Chitotriosidase Activity Is Counterproductive in a Mouse Model of Systemic Candidiasis

Mammalian cells do not produce chitin, an insoluble polymer of N-acetyl-D-glucosamine (GlcNAc), although chitin is a structural component of the cell wall of pathogenic microorganisms such as Candida albicans. Mammalian cells, including cells of the innate immune system elaborate chitinases, including chitotriosidase (Chit1), which may play a role in the anti-fungal immune response. In the current study, using knockout mice, we determined the role of Chit1 against systemic candidiasis. Chit1-deficient mice showed significant decrease in kidney fungal burden compared to mice expressing the functional enzyme. Using in vitro anti-candidal neutrophil functional assays, the introduction of the Chit1:chitin digestion end-product, chitobiose (N-acetyl-D-glucosamine dimer, GlcNAc2), decreased fungal-induced neutrophil swarming and Candida killing in vitro. Also, a role for the lectin-like binding site on the neutrophil integrin CR3 (Mac-1, CD11b/CD18) was found through physiological competitive interference by chitobiose. Furthermore, chitobiose treatment of wild type mice during systemic candidiasis resulted in the significant increase in fungal burden in the kidney. These data suggest a counterproductive role of Chit1 in mounting an efficient anti-fungal defense against systemic candidiasis.

Regional Pelagic Rotifer Biodiversity in a Tropical Karst Lake District

The species richness, composition, abundance, and biomass of pelagic rotifers were determined in 17 karst lakes of the “Lagunas de Montebello” National Park, Chiapas, Mexico. The species richness of the region (21 species) and single lakes (1–12 species) was smaller than that of other Mexican, tropical, and temperate lakes. It is worth noting the high dissimilarity in species composition—about half (52%) of the species were observed in only 1–3 lakes. A total of eight rotifer families, all from the Monogononta subclass, were recorded. Keratella americana was the species with the highest occurrence (13 lakes), followed by Ptygura sp. (8 lakes). The abundance (0 to 536 ind L−1) and biomass (0 to 21 µg L−1) of rotifers were low. The highest values of species richness, abundance, and biomass were found in eutrophic lakes, and the lowest in oligotrophic lakes. The low values of rotifer biodiversity, abundance, and biomass in the Montebello lakes are probably the product of the interaction of different factors—such as environmental homogeneity (all water bodies are karst lakes), the low availability of “good-quality” food, and predation by cyclopoid copepods in the eutrophic lakes, and the low availability of food, and competitive interference by calanoid copepods and cladocerans in the oligotrophic lakes.

More Than a Functional Group: Diversity within the Legume–Rhizobia Mutualism and Its Relationship with Ecosystem Function

Studies of biodiversity and ecosystem function (BEF) have long focused on the role of nitrogen (N)-fixing legumes as a functional group that occupies a distinct and important niche relative to other plants. Because of their relationship with N-fixing rhizobial bacteria, these legumes access a different pool of N than other plants and therefore directly contribute to increases in productivity and N-cycling. Despite their recognized importance in the BEF literature, the field has not moved far beyond investigating the presence/absence of the legume functional group in species mixtures. Here, we synthesize existing information on how the diversity (species richness and functional diversity) of both legumes and the rhizobia that they host impact ecosystem functions, such as nitrogen fixation and primary productivity. We also discuss the often-overlooked reciprocal direction of the BEF relationship, whereby ecosystem function can influence legume and rhizobial diversity. We focus on BEF mechanisms of selection, complementarity, facilitation, competitive interference, and dilution effects to explain how diversity in the legume–rhizobia mutualism can have either positive or negative effects on ecosystem function—mechanisms that can operate at scales from rhizobial communities affecting individual legume functions to legume communities affecting landscape-scale ecosystem functions. To fully understand the relationship between biodiversity and ecosystem function, we must incorporate the full diversity of this mutualism and its reciprocal relationship with ecosystem function into our evolving BEF framework.

The Globalization of Hybrid Warfare and the Need for Plausible Deniability

Nuclear powers battle indirectly through competitive interference within the political systems of third actors in addition to targeting not only each other, but also their own national public opinion. Postwar global human rights norms developed to include national self-determination for all. Covert intervention became politically preferable domestically to avoid negative domestic political reactions to perceived imperialism. Covert intervention decreases political resistance and costs to the intervenor. The nature of social media content distribution makes propaganda and disinformation distribution very extensive at relatively very low cost. These trends and advantages furthered the stress on covert intervention and the formation of national security bureaucracies for engaging in it. Russian state agency internet-based covert intervention via social media in the 2016 US national elections demonstrated that the US is part of the politically globalizing postmodern world that it helped create after 1945. The surveillance capabilities of the national security state will be strengthened.

Temperature accelerates the rate fields become forests

Secondary succession, the postdisturbance transition of herbaceous to woody-dominated ecosystems, occurs faster at lower latitudes with important ramifications for ecosystem processes. This pattern could be driven by the direct effect of temperature on tree growth; however, an alternative mechanism is tree–herb competition, which may be more intense in more fertile northern soils. We manipulated soil fertility and herbaceous species composition in identical experiments at six sites spanning the Eastern United States (30–43° N) and monitored the growth and survival of four early successional trees. Tree seedling mass 2 years after sowing was strongly associated with site differences in mean growing season temperature, regardless of species or soil treatment. The effect of temperature was twofold: seedlings grew faster in response to warmer site temperatures, but also due to the reduction of competitive interference from the herbaceous community, which was inhibited in warmer sites. Our results suggest that increasing temperatures will promote a faster transition of fields to forests in temperate ecosystems.

Influence of invasive shrubs and deer browsing on regeneration in temperate deciduous forests

While both chronic white-tailed deer (Odocoileus virginianus Zimmermann) overbrowsing and invasive shrubs have been linked to native regeneration failure in temperate hardwood forests, little is known of their relative importance and possible synergistic effects. Therefore, we established three study areas in Connecticut to examine the interaction of three levels of invasive shrub control and absence or presence of deer herbivory on forest regeneration over 9 years. Five observations suggest that obtaining forest regeneration requires a comprehensive management strategy. First, competitive interference by invasive shrubs in intact thickets continued to impede forest regeneration, especially taller seedlings, after deer were excluded. Second, density of small seedlings increased following removal of the competitive interference by invasive shrubs. Third, deer browsing depressed growth of small seedlings into taller height classes. Fourth, preferential browsing reduced species richness, especially in taller seedling classes, by favoring growth of low palatability species such as beech. Lastly, if a disturbance (e.g., cutting) does not kill the root system of the invasive shrubs, the window of forest regeneration recruitment may be narrow because invasive shrubs can quickly recover. In stands with both established shrub thickets and high deer densities, invasive shrub control and multiyear reduction of deer densities are both recommended to obtain adequate forest regeneration.

Are two brands better than one? Investigating the effects of co-branding in advertising on audience memory

Co-branded advertising, where advertisements feature two partnered brands from different categories, should ideally benefit both brands. We test this assertion by studying the effect of featuring a second brand in advertisements on ad and brand name memorability, and the role of category context on which brand is recalled. Our test covers online display advertisements for consumer-packaged brands paired with charity and retailer brands in three markets (USA, UK, and Australia). Independent sample comparisons across 54 brand pairs show that advertising two brands has a neutral effect on ad memorability and negative effect on brand memorability. Furthermore, the advertisement’s category context determines which of the brands is recalled. Our findings support a competitive interference theory of dual-brand processing, whereby the two brands compete for attention resources. The results have implications for the return on investment from advertising expenditure, which will vary substantively depending on whether the costs of advertising are shared or borne by one brand in the pair.