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At least 217 records · Page 12Linked to original sources
PubMed2006

Improved immunogenicity of a H44/76 group B outer membrane vesicle vaccine with over-expressed genome-derived Neisserial antigen 1870.

A broadly protective vaccine against meningococcal group B disease is not available. We previously reported that an outer membrane vesicle (OMV) vaccine containing over-expressed genome-derived antigen (GNA) 1870 elicited broader protective antibody responses than recombinant GNA1870 or conventional OMV vaccines prepared from a strain that naturally expresses low amounts of GNA1870. Certain wildtype strains such as H44/76 naturally express larger amounts of GNA1870 and, potentially, could be used to prepare an improved OMV vaccine without genetic over-expression of the antigen. We transformed H44/76 with a shuttle vector to over-express variant 1 (v.1) GNA1870 and compared the immunogenicity in mice of OMV vaccines prepared from wildtype H44/76 (v.1), the mutant, and a recombinant v.1 GNA1870 vaccine. Mice immunized with OMV with over-expressed GNA1870 developed broader serum bactericidal and/or greater C3 deposition activity on the surface of encapsulated strains of N. meningitidis than control mice immunized with the OMV vaccine prepared from the wildtype strain, or the rGNA1870 vaccine. When a panel of group B strains from patients in California was tested, sera from mice immunized with the OMV vaccine containing over-expressed GNA1870 were bactericidal against 100% of the v.1 strains. In contrast, only 20% of isolates that expressed subvariants of the v.1 GNA1870 protein were susceptible to bactericidal activity of antibodies elicited by the rGNA1870 or conventional OMV vaccines. Thus, even a modest increase in GNA1870 expression in a strain that naturally is a high producer of GNA1870 results in an OMV vaccine that elicits broader protection against meningococcal disease.

Animals↗
PubMed2006

The effect of capsid mutations on HIV-1 uncoating.

Efficient uncoating requires not only an optimal cellular environment, but also some intrinsic properties of the viral capsid protein itself. Using an in vitro uncoating model, we demonstrated that substitution of each serine residue with alanine at the three major phosphorylation sites of HIV-1 capsid protein, i.e. Ser-109, Ser-149 and Ser-178, could significantly reduce uncoating activity of purified core particles. We also showed that the core stability of mutant viruses was lower than that of the wild-type virus so that the lack of efficient uncoating of each mutant could not be due to an increase in capsid physical stability. However, serine-to-aspartic acid mutation to mimic the negative charge of phosphor-serine could not restore either uncoating activity or infectivity, and treatment of purified core particles with a phosphatase did not alter the uncoating activity. Our data indicated that mutations at phosphoacceptor sites of capsid disturbed the uncoating mechanism, but the defect may not be directly caused by the lack of phosphate on the core particles undergoing uncoating.

Amino Acid Substitution↗
PubMed2006

A second-site suppressor significantly improves the defective phenotype imposed by mutation of an aromatic residue in the N-terminal domain of the HIV-1 capsid protein.

The HIV-1 capsid (CA) protein plays an important role in virus assembly and infectivity. Previously, we showed that Ala substitutions in the N-terminal residues Trp23 and Phe40 cause a severely defective phenotype. In searching for mutations at these positions that result in a non-lethal phenotype, we identified one candidate, W23F. Mutant virions contained aberrant cores, but unlike W23A, also displayed some infectivity in a single-round replication assay and delayed replication kinetics in MT-4 cells. Following long-term passage in MT-4 cells, two second-site mutations were isolated. In particular, the W23F/V26I mutation partially restored the wild-type phenotype, including production of particles with conical cores and wild-type replication kinetics in MT-4 cells. A structural model is proposed to explain the suppressor phenotype. These findings describe a novel occurrence, namely suppression of a mutation in a hydrophobic residue that is critical for maintaining the structural integrity of CA and proper core assembly.

Capsid Proteins↗
PubMed2005

Microbial community activities during establishment, performance, and decline of bench-scale passive treatment systems for mine drainage.

Permeable reactive barrier (PRB) technology, in which sulfate-reducing bacteria (SRB) facilitate precipitation of metal sulfides, is a promising approach for remediation of sulfate- and metal-laden mine drainage. While PRBs are easily established, they often decline for reasons not well understood. SRB depend on or compete with multiple dynamic microbial populations within a PRB; as a result, performance depends on the changing PRB chemical composition and on succession and competition within the microbial community. To investigate these interactions, we constructed and monitored eight bench-scale PRBs to define periods of establishment, performance, and decline. We then conducted short-term batch studies, using substrate-supplemented column materials, on Days 0 (pre-establishment), 27 (establishment), 41 (performance), and 99 (decline) to reveal potential activities of cellulolytic bacteria, fermenters + anaerobic respirers, SRB, and methanogens. PRBs showed active sulfate reduction, with sulfate removal rates (SRR) of approximately 1-3 mol/m3/d, as well as effective removal of Zn2+. Potential activities of fermentative + anaerobic respiratory bacteria were initially high but diminished greatly during establishment and dropped further during performance and decline. In contrast, potential SRB activity rose during establishment, peaked during performance, and diminished as performance declined. Potential methanogen activity was low; in addition, SRB-methanogen substrate competition was shown not to limit SRB activity. Cellulolytic bacteria showed no substrate limitation at any time. However, fermenters experienced substrate limitation by Day 0, SRB by Day 27, and methanogens by Day 41, showing the dependence of each group on upstream populations to provide substrates. All potential activities, except methanogenesis, were ultimately limited by cellulose hydrolysis; in addition, all potential activities except methanogenesis declined substantially by Day 99, showing that long-term substrate deprivation strongly diminished the intrinsic capacity of the PRB community to perform.

Alkalies↗
PubMed2006

Long-term storage conditions for carriers with denitrifying biomass of the fluidized, methanol-fed denitrification reactor of the Montreal Biodome, and the impact on denitrifying activity and bacterial population.

The Montreal Biodome has a denitrification system to stabilize the nitrate concentration in its 3 million liter seawater aquarium. However, this microbial process has failed periodically due to various technical problems. The system can take several weeks to recover its full denitrification capacity. In order to provide the denitrification system with a backup of active biomass, different freezing conditions for the denitrifying biomass were tested. The biomass was conserved for 1 week-17 months at -20 degrees C with and without glycerol or at -80 degrees C with and without glycerol, and the denitrifying activity was tested in batch culture for 140 h periods at various intervals. Our results showed that glycerol was required for fast recovery of the microbial community's denitrifying activity. The -20 degrees C and -80 degrees C conservation temperatures with glycerol gave similar results although there was a short period of nitrite accumulation in the -20 degrees C sample. There were no substantial changes in the microbial community of any of the frozen samples after 17 months of conservation as monitored by denaturing gradient gel electrophoresis. This is the first report on the long-term conservation of a complex denitrifying population by freezing.

Biomass↗
PubMed2006

Evidence-based model for hand transmission during patient care and the role of improved practices.

Hand cleansing is the primary action to reduce health-care-associated infection and cross-transmission of antimicrobial-resistant pathogens. Patient-to-patient transmission of pathogens via health-care workers' hands requires five sequential steps: (1) organisms are present on the patient's skin or have been shed onto fomites in the patient's immediate environment; (2) organisms must be transferred to health-care workers' hands; (3) organisms must be capable of surviving on health-care workers' hands for at least several minutes; (4) handwashing or hand antisepsis by the health-care worker must be inadequate or omitted entirely, or the agent used for hand hygiene inappropriate; and (5) the caregiver's contaminated hand(s) must come into direct contact with another patient or with a fomite in direct contact with the patient. We review the evidence supporting each of these steps and propose a dynamic model for hand hygiene research and education strategies, together with corresponding indications for hand hygiene during patient care.

Education↗
PubMed2005

Improvement of immunodetection of bacterial spore antigen by ultrasonic cavitation.

Ultrasonic cavitation was employed to enhance sensitivity of bacterial spore immunoassay detection, specifically, enzyme-linked immunosorbent assay (ELISA) and resonant mirror (RM) sensing. Bacillus spore suspensions were exposed to high-power ultrasound in a tubular sonicator operated at 267 kHz in both batch and flow modes. The sonicator was designed to deliver high output power and is in a form that can be cooled efficiently to avoid thermal denaturation of antigen. The 30-s batch and cooled flow (0.3 mL/min) sonication achieved an approximately 20-fold increase in ELISA sensitivity compared to unsonicated spores by ELISA. RM sensing of sonicated spores achieved detection sensitivity of approximately 10(6) spores/mL, whereas unsonicated spores were undetectable at the highest concentration tested. Improvements in detection were associated with antigen released from the spores. Equilibrium temperature increase in the tubular sonicator was limited to 14 K after 30 min and was maintained for 6 h with cooling and flow (0.3 mL/min). The work described here demonstrates the utility of the tubular sonicator for the improvement in the sensitivity of the detection of spores and its suitability as an in-line component of a rapid detection system.

Antigens, Bacterial↗
PubMed2005

Desorption/ionization fluence thresholds and improved mass spectral consistency measured using a flattop laser profile in the bioaerosol mass spectrometry of single Bacillus endospores.

Bioaerosol mass spectrometry is being developed to analyze and identify biological aerosols in real time. Mass spectra of individual Bacillus endospores were measured with a bipolar aerosol time-of-flight mass spectrometer in which molecular desorption and ionization were produced using a single laser pulse from a Q-switched, frequency-quadrupled Nd:YAG laser that was modified to have an approximately flattop profile. The flattened laser profile allowed the minimum fluence required to desorb and ionize significant numbers of ions from single aerosol particles to be determined. For Bacillus spores, this threshold had a mean value of approximately 1 nJ/microm(2) (0.1 J/cm(2)). Thresholds for individual spores, however, could apparently deviate by 20% or more from the mean. Threshold distributions for clumps of MS2 bacteriophage and bovine serum albumin were subsequently determined. Finally, the flattened profile was observed to increase the reproducibility of single-spore mass spectra. This is consistent with the general conclusions of our earlier paper on the fluence dependence of single-spore mass spectra and is particularly significant because it is expected to enable more robust differentiation and identification of single bioaerosol particles.

Aerosols↗
PubMed2025

Rv2741 Promotes Mycobacterium Survival by Modulating Macrophage Function via the IL-1α-MAPK Axis.

One of the primary healthcare problems in the world today is tuberculosis (TB), a chronic infectious illness brought on by Mycobacterium tuberculosis (M. tuberculosis). A distinct family of PE_PGRS proteins, encoded by the M. tuberculosis genome, has attracted more attention because of their involvement in immune evasion and bacterial pathogenicity. Nevertheless, the specific functions and mechanisms of action for the majority of PE_PGRS proteins remain largely unexplored. This study focuses on the Rv2741 (PE_PGRS47) gene, which is exclusively present in pathogenic mycobacteria. To examine the function of Rv2741 in host-pathogen interactions, we created recombinant strains of Mycobacterium smegmatis (M. smegmatis) that expressed the M. tuberculosis Rv2741 gene. IL-1α was found to be a key mediator of host response modulation by Rv2741. Rv2741 downregulates the secretion of IL-1α and inhibits the MAPK signaling pathway, particularly the p38 and ERK1/2 pathways, thereby cooperatively inhibiting macrophage autophagy and apoptosis. Meanwhile, the decrease in IL-1α secretion directly leads to changes in the cytokine secretion pattern and a reduction in nitric oxide (NO) production. This multifaceted regulatory mechanism ultimately favors the survival of M. smegmatis in macrophages. This research significantly expands our understanding of Rv2741 function, revealing its crucial role as a multifunctional virulence factor in the immune evasion of M. tuberculosis.

Interleukin-1alpha↗
PubMedDate not supplied

Stochastic modeling of S. cerevisiae inactivation by supercritical CO2.

Pasteurization of S. cerevisiae in a simple substrate with supercritical CO(2) was performed at 36 degrees C on a laboratory multibatch apparatus of a total volume of 150 mL. The pressure values ranged from 100 to 300 bar. The results show a clear dependence between inactivation ratio and increase of pressure. A mathematical modeling of the process was exploited to fit the experimental evidences: inactivation curves were analyzed using a stochastic model based on the multihit model (1). The nonlinear survival curve shows a shoulder and a tail which represent the lag and the resistant phase, respectively. The meaning of the nonlinear relationship between inactivation ratio and time is also discussed; the effect of pressure on the values assumed by the parameters of the model proposed was investigated.

Carbon Dioxide↗
PubMed2005

Seasonal temperature fluctuations induces rapid inactivation of Cryptosporidium parvum.

This study measured the inactivation rate of bovine genotype A Cryptosporidium parvum oocysts attributable to diurnal oscillations of ambient temperature and solar radiation typical of California rangelands and dairies from spring through autumn. We first measured the relationship between air temperature and the internal temperature of bovine feces exposed to sunlight on commercial operations throughout California. Once maximum air temperature exceeded the mid 20 degrees C, diurnal thermal regimes of bovine fecal material exhibited peaks of over 40, 50, 60, and 70 degrees C. These diurnal thermal regimes were emulated using a thermocycler, with oocysts suspended in distilled water or fecal-water mix. Using oral inoculations of 10(5) C. parvum oocysts per neonatal Balb/c mouse (>1000-fold the ID50), no infections were observed using 1 to 5-day cycles of these thermal regimes. Loss of infectivity induced bythese thermal regimes was primarily due to partial or complete in vitro excystation during the first 24-h diurnal cycle and secondarily to thermal inactivation of the remaining intact or partial oocysts. These results suggest that as ambient conditions generate internal fecal temperatures > or = 40 degrees C via conduction, radiation, and convection, rapid environmental inactivation occurs at a rate of > or = 3.27 log reduction d(-1) for C. parvum oocysts deposited in the feces of cattle.

Animals↗
PubMed2005

Review of factors affecting microbial survival in groundwater.

This review quantitatively examines a number of published studies that evaluated survival and inactivation of public-health-related microorganisms in groundwater. Information from reviewed literature is used to express microbial inactivation in terms of log10 decline per day for comparison to other studies and organisms. The geometric mean value for inactivation rates for coliphage, poliovirus, echovirus, coliform bacteria, enterococci, and Salmonella spp. were similar at approximately 0.07-0.1 log10 day(-1), while geometric mean inactivation rates for hepatitis A virus, coxsackievirus, and phage PRD-1 were somewhat less at 0.02-0.04 log10 day(-1). Viruses show a temperature dependency with greater inactivation at greater temperatures; however this occurs largely at temperatures greater than 20 degrees C. Coliform bacteria die off in groundwater does not show the temperature dependency that viruses show, likely indicating a complex interplay of inactivation and reproduction subject to influences from native groundwater organisms, temperature, and water chemistry. The presence of native microorganisms seems to negatively impact E. coli survival more so than viruses, but in most cases, nonsterile conditions led to a greater inactivation for viruses also. The effect of attachment to solid surfaces appears to be virus-type-dependent, with PRD-1 more rapidly inactivated as a result of attachment and hepatitis A and poliovirus survival prolonged when attached.

Bacterial Physiological Phenomena↗
PubMed2005

Inactivation of Microcystis aeruginosa by continuous electrochemical cycling process in tube using Ti/RuO2 electrodes.

Algae in waters often bring about influence in drinking water supplies. In this study, an electrochemical tube employing titanium coated with RuO2 as anode was constructed for inactivation of cyanobacteria (often called bluegreen algae) Microcystis aeruginosa. Suspensions containing M. aeruginosa (2-4 x 10(9) L(-1)) were exposed to current densities ranging from 1 to 10 mA cm(-2) in a detention time of 52 min. The variations of cell density, chlorophyll-a, optical density, pH, and conductivity were examined during the treatment. After 3.5 min the population of M. aeruginosa dropped rapidly and was reduced from 3 x 10(9) to 0.6 x 10(9) L(-1) after 52 min at current densities from 5 to 10 mA cm(-2). The cell density and optical density of M. aeruginosa decreased proportionally to the current density and the detention time. Scanning electron microscopy investigation of algae revealed surface damage and apparent leakage of intracellular contents after electrochemical cycling process. Due to the damage of cells, the chlorophyll-a released from the cells was degraded by electrochemical oxidation. The removal rate of chlorophyll-a could reach 96% at the current density of 10 mA cm(-2). Electrochemical treatment caused minor variation of pH values and conductivity of the suspensions. After electrochemical cycling processes, the optical density at 680 nm of algal cell suspensions remained below 0.1 after 6 days, and it showed that cells had no potential to survive and grow. The results implicated that the inactivation of M. aeruginosa was successfully performed by the electrochemical treatment, and it made the algal cells lose ability to survive, demonstrating the potential of such an alternative process for efficient water purification.

Analysis of Variance↗
PubMed2006

The Bogorol family of antibiotics: template-based structure elucidation and a new approach to positioning enantiomeric pairs of amino acids.

The sequence positions of d and l Leu and Lys residues in bogorol A (1) have been defined by a simple and novel approach that utilizes small amounts of sample and focuses on detecting the order in which amino acids are liberated from the parent peptide during acid-catalyzed hydrolysis. This technique builds on a previously established relationship between the steric and electronic features of amino acids and their predilection for acidic liberation from polypeptides via dipeptides. The results, which complete the structure of bogorol A, have been confirmed by traditional degradation experiments. Utilizing the knowledge of the structure of bogorol A (1) as a template, we rapidly elucidated the structures of bogorols B-E (2-5) via analysis of ESI-MS and ESI-MS/MS data and GC analysis of degradation products. The bogorol cationic peptide antibiotics contain a number of unusual structural features, which include the reduction of the C-terminal residue to valinol, an N-terminal residue of 2-hydroxy-3-methylpentanoic acid, the incorporation of four d amino acids, and the presence of a dehydroamino acid. Bogorols show selective and relatively potent activity against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus spp., as well as moderate activity against Escherichia coli.

Amino Acid Sequence↗
PubMed2006

CFTR regulates phagosome acidification in macrophages and alters bactericidal activity.

Acidification of phagosomes has been proposed to have a key role in the microbicidal function of phagocytes. Here, we show that in alveolar macrophages the cystic fibrosis transmembrane conductance regulator Cl- channel (CFTR) participates in phagosomal pH control and has bacterial killing capacity. Alveolar macrophages from Cftr-/- mice retained the ability to phagocytose and generate an oxidative burst, but exhibited defective killing of internalized bacteria. Lysosomes from CFTR-null macrophages failed to acidify, although they retained normal fusogenic capacity with nascent phagosomes. We hypothesize that CFTR contributes to lysosomal acidification and that in its absence phagolysosomes acidify poorly, thus providing an environment conducive to bacterial replication.

Animals↗
PubMed2006

Persister cells, dormancy and infectious disease.

Several well-recognized puzzles in microbiology have remained unsolved for decades. These include latent bacterial infections, unculturable microorganisms, persister cells and biofilm multidrug tolerance. Accumulating evidence suggests that these seemingly disparate phenomena result from the ability of bacteria to enter into a dormant (non-dividing) state. The molecular mechanisms that underlie the formation of dormant persister cells are now being unravelled and are the focus of this Review.

Adaptation, Physiological↗
PubMed2026

Mycobacterium tuberculosis MEM39 (Rv1977) hijacks host aldolase A (ALDOA) to subvert immunometabolism to facilitate bacterial intracellular survival.

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), is the leading cause of infectious disease-related death. As a major intracellular pathogen, Mtb can escape clearance by the immune system, but the underlying molecular mechanisms remain incompletely elucidated. Specific genomic regions of deletion (RD)-encoded proteins in virulent Mtb H37Rv have been implicated in modulating pathogenicity and immunity. Here, we report a novel RD15-encoding protein, Rv1977 (a mycobacterial cell wall protein with a size of 39 kDa, named MEM39), which facilitates Mtb survival in macrophages. The survival of the Mtb H37Rv MEM39-deficient strain is reduced in both macrophage and murine infection models. Furthermore, the mycobacterial MEM39 protein binds fructose-diphosphate aldolase A (ALDOA), a key enzyme of glycolysis, thereby impairing ALDOA enzyme activity, disrupting macrophage metabolite flux, and reducing lactate production. The MEM39-ALDOA interaction also suppresses lysosomal acidification; reduces NLRP3 inflammasome activation and the production of proinflammatory cytokines (TNF-α, IL-6 and IL-1β); and thereby promotes bacterial survival within macrophages. Disruption of the interaction between MEM39-ALDOA and a cell-penetrating synthetic peptide (VLARYASICQ) significantly suppressed Mtb survival by restoring lactate production, lysosome acidification and proinflammatory cytokine production in both macrophage and mouse infection models. These findings revealed that mycobacterial MEM39 negatively regulates host immune defense through reprogramming ALDOA-mediated glycolysis in macrophages, thereby forming a "mycobacterial MEM39 virulence factor-glycolysis metabolism-immunity" regulatory axis. Targeting MEM39 or the MEM39-ALDOA interaction interface holds promise as a new therapeutic strategy against tuberculosis.

Mycobacterium tuberculosis↗