Unraveling the antibacterial mode of action of a clay from the Colombian Amazon

Natural antibacterial clays can inhibit growth of human pathogens; therefore, understanding the antibacterial mode of action may lead to new applications for health. The antibacterial modes of action have shown differences based on mineralogical constraints. Here we investigate a natural clay from the Colombian Amazon (AMZ) known to the Uitoto natives as a healing clay. The physical and chemical properties of the AMZ clay were compared to standard reference materials: smectite (SWy-1) and kaolinite (API #5) that represent the major minerals in AMZ. We tested model Gram-negative (Escherichia coli ATCC #25922) and Gram-positive (Bacillus subtilis ATCC #6633) bacteria to assess the clay’s antibacterial effectiveness against different bacterial types. The chemical and physical changes in the microbes were examined using bioimaging and mass spectrometry of clay digests and aqueous leachates. Results indicate that a single dose of AMZ clay (250 mg/mL) induced a 4–6 order of magnitude reduction in cell viability, unlike the reference clays that did not impact bacterial survival. AMZ clay possesses a relatively high specific surface area (51.23 m²/g) and much higher total surface area (278.82 m²/g) than the reference clays. In aqueous suspensions (50 mg clay/mL water), soluble metals are released and the minerals buffer fluid pH between 4.1 and 4.5. We propose that the clay facilitates chemical interactions detrimental to bacteria by absorbing nutrients (e.g., Mg, P) and potentially supplying metals (e.g., Al) toxic to bacteria. This study demonstrates that native traditional knowledge can direct scientific studies.     

Structural Features and Water Interactions of Etherified Xylan Thin Films

In this paper, the model film approach was used to investigate the structural features and humidity induced changes of the etherified xylan derivatives by using surface sensitive methods. Two routes to modify the birch xylan to generate either cross-linking xylan or more hydrophobic xylan were mastered via allylation and butylation, respectively. Thin nanometer scale model films were prepared by spin-coating and the films were further treated by UV-radical treatment and heat. The structural changes and wetting behaviour of the films before and after the post-treatment procedures were studied using atomic force microscopy and water contact angle measurements. In addition, the water vapour uptake of the xylan derivative films was monitored using quartz crystal microbalance with dissipation (QCM-D) equipped with the humidity module. With the QCM-D, the mass uptake due to the water vapour binding was defined. Simultaneously the changes in the viscoelastic properties of the films when subjected to different relative humidity conditions were determined. We show that the water sensitivity and wetting behaviour of the water soluble xylan derivatives can be altered by cross-linking the film structure and through the molecular rearrangements. Cross-linking and the conformational rearrangements of the allylated xylan reduced the water vapour uptake ability approximately 80?%. Butylated xylan as being a more hydrophobic derivative showed lower ability to uptake water vapour when compared to more hydrophilic xylan derivative. This ability was even further reduced after the post-treatments mainly due to the reassembly of the hydrophobic groups.     

Are 'other gainful activities' on farms good for the environment?

There has been a lot of academic interest in the pursuit of diversification activities and off-farm employment by farm household members. This is regarded as an important strategy for mitigating the effects of low agricultural income. One aspect of the debate about these so-called 'Other Gainful Activities' (OGAs) is whether they are associated with any environmental improvement on farms. In this paper, we use three approaches to analyse this issue. We examine whether measures of agricultural intensity are associated with the pursuit of OGAs by farmers and their spouses. We examine whether OGAs are more likely on farms where there is an ESA Management Agreement. Finally, we examine whether OGAs are associated with the farmer's stated environmental intentions. Although we tentatively conclude that there is a relationship between OGA involvement and these measures of environmental performance or concern by farmers, the magnitude of the association is small relative to other variables such as farm size, the type of land use, the form of business and recent agricultural training.     

MORPHOLOGIC RESPONSE OF SUBALPINE STREAMS TO TRANSBASIN FLOW DIVERSION1

ABSTRACT: Flow has been diverted from Rocky Mountain streams for many years with little documentation of the impacts on physical form and biological function of the losing stream system. This study addresses whether differences in form can be detected in subalpine step-pool, plane bed, or pool-riffle channels and linked to changes in flow regime from diversion. Total annual discharge was reduced between 20 and 60 percent and average annual peak flow was reduced up to 45 percent in the subalpine systems assessed; channels were diverted between 20 and 100 years. Expected impacts include reduced conveyance and changes in vegetation growth patterns because formerly active surfaces are colonized by riparian species, effectuating shrinking channel capacity. In this study, reduced channel width is used as an indicator of morphologic response. Observed reductions in width, ranging from 35 to 50 percent at some sites, resulted not only from vegetation invasion of stable surfaces but also from the development of an inset beside former cut banks. This observation, however, was restricted to wider pool-riffle channels with gravel bars. Outside of these areas, morphologic changes were either subtle or absent. The absence of widespread response is attributed primarily to periodic “flooding” of the diverted channel. During wetter-than-average years when excess water is available, minimal flow is diverted and the hydrograph resembles a free-flowing regime. The release of high flow to the natural channel potentially offsets changes in form incurred during “dry” periods. The stable nature and structure of subalpine channels also contributes to the absence of reduced capacity.     

How “Natural” are inland wetlands? an example from the trail wood audubon sanctuary in Connecticut,USA

We examined the geology of a small inland wetland in Hampton, Connecticut to determine its postglacial history and to assess the severity of human impact at this remote wooded site. Using stratigraphic evidence, we dernonstrate that the present wetland was created when sediment pollution from a 19th-century railroad filled a preexisting artificial reservoir, and that the prehistoric wetland was a narrow drainage swale along Hampton Brook. This same, severely impacted wetland was interpreted by the Pulitzer Prize-winning naturalist Edwin Way Teale as a beautiful wilderness area of particular interest. These conflicting perceptions indicate that artificial wetlands can be naturally mitigated in less than a century of healing, even in the absence of deliberate management. We also point out that the “wilderness” value of the Teale wetland was in the eye of the beholder and that unseen human impacts may have improved the aesthetic experience.