bluuebunny/crossref_metadata_2025_split huggingface dataset:
(1→6)-β-d-Glucan as Cell Wall Receptor forPichia membranifaciensKiller Toxin
Authors: Santos A. , Marquina D. , Leal J. A. , Peinado J. M. 
Published: July 2002

ABSTRACTThe killer toxin fromPichia membranifaciensCYC 1106, a yeast isolated from fermenting olive brines, binds primarily to the (1→6)-β-d-glucan of the cell wall of a sensitive yeast (Candida boidiniiIGC 3430). The (1→6)-β-d-glucan was purified from cell walls ofC. boidiniiby alkali and hot-acetic acid extraction, a procedure which solubilizes glucans. The major fraction of receptor activity remained with the alkali-insoluble (1→6)-β- and (1→3)-β-d-glucans. The chemical (gas-liquid chromatography) and structural (periodate oxidation, infrared spectroscopy, and1H nuclear magnetic resonance) analyses of the fractions obtained showed that (1→6)-β-d-glucan was a receptor. Adsorption of most of the killer toxin to the (1→6)-β-d-glucan was complete within 2 min. Killer toxin adsorption to the linear (1→6)-β-d-glucan, pustulan, and a glucan fromPenicillium allahabadensewas observed. Other polysaccharides with different linkages failed to bind the killer toxin. The specificity of the killer toxin for its primary receptor provides an effective means to purify the killer toxin, which may have industrial applications for fermentations in which salt is present as an adjunct, such as olive brines. This toxin shows its maximum killer activity in the presence of NaCl. This report is the first to identify the (1→6)-β-d-glucan as a receptor for this novel toxin.
Mutants with Enhanced Nitrogenase Activity in HydroponicAzospirillum brasilense-Wheat Associations
Authors: Pereg Gerk Lily , Gilchrist Kate , Kennedy Ivan R. 
Published: July 2002

ABSTRACTThe effect of a mutation affecting flocculation, differentiation into cyst-like forms, and root colonization on nitrogenase expression byAzospirillum brasilenseis described. The geneflcAof strain Sp7 restored these phenotypes in spontaneous mutants of both strains Sp7 and Sp245. Employing both constitutive pLA-lacZandnifH-lacZreporter fusions expressed in situ, the colony morphology, colonization pattern, and potential for nitrogenase activity of spontaneous mutants andflcATn5-induced mutants were established. The results of this study show that the ability of Sp7 and Sp245 mutant strains to remain in a vegetative form improved their ability to express nitrogenase activity in association with wheat in a hydroponic system. Restoring the cyst formation and colonization pattern to the spontaneous mutant Sp7-S reduced nitrogenase activity rates in association with plants to that of the wild-type Sp7. Although Tn5-inducedflcAmutants showed higher potentials for nitrogenase expression than Sp7, their potentials were lower than that of Sp7-S, indicating that other factors in this strain contribute to its exceptional nitrogenase activity rates on plants. The lack of lateral flagella is not one of these factors, as Sp7-PM23, a spontaneous mutant impaired in swarming and lateral-flagellum production but not in flocculation, showed wild-type nitrogenase activity and expression. The results also suggest factors of importance in evolving an effective symbiosis betweenAzospirillumand wheat, such as increasing the availability of microaerobic niches along the root, increased supply of carbon sources by the plant, and the retention of the bacterial cells in vegetative form for faster metabolism.
Growth and Phylogenetic Properties of Novel Bacteria Belonging to the Epsilon Subdivision of the
Proteobacteria
Enriched from
Alvinella pompejana
and Deep-Sea Hydrothermal Vents
Authors: Campbell Barbara J. , Jeanthon Christian , Kostka Joel E. , Luther George W. , Cary S. Craig 
Published: July 2002

ABSTRACT

Recent molecular characterizations of microbial communities from deep-sea hydrothermal sites indicate the predominance of bacteria belonging to the epsilon subdivision of
Proteobacteria
(epsilon
Proteobacteria
). Here, we report the first enrichments and characterizations of four epsilon
Proteobacteria
that are directly associated with
Alvinella pompejana
, a deep sea hydrothermal vent polychete, or with hydrothermal vent chimney samples. These novel bacteria were moderately thermophilic sulfur-reducing heterotrophs growing on formate as the energy and carbon source. In addition, two of them (Am-H and Ex-18.2) could grow on sulfur lithoautrotrophically using hydrogen as the electron donor. Optimal growth temperatures of the bacteria ranged from 41 to 45°C. Phylogenetic analysis of the small-subunit ribosomal gene of the two heterotrophic bacteria demonstrated 95% similarity to
Sulfurospirillum arcachonense
, an epsilon
Proteobacteria
isolated from an oxidized marine surface sediment. The autotrophic bacteria grouped within a deeply branching clade of the epsilon
Proteobacteria
, to date composed only of uncultured bacteria detected in a sample from a hydrothermal vent along the mid-Atlantic ridge. A molecular survey of various hydrothermal vent environments demonstrated the presence of two of these bacteria (Am-N and Am-H) in more than one geographic location and habitat. These results suggest that certain epsilon
Proteobacteria
likely fill important niches in the environmental habitats of deep-sea hydrothermal vents, where they contribute to overall carbon and sulfur cycling at moderate thermophilic temperatures.
Quantitative Detection of Microbial Genes by Using DNA Microarrays
Authors: Cho Jae-Chang , Tiedje James M. 
Published: July 2002

ABSTRACT

To quantify target genes in biological samples using DNA microarrays, we employed reference DNA to normalize variations in spot size and hybridization. This method was tested using nitrate reductase (
nirS
), naphthalene dioxygenase (
nahA
), and
Escherichia coli
O157 O-antigen biosynthesis genes as model genes and lambda DNA as the reference DNA. We observed a good linearity between the log signal ratio and log DNA concentration ratio at DNA concentrations above the method's detection limit, which was approximately 10 pg. This approach for designing quantitative microarrays and the inferred equation from this study provide a simple and convenient way to estimate the target gene concentration from the hybridization signal ratio.
Highly Active Antiretroviral Therapy (HAART) and Circulating Markers of Immune Activation: Specific Effect of HAART on Neopterin
Authors: Amirayan-Chevillard Nathalie , Tissot-Dupont Herve , Obadia Yolande , Gallais Herve , Mege Jean-Louis , Capo Christian 
Published: July 2002

ABSTRACT
The circulating levels of immune activation markers, including neopterin, tumor necrosis factor receptor type II, and interleukin-2 receptors, are increased in human immunodeficiency virus-infected patients. We show here that highly active antiretroviral therapy significantly decreased neopterin levels. This effect is reversible, since neopterin levels increased after the arrest of treatment. Their determination may be useful in the evaluation of the efficacy of antiretroviral therapy.
Chemokine C10 Promotes Disease Resolution and Survival in an Experimental Model of Bacterial Sepsis
Authors: Steinhauser M. L. , Hogaboam C. M. , Matsukawa A. , Lukacs N. W. , Strieter R. M. , Kunkel S. L. 
Published: July 2002

ABSTRACTPrevious studies have suggested that the C-C chemokine C10 is involved in the chronic stages of host defense reactions. The present study addressed the role of C10 in a murine model of septic peritonitis, induced by cecal ligation and puncture (CLP). Unlike other C-C chemokines, C10 levels in the peritoneal wash were increased approximately 30-fold above baseline levels at 48 h after CLP surgery. Immunoneutralization of peritoneal C10 levels with polyclonal anti-C10 antiserum during CLP-induced peritonitis negatively impacted mouse survival over 4 days. In contrast, when 500 ng of recombinant murine C10 was administered immediately after CLP surgery, the 4-day survival rate increased from 20% to over 60%. The C10 therapy appeared to facilitate a rapid and significant enhancement of the levels of tumor necrosis factor alpha (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) and a later increase in interleukin-13 (IL-13) levels in the peritoneal cavity. In vitro studies showed that the combination of IL-1β and C10 markedly augmented TNF-α synthesis by peritoneal macrophages and that C10 synthesis was induced in these cells following their exposure to IL-13. At 24 h after CLP surgery, only 25% of C10-treated mice were bacteremic versus 85% of the control group that exhibited dissemination of bacteria into the circulation. The lack of bacteremia in C10-treated mice appeared to be related, in part, to in vitro evidence that C10 significantly enhanced the bacterial phagocytic activity of peritoneal macrophages. In addition, in vivo evidence suggested that C10 therapy significantly reduced the amount of material that leaked from the damaged gut. Taken together, the results of this study demonstrate that the C10 chemokine rapidly promotes disease resolution in the CLP model through its direct effects on the cellular events critically involved in host defense during septic peritonitis.
Phagocytosis and Protein Processing Are Required for Presentation ofCryptococcus neoformansMitogen to T Lymphocytes
Authors: Syme Rachel M. , Spurrell Jason C. L. , Ma Ling Ling , Green Francis H. Y. , Mody Christopher H. 
Published: July 2002

ABSTRACTIn addition to eliciting antigen specific T-cell-mediated immunity,Cryptococcus neoformanspossesses a mitogen (CnM) that activates naive T cells to proliferate. This mechanism of T-cell activation is accessory cell dependent and major histocompatibility complex unrestricted. CnM-induced T-cell proliferation correlates with internalization of the organism, suggesting that intracellular processing is required to liberate CnM prior to presentation to T cells. To determine whether phagocytosis and processing are required, various inhibitors of accessory cell uptake and processing were used.C. neoformanswas observed within the accessory cells. Paraformaldehyde fixation of the accessory cell abrogated presentation of CnM to T cells, indicating that a dynamic accessory cell surface was required. A lysosomotropic agent abrogated the response to CnM but had no effect on a control stimulus that did not require processing. Both aspartic acid and cysteine protease inhibitors blocked effective processing of CnM, so that it was unable to stimulate T cells. Finally, an inhibitor of microfilament polymerization abrogated proliferation to CnM. These results indicate that the mitogenic activity ofC. neoformansrequires phagocytosis of the organism, lysosomal or endosomal processing, proteolytic activity, and microfilament polymerization and intracellular transport as a prerequisite for T-cell proliferation.
Identification of Polymorphonuclear Leukocyte and HL-60 Cell Receptors for Adhesins ofStreptococcus gordoniiandActinomyces naeslundii
Authors: Ruhl Stefan , Cisar John O. , Sandberg Ann L. 
Published: July 2002

ABSTRACTInteractions of oral streptococci and actinomyces with polymorphonuclear leukocytes (PMNs), mediated by sialic acid- and Gal/GalNAc-reactive adhesins, respectively, result in activation of the PMNs and thereby may contribute to the initiation of oral inflammation. Sialidase treatment of PMNs or HL-60 cells abolished adhesion ofStreptococcus gordoniibut was required for adhesion ofActinomyces naeslundii. The same effects of sialidase were noted for adhesion of these bacteria to a major 150-kDa surface glycoprotein of either PMNs or undifferentiated HL-60 cells and to a 130-kDa surface glycoprotein of differentiated HL-60 cells. These glycoproteins were both identified as leukosialin (CD43) by immunoprecipitation with a specific monoclonal antibody (MAb). Adhesion of streptococci and actinomyces to a 200-kDa minor PMN surface glycoprotein was also detected by bacterial overlay of untreated and sialidase-treated nitrocellulose transfers, respectively. This glycoprotein was identified as leukocyte common antigen (CD45) by immunoprecipitation with a specific MAb. CD43 and CD45 both possess extracellular mucinlike domains in addition to intracellular domains that are implicated in signal transduction. Consequently, the interactions of streptococci and actinomyces with the mucinlike domains of these mammalian cell surface glycoproteins result not only in adhesion but, in addition, may represent the initial step in PMN activation by these bacteria.
Construction and Characterization of a Nonproliferative El Tor Cholera Vaccine Candidate Derived from Strain 638
Authors: Valle Edgar , Ledón Talena , Cedré Bárbara , Campos Javier , Valmaseda Tania , Rodríguez Boris , García Luis , Marrero Karen , Benítez Jorge , Rodríguez Sandra , Fando Rafael 
Published: July 2002

ABSTRACT

In recent clinical assays, our cholera vaccine candidate strain,
Vibrio cholerae
638 El Tor Ogawa, was well tolerated and immunogenic in Cuban volunteers. In this work we describe the construction of 638T, a thymidine auxotrophic version of improved environmental biosafety. In so doing, the
thyA
gene from
V. cholerae
was cloned, sequenced, mutated in vitro, and used to replace the wild-type allele. Except for its dependence on thymidine for growth in minimal medium, 638T is essentially indistinguishable from 638 in the rate of growth and morphology in complete medium. The two strains showed equivalent phenotypes with regard to motility, expression of the
celA
marker, colonization capacity in the infant mouse cholera model, and immunogenicity in the adult rabbit cholera model. However, the ability of this new strain to survive environmental starvation was limited with respect to that of 638. Taken together, these results suggest that this live, attenuated, but nonproliferative strain is a new, promising cholera vaccine candidate.
Hemolytic and Hemoxidative Activities inMycoplasma penetrans
Authors: Kannan T. R. , Baseman Joel B. 
Published: July 2002

ABSTRACTMycoplasma penetransis a newly isolatedMollicutefrom the urine of patients infected with human immunodeficiency virus that demonstrates the capacity to adhere to and invade human cells. A previous report, based on assays with mouse red blood cells (RBCs), indicated thatM. penetranslacked hemolytic activity. In our studies, we incubated different isolates ofM. penetranswith various RBC species and observed hemolytic zones surrounding individual mycoplasma colonies. AllM. penetransstrains displayed hemolysis after 2 to 3 days of incubation. Hemolytic activity diffused from single colonies, eventually causing complete lysis. Hemolysis was most pronounced with sheep RBCs, followed by horse, chicken, and human cells. Furthermore, hemolytic activity was demonstrable in both intact mycoplasma cell preparations and spent culture supernatant. However, unlike intact mycoplasmas, the hemolytic activity in the supernatant was dependent on the reducing agent, cysteine. In addition to hemolysis, a brown precipitate was closely associated with mycoplasma colonies, suggesting oxidation of hemoglobin. Absorption spectra indicated that hemoglobin was oxidized to methemoglobin, and the addition of catalase demonstrated H2O2-mediated hemoxidation. Other experiments suggested that hemoxidation enhanced total hemolysis, providing the first evidence of both hemolytic and hemoxidative activities inM. penetrans.
Temporal Pore Formation-Mediated Egress from Macrophages and Alveolar Epithelial Cells byLegionella pneumophila
Authors: Alli O. A. Terry , Gao Lian-Yong , Pedersen Lisa L. , Zink Steven , Radulic Marina , Doric Miljenko , Abu Kwaik Yousef 
Published: July 2002

ABSTRACTLegionella pneumophiladoes not induce apoptosis in the protozoan host, but induces pore formation-mediated cytolysis after termination of intracellular replication (L.-Y. Gao and Y. Abu Kwaik, Environ. Microbiol. 2:79–90, 2000). In contrast to this single mode of killing of protozoa, we have recently proposed a biphasic model by whichL. pneumophilakills macrophages, in which the first phase is manifested through the induction of apoptosis during early stages of the infection, followed by an independent and temporal induction of necrosis during late stages of intracellular replication. Here we show that, similar to the protozoan host, the induction of necrosis and cytolysis of macrophages byL. pneumophilais mediated by the pore-forming toxin or activity. This activity is temporally and maximally expressed only upon termination of bacterial replication and correlates with cytolysis of macrophages and alveolar epithelial cells in vitro. We have identified fiveL. pneumophilamutants defective in the pore-forming activity. The phagosomes harboring the mutants do not colocalize with the late endosomal or lysosomal marker Lamp-1, and the mutants replicate intracellularly similar to the parental strain. Interestingly, despite their prolific intracellular replication, the mutants are defective in cytotoxicity and are “trapped” within and fail to lyse and egress from macrophages and alveolar epithelial cells upon termination of intracellular replication. However, the mutants are subsequently released from the host cell, most likely due to apoptotic death of the host cell. Data derived from cytotoxicity assays, confocal laser scanning microscopy, and electron microscopy confirm the defect in the mutants to induce necrosis of macrophages and the failure to egress from the host cell. Importantly, the mutants are completely defective in acute lethality (24 to 48 h) to intratracheally inoculated A/J mice. We conclude that the pore-forming activity ofL. pneumophilais not required for phagosomal trafficking or for intracellular replication. This activity is expressed upon termination of bacterial replication and is essential to induce cytolysis of infected macrophages to allow egress of intracellular bacteria. In addition, this activity plays a major role in pulmonary immunopathology in vivo.
Expression of Peptidoglycan-Associated Lipoprotein Is Required for Virulence in the Human Model ofHaemophilus ducreyiInfection
Authors: Fortney Kate R. , Young Royden S. , Bauer Margaret E. , Katz Barry P. , Hood Antoinette F. , Munson Robert S. , Spinola Stanley M. 
Published: July 2002

ABSTRACTHaemophilus ducreyiexpresses a peptidoglycan-associated lipoprotein (PAL) that exhibits extensive homology toHaemophilus influenzaeprotein 6. We constructed an isogenic PAL mutant (35000HP-SMS4) by the use of a suicide vector that containslacZas a counterselectable marker.H. ducreyi35000HP-SMS4 and its parent, 35000HP, had similar growth rates in broth and similar lipooligosaccharide profiles. 35000HP-SMS4 formed smaller, more transparent colonies than 35000HP and, unlike its parent, was hypersensitive to antibiotics. Complementation of the mutant intransrestored the parental phenotypes. To test whether expression of PAL is required for virulence, nine human volunteers were experimentally infected. Each subject was inoculated with two doses (41 to 89 CFU) of live 35000HP and one dose of heat-killed bacteria on one arm and with three doses (ranging from 28 to 800 CFU) of live 35000HP-SMS4 on the other arm. Papules developed at similar rates at sites inoculated with the mutant or parent but were significantly smaller at mutant-inoculated sites than at parent-inoculated sites. The pustule formation rate was 72% (95% confidence interval [CI], 46.5 to 90.3%) at 18 parent sites and 11% (95% CI, 2.4 to 29.2%) at 27 mutant sites (P< 0.0001). The rates of recovery ofH. ducreyifrom surface cultures were 8% (n= 130; 95% CI, 4.3 to 14.6%) for parent-inoculated sites and 0% (n= 120; 95% CI, 0.0 to 2.5%) for mutant-inoculated sites (P< 0.001).H. ducreyiwas recovered from six of seven biopsied parent-inoculated sites and from one of three biopsied mutant-inoculated sites. Confocal microscopy confirmed that the bacteria present in a mutant inoculation site pustule lacked a PAL-specific epitope. Although biosafety regulations precluded our testing the complemented mutant in humans, these results suggest that expression of PAL facilitates the ability ofH. ducreyito progress to the pustular stage of disease.
Identification of an Antigen Localized to an Apparent Septum within Dividing Chlamydiae
Authors: Brown W. J. , Rockey D. D. 
Published: July 2002

ABSTRACT

The process of chlamydial cell division has not been thoroughly investigated. The lack of detectable peptidoglycan and the absence of an FtsZ homolog within chlamydiae suggest an unusual mechanism for the division process. Our laboratory has identified an antigen (SEP antigen) localized to a ring-like structure at the apparent septum within dividing chlamydial reticulate bodies (RB). Antisera directed against SEP show similar patterns of antigen distribution in
Chlamydia trachomatis
and
Chlamydia psittaci
RB. In contrast to localization in RB, SEP in elementary bodies appears diffuse and irregular, suggesting that the distribution of the antigen is developmental-stage specific. Treatment of chlamydiae with inhibitors of peptidoglycan synthesis or culture of chlamydiae in medium lacking tryptophan leads to the formation of nondividing, aberrant RB. Staining of aberrant RB with anti-SEP reveals a marked redistribution of the antigen. Within
C. trachomatis
-infected cells, ampicillin treatment leads to high levels of SEP accumulation at the periphery of aberrant RB, while in
C. psittaci
, treatment causes SEP to localize to distinct punctate sites within the bacteria. Aberrancy produced via tryptophan depletion results in a different pattern of SEP distribution. In either case, the reversal of aberrant formation results in the production of normal RB and a redistribution of SEP to the apparent plane of bacterial division. Collectively these studies identify a unique chlamydial-genus-common and developmental-stage-specific antigen that may be associated with RB division.
Intracellular Infection by the Human Granulocytic Ehrlichiosis Agent Inhibits Human Neutrophil Apoptosis
Authors: Yoshiie Kiyotaka , Kim Hyung-Yong , Mott Jason , Rikihisa Yasuko 
Published: July 2002

ABSTRACTIn patients with human granulocytic ehrlichiosis (HGE), the HGE agent has been seen only in the peripheral blood granulocytes, which have a life span too short for ehrlichial proliferation. To determine if the HGE agent delays the apoptosis of human peripheral blood neutrophils for its advantage, peripheral blood granulocytes consisting mostly of neutrophils were incubated with freshly freed host cell-free HGE agent in vitro. The HGE agent induced a significant delay in morphological apoptosis and the cytoplasmic appearance of histone-associated DNA fragments in the granulocytes. This antiapoptotic effect was dose dependent. Although much weaker than the HGE agent freshly freed from the host cells, noninfectious purified HGE agent stored frozen and thawed also had antiapoptotic effect, which was lost with proteinase K treatment but not with periodate treatment. Treatment of neutrophils with a transglutaminase inhibitor, monodansylcadaverine, blocked the antiapoptotic effect of the HGE agent. Addition of oxytetracycline, however, did not prevent or reverse the antiapoptotic effect of the HGE agent. These results suggest that binding of a protein component(s) of the HGE agent to neutrophils and subsequent cross-linking and/or internalization of the receptor and ehrlichiae are required for antiapoptotic signaling, but ehrlichial protein synthesis and/or proliferation is not required. MG-132, a proteasome inhibitor, and cycloheximide accelerated the apoptosis of neutrophils and overrode the antiapoptotic effect of the HGE agent. Studies with specific inhibitors suggest that protein kinase A, NF-κB, and interleukin 1β are not involved in the antiapoptotic mechanism of the HGE agent.