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At least 793 records · Page 44Linked to original sources
PubMed2006

Stimulatory and inhibitory effects of organohalides on the dehalogenating activities of PCB-dechlorinating bacterium o-17.

Bacterium o-17, a microorganism capable of the ortho dechlorination of 2,3,5,6-polychlorinated biphenyl (PCB), is a member of a sediment-free, nonmethanogenic mixed culture. The culture was examined for the ability to dechlorinate 26 PCB congeners, 12 chlorobenzenes (CBZs), and 6 chlorinated ethenes (CEs). Eight of the PCBs and 4 of the CBZs were dechlorinated including single-flanked ortho PCB chlorines, but double-flanked chlorines of PCBs and CBZs were preferentially dechlorinated. The dechlorination of three of the PCBs (2,3,4,5,6-, 2,3,4,6-, and 2,3,5,6-PCB), three of the CBZs (hexa-, penta-, and 1,2,3-CBZ), and PCE could be sustained for three or more sequential transfers of the bacterial community. Two PCBs (2,3,4- and 2,3,5-PCB), two CBZs (1,2,3,5- and 1,2,4,5-CBZ), and trichloroethene were dechlorinated only when a more extensively chlorinated parent compound was present. Aroclor 1260 and 2,4,6-PCB, not dechlorinated by the culture, inhibited the dechlorination of 2,3,5,6-PCB. Within the culture only bacterium o-17 was linked to dechlorination by PCR-DGGE analysis, confirming that this dehalogenating species was the catalyst for the dechlorination of the compounds tested. The microorganism is capable of dechlorinating several different congeners of PCBs, CBZs, and CEs, and it remains a rare example of an ortho-PCB dechlorinator. However, its limited ability to dechlorinate more extensively chlorinated congeners and Aroclor plus the inhibitory effects of some PCB congeners upon the bacterium is consistent with the observed infrequency of this reaction in the environment. An assessment of bioremediation potential of this microorganism in situ will require a greater understanding of the synergistic, cometabolic and competitive interactions of PCB dechlorinating microbial communities.

Bacteria↗
PubMed1996

Excipient interaction with cetylpyridinium chloride activity in tablet based lozenges.

PURPOSE: The purpose of the investigation was to determine the effect of tablet excipients on the activity of cetylpyridinium chloride (CPC) and the relative interaction between excipients and CPC. METHODS: An analytical assay was developed to evaluate the interaction between CPC and the excipients. In vivo activity was investigated using six volunteers by determining the reduction in colony forming units recoverable from the oropharynx after sucking each proprietary lozenge separately on different days. In vitro determinations investigated the relative antimicrobial activity of aqueous solutions of the lozenges and, the effect of pH and tablet base excipients on that activity against Staphylococcus aureus, Streptococcus pyogenes and Candida albicans. RESULTS: Both in vivo and in vitro results showed that the tablet based lozenges had markedly reduced antimicrobial activities compared with previous results with a candy based lozenge (in vivo and in vitro) or the same concentration of aqueous CPC (in vitro). Magnesium stearate suspensions in CPC 250 micrograms/ml indicated that magnesium stearate adsorbed CPC and at 0.4% lozenge weight and above significantly reduced the antimicrobial activity of CPC 250 micrograms/ml. CONCLUSIONS: The reduced activity of CPC in tablet based lozenges resulted from a decreased availability of CPC in solution due to an adsorption of CPC on magnesium stearate. To avoid this reduction in activity tablet based lozenges containing CPC 250 micrograms/ml, or similar concentrations, plus magnesium stearate should contain not more than 0.3% w/w lozenge weight of the lubricant.

Administration, Oral↗
PubMed2004

Monomeric analogues of halocidin.

Halocidin is a heterodimeric antimicrobial peptide isolated from a tunicate, Halocynthia aurantium. We used the most active of the two monomers, an 18 residue amidated peptide, as lead structure and determined the role of each amino acid with alanine scanning. The results obtained led to the synthesis of a first generation of analogues with antimicrobial activity. The selectivity towards bacterial versus mammalian cells has been explored, as well as the specificity for gram positive (Staphylococcus aureus ATCC 25923) versus gram negative bacteria (Escherichia coli ATCC 25922). GRAVY (grand average of hydropathicity) was used to analyze the results.

Alanine↗
PubMed2000

Interaction of dendritic cells with mycobacteria: where the action starts.

Dendritic cells (DC) are the major antigen-presenting cells in the induction of cellular responses to intracellular pathogens, such as mycobacteria. Recent studies have shown that they also play a critical role in the regulation of immune responses. The interaction of DC with microbial antigens may be the controlling factor in the development of a Th1-orientated protective immunity. Analysis of the innate response of DC to mycobacteria and the involvement of the DC receptors in antigen recognition have highlighted the pivotal role of these cells in T-cell activation. Mycobacteria-infected DC have an enhanced capacity to release pro-inflammatory cytokines and chemokines and are potent inducers of interferon-gamma-producing cells in vivo. Therefore, DC manipulation for maximal antigen presentation and Th1 cytokine production may form the basis of a new generation of vaccines, with improved efficacy against mycobacterial infections.

Animals↗
PubMed2006

STAT3 activation regulates growth, inflammation, and vascularization in a mouse model of gastric tumorigenesis.

BACKGROUND & AIMS: The gp130(757F/F) mouse is a well-characterized and robust model of distal gastric tumorigenesis displaying many of the characteristics of human intestinal type gastric cancer. Key to the development of tumors in this model, and in many examples of human tumor development, is hyperactivation of the transcription factor STAT3. This study addressed the requirement for STAT3 activation in tumor initiation and characterized some of the genes downstream of STAT3 required for tumor development. Furthermore, the interaction among STAT3, the microbial environment, and tumorigenesis was evaluated. METHODS: The role of STAT3 in gastric tumor development was assessed in detail in gp130(757F/Y757F):STAT3(+/-) mice displaying reduced STAT3 activity. Tumor size was quantified morphologically, and the effects on endocrine cell populations, neovascularization, and inflammatory cell infiltration as well as the outcome of STAT3 activation on transcription of a number of genes relevant in growth and inflammation were quantified. RESULTS: Loss of one STAT3 allele in gp130(757F/F) mice reduced the frequency and rate of tumor development because of inhibition of proliferation-induced glandular hyperplasia. There was also a concomitant reduction in the degree of inflammatory infiltration and cytokine and chemokine expression, angiogenesis, and expression of metalloproteinases and growth factors. Antimicrobial treatment of gp130(757F/F) mice slowed tumor growth coincident with reduced macrophage and neutrophil infiltration. CONCLUSIONS: Activation of STAT3 and the microbial environment are pivotal for gastric tumor initiation and development in the gp130(757F/F) mouse, thus supporting the notion that STAT3 activation may play a role in human gastric cancer development.

Animals↗
PubMed2007

Mechanisms underlying the resistance to diet-induced obesity in germ-free mice.

The trillions of microbes that colonize our adult intestines function collectively as a metabolic organ that communicates with, and complements, our own human metabolic apparatus. Given the worldwide epidemic in obesity, there is interest in how interactions between human and microbial metabolomes may affect our energy balance. Here we report that, in contrast to mice with a gut microbiota, germ-free (GF) animals are protected against the obesity that develops after consuming a Western-style, high-fat, sugar-rich diet. Their persistently lean phenotype is associated with increased skeletal muscle and liver levels of phosphorylated AMP-activated protein kinase (AMPK) and its downstream targets involved in fatty acid oxidation (acetylCoA carboxylase; carnitine-palmitoyltransferase). Moreover, GF knockout mice lacking fasting-induced adipose factor (Fiaf), a circulating lipoprotein lipase inhibitor whose expression is normally selectively suppressed in the gut epithelium by the microbiota, are not protected from diet-induced obesity. Although GF Fiaf-/- animals exhibit similar levels of phosphorylated AMPK as their wild-type littermates in liver and gastrocnemius muscle, they have reduced expression of genes encoding the peroxisomal proliferator-activated receptor coactivator (Pgc-1alpha) and enzymes involved in fatty acid oxidation. Thus, GF animals are protected from diet-induced obesity by two complementary but independent mechanisms that result in increased fatty acid metabolism: (i) elevated levels of Fiaf, which induces Pgc-1alpha; and (ii) increased AMPK activity. Together, these findings support the notion that the gut microbiota can influence both sides of the energy balance equation, and underscore the importance of considering our metabolome in a supraorganismal context.

AMP-Activated Protein Kinases↗
PubMed1991

Structural basis for differential binding of staphylococcal enterotoxin A and toxic shock syndrome toxin 1 to class II major histocompatibility molecules.

The related staphylococcal toxins staphylococcal enterotoxin A (SEA) and toxic shock syndrome toxin 1 (TSST-1) are microbial superantigens. They require interaction with class II major histocompatibility complex (MHC) molecules to activate T cells. We have previously identified a binding site on SEA, the N-terminal 45 amino acids, as well as its corresponding receptor on the MHC antigen, residues 65-85 of the beta chain. To further characterize the structural basis for SEA binding to class II MHC molecules we have examined its relationship to TSST-1 binding. Both toxins bound similarly to murine A20 cells, but blockage of binding was observed only with the homologous toxin, which suggests that the binding sites for the two toxins on A20 cells are distinct. In contrast, specific binding of SEA was greater than that of TSST-1 on human Raji cells. Further, SEA was a better inhibitor of TSST-1 binding than was TSST-1 itself at low concentrations, but TSST-1 only minimally inhibited SEA binding. The data suggest that TSST-1 interacts with Raji cells at an SEA binding site, but with a lower affinity. The peptides SEA-(1-45) and I-A beta b-(65-85) were capable of blocking SEA binding on both A20 and Raji cells, but blockage was more effective on A20 cells. Neither peptide was capable of blocking TSST-1 binding on either cell line. The data are compatible with a model in which SEA has a binding site on A20 cells involving SEA-(1-45) and I-A beta b-(65-85) which is distinct from that which binds TSST-1, while at least two binding sites are present on Raji cells. One site involves predominantly the residue 1-45 region on SEA and the 65-85 region of the MHC beta chain, while the other site involves both a different region on the SEA molecule and a different site on the class II MHC molecule to which it binds. This latter site also binds TSST-1.

Animals↗
PubMed2002

Crystal structures of transcription factor NusG in light of its nucleic acid- and protein-binding activities.

Microbial transcription modulator NusG interacts with RNA polymerase and termination factor rho, displaying striking functional homology to eukaryotic Spt5. The protein is also a translational regulator. We have determined crystal structures of Aquifex aeolicus NusG showing a modular design: an N-terminal RNP-like domain, a C-terminal element with a KOW sequence motif and a species-specific immunoglobulin-like fold. The structures reveal bona fide nucleic acid binding sites, and nucleic acid binding activities can be detected for NusG from three organisms and for the KOW element alone. A conserved KOW domain is defined as a new class of nucleic acid binding folds. This module is a close structural homolog of tudor protein-protein interaction motifs. Putative protein binding sites for the RNP and KOW domains can be deduced, which differ from the areas implicated in nucleic acid interactions. The results strongly argue that both protein and nucleic acid contacts are important for NusG's functions and that the factor can act as an adaptor mediating indirect protein-nucleic acid associations.

Amino Acid Sequence↗
PubMed2025

Genome insights into the Bacillus paramycoides RZ3MS14: a multitrait plant growth-promoting rhizobacterium from Amazonian rainforest able to improve the sugarcane growth.

The genus Bacillus features species with remarkable plant growth-promoting traits (PGPTs) and is widely recognized for its biotechnological potential in sustainable agriculture. Among them, Bacillus paramycoides has recently attracted attention for its versatility in green synthesis of biopolymers, metal-based nanoparticles, and inhibition fungal phytopathogens; however, its PGPTs remain poorly underexplored. In this study, an integrated genomic and physiological approach was applied to B. paramycoides RZ3MS14, isolated from the guarana rhizosphere in Amazonian rainforest, to explore and correlate its potential PGPTs through in vitro and in vivo assays. The genome of B. paramycoides RZ3MS14 harbors genes related to N/P/Fe mobilization, bacillibactin synthesis, exopolysaccharides and biofilm formation, plant signaling, stress tolerance, biocontrol, and antibiotic resistance. Functional validation through in vitro assays, confirmed the strain's ability to solubilize phosphate, mineralize phytate, and produce siderophores, auxins, exopolysaccharides, and biofilm. These findings point diverse plant-growth promoting (PGP) traits that contributed to significant improvements in sugarcane growth and root architecture in the greenhouse. Specifically, root dry mass, shoot dry mass, root length, root surface area, and root volume increased by 225.92%, 520.89%, 231.47%, 242.25%, and 252.92%, respectively. Bacillus paramycoides RZ3MS14 exhibited a low antagonistic effect against the phytopathogenic fungi Fusarium verticillioides and Ceratocystis paradoxa. In contrast, microbial volatiles defined synergistic interactions with beneficial fungi Trichoderma afroharzianum and Purpureocillium lilacinum. This is the first study to unveil the PGP attributes of B. paramycoides, underscoring RZ3MS14's potential as a sugarcane bioinput and providing insights into its combined application with other microorganisms.

Saccharum↗
PubMed1985

In-vitro activity of the combinations of ampicillin with mecillinam or with beta-lactamase inhibitors against strains resistant to ampicillin.

The in-vitro activity of ampicillin, of mecillinam and of combinations of ampicillin with mecillinam, clavulanic acid or 6 beta-bromopenicillanic acid has been studied against 126 Enterobacteriaceae resistant to ampicillin. The combination of ampicillin with mecillinam showed synergy or addition in 60% of the combinations tested. Synergy was seen especially when the strains were resistant to mecillinam, indifference when they were susceptible to mecillinam. The combination of ampicillin with mecillinam was more active than the combination with clavulanic acid against Escherichia coli, Klebsiella and Enterobacter, but not against Proteus, Morganella and Providencia. The combination of ampicillin with clavulanic acid was more active than the combination with 6 beta-bromopenicillanic acid in E. coli, Klebsiella and Enterobacter strains.

Amdinocillin↗
PubMed1987

Chequerboard titrations: the influence of the composition of serial dilutions of antibiotics on the fractional inhibitory concentration index and fractional bactericidal concentration index.

Chequerboard titrations carried out with modified serial dilutions of antibiotics such that consecutive concentrations in these series were four times smaller than those in two-fold serial dilutions enable MICs and MBCs to be determined with greater accuracy. Interaction indices calculated by this method can differ markedly from those calculated on the basis of two-fold serial dilutions. The differences calculated in this study ranged from -0.30 to +1.06.

Cefsulodin↗
PubMed1991

Interactions in vitro between polyenes and imidazoles against yeasts.

The polyenes, amphotericin B and mepartricin and the imidazoles, miconazole, ketoconazole, itraconazole and fluconazole, were studied either alone or in paired polyene-imidazole combinations to determine their activity in vitro against clinical yeast isolates. The methods included shaken and standing liquid cultures, continuous cultures and chequerboard titrations, with or without the incorporation of pooled human plasma. The polyenes were found to exert an immediate cidal action even with high cell populations whereas the imidazoles demonstrated a time-dependent fungistatic activity which increased very slowly with increase in drug concentration. The interactions observed with the paired combinations were consistent and were found to be anomalous with all methods used. The activity of the imidazoles was enhanced by the presence of the polyenes; by contrast the polyenes were strongly antagonized by the imidazoles.

Antifungal Agents↗
PubMed2006

Root exudation from Hordeum vulgare in response to localized nitrate supply.

Root proliferation as a response to exploit zones of nutrient enrichment in soil has been demonstrated for a wide range of plant species. However, the effectiveness of this as a strategy to acquire nutrients is also dependent on interactions with the soil microbial community. Specifically, C-flow from roots modifies microbial activity and probably the balance between nutrient mineralization and immobilization processes in the rhizosphere. In this study, near-natural abundance 13C-labelling and gene-reporter methods were applied to determine the effects of uneven nitrate supply to roots of Hordeum vulgare on assimilate partitioning and root exudation. Plants were initially grown in uniform nitrate supply in split-root, sand microcosms after which one treatment continued to receive uniform supply, and the other received nitrate to one root compartment only. At the time of imposing the treatments, the CO2 supplied to the plants was switched to a cylinder source, providing a distinct delta13C-signature and allowing the fate of new assimilate within the plants to be determined. The labelling approach allowed quantification of the expected preferential allocation of new C-assimilate to roots in enriched nitrate, prior to any measurable effect on whole biomass or root architecture. Biosensor (lux-marked Pseudomonas fluorescens 10586 pUCD607) bioluminescence, quantified spatially by CCD imaging, demonstrated that root exudation was significantly increased for roots in enriched nitrate. This response of root exudation, being primarily associated with root apices and concurrent with enhanced assimilate supply, strongly suggests that C-flow from roots is an integral component of the proliferation response to nitrate.

Biosensing Techniques↗