Environmental context. Biological ice nucleators have been found to freeze water at very warm temperatures. The potential of bio-aerosols to greatly influence cloud chemistry and microphysics is becoming increasingly apparent, yet detailed knowledge of their actual role in atmospheric processes is lacking. The formation of ice in the atmosphere has significant local, regional and global influence, ranging from precipitation to cloud nucleation and thus climate. Ice nucleation tests on bacteria isolated from snow and laboratory-grown bacteria, in comparison with those of known organic and inorganic aerosols, shed light on this issue. Abstract.Ice nucleation experiments on bacteria isolated from snow as well as grown in the laboratory, in comparison with those of known organic and inorganic aerosols, examined the importance of bio-aerosols on cloud processes. Snow samples were collected from urban and suburban sites in the greater Montreal region in Canada (45 • 28 N, 73 • 45 W). Among many snow bacterial isolates, eight types of bacterial species, none belonging to known effective ice nucleators such as Pseudomonas or Erwinia genera, were identified to show an intermediate range of ice nucleation activity (−12.9 ± 1.3 • C to −17.5 ± 2.8 • C). Comparable results were also obtained for molten snow samples and inorganic suspensions (kaolin and montmorillonite) of buffered water solutions. The presence of organic molecules (oxalic, malonic and succinic acids) had minimal effect (<2 • C) on ice nucleation. Considering experimental limitations, and drawing from observation in snow samples of a variety of bacterial populations with variable ice-nucleation ability, a shift in airborne-species population may significantly alter glaciation processes in clouds.
International audienceField and laboratory studies of organic compounds in snow (12 species; concentrations <= 17 μg L-1) were conducted and microorganisms in snow and aerosols at urban and Arctic sites were investigated (snow: total bacteria count <= 40000 colony forming units per millilitre (CFU mL(-1)), fungi <= 400 CFU mL(-1); air: bacteria <= 2.2 x 10(7) CFU m(-3), fungi <= 84 CFU m(-3)). Bio-organic material is transferred between snow and air and influence on snow-air exchange processes is demonstrated. Volatile organic compounds in snow are released into the air upon melting. In vitro photochemistry indicated an increase of <= 60 μg L-1 for 1,3- and 1,4-dimethylbenzenes. Bacillus cereus was identified and observed in snow and air with ice-nucleating being P. syringae absent. As a result snow photobiochemical reactions should be considered in describing organic matter air-snow exchanges, and the investigation of climate change
Abstract. During the spring of 2009, as part of the OceanAtmosphere-Sea Ice-Snowpack (OASIS) campaign in Barrow, Alaska, USA, we examined the identity, population diversity, freezing nucleation ability of the microbial communities of five different snow types and frost flowers. In addition to the culturing and gene-sequence-based identification approach, we utilized a state-of-the-art genomic next-generation sequencing (NGS) technique to examine the diversity of bacterial communities in Arctic samples. Known phyla or candidate divisions were detected (11-18) with the majority of sequences (12.3-83.1 %) belonging to one of the five major phyla: Proteobacteria, Actinobacteria, Bacteroidetes, Firmicutes, and Cyanobacteria. The number of genera detected ranged from, 101-245. The highest number of cultivable bacteria was observed in frost flowers (FFs) and accumulated snow (AS) with 325 ± 35 and 314 ± 142 CFU m L −1 , respectively; and for cultivable fungi 5 ± 1 CFU m L −1 in windpack (WP) and blowing snow (BS). Morphology/elemental composition and ice-nucleating abilities of the identified taxa were obtained using high resolution electron microscopy with energy-dispersive X-ray spectroscopy and ice nucleation cold-plate, respectively. Freezing point temperatures for bacterial isolates ranged from −20.3 ± 1.5 to −15.7 ± 5.6 • C, and for melted snow samples from −9.5 ± 1.0 to −18.4 ± 0.1 • C. An isolate belonging to the genus Bacillus (96 % similarity) had ice nucleation activity of −6.8 ± 0.2 • C. Comparison with Montreal urban snow, revealed that a seemingly diverse community of bacteria exists in the Arctic with some taxa possibly originating from distinct ecological environments. We discuss the potential impact of snow microorganisms in the freezing and melting process of the snowpack in the Arctic.
Micro-organisms and organic compounds of biogenic or anthropogenic origins are important constituents of atmospheric aerosols, which are involved in atmospheric processes and climate change. In order to investigate the role of fungi and their metabolisation activity, we collected airborne fungi using a biosampler in an urban location of Montreal, Quebec, Canada (45 degrees 28' N, 73 degrees 45' E). After isolation on Sabouraud dextrose agar, we exposed isolated colonies to dicarboxylic acids (C(2)-C(7)), a major group of organic aerosols and monitored their growth. Depending on the acid, total fungi numbers varied from 35 (oxalic acid) to 180 CFU/mL (glutaric acid). Transformation kinetics of malonic acid, presumably the most abundant dicarboxylic acid, at concentrations of 0.25 and 1.00 mM for isolated airborne fungi belonging to the genera Aspergillus, Penicillium, Eupenicillium, and Thysanophora with the fastest transformation rate are presented. The initial concentration was halved within 4.5 and 11.4 days. Other collected fungi did not show a significant degradation and the malonic acid concentration remained unchanged (0.25 and 1.00 mM) within 20 days. Degradation of acid with formation of metabolites was followed using high performance liquid chromatography-ultraviolet detection (HPLC/UV) and gas chromatography-mass spectrometry (GC/MS), as well as monitoring of (13)C labelled malonic acid degradation with solid-state nuclear magnetic resonance spectroscopy (NMR). Using GC/MS we identified two processes driving chemical modifications of organic aerosol solutions: (I) formation of metabolites within several days, and (II) rapid release (< or =2 min) of organic molecules from fungal species upon the insertion of taxa in organic aerosol solutions. Metabolites included aromatic compounds and alcohols (e.g. trimethylbenzene and butanol). Potential atmospheric implications of our results are discussed.
Bio-organic chemicals are ubiquitous in the Earth's atmosphere and at air-snow interfaces, as well as in aerosols and in clouds. It has been known for centuries that airborne biological matter plays various roles in the transmission of disease in humans and in ecosystems. The implication of chemical compounds of biological origins in cloud condensation and in ice nucleation processes has also been studied during the last few decades, and implications have been suggested in the reduction of visibility, in the influence on oxidative potential of the atmosphere and transformation of compounds in the atmosphere, in the formation of haze, change of snow-ice albedo, in agricultural processes, and bio-hazards and bio-terrorism. In this review we critically examine existing observation data on bio-organic compounds in the atmosphere and in snow. We also review both conventional and cutting-edge analytical techniques and methods for measurement and characterisation of bio-organic compounds and specifically for microbial communities, in the atmosphere and snow. We also explore the link between biological compounds and nucleation processes. Due to increased interest in decreasing emissions of carbon-containing compounds, we also briefly review (in an Appendix) methods and techniques that are currently deployed for bio-organic remediation.
We undertook an extensive study of population and type of viable microorganisms at several indoor construction sites in a 50-year-old chemical building which housed both laboratory and office spaces. Results were compared to neighbouring public buildings (office and shopping malls), as well as outdoor (green areas and traffic zones) in downtown Montreal, (45 30 0 N, 73 35 0 W). The highest number of microorganisms was observed in the major shopping street (bacteria: 602,865 cfu/m 3 ; fungi: 109,612 cfu/m 3 ). During moving/construction process, the mean population of airborne bacteria and fungi were 89,281 and 50,386 cfu/m 3 , respectively. Mean bacterial and fungal population in demolished laboratory sites were 37,127 and 17,679 cfu/m 3 , respectively. After the termination of laboratory renovations, continued elevation of airborne taxa population (bacteria: 25,635 cfu/m 3 ; fungi: 6188 cfu/m 3 ) was observed. At the construction site, the 16S rDNA sequence of bacteria isolates, R. equi, was identified as human pathogen and R. jostii RHA1 in an organic demolished laboratory site, with the ability to degrade a variety of xenobiotic compounds such as polychlorinated biphenyls. Our study showed that renovation/construction activities could create a distinct large pool of microorganisms that could be released into indoor environments which may persist even after the completion of renovations. Potential health effects and suggestions for future research are discussed in this paper.
Bai Y, Ye S, Mortazavi R, Campese V, Vaziri ND. Effect of renal injury-induced neurogenic hypertension on NO synthase, caveolin-1, AKt, calmodulin and soluble guanylate cyclase expressions in the kidney. Am J Physiol Renal Physiol 292: F974 -F980, 2007. First published November 22, 2006; doi:10.1152/ajprenal.00157.2006.-Single injection of a small quantity of phenol into the cortex of one kidney in rats results in development of persistent hypertension (HTN) which is thought to be mediated by activation of renal afferent and efferent sympathetic pathways and sodium retention. Nitric oxide (NO) plays a major role in regulation of renal vascular resistance, tubular Na ϩ reabsorption, pressure natriuresis, and thereby systemic arterial pressure. The present study was performed to test the hypothesis that chronic renal injury-induced HTN may be associated with dysregulation of NO system in the kidney. Accordingly, urinary NO metabolite (NO x) and cGMP excretions as well as renal cortical tissue (right kidney) expressions of NO synthase (NOS) isoforms [endothelial, neuronal, and inducible NOS, respectively (eNOS, nNOS, and iNOS)], NOS-regulatory factors (Caveolin-1, phospho-AKt, and calmodulin), and second-messenger system (soluble guanylate cyclase [sGC] and phosphodiesterase-5 [PDE-5]) were determined in male Sprague-Dawley rats 4 wk after injection of phenol (50 l of 10% phenol) or saline into the lower pole of left kidney. The phenol-injected group exhibited a significant elevation of arterial pressure, marked reductions of urinary NO x and cGMP excretions, downregulations of renal tissue nNOS, eNOS, Phospho-eNOS, iNOS, and alpha chain of sGC. However, renal tissue AKt, phospho-AKT, Calmodulin, and PDE-5 proteins were unchanged in the phenol-injected animals. In conclusion, renal injury in this model results in significant downregulations of NOS isoforms and sGC and consequent reductions of NO production and cGMP generation by the kidney, events that may contribute to maintenance of HTN in this model. sympathetic activity; salt retention; cardiovascular disease; L-arginine/ nitric oxide system; cGMP; phosphodiesterase-5 SINGLE INJECTION of a small quantity of phenol into the cortex of one kidney results in development of neurogenic hypertension (HTN) in genetically normal rats (3,32,33). The associated HTN persists long after complete healing of the initial injury and recession of the lesion to a microscopic scar. The intrarenal lesion in this model results in activation of renal afferent sympathetic pathway, which integrates with central noradrenergic control systems, resulting in activation of renal efferent sympathetic pathway. The latter, in turn, raises arterial pressure by augmenting renal vascular resistance and tubular sodium reabsorption and by modulating pressure natriuresis (31). The role of activation of renal afferent sympathetic pathway in the pathogenesis of HTN in this model is enforced by the observations that renal afferent impulses are enhanced (33) and HTN is prevented by renal denervation be...
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