Seasonal and depth-related dynamics of prokaryotes and viruses in surface and deep waters of the northwestern Mediterranean Sea

International audienceno abstrac

Reduction of Cell Proliferation and Potentiation of Fas-Induced Apoptosis by the Selective Kappa-Opioid Receptor Agonist U50 488 in the Multiple Myeloma LP-1 Cells.

International audienc

Bottom-up control of the groundwater microbial food-web in an alpine aquifer.

Groundwater ecosystems are typically poor in organic carbon and productivity sustaining a low standing stock of microbial biomass. In consequence, microbial food webs in oligotrophic groundwater are hypothesized to be bottom-up controlled. To date, quantitative information on groundwater microbial communities, food web interactions, and carbon flow is relatively lacking in comparison to that of surface waters. Studying a shallow, porous alpine aquifer we collected data on the numbers of prokaryotes, virus-like particles and heterotrophic nanoflagellates (HNFs), the concentration of dissolved (DOC) and assimilable organic carbon (AOC), bacterial carbon production (BCP), and physical-chemical conditions for a 1 year hydrological cycle. The potential effects of protozoan grazing and viral lysis onto the prokaryotic biomass was tested. Flow of organic carbon through the microbial food web was estimated based on data from the literature. The abundance of prokaryotes in groundwater was low with 6.1 ± 6.9 × 104 cells mL–1, seasonally influenced by the hydrological dynamics, with higher densities coinciding with a lower groundwater table. Overall, the variability in cell numbers was moderate, and so it was for HNFs (179 ± 103 HNFs mL–1) and virus-like particles (9.6 ± 5.7 × 105 VLPs mL–1). The virus to prokaryotes and prokaryote to HNF ratios ranged between 2–230 and 33–2,084, respectively. We found no evidence for a viral control of prokaryotic biomass, and the biomass of HNFs being bottom-up controlled. First estimations point at carbon use efficiencies of 0.2–4.2% with prokaryotic production, and carbon consumed and recycled by HNFs and phages to be of minor importance. This first groundwater microbial food web analysis strongly hints at a bottom-up control on productivity and standing stock in oligotrophic groundwater ecosystems. However, direct measurement of protozoan grazing and phage mediated lysis rates of prokaryotic cells are urgently needed to deepen our mechanistic understanding. The effect of microbial diversity on the population dynamics still needs to be addressed

Bacterial community composition and potential controlling mechanisms along a trophic gradient in a barrier reef system

International audienc

Bacterial community composition and potential controlling mechanisms along a trophic gradient in a barrier reef system

Bacterial abundance and community composition were investigated along trophic gradients in the barrier reef lagoon of Noumea, New Caledonia. Bacterial abundance and the percentage of high nucleic acid (%HNA) bacteria (a potential indicator for bacterial production) increased from offshore waters towards the head of the bays. 16S rRNA gene PCR and denaturing gradient gel electrophoresis (DGGE) were used as genetic fingerprints for assessing differences in bacterial community composition. Sequences of DGGE bands were assigned to (1) the genera Rugeria and Roseobacter (Rhodobacteriaceae), (2) the SAR11 cluster, (3) other Alphaproteobacteria, and (4) the genus Alteromonas. Removal of the operationally defined attached bacteria by prefiltration did not affect community profiles in offshore waters but had a strong influence in the bays, probably clue to the much higher particle load and thus, attached bacteria in the bays. For the free-living community, the number of bands decreased linearly with increasing water residence time, chlorophyll a concentration, and viral abundance. Specific bands were found for offshore waters and the 2 investigated semi-enclosed bays, whereas the lagoon showed no specific bands. A similarity analysis showed specific clusters for offshore water, the lagoon, and the bays. A principle component analysis together with cluster and correlation analysis indicated that water residence time, viruses, and a complex top-down cascading effect of ciliate grazers on flagellates influenced community composition. Also, data from fingerprints of the total and free-living communities suggest that the free-living and the attached community are controlled by different mechanisms

RGTA OTR4120, a heparan sulfate mimetic, is a possible long-term active agent to heal burned skin

International audienc

RGTA OTR4120, a heparan sulfate mimetic, is a possible long-term active agent to heal burned skin.

Burn-related skin fibrosis leads to loss of tissue function and hypertrophic scar formation with damaging consequences for the patient. There is therefore a great need for an efficient agent to treat burned skin. We report that ReGeneraTing Agent (RGTA) reduces burn-induced skin alteration. The tissue-regenerating effect of RGTA OTR4120 was evaluated after 1-6 days and after 10 months in a rat skin burn model. This effect was also examined in vitro using fibroblasts isolated from control and 6-day-old burned skins. We measured production of dermal collagen I, III, and V and activities of metalloproteinases 2 and 9 (MMP-2 and MMP-9). Ratio of collagen III over collagen I production increased 6 days after the burn, because of a decrease in collagen I production. After 10 months, ratio of collagen III over collagen I in burn sites was still increased compared with control skin, because of an increase in collagen III production. Both abnormalities were corrected by OTR4120. OTR4120 increased pro- and active MMP-2 and MMP-9, compared with healthy and burned controls and therefore accelerated remodeling. Similar data were obtained with cultured fibroblasts from healthy and burned skins. OTR4120 enhanced healing in short- and long-term after burns, reducing the formation of fibrotic tissue, and then represents a potential agent to improve burned skin healing. (c) 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006

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