bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface Accessibility of the 70-KilodaltonChlamydia trachomatisHeat Shock Protein following Reduction of Outer Membrane Protein Disulfide Bonds
Authors: Raulston Jane E. , Davis Carolyn H. , Paul Terry R. , Hobbs J. Dave , Wyrick Priscilla B. 
Published: July 2002

ABSTRACTNumerous investigations have shown that 70-kDa heat shock protein (Hsp70) homologs interact tightly with hydrophobic proteins and functionally assist proteins in membranous organelles and environments. One such protein is theChlamydia trachomatisHsp70 that is associated with isolated outer membrane complexes of infectious elementary bodies (EB). Previous observations have indicated that chlamydial Hsp70 plays a role in EB attachment to, or entry into, endometrial epithelial cells. In this study, immunofluorescence microscopy and transmission electron microscopy observations showed that chlamydial Hsp70 is not a surface-displayed ligand on purified EB. However, brief exposure of EB to the thiol reducing agent dithiothreitol (DTT) led to surface accessibility of the Hsp70 substrate-binding domain. Reduction of the highly disulfide-cross-linked EB outer membrane proteins with DTT resulted in a decrease in EB attachment and infectivity. Interestingly, exposure of EB to the membrane-impermeable thiol-alkylating reagent 5,5′-dithiobis(2-nitrobenzoic acid) enhanced attachment but compromised infectivity, suggesting that EB outer membrane proteins must be reduced for entry and productive infection. Together, our data suggest that (i) the structural integrity of the EB outer membrane, maintained by protein disulfide bonds, is important during the initial stages of attachment; (ii) reduction occurs within the localized microenvironment of host cell surfaces once intimate contact is established between EB and host cells; and (iii) subsequent conformational changes in EB ultrastructure allow productive infection in host cells. The accessibility of the Hsp70 substrate-binding domain may support the hypothesis that this protein plays a role in events following the initial stage of attachment instead of serving as a primary, surface-displayed adhesin.
Mycoplasma pneumoniae
Induces Chronic Respiratory Infection, Airway Hyperreactivity, and Pulmonary Inflammation: a Murine Model of Infection-Associated Chronic Reactive Airway Disease
Authors: Hardy Robert D. , Jafri Hasan S. , Olsen Kurt , Hatfield Jeanine , Iglehart Janie , Rogers Beverly B. , Patel Padma , Cassell Gail , McCracken George H. , Ramilo Octavio 
Published: July 2002

ABSTRACT

Because chronic
Mycoplasma pneumoniae
respiratory infection is hypothesized to play a role in asthma, the potential of
M. pneumoniae
to establish chronic respiratory infection with associated pulmonary disease was investigated in a murine model. BALB/c mice were intranasally inoculated once with
M. pneumoniae
and examined at 109, 150, 245, 368, and 530 days postinoculation.
M. pneumoniae
was detected in bronchoalveolar lavage fluid by culture or PCR in 70 and 22% of mice at 109 and 530 days postinoculation, respectively. Lung histopathology was normal up to 368 days postinoculation. At 530 days, however, 78% of the mice inoculated with
M. pneumoniae
demonstrated abnormal histopathology characterized by peribronchial and perivascular mononuclear infiltrates. A mean histopathologic score (HPS) at 530 days of 5.1 was significantly greater (
P
< 0.01) than that for controls (HPS score of 0). Serum anti-
M. pneumoniae
immunoglobulin G was detectable in all of the mice inoculated with
M. pneumoniae
and was inversely correlated with HPS (
r
= −0.95,
P
= 0.01) at 530 days postinoculation. Unrestrained whole-body plethysmography measurement of enhanced pause revealed significantly elevated airway methacholine reactivity in
M. pneumoniae
-inoculated mice compared with that in controls at 245 days (
P
= 0.03) and increased airway obstruction at 530 days (
P
= 0.01). Murine
M. pneumoniae
respiratory infection can lead to chronic pulmonary disease characterized by airway hyperreactivity, airway obstruction, and histologic inflammation.
Use of Bacteriophage Ba1 To Identify Properties Associated withBordetella aviumVirulence
Authors: Shelton Celia B. , Temple Louise M. , Orndorff Paul E. 
Published: July 2002

ABSTRACTBordetella aviumcauses bordetellosis, an upper respiratory disease of birds. Commercially raised turkeys are particularly susceptible. We report here on the use of a recently describedB. aviumbacteriophage, Ba1, as a tool for investigating the effects of lysogeny and phage resistance on virulence. We found that lysogeny had no effect on any of the in vivo or in vitro measurements of virulence we employed. However, two-thirds (six of nine) spontaneous phage-resistant mutants of our virulent laboratory strain, 197N, were attenuated. Phage resistance was associated, in all cases, with an inability of the mutants to bind phage. Further tests of the mutants revealed that all had increased sensitivities to surfactants, and increased amounts of incomplete (O-antigen-deficient) lipopolysaccharide (LPS) compared to 197N. Hot phenol-water-extracted 197N LPS inactivated phage in a specific and dose-dependent manner. Acid hydrolysis and removal of lipid A had little effect upon the ability of isolated LPS to inactivate Ba1, suggesting that the core region and possibly the O antigen were required for phage binding. All of the mutants, with one exception, were significantly more sensitive to naive turkey serum and, without exception, significantly less able to bind to tracheal rings in vitro than 197N. Interestingly, the three phage-resistant mutants that remained virulent appeared to be O antigen deficient and were among the mutants that were the most serum sensitive and least able to bind turkey tracheal rings in vitro. This observation allowed us to conclude that even severe defects in tracheal ring binding and serum resistance manifested in vitro were not necessarily indicative of attenuation and that complete LPS may not be required for virulence.
Identification of a
Mycobacterium tuberculosis
Putative Classical Nitroreductase Gene Whose Expression Is Coregulated with That of the
acr
Gene within Macrophages, in Standing versus Shaking Cultures, and under Low Oxygen Conditions
Authors: Purkayastha Anjan , McCue Lee Ann , McDonough Kathleen A. 
Published: July 2002

ABSTRACT

Tuberculosis remains a leading killer worldwide, and new approaches for its treatment and prevention are urgently needed. This effort will benefit greatly from a better understanding of gene regulation in
Mycobacterium tuberculosis,
particularly with respect to this pathogen's response to its host environment. We examined the behavior of two promoters from the divergently transcribed
M. tuberculosis
genes
acr
/
hsp
X/Rv2031c (α-crystallin homolog) and Rv2032/
acg
(
acr
-coregulated gene) by using a promoter-GFP fusion assay in
Mycobacterium bovis
BCG. We found that Rv2032 is a novel macrophage-induced gene whose expression is coregulated with that of
acr
. Relative levels of intracellular induction for both promoters were significantly affected by shallow standing versus shaking bacterial culture conditions prior to macrophage infection, and both promoters were strongly induced under low oxygen conditions. Deletion analyses showed that DNA sequences within a 43-bp region were required for expression of these promoters under all conditions. Multiple sequence alignment and database searches performed with PROBE indicated that Rv2032 is one of eight
M. tuberculosis
genes of previously unknown function that belong to an unusual superfamily of classical nitroreductases, which may have a role for bacteria within the host environment. These findings show that mycobacterial culture conditions can greatly influence the results and interpretation of subsequent gene regulation experiments. We propose that these differences might be exploited for dissection of the regulatory factors that affect mycobacterial gene expression within the host.
Antibody-Mediated Protection in MurineCryptococcus neoformansInfection Is Associated with Pleotrophic Effects on Cytokine and Leukocyte Responses
Authors: Feldmesser Marta , Mednick Aron , Casadevall Arturo 
Published: July 2002

ABSTRACTCryptococcus neoformans, an encapsulated yeast, is a common cause of life-threatening meningoencephalitis in immunosuppressed patients. We previously observed that administration of a monoclonal antibody (MAb) to the capsular polysaccharide to mice with pulmonary infection prolonged survival and enhanced granulomatous inflammation without reducing lung CFU. To understand the mechanism of MAb action, we studied leukocyte recruitment and cytokine profiles in lungs of A/JCr mice. B lymphocytes were the predominant cell type in lung infiltrates, comprising 15 to 30% of the leukocytes. Despite alterations in histological appearance, fluorescence-activated cell sorter analysis revealed no significant difference in total numbers of lung leukocytes in MAb-treated mice and controls. Differences in the immune response toC. neoformansbetween MAb-treated mice and controls included (i) an increase in the percentage of granulocytes among lung leukocytes on day 14, (ii) higher macrophage surface expression of CD86 on day 28, (iii) larger amounts of IL-10 in lung homogenates at day 7, (iv) a trend toward smaller amounts of gamma interferon mRNA and protein on day 7, and (v) a smaller increase in the levels of interleukin-4 mRNA and protein on day 7. Hence, the immune responses toC. neoformansinfection in the presence and absence of specific antibody were qualitatively similar, and antibody administration was associated with several subtle quantitative differences in immune response parameters that could translate into enhanced survival. MAb may function partly by down-regulating the inflammatory response and reducing host damage. Our findings demonstrate unexpected complexity in the interaction between specific MAb and other components of the host immune response.
Lipopolysaccharide-Specific but Not Anti-Flagellar Immunoglobulin A Monoclonal Antibodies PreventSalmonella entericaSerotype Enteritidis Invasion and Replication within HEp-2 Cell Monolayers
Authors: Iankov Ianko D. , Petrov Dragomir P. , Mladenov Ivan V. , Haralambieva Iana H. , Mitov Ivan G. 
Published: July 2002

ABSTRACTThe protective potential of immunoglobulin A (IgA) monoclonal antibodies (MAbs) directed against O and H antigens ofSalmonella entericaserotype Enteritidis to prevent bacterial adhesion to and invasion of HEp-2 cells was evaluated. Although anti-flagellar IgA MAbs showed strong agglutinating capacities, they did not protect cell monolayers. In contrast, IgA MAbs specific for the O:9 epitope ofSalmonellalipopolysaccharide antigen alone preventedS. entericaserotype Enteritidis entry and replication within HEp-2 cells, and the protection was not mediated by direct binding of antibodies to bacterial adhesins or by agglutination of microorganisms.
Host Immune Response toSalmonella entericaSerovar Typhimurium Infection in Mice Derived from Wild Strains
Authors: Sebastiani Giovanna , Blais Véronique , Sancho Vanessa , Vogel Stefanie N. , Stevenson Mary M. , Gros Philippe , Lapointe Jean-Martin , Rivest Serge , Malo Danielle 
Published: July 2002

ABSTRACTStudies of mouse models of endotoxemia and sepsis with gram-negative bacteria have shown that the host response is genetically controlled. Mice infected with the gram-negative bacteriumSalmonella entericaserovar Typhimurium exhibit marked genetic differences in disease manifestation, and the wild-derived strainMus musculus molossinusMOLF/Ei is extremely susceptible toS. entericaserovar Typhimurium. The kinetics of bacterial proliferation within the liver and the spleen and histological examination of tissue sections have suggested that MOLF/Ei mice do not succumb to infection because of overwhelming bacterial growth in the reticuloendothelial organs or massive tissue necrosis, as observed in otherSalmonella-susceptible strains. MOLF/Ei mice respond normally to lipopolysaccharide (LPS) in vivo and in vitro, as determined by the production of tumor necrosis factor alpha and spleen cell mitogenesis. However, they have a unique cytokine profile in response to infection compared to that observed for otherSalmonella-susceptible mice. There was increased expression of mRNA of the interleukin-1α (IL-1α) and IL-1β genes as the infection in the spleens and livers of MOLF/Ei mice progressed. Despite the fact that MOLF/Ei mice have the ability to respond to LPS and the fact that there are significant increases in IL-1α and IL-1β mRNA,Nos2in the spleen is not upregulated and nitrite production by spleen cells is reduced. At the central level, the inflammatory response is characterized by strong upregulation of the inhibitory factor kappa B alpha and Toll-like receptor 2 genes, two genes known to be regulated by LPS and IL-1 in the brain. The high levels of IL-1 expression in the spleens and livers of MOLF/Ei mice may have important implications for the activation of peripheral and central innate immune mechanisms.
Intravaginal and Intranasal Immunizations Are Equally Effective in Inducing Vaginal Antibodies and Conferring Protection against Vaginal Candidiasis
Authors: De Bernardis Flavia , Boccanera Maria , Adriani Daniela , Girolamo Antonietta , Cassone Antonio 
Published: July 2002

ABSTRACT

Oophorectomized, estrogen-treated rats were immunized by the intravaginal or intranasal route with a mannoprotein extract (MP) or secreted aspartyl proteinases (Sap) of
Candida albicans
, with or without cholera toxin as a mucosal adjuvant. Both routes of immunization were equally effective in (i) inducing anti-MP and anti-Sap vaginal antibodies and (ii) conferring a high degree of protection against the vaginal infection by the fungus. These data suggest that appropriate fungal antigens and adjuvant can be used to protect against candidal vaginitis, by either route.
Mycobacterium aviumGenes Expressed during Growth in Human Macrophages Detected by Selective Capture of Transcribed Sequences (SCOTS)
Authors: Hou Joan Y. , Graham James E. , Clark-Curtiss Josephine E. 
Published: July 2002

ABSTRACTSelective capture of transcribed sequences (SCOTS) has been employed to identify 54 cDNA molecules that represent 46 genes that are expressed byMycobacterium aviumduring growth in human macrophages. Some cDNA molecules correspond to genes that are apparently expressed 48 h after infection of macrophages, while others correspond to genes expressed 110 h after infection, and still others correspond to genes expressed throughout the course of infection in our model system. Genes expressed byM. aviumduring growth in macrophages include genes encoding enzymes of several biosynthetic pathways (pyrimidines, mycobactin, and polyketides); genes that encode enzymes involved in intermediary metabolism, energy metabolism (tricarboxylic acid cycle, glyoxalate shunt), and nitrogen metabolism; and genes that encode regulatory proteins. A number of genes of unknown function were also identified, including genes that code for proteins similar to members of the PPE family of proteins ofMycobacterium tuberculosisand proteins similar to those encoded by theM. tuberculosis mcegenes, which have been previously associated with mycobacterial virulence. The SCOTS technique, followed by enrichment for cDNA molecules that are up-regulated or are uniquely expressed byM. aviumduring growth in human macrophages (compared to growth in laboratory broth culture), allows recovery and identification of a greater diversity of cDNA molecules than does subtractive hybridization between cDNA mixtures from macrophage-grown and broth-grownM. avium.Data are presented demonstrating the reproducibility of recovery of a subset of cDNA molecules from cDNA mixtures purified by SCOTS on several different occasions. These results further demonstrate the beneficial utility of the SCOTS technique for identifying genes whose products are needed for successful survival and growth by an organism in a specific environment.
Fibrinogen Binding to Intercellular Adhesion Molecule 1: Implications forPlasmodium falciparumAdhesion
Authors: Gray Carolyn , Craig Alister 
Published: July 2002

ABSTRACTIntercellular adhesion molecule 1 (ICAM-1) is an endothelial cell adhesion molecule implicated in cerebral malaria. We investigated whether fibrinogen affectsPlasmodium falciparumbinding to ICAM-1, as the ICAM-1 binding sites ofP. falciparumand fibrinogen overlap. We show that fibrinogen dramatically reducesP. falciparumadhesion to ICAM-1 under flow conditions.
ThessuLocus Plays a Key Role in Organosulfur Metabolism inPseudomonas putidaS-313
Authors: Kahnert Antje , Vermeij Paul , Wietek Claudia , James Peter , Leisinger Thomas , Kertesz Michael A. 
Published: July 2002

ABSTRACTPseudomonas putidaS-313 can utilize a broad range of aromatic sulfonates as sulfur sources for growth in sulfate-free minimal medium. The sulfonates are cleaved monooxygenolytically to yield the corresponding phenols. miniTn5mutants of strain S-313 which were no longer able to desulfurize arylsulfonates were isolated and were found to carry transposon insertions in thessuEADCBFoperon, which contained genes for an ATP-binding cassette-type transporter (ssuABC), a two-component reduced flavin mononucleotide-dependent monooxygenase (ssuED) closely related to theEscherichia colialkanesulfonatase, and a protein related to clostridial molybdopterin-binding proteins (ssuF). These mutants were also deficient in growth with a variety of other organosulfur sources, including aromatic and aliphatic sulfate esters, methionine, and aliphatic sulfonates other than the natural sulfonates taurine and cysteate. This pleiotropic phenotype was complemented by thessuoperon, confirming its key role in organosulfur metabolism in this species. Further complementation analysis revealed that thessuFgene product was required for growth with all of the tested substrates except methionine and that the oxygenase encoded byssuDwas required for growth with sulfonates or methionine. The flavin reductase SsuE was not required for growth with aliphatic sulfonates or methionine but was needed for growth with arylsulfonates, suggesting that an alternative isozyme exists for the former compounds that is not active in transformation of the latter substrates. Aryl sulfate ester utilization was catalyzed by an arylsulfotransferase, and not by an arylsulfatase as in the related speciesPseudomonas aeruginosa.
lon
Incompatibility Associated with Mutations Causing SOS Induction: Null
uvrD
Alleles Induce an SOS Response in
Escherichia coli
Authors: SaiSree L. , Reddy Manjula , Gowrishankar J. 
Published: July 2002

ABSTRACT

The
uvrD
gene in
Escherichia coli
encodes a 720-amino-acid 3′-5′ DNA helicase which, although nonessential for viability, is required for methyl-directed mismatch repair and nucleotide excision repair and furthermore is believed to participate in recombination and DNA replication. We have shown in this study that null mutations in
uvrD
are incompatible with
lon
, the incompatibility being a consequence of the chronic induction of SOS in
uvrD
strains and the resultant accumulation of the cell septation inhibitor SulA (which is a normal target for degradation by Lon protease).
uvrD-lon
incompatibility was suppressed by
sulA
,
lexA3
(Ind
−
), or
recA
(Def) mutations. Other mutations, such as
priA
,
dam
,
polA
, and
dnaQ
(
mutD
) mutations, which lead to persistent SOS induction, were also
lon
incompatible. SOS induction was not observed in
uvrC
and
mutH
(or
mutS
) mutants defective, respectively, in excision repair and mismatch repair. Nor was
uvrD
-mediated SOS induction abolished by mutations in genes that affect mismatch repair (
mutH
), excision repair (
uvrC
), or recombination (
recB
and
recF
). These data suggest that SOS induction in
uvrD
mutants is not a consequence of defects in these three pathways. We propose that the UvrD helicase participates in DNA replication to unwind secondary structures on the lagging strand immediately behind the progressing replication fork, and that it is the absence of this function which contributes to SOS induction in
uvrD
strains.
Phosphorylated PmrA Interacts with the Promoter Region of
ugd
in
Salmonella enterica
Serovar Typhimurium
Authors: Aguirre Andrés , Lejona Sergio , Véscovi Eleonora García , Soncini Fernando C. 
Published: July 2002

ABSTRACT

The
Salmonella
PmrA-PmrB system controls the expression of genes necessary for polymyxin B resistance. Four loci were previously identified as part of the regulon, and interaction of PmrA with the promoter region of three of them was observed. Here we characterized the interaction of PmrA with the promoter region of
ugd
, previously suggested to be regulated indirectly by PmrA. Our results indicate that PmrA controls the expression of
ugd
by interacting with a specific sequence in the promoter region of this gene.
A PhoP-Regulated Outer Membrane Protease of
Salmonella enterica
Serovar Typhimurium Promotes Resistance to Alpha-Helical Antimicrobial Peptides
Authors: Guina Tina , Yi Eugene C. , Wang Houle , Hackett Murray , Miller Samuel I. 
Published: July 2002

ABSTRACT

The outer membrane protein contents of
Salmonella enterica
serovar Typhimurium strains with PhoP/PhoQ regulon mutations were compared by two-dimensional gel electrophoresis. At least 26 species of outer membrane proteins (OMPs) were identified as being regulated by PhoP/PhoQ activation. One PhoP/PhoQ-activated OMP was identified by semiautomated tandem mass spectrometry coupled with electronic database searching as PgtE, a member of the
Escherichia coli
OmpT and
Yersinia pestis
Pla family of outer membrane proteases.
Salmonella
PgtE expression promoted resistance to alpha-helical cationic antimicrobial peptides (α-CAMPs). Strains expressing PgtE cleaved C18G, an 18-residue α-CAMP present in culture medium, indicating that protease activity is likely to be the mechanism of OmpT-mediated resistance to α-CAMPs. PhoP/PhoQ did not regulate the transcription or export of PgtE, indicating that another PhoP/PhoQ-dependent mechanism is required for PgtE outer membrane localization. PgtE is a posttranscriptionally regulated component of the PhoP/PhoQ regulon that contributes to
Salmonella
resistance to innate immunity.
Cooperative Regulation of
DOG2
, Encoding 2-Deoxyglucose-6-Phosphate Phosphatase, by Snf1 Kinase and the High-Osmolarity Glycerol–Mitogen-Activated Protein Kinase Cascade in Stress Responses of
Saccharomyces cerevisiae
Authors: Tsujimoto Yoshiyuki , Izawa Shingo , Inoue Yoshiharu 
Published: July 2002

ABSTRACT

We screened the genome of
Saccharomyces cerevisiae
for the genes responsive to oxidative stress by using the
lacZ
transposon-insertion library. As a result, we found that expression of the
DOG2
gene coding for 2-deoxyglucose-6-phosphate phosphatase was induced by oxidative stress. The expression of
DOG2
was also induced by osmotic stress. We found a putative
cis
element (STRE, a stress response element) in the
DOG2
promoter adjacent to a consensus sequence to which the Mig1p repressor is known to bind. The basal levels of
DOG2
gene expression were increased in a
mig1
Δ mutant, while the derepression of
DOG2
was not observed in a
snf1
Δ mutant under glucose-deprived conditions. Induction of the
DOG2
gene expression by osmotic stress was observed in any of the three disruptants
pbs2
Δ,
hog1
Δ, and
snf1
Δ. However, the osmotic induction was completely abolished in both the
snf1Δ pbs2
Δ mutant and the
snf1Δ hog1
Δ mutant. Additionally, these single mutants as well as double mutants failed to induce
DOG2
expression by oxidative stress. These results suggest that Snf1p kinase and the high-osmolarity glycerol–mitogen-activated protein kinase cascade are likely to be involved in the signaling pathway of oxidative stress and osmotic stress in regulation of
DOG2
.