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Abstract

The physiological colonization resistance exerted by the murine gut microbiota prevents conventional mice from Campylobacter jejuni infection. In the present study we addressed whether this also held true for Campylobacter coli. Following peroral application, C. coli as opposed to C. jejuni could stably establish within the gastrointestinal tract of conventionally colonized mice until 3 weeks post-challenge. Neither before nor after either Campylobacter application any changes in the gut microbiota composition could be observed. C. coli, but not C. jejuni challenge was associated with pronounced regenerative, but not apoptotic responses in colonic epithelia. At day 21 following C. coli versus C. jejuni application mice exhibited higher numbers of adaptive immune cells including T-lymphocytes and regulatory T-cells in the colonic mucosa and lamina propria that were accompanied by higher large intestinal interferon-γ (IFN-γ) concentrations in the former versus the latter but comparable to naive levels. Campylobacter application resulted in decreased splenic IFN-γ, tumor necrosis factor-α (TNF-α), and IL-6 concentrations, whereas IL-12p70 secretion was increased in the spleens at day 21 following C. coli application only. In either Campylobacter cohort decreased IL-10 concentrations could be measured in splenic and serum samples. In conclusion, the commensal gut microbiota prevents mice from C. jejuni, but not C. coli infection.

Open access

Abstract

Stenotrophomonas maltophilia is an aerobic, oxidase-negative and catalase-positive bacillus. S. maltophilia is a recognized opportunistic pathogen. Due to the advancements in invasive medical procedures, organ transplantation and chemotherapy of malignant illnesses, the relevance of this pathogen increased significantly. The therapy of S. maltophilia infections is challenging, as these bacteria show intrinsic resistance to multiple classes of antibiotics, the first-choice drug is sulfamethoxazole/trimethoprim. Our aim was to assess the epidemiology of S. maltophilia from various clinical samples and the characterization of resistance-levels and resistotyping of these samples over a long surveillance period. The study included S. maltophilia bacterial isolates from blood culture samples, respiratory samples and urine samples and the data for the samples, received between January 2008 until December 2017, a total of 817 S. maltophilia isolates were identified (respiratory samples n = 579, 70.9%, blood culture samples n = 175, 21.4% and urine samples n = 63, 7.7%). Levofloxacin and colistin-susceptibility rates were the highest (92.2%; n = 753), followed by tigecycline (90.5%, n = 739), the first-line agent sulfamethoxazole/trimethoprim (87.4%, n = 714), while phenotypic resistance rate was highest for amikacin (72.5% of isolates were resistant, n = 592). The clinical problem of sulfamethoxazole/trimethoprim-resistance is a complex issue, because there is no guideline available for the therapy of these infections.

Open access

Probiotic Escherichia coli strain Nissle 1917 (EcN) has a long history of safe use. However, the recently discovered presence of a pks locus in its genome presumably producing colibactin has questioned its safety, as colibactin has been implicated in genotoxicity. Here, we assess the genotoxic potential of EcN. Metabolic products were tested in vitro by the Ames test, a mutagenicity assay developed to detect point mutation-inducing activity. Live EcN were tested by an adapted Ames test. Neither the standard nor the adapted Ames test resulted in increased numbers of revertant colonies, indicating that EcN metabolites or viable cells lacked mutagenic activity. The in vivo Mammalian Alkaline Comet Assay (the gold standard for detecting DNA-strand breaks) was used to determine potentially induced DNA-strand breaks in cells of the gastro-intestinal tract of rats orally administered with viable EcN. Bacteria were given at 109–1011 colony forming units (CFU) per animal by oral gavage on 2 consecutive days and daily for a period of 28 days to 5 rats per group. No significant differences compared to negative controls were found. These results demonstrate that EcN does not induce DNA-strand breaks and does not have any detectable genotoxic potential in the test animals.

Open access

The gastric pathogen Helicobacter pylori colonizes approximately half of the human world population. The bacterium injects the effector protein cytotoxin associated gene A (CagA) via a type-IV secretion system into host epithelial cells, where the protein becomes phosphorylated at specific EPIYA-motifs by cellular kinases. Inside the host cell, CagA can interact with over 25 different proteins in both phosphorylation-dependent and phosphorylation-independent manners, resulting in manipulation of host-cell signaling pathways. During the course of an H. pylori infection, certain host-cell proteins undergo tyrosine dephosphorylation in a CagA-dependent manner, including the actin-binding proteins cortactin and vinculin. A predominant response of intracellular CagA is the binding and activation of tyrosine phosphatase, the human Src-homology-region-2-domain-containing-phosphatase-2 (SHP2). Here, we considered the possibility that activated SHP2 might be responsible for the dephosphorylation of cortactin and vinculin. To investigate this, phosphatase inhibitor studies were performed. Additionally, a complete knockout mutant of SHP2 in AGS cells was created by CRISPR/Cas9 technology, and these cells were infected with H. pylori. However, neither the presence of an inhibitor nor the inactivation of SHP2 prevented the dephosphorylation of cortactin and vinculin upon CagA delivery. Tyrosine dephosphorylation of these proteins is therefore independent of SHP2 and instead must be caused by another, as yet unidentified, protein tyrosine phosphatase.

Open access

Introduction

Since Populus has veritable value as timber, plywood, pulp, and paper, genomic research should create the sound basis for further breeding toward desirable wood quality attributes.

Materials and methods

In this study, we addressed the need for a research methodology that initially identifies and then characterize candidate genes encoding enzymes with wood property phenotypic traits, toward the aim of developing a genomics-based breeding technology.

Results

On 23 different poplar species/hybrid samples, we successfully amplified 55 primers designed on Populus trichocarpa L. Considering the number of polymorphic sites, out of 73,206 bp, 51 SNPs and 31 indel events were found. Non-synonymous single base mutations could be detected in number of 30, 21 out of 164 sequences were the number of minimum recombination events and 41 significant pairwise comparisons between loci could be detected.

Discussion and conclusion

Our results provide a roadmap for a future association genetic study between nucleotide diversity and precise evaluation of phenotype.

Open access

Introduction

Several Aristolochia species were used as medicinal herb across Europe and in recent years, their antimicrobial activity has also been investigated.

Materials and methods

In this study, A. clematitis was selected to evaluate the aristolochic acids I and II (AA I and AA II) concentrations and the antimicrobial activity of methanol, hexane, butanol, and ethyl acetate extracts of the root, stem, leaf, root, and fruit. AA I and AA II contents were measured by a validated high-performance liquid chromatography–ultraviolet method.

Results

Each fraction of the plant contained AA I and AA II and the root was found to have the highest contents of AA I (1.09%) and AA II (0.7454%). The minimum inhibitory concentrations of all extracts were determined by standard microdilution method. The fruit’s extracts showed the most efficient antimicrobial effect against both methicillin sensitive and resistant Staphylococcus aureus strains.

Conclusion

Correlation between the AA I and AA II concentrations and the antimicrobial effect was not found.

Open access

Abstract

Ecological communities are shaped by a complex interplay between abiotic forcing, biotic regulation and demographic stochasticity. However, community dynamics modelers tend to focus on abiotic forcing overlooking biotic interactions, due to notorious challenges involved in modeling and quantifying inter-specific interactions, particularly for species-rich systems such as planktonic assemblages. Nevertheless, inclusive models with regard to the full range of plausible drivers are essential to characterizing and predicting community response to environmental changes. Here we develop a Bayesian model for identifying, from in-situ time series, the biotic, abiotic and stochastic factors underlying the dynamics of species-rich communities, focusing on the joint biomass dynamics of biologically meaningful groups. We parameterize a multivariate model of population co-variation with an explicit account for demographic stochasticity, density-dependent feedbacks, pairwise interactions, and abiotic stress mediated by changing environmental conditions and resource availability, and work out explicit formulae for partitioning the temporal variance of each group in its biotic, abiotic and stochastic components. We illustrate the methodology by analyzing the joint biomass dynamics of four major phytoplankton functional types namely, diatoms, dinoflagellates, coccolithophores and phytoflagellates at Station L4 in the Western English Channel using weekly biomass records and coincident measurements of environmental covariates describing water conditions and potentially limiting resources. Abiotic and biotic factors explain comparable amounts of temporal variance in log-biomass growth across functional types. Our results demonstrate that effective modelling of resource limitation and inter-specific interactions is critical for quantifying the relative importance of abiotic and biotic factors.

Full access

Due to its overall environmental impact, the residual dye in the wastewater from the synthetic dye manufacturing and textile industries is a global concern. The discharge contains a high content of pigments and other additives, possessing complex structures. As per the requirement for dyed clothing, dyestuff in the effluent is less susceptible to acids, bases, and oxygen. Thus, conventional physical and chemical methods are not always efficient in degrading the dyes. Some microorganisms growing in an area affected with textile effluent have the capability to utilize the dyes as a source of carbon or nitrogen or both. As a very clean, inexpensive, and sufficient alternative, bioremediation of textile wastewater using these microorganisms has gained major popularity. This review primarily centers the contribution of bacteria in this sector and the isolation of such bacteria from textile effluent. A secondary focus is discussing the factors which influence the performance by different bacteria.

Open access

Purpose

This study aims to characterize plant growth-promoting rhizobacteria (PGPR) in sunflowers growing in different locations at North West of Iran.

Materials and methods

Sunflower plants were collected from different regions of West Azarbaijan, and rhizospheric bacterial strains were isolated and screened for PGP traits. Identification and characterization of the PGPR were conducted based on 16s rDNA sequences and phenotypic analysis, the strains clustered for genetic diversity by rep-PCR method.

Results

Among the 80 bacterial isolates, 20 showed PGP traits and were selected for other potentials. All the selected isolates produced indole-3-acetic acid at the rate of 9.2–33.7 mg/ml. In addition, 13, 15, 12, and 16 were positive for phosphate solubilization, siderephore, hydrogen cyanide, and ammonia production, respectively. The results from a subsequent pot experiment indicated that PGPRs distinctly increased sun flower shoot and root length, shoot and root fresh weight, as well as shoot and root dry weight. Based on 16S rDNA sequences and biochemical and physiological characteristics, 20 PGPRs were identified as Pseudomonas fluorescens (five isolates), Pseudomonas aeruginosa (four isolates), Pseudomonas geniculata (one isolate), Bacillus subtilis (four isolates), Bacillus pumilus (two isolates), Stenotrophomonas maltophilia (two isolates), and Brevibacterium frigoritolerans (two isolates). In rep-PCR, PGPR isolates were differentiated into seven clusters (A–G) at 65% similarity level. These results demonstrated the existence of a considerable species richness and genetic diversity among PGPRs isolated from different regions of North West of Iran.

Conclusions

To the best of our knowledge, this is first report for the identification and characterization of B. frigoritolerans as PGPR in sunflower plants.

Full access

Background and aims

The aim of this study was to verify that the comet assay can be used to investigate the DNA damaging effects of T-2 and HT-2 toxins in the liver of broiler chickens. The comet assay is a favorable genotoxic analysis because it is cheap, simple, and can be used in many organisms and different tissues.

Materials and methods

Male broiler chickens were fed with T-2/HT-2 toxins-contaminated diet for 14 days. The comet assay was successfully adapted to chicken liver cells, and the DNA damage was determined by a decrease in the comet parameter (DNA % in the tail) in the experimental groups.

Results

The method of evaluation was found to be critical because DNA damage could not be detected exactly using the CometScore software, due to inaccurate separation of head and comet. However, this problem can be solved by visual evaluation.

Conclusion

In the case of the visual evaluation, each toxin-treated group differed significantly from the control group, indicating that the assay can be useful for the assessment of primary DNA damage caused by T-2/HT-2 toxins.

Open access