1,721,067 research outputs found
The cag-pathogenicity island encoded CncR1 sRNA oppositely modulates Helicobacter pylori motility and adhesion to host cells
No full textSmall regulatory RNAs (sRNAs) are emerging as key post-transcriptional regulators in many bacteria. In the human pathobiont Helicobacter pylori a plethora of trans- and cis-encoded sRNAs have been pinpointed by a global transcriptome study. However, only two have been studied in depth at the functional level. Here we report the characterization of CncR1, an abundant and conserved sRNA encoded by the virulence-associated cag pathogenicity island (cag-PAI) of H. pylori. Growth-phase dependent transcription of CncR1 is directed by the PcagP promoter, which resulted to be a target of the essential transcriptional regulator HsrA (HP1043). We demonstrate that the 213 nt transcript arising from this promoter ends at an intrinsic terminator, few bases upstream of the annotated cagP open reading frame, establishing CncR1 as the predominant gene product encoded by the cagP (cag15) locus. Interestingly, the deletion of the locus resulted in the deregulation en masse of σ54-dependent genes, linking CncR1 to flagellar functions. Accordingly, the enhanced motility recorded for cncR1 deletion mutants was complemented by ectopic reintroduction of the allele in trans. In silico prediction identified fliK, encoding a flagellar checkpoint protein, as likely regulatory target of CncR1. The interaction of CncR1 with the fliK mRNA was thus further investigated in vitro, demonstrating the formation of strand-specific interactions between the two RNA molecules. Accordingly, the full-length translational fusions of fliK with a lux reporter gene were induced in a cncR1 deletion mutant in vivo. These data suggest the involvement of CncR1 in the post-transcriptional modulation of H. pylori motility functions through down-regulation of a critical flagellar checkpoint factor. Concurrently, the cncR1 mutant revealed a decrease of transcript levels for several H. pylori adhesins, resulting in a phenotypically significant impairment of bacterial adhesion to a host gastric cell line. The data presented support a model in which the cag-PAI encoded CncR1 sRNA is able to oppositely modulate bacterial motility and adhesion to host cells
Temperature sensing and virulence regulation in pathogenic bacteria
Full text linkPathogenic bacteria can detect a variety of environmental signals, including temperature changes. While sudden and significant temperature variations act as danger signals that trigger a protective heat-shock response, minor temperature fluctuations typically signal to the pathogen that it has moved from one environment to another, such as entering a specific niche within a host during infection. These latter temperature fluctuations are utilized by pathogens to coordinate the expression of crucial virulence factors. Here, we elucidate the critical role of temperature in governing the expression of virulence factors in bacterial pathogens. Moreover, we outline the molecular mechanisms used by pathogens to detect temperature fluctuations, focusing on systems that employ proteins and nucleic acids as sensory devices. We also discuss the potential implications and the extent of the risk that climate change poses to human pathogenic diseases
Wood Distillate Mitigates Ozone-Induced Visible and Photosynthetic Plant Damage: Evidence from Ozone-Sensitive Tobacco (Nicotiana tabacum L.) BelW3
No full textThe use of wood distillate (WD) is emerging as a valuable strategy for protecting horticultural crops from the oxidizing effects of ozone (O3). To fully understand its effectiveness, extensive testing on different plant species is needed. As a viable interim measure, an assessment of WD efficacy in model plants can be made until species-specific results become available. The aim of this study is to evaluate the ability of WD to protect the ozone-sensitive tobacco plant (Nicotiana tabacum L.) BelW3 from the oxidizing effects of O3, using the ozone-resistant tobacco plant BelB as a benchmark. The protective effect was evaluated during treatment applications and three weeks after these were completed. Ten BelW3 and five BelB plants were grown just outside Parma from June to October 2023, a period when average maximum O3 concentrations were at least 120 ppb. Starting from July, five BelW3 plants were sprayed weekly with WD at 0.2% for two months. Morphometric and photosynthetic measurements were then taken after six and 11 weeks from the beginning of treatments and three weeks after the end to assess protection persistence (if any). BelW3 showed a significant effect of O3 compared to BelB plants for both morphometric and photosynthetic measurements, exhibiting increased necrotic areas on the leaf blade, reduced number of viable leaves, reduced average plant height, together with reduced chlorophyll content and impaired photosynthetic system functionality. BelW3 plants also showed a significant decrease in the efficiency of parameters related to PSII and PSI when compared to BelB. Wood distillate application, however, successfully mitigated O3 effects on BelW3, as revealed by morphometric and photosynthetic values, which were in line with those observed in BelB. Notably, WD protective effect persisted 3 weeks after treatment cessation, highlighting the short-term protective capacity of the distillate against the oxidative action of O3
Estimating atmospheric mercury concentrations with lichens
No full textThe uptake kinetics of elemental gaseous Hg (Hg0) in three species of epiphytic lichens (Pseudevernia furfuracea, Evernia prunastri, and Xanthoria parietina) were investigated under four different Hg concentrations (10, 15, 30, and 45 μg/m3) and three different temperatures (10, 20, and 30 °C) with the aim of evaluating the lichen efficiency for Hg 0 accumulation and their potential use in the estimate of atmospheric concentrations of this metal in the field. The results showed that under our experimental conditions the lichens accumulated Hg according to exposure time and that the metal is not released back to the atmosphere after Hg0 was removed from the air (clearance). Pseudevernia furfuracea showed the highest Hg accumulation capacity and Evernia prunastri showed the lowest, but in these species the metal uptake kinetics was affected by temperature. Xanthoria parietina showed an intermediate metal accumulation capacity and a Hg accumulation rate independent of temperature (in the range 10-30 °C). The use of first-order kinetics equations for Hg uptake in X. parietina and available field data on Hg bioaccumulation in this species allowed reliable estimates of atmospheric Hg concentrations in the environment. © 2014 American Chemical Society
Lichens “travelling” in smokers' cars are suitable biomonitors of indoor air quality
No full textIn this work, two hypotheses have been tested: 1) that lichen transplants “travelling” in smokers' cars accumulate relevant amounts of nicotine and heavy metals from cigarette smoke, and 2) that such exposure affects their vitality. Lichen samples (Evernia prunastri) were exposed for two months inside the cabin of 10 volunteer's cars, equally distributed between smokers and non-smokers. Travelling in a smoker's car for two months increased the content of nicotine and heavy metals (Al, As, Cd, Cr, Cu, Ni, Pb and Sb) in the lichen. Exposed to Control (EC) ratios revealed an indoor uptake also for Cu and Sb in non-smoker's cars, caused by traffic pollution. A smoke factor, calculated as the ratio between values of smokers’ and non-smokers’ cars, indicated a 85.6-fold contribution for nicotine and contributions in the range 1.2 (Pb) to 2 (Ni) for heavy metals; in addition, after travelling in smokers' cars, lichens showed a remarkable (60%) reduction of their vitality, as indicated by the potential quantum yield of primary photochemistry. The study demonstrated that the effects of indoor pollution by cigarette smoke can be detected using lichen transplants
May lichen biomonitoring of air pollution be used for environmental justice assessment? A case study from an area of N Italy with a municipal solid waste incinerator
No full textIn this work, we aimed to identify the contribution of a municipal solid waste incinerator (MSWI) to the air contamination of a complex urbanized area of N Italy using lichen transplants as biomonitors, and to compare the values of contamination with the data of socioeconomic deprivation of the population living in the area.
The method adopted allowed the identification of the elements of atmospheric origin that contaminate the study area. Although not distinguishable from the background, the contribution of the MSWI could be apportioned and mercury emerged as atmospheric tracer. Although not posing immediate risk, it is advisable to monitor in time the accumulation of Hg in biological systems.
Consistently with similar studies, in the surrounding of the MSWI, we observed also the highest socio-economic deprivation. Overall, we found a close correlation between socioeconomic deprivation and air pollution, clearly showing that the most disadvantaged population is clustered in the most polluted areas
Effects of wood distillate and soy lecithin on the photosynthetic performance and growth of lettuce (Lactuca sativa L.)
Full text linkThis study investigated the effectiveness of foliar application of sweet chestnut wood distillate on the photosynthetic performance and growth of lettuce (Lactuca sativa L. cv ‘Canasta’), both alone and in combination with soybean lecithin used as biosurfactant. Seedlings of lettuce were treated with a foliar application of either mineral water (control), or 1:500 solutions of 3% soy lecithin, wood distillate and wood distillate plus 3% soy lecithin. After 1 week, the chlorophyll content, chlorophyll fluorescence, chlorophyll reflectance and dry biomass were measured. The results showed that both wood distillate and lecithin exerted a positive effect on chlorophyll content and biomass production, but the joint use of wood distillate and lecithin quickly stimulated a ca. 50% increase in these parameters and is thus recommended
Disentangling sources of trace element air pollution in complex urban areas by lichen biomonitoring. A case study in Milan (Italy)
Full text linkIn this study we investigated the bioaccumulation of selected trace elements in lichen samples transplanted for three months in Milan, Italy, with the aim of assessing the main environmental contaminants
and the overall pollution load, and of disentangling the main air pollution sources as well as of estimating fluxes of element deposition. The results highlighted Cu and Sb as important contaminants and
suggested a common origin for these two elements from railways and non-exhaust sources of vehicular
traffic such as brake abrasion. High or very high global air pollution emerged for all study sites. Source
apportionment outlined three main factors, that found reliable correlation with distance from major
roads and railways, an industrial plant, and soil resuspension. Ranges of estimated mean annual element
deposition rates in the study area were similar to those reported for other cities
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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