introns. The present study shows that CPF-G2Im is capable of splicing in bothC. perfringensandE. coli. To our knowledge, this is the first report that a group II intron without an open reading frame (ORF) is located in thecpaORF ofC. perfringens.
hpaR, a PutativemarRFamily Transcriptional Regulator, Is Positively Controlled by HrpG and HrpX and Involved in the Pathogenesis, Hypersensitive Response, and Extracellular Protease Production ofXanthomonas campestrisPathovar campestris
Authors: Wei Ke , Tang Dong-Jie , He Yong-Qiang , Feng Jia-Xun , Jiang Bo-Le , Lu Guang-Tao , Chen Baoshan , Tang Ji-Liang 
Published: December 2006

ABSTRACTThe MarR family of transcriptional regulators of bacteria are involved in the regulation of many cellular processes, including pathogenesis. In this work, we have demonstrated genetically thathpaR(hpa,hrpassociated), which encodes a putative MarR family regulator, is involved in the hypersensitive response (HR), pathogenicity, and extracellular protease production of the phytopathogenic bacteriumXanthomonas campestrispathovar campestris. A mutation inhpaRresulted in complete loss of virulence in the host plant cabbage, a delayed and weakened HR in the nonhost plant pepper ECW-10R, and an increase in extracellular protease production. Detection of the β-glucuronidase activity of a plasmid-drivenhpaRpromoter-gusAreporter revealed that the expression ofhpaRis positively controlled by HrpG and HrpX and is suppressed in rich medium while being strongly induced in minimal andhrp-inducing media and inside the host. These findings indicate thathpaRbelongs to thehrpGandhrpXregulon and that HrpX regulates the extracellular protease production viahpaRinX. campestrispv. campestris.
Divergence and Redundancy of Transport and Metabolic Rate-Yield Strategies in a SingleEscherichia coliPopulation
Authors: Maharjan Ram Prasad , Seeto Shona , Ferenci Thomas 
Published: December 2006

ABSTRACTThe energetic efficiency of nutrient uptake and conversion into biomass is a key factor in the ecological behavior of microorganisms. The constraints shaping the metabolic rate-yield trade-off in bacteria are not well understood. To examine whether metabolic rate-yield settings and physiological strategies evolve toward a particular optimum in a constant environment, we studied multipleEscherichia coliisolates evolving in a glucose-limited chemostat population. A major divergence in transport and metabolic strategies was observed, and the isolates included inefficient rate strategists (polluters or cheaters) and yield strategists (conservationists), as well as various hybrid rate-yield strategists and alternative ecotypes (dropouts). Sugar transport assays, strain comparisons based on metabolomics, and Biolog profiling revealed variance to the point of individuality within an evolving population. Only 68 of 177 metabolites assayed were not affected in 10 clonally related strains. The parallel enrichment of rate and yield strategists and the divergence in metabolic phylogenies indicate that bacteria do not converge on a particular rate-yield balance or unique evolutionary solutions. Redundancies in transport and metabolic pathways are proposed to have laid the framework for the multiplicity of bacterial adaptations.
Characterization of the Helicase Activity and Substrate Specificity of
Mycobacterium tuberculosis
UvrD
Authors: Curti Elena , Smerdon Stephen J. , Davis Elaine O. 
Published: December 2006

ABSTRACT

UvrD is a helicase that is widely conserved in gram-negative bacteria. A
uvrD
homologue was identified in
Mycobacterium tuberculosis
on the basis of the homology of its encoded protein with
Escherichia coli
UvrD, with which it shares 39% amino acid identity, distributed throughout the protein. The gene was cloned, and a histidine-tagged form of the protein was expressed and purified to homogeneity. The purified protein had in vitro ATPase activity that was dependent upon the presence of DNA. Oligonucleotides as short as four nucleotides were sufficient to promote the ATPase activity. The DNA helicase activity of the enzyme was only fueled by ATP and dATP. UvrD preferentially unwound 3′-single-stranded tailed duplex substrates over 5′-single-stranded ones, indicating that the protein had a duplex-unwinding activity with 3′-to-5′ polarity. A 3′ single-stranded DNA tail of 18 nucleotides was required for effective unwinding. By using a series of synthetic oligonucleotide substrates, we demonstrated that
M. tuberculosis
UvrD has an unwinding preference towards nicked DNA duplexes and stalled replication forks, representing the likely sites of action in vivo. The potential role of
M. tuberculosis
UvrD in maintenance of bacterial genomic integrity makes it a promising target for drug design against
M. tuberculosis
.
Probing the In Vivo Dynamics of Type I Protein Secretion Complex Association through Sensitivity to Detergents
Authors: Cescau Sandra , Debarbieux Laurent , Wandersman Cécile 
Published: December 2006

ABSTRACT

The
Serratia marcescens
hemophore is secreted by a type I secretion system consisting of three proteins: a membrane ABC protein, an adaptor protein, and the TolC-like outer membrane protein. Assembly of these proteins is induced by substrate binding to the ABC protein. Here we show that a hemophore mutant lacking the last 14 C-terminal amino acids is not secreted but rather interacts with the ABC protein and promotes a stable multiprotein complex. Strains expressing the transporter and the mutant protein are sensitive to detergents (sodium dodecyl sulfate [SDS]). TolC is trapped in the transporter jammed by the truncated substrate and therefore is not present at sufficient concentrations to allow the efflux pumps to expel detergents. Using an SDS sensitivity assay, we showed that the hemophore interacts with the ABC protein via two nonoverlapping sites. We also demonstrated that the C-terminal peptide, which functions as an intramolecular signal sequence in the complete substrate, may also have intermolecular activity and triggers complex dissociation in vivo when it is provided as a distinct peptide. The SDS sensitivity test on plates enables workers to study type I secretion protein association and dissociation independent of the secretion process itself.
SwmB, a 1.12-Megadalton Protein That Is Required for Nonflagellar Swimming Motility in
Synechococcus
Authors: McCarren J. , Brahamsha B. 
Published: December 2006

ABSTRACT

SwmB is required for swimming motility in
Synechococcus
sp. strain WH8102. This highly repetitive 1.12-MDa polypeptide is associated with the cell surface, where it is arranged in a punctate manner. Inactivation of
swmB
does not affect the localization of SwmA, an S-layer protein also required for swimming.
An Active Nonautonomous Mobile Element in
Sulfolobus islandicus
REN1H1
Authors: Berkner Silvia , Lipps Georg 
Published: December 2006

ABSTRACT

In the crenarchaeote
Sulfolobus islandicus
REN1H1, a mobile element of 321 bp length has been shown to be active. It does not contain terminal inverted repeats and transposes by a replicative mechanism. This newly discovered element has been named SMN1 (for
Sulfolobus
miniature noninverted repeat transposable element).
Amino Acid Residues Required for Maturation, Cell Uptake, and Processing of Translation Inhibitor Microcin C
Authors: Kazakov Teymur , Metlitskaya Anastasia , Severinov Konstantin 
Published: December 2006

ABSTRACT
Microcin C (McC), a peptide-nucleotide Trojan horse antibiotic, targets aspartyl-tRNA synthetase. We present the results of a systematic mutational study of the 7-amino-acid ribosomally synthesized peptide moiety of McC. Our results define amino acid positions important for McC maturation and cell uptake and processing and open the way for creation of more potent McC-based inhibitors.
The SXT Conjugative Element and Linear Prophage N15 Encode Toxin-Antitoxin-Stabilizing Systems Homologous to the
tad-ata
Module of the
Paracoccus aminophilus
Plasmid pAMI2
Authors: Dziewit Lukasz , Jazurek Magdalena , Drewniak Lukasz , Baj Jadwiga , Bartosik Dariusz 
Published: December 2006

ABSTRACT

A group of proteic toxin-antitoxin (TA) cassettes whose representatives are widely distributed among bacterial genomes has been identified. These cassettes occur in chromosomes, plasmids, bacteriophages, and noncomposite transposons, as well as in the SXT conjugative element of
Vibrio cholerae
. The following four homologous loci were subjected to detailed comparative studies: (i)
tad-ata
from plasmid pAMI2 of
Paracoccus aminophilus
(the prototype of this group), (ii)
gp49-gp48
from the linear bacteriophage N15 of
Escherichia coli
, (iii) s045-s044 from SXT, and (iv) Z3230-Z3231 from the genomic island of enterohemorrhagic
Escherichia coli
O157:H7 strain EDL933. Functional analysis revealed that all but one of these loci (Z3230-Z3231) are able to stabilize heterologous replicons, although the host ranges varied. The TA cassettes analyzed have the following common features: (i) the toxins are encoded by the first gene of each operon; (ii) the antitoxins contain a predicted helix-turn-helix motif of the XRE family; and (iii) the cassettes have two promoters that are different strengths, one which is located upstream of the toxin gene and one which is located upstream of the antitoxin gene. All four toxins tested are functional in
E. coli
; overexpression of the toxins (in the absence of antitoxin) results in a bacteriostatic effect manifested by elongation of bacterial cells and growth arrest. The toxins have various effects on cell viability, which suggests that they may recognize different intracellular targets. Preliminary data suggest that different cellular proteases are involved in degradation of antitoxins encoded by the loci analyzed.
The Number of G Residues in the
Bacillus subtilis pyrG
Initially Transcribed Region Governs Reiterative Transcription-Mediated Regulation
Authors: Elsholz Alexander K. W. , Jørgensen Casper Møller , Switzer Robert L. 
Published: December 2006

ABSTRACT

Derepression of
pyrG
expression in
Bacillus subtilis
involves CTP-sensitive reiterative transcription, which introduces up to 11 extra G residues at the 5′ ends of
pyrG
transcripts. Insertion of three or more additional Gs at the 5′ end of the
pyrG
initially transcribed region abolished reiterative transcription and caused constitutive expression.
Isolation and Characterization of Dominant Mutations in theBacillus subtilisStressosome Components RsbR and RsbS
Authors: Reeves Adam , Haldenwang W. G. 
Published: December 2006

ABSTRACTThe general stress response ofBacillus subtilisis controlled by the activity state of the σBtranscription factor. Physical stress is communicated to σBvia a large-molecular-mass (>106-Da) structure (the stressosome) formed by one or more members of a family of homologous proteins (RsbR, YkoB, YojH, YqhA). The positive regulator (RsbT) of the σBstress induction pathway is incorporated into the complex bound to an inhibitor protein (RsbS). Exposure to stress empowers an RsbT-dependent phosphorylation of RsbR and RsbS, with the subsequent release of RsbT to activate downstream processes. The mechanism by which stress initiates these reactions is unknown. In an attempt to identify changes in stressosome components that could lead to σBactivation, a DNA segment encoding these proteins was mutagenized and placed intoB. subtilisto create a merodiploid strain for these genes. Eight mutations that allowed heightened σBactivity in the presence of their wild-type counterparts were isolated. Two of the mutations are missense changes inrsbR, and six are amino acid changes inrsbS. Additional experiments suggested that both of thersbRmutations and three of thersbSmutations likely enhance σBactivity by elevating the level of RsbS phosphorylation. All of the mutations were found to be dominant over wild-type alleles only when they are cotranscribed within anrsbR rsbS rsbToperon. The data suggest that changes in RsbR can initiate the downstream events that lead to σBactivation and that RsbR, RsbS, and RsbT likely interact with each other concomitantly with their synthesis.
Autoregulation Is Essential for Precise Temporal and Steady-State Regulation by theBordetellaBvgAS Phosphorelay
Authors: Williams Corinne L. , Cotter Peggy A. 
Published: December 2006

ABSTRACTTheBordetellaBvgAS virulence control system is prototypical of phosphorelays that use a polydomain sensor and a response regulator to control gene expression in response to environmental cues. BvgAS controls the expression of at least three distinct phenotypic phases (Bvg−, Bvgi, and Bvg+) by differentially regulating the expression of at least four classes of genes. Among the loci regulated by BvgAS isbvgASitself. We investigated the role of autoregulation in the ability of BvgAS to control multiple gene expression patterns in a temporal and steady-state manner by constructingBordetella bronchisepticastrains in which thebvgASpromoter was replaced with constitutively active promoters. Our results show that positive autoregulation ofbvgAStranscription is required for the temporal expression of multiple phenotypic phases that occurs in response to a shift from Bvg−-phase conditions to Bvg+-phase conditions. Autoregulation was also shown to contribute to steady-state regulation; it influences the sensitivity of the system in response to subtle differences in signal intensity. In addition, considered in relation to BvgA and BvgS activities demonstrated in vitro, our results provide insight into how BvgA and BvgS function mechanistically.
ArylamineN-Acetyltransferase Responsible for Acetylation of 2-Aminophenols inStreptomyces griseus
Authors: Suzuki Hirokazu , Ohnishi Yasuo , Horinouchi Sueharu 
Published: December 2006

ABSTRACTAn arylamineN-acetyltransferase (NAT) responsible for the N acetylation of exogenous 3-amino-4-hydroxybenzoic acid inStreptomyces griseuswas identified and characterized. This enzyme was distinct from other eukaryotic and bacterial NATs in that it acetylated various 2-aminophenol derivatives more effectively than it acetylated 5-aminosalicylic acid, and thus it may be involved in the metabolism of xenobiotic compounds.