Monensin-induced modifications of ionic gradients on Streptococcus faecalis. A

The study of Na+ (23Na NMR), H+ (31P NMR) and K+ (atomic absorption) movements was performed on Streptococcus faecalis cells, with or without monensin addition. Our approach with energized or de-energized cells allowed the distinction between the ionophore effect and the bacterial carriers response. At high monensin concentration the intrinsic systems of the bacteria were unable to re-establish normal ionic gradients. The high selectivity of transport of the ionophore for Na+ / K+ as measured in model physico-chemical sytems, was not determining “in vivo” as the most important damage caused to the bacteria was a large K+ efflux

The sensitivity of natural cloud water to photochemical processes

Formaldehyde and hydrogen peroxide are key constituents of atmospheric photochemical processes, in particular those involved in the HOx and NOx cycles. Direct photolysis of hydrogen peroxide is a source of radicals in both gas and aqueous phases and could therefore be used as an indicator of photochemical activity. Formaldehyde is both a primary pollutant and is produced by oxidation of organic compounds by reactions that can take place both in gas and liquid phases. As such, it can be considered an indicator of organic matter state of oxidation. Quantifying the behaviour of these 2 species in clouds is therefore of importance to better constraining the relative importance of gaseous versus liquid phase processes and to check the validity of current cloud chemistry models. In this study, we have used four years of cloud samples collected at the puy de Dôme atmospheric station to investigate the seasonal and diurnal dependence of both H2O2 and HCHO concentrations. A significant seasonal and diurnal dependence of H2O2 concentration in cloud droplets is found with maxima during summer time and round noon time. This shows that solar radiation is one of the most important factors that drive the cloud aqueous hydrogen peroxide concentration. On the contrary, the aqueous concentrations of HCHO do not appear to be linked to solar intensity. In addition, cloud samples collected at puy de Dôme have been used in laboratory experiments to better understand chemical phase processes. Both natural cloud samples and artificial cloud solutions were irradiated in a photo-reactor and the variations of pH, redox potential and key atmospheric substances (HCHO, H2O2, dissolved organic carbon (DOC), and carboxylic acids) were continuously monitored during the experiments. The behaviour of cloud samples differs significantly from that of artificial solutions. H2O2 concentration during the irradiations shows a decrease of about 15% h−1 while it usually increases for artificial solutions. DOC is not varying, while the behaviour of carboxylic acids and formaldehyde appears to depend on the cloud pH. These results lead to the conclusion that H2O2 in cloud is mainly produced by gas-to liquid transfer and subsequently photo-chemically consumed in the cloud water. Instead, the processes controlling the concentration of HCHO are more complex and clearly change with cloud pH, and hence the degree of anthropogenic influence of the air mass

Hailstones: A Window into the Microbial and Chemical Inventory of a Storm Cloud

Storm clouds frequently form in the summer period in temperate climate zones. Studies on these inaccessible and short-lived atmospheric habitats have been scarce. We report here on the first comprehensive biogeochemical investigation of a storm cloud using hailstones as a natural stochastic sampling tool. A detailed molecular analysis of the dissolved organic matter in individual hailstones via ultra-high resolution mass spectrometry revealed the molecular formulae of almost 3000 different compounds. Only a small fraction of these compounds were rapidly biodegradable carbohydrates and lipids, suitable for microbial consumption during the lifetime of cloud droplets. However, as the cloud environment was characterized by a low bacterial density (Me = 1973 cells/ml) as well as high concentrations of both dissolved organic carbon (Me = 179 µM) and total dissolved nitrogen (Me = 30 µM), already trace amounts of easily degradable organic compounds suffice to support bacterial growth. The molecular fingerprints revealed a mainly soil origin of dissolved organic matter and a minor contribution of plant-surface compounds. In contrast, both the total and the cultivable bacterial community were skewed by bacterial groups (γ-Proteobacteria, Sphingobacteriales and Methylobacterium) that indicated the dominance of plant-surface bacteria. The enrichment of plant-associated bacterial groups points at a selection process of microbial genera in the course of cloud formation, which could affect the long-distance transport and spatial distribution of bacteria on Earth. Based on our results we hypothesize that plant-associated bacteria were more likely than soil bacteria (i) to survive the airborne state due to adaptations to life in the phyllosphere, which in many respects matches the demands encountered in the atmosphere and (ii) to grow on the suitable fraction of dissolved organic matter in clouds due to their ecological strategy. We conclude that storm clouds are among the most extreme habitats on Earth, where microbial life exists

Dust Rains Deliver Diverse Assemblages of Microorganisms to the Eastern Mediterranean

Dust rains may be particularly effective at delivering microorganisms, yet their biodiversities have been seldom examined. During 2011 and 2012 in Beirut, Lebanon, 16 of 21 collected rainfalls appeared dusty. Trajectory modelling of air mass origins was consistent with North African sources and at least one Southwest Asian source. As much as ~4 g particulate matter, ~20 μg DNA, and 50 million colony forming units were found deposited per square meter during rainfalls each lasting less than one day. Sequencing of 93 bacteria and 25 fungi cultured from rain samples revealed diverse bacterial phyla, both Gram positive and negative, and Ascomycota fungi. Denaturing Gradient Gel Electrophoresis of amplified 16S rDNA of 13 rains revealed distinct and diverse assemblages of bacteria. Dust rain 16S libraries yielded 131 sequences matching, in decreasing order of abundance, Betaproteobacteria, Alphaproteobacteria, Firmicutes, Actinobacteria, Bacteroidetes, Cyanobacteria, Epsilonproteobacteria, Gammaproteobacteria, and Deltaproteobacteria. Clean rain 16S libraries yielded 33 sequences matching only Betaproteobacteria family Oxalobacteraceae. Microbial composition varied between dust rains, and more diverse and different microbes were found in dust rains than clean rains. These results show that dust rains deliver diverse communities of microorganisms that may be complex products of revived desert soil species and fertilized cloud species

Breast cancer and obesity: in vitro interferences between adipokines and proangiogenic features and/or antitumor therapies?

International audienceObesity is now considered as a risk factor for breast cancer in postmenopausal women. Adipokine levels are modulated in obesity, and may play a role in carcinogenesis. Moreover, obesity increases risk of cancer mortality. Here, we hypothesized that this increase could be due to a modification in angiogenesis, capital event in the development of metastases, and/or in effectiveness of cancer treatments. To test these assumptions, following a same experimental design and simultaneously the effects of leptin and adiponectin on angiogenesis were investigated, and the impact of hyperleptinemia on anticancer drug effectiveness was measured in physiological and obesity situations. Focusing on angiogenesis, the proliferation of endothelial cells (HUVEC), which expressed leptin and adiponectin receptors, was stimulated by leptin and inhibited by adiponectin. Both adipokines globally reduced apoptosis and caspase activity. Leptin increased migration whereas adiponectin decreased migration, and leptin enhanced the area of the tubes formed by HUVEC cells while adiponectin inhibited their formation. MCF7 and MDA-MB-231 cells treated with leptin secreted more VEGF than untreated cells, whereas adiponectin treatment inhibited VEGF secretion. Finally, MCF7 cells pre-treated with leptin were more invasive than untreated cells. This effect was not reproduced in MDA-MB-231 cells. In the MCF7 breast cancer cell line, leptin could induce cell proliferation and reduced the efficacy of all breast cancer therapies (tamoxifen, 5-fluorouracil, taxol and vinblastin). These results suggest that, in obesity situation, leptin-in contrast to adiponectin - may promote tumor invasion and angiogenesis, leading to metastases 'apparition, and reduce treatment efficacy, which could explain the increased risk of cancer mortality in cases of overweight. The evidence suggests adipokines influence breast cancer issue and could play a significant role, especially in obese patients for which hyperleptinemia, hypoadiponectinemia and increased metastatic potential are described

Tracing historical introductions in the Mediterranean Basin: the success story of the common genet (Genetta genetta) in Europe

The successful introduction of the common genet (Genetta genetta) into Europe has been traditionally associated to the Muslim invasion of Iberia, although diverse evidence suggested an earlier arrival. In this study, we assessed genetic variation at 11 microsatellite loci in 199 individuals from the Mediterranean Basin and used approximate Bayesian computation (ABC) combining genotypes and published mitochondrial sequences. Our objectives were to (1) test alternative scenarios of introduction of the species in Europe, (2) re-assess the mitochondrial signatures of ‘introduction hotspots’ in Iberia, and (3) evaluate how post-introduction demographic processes have shaped genetic structure in the invaded range. ABC estimates favored a scenario of independent introductions from Maghreb into the Balearic Isl. and Iberia; the latter was dated between the Upper Palaeolithic and the end of Phoenicians’ influence. Patterns of genotypic diversity broadened the Andalusian introduction hotspot to the antique Tartessos Kingdom and suggested multiple introductions and/or long-term genetic drift. The best fit ABC scenario implied a natural spread from Iberia to France, but was in potential conflict with our delimitation of two genetic clusters (France and Iberia) in continental Europe. In fact, southwestern France populations showed a fair proportion of alleles shared with Maghreb and low levels of heterozygosity that may reflect subsequent introduction from Iberia, in line with the high error rates in favor of this alternative scenario. Significant patterns of isolation-by-distance among individuals within both genetic clusters are suggestive of natural dispersal from both Iberian and French introduction sites resulting in a secondary contact zone in northern Iberia. Overall, our study strongly suggests that the common genet was intentionally introduced in southern Iberia at a time antedating the Muslim invasion, possibly via Phoenicians’ commercial routes. Subsequent introduction in France, long-term genetic drift and admixture likely shaped the species genetic variation currently observed in continental Europe