Heparin, known for its anticoagulant activity, is commonly used in catheter locks. Staphylococcus aureus, a versatile human and animal pathogen, is commonly associated with catheter-related bloodstream infections and has evolved a number of mechanisms through which it adheres to biotic and abiotic surfaces. We demonstrate that heparin increased biofilm formation by several S. aureus strains. Surface coverage and the kinetics of biofilm formation were stimulated, but primary attachment to the surface was not affected. Heparin increased S. aureus cell-cell interactions in a protein synthesis-dependent manner. The addition of heparin rescued biofilm formation of hla, ica, and sarA mutants. Our data further suggest that heparin stimulation of biofilm formation occurs neither through an increase in sigB activity nor through an increase in polysaccharide intracellular adhesin levels. These finding suggests that heparin stimulates S. aureus biofilm formation via a novel pathway.
Silver (Ag) nanomaterials are increasingly used in a variety of commercial applications. This study examined the effect of size (20 and 110 nm) and surface stabilization (citrate and PVP coatings) on toxicity, particle uptake and NLRP3 inflammasome activation in a variety of macrophage and epithelial cell lines. The results indicated that smaller Ag (20 nm), regardless of coating, were more toxic in both cell types and most active in the THP-1 macrophages. TEM imaging demonstrated that 20 nm Ag nanospheres dissolved more rapidly than 110 nm Ag nanospheres in acidic phagolysosomes consistent with Ag ion mediated toxicity. In addition, there were some significant differences in epithelial cell line in vitro exposure models. The order of the epithelial cell lines’ sensitivity to Ag was LA4 > MLE12 > C10. The macrophage sensitivity to Ag toxicity was C57BL/6 AM > MARCO null AM, which indicated that the MARCO receptor was involved in uptake of the negatively charged Ag particles. These results support the idea that Ag nanosphere toxicity and NLRP3 inflammasome activation are determined by the rate of surface dissolution, which is based on relative surface area. This study highlights the importance of utilizing multiple models for in vitro studies to evaluate nanomaterials.
Monitoring data over the period 1994-2007 were analysed for three streams (Cottage Hill Sike, CHS; Rough Sike, RS; Trout Beck, TB) draining blanket peat underlain by glacial clay and limestone-rich sub-strata at Moor House (Northern England). Dissolved organic carbon concentration, [DOC], showed complex relationships with both discharge and calcium concentration, [Ca]. A model based on [Ca] was constructed to simulate stream [DOC] by mixing dissolved organic matter (DOM) from shallow peat, quantified by measured [DOC](15-30 mg l -1 ) in peat porewater, with DOM assumed to be present at a constant concentration (c. 5 mg l -1 ) in groundwater. A temperature-based adjustment to the measured porewater [DOC] was required to account for relatively low streamwater [DOC] during winter and spring. The fitted model reproduced short-term variation in streamwater [DOC] satisfactorily, in particular variability in RS and TB due to groundwater contributions. Streamwater DOM is largely derived from surface peat, which accounts for more than 96% of the total DOC flux in both RS and TB, and 100% in CHS. Model outputs were combined with streamwater and porewater DO 14 C data to estimate the 14 C contents, and thereby the ages, of DOM from peat and groundwater. The peat-derived DOM is 5 years old on average, with most of it very recently formed. The derived age of groundwater DOM (8,500 years) is comparable to the 4,000-7,000 years estimated from the DO 14 C of water extracts of clay underlying the peat, suggesting that the clay is the source of groundwater DOM.
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