Role of Toll-Like Receptor (TLR) 2 in Experimental Bacillus cereus Endophthalmitis

Bacillus cereus causes a uniquely rapid and blinding intraocular infection, endophthalmitis. B. cereus replicates in the eye, synthesizes numerous toxins, and incites explosive intraocular inflammation. The mechanisms involved in the rapid and explosive intraocular immune response have not been addressed. Because Toll-like receptors (TLRs) are integral to the initial recognition of organisms during infection, we hypothesized that the uniquely explosive immune response observed during B. cereus endophthalmitis is directly influenced by the presence of TLR2, a known Gram-positive pathogen recognition receptor. To address this hypothesis, we compared the courses of experimental B. cereus endophthalmitis in wild type C57BL/6J mice to that of age-matched homozygous TLR2-/- mice. Output parameters included analysis of bacterial growth, inflammatory cell (PMN) infiltration, cytokine/chemokine kinetics, retinal function testing, and histology, with N≥4 eyes/assay/time point/mouse strain. B. cereus grew at similar rates to108 CFU/eye by 12 h, regardless of the mouse strain. Retinal function was preserved to a greater degree in infected TLR2-/- eyes compared to that of infected wild type eyes, but infected eyes of both mouse strains lost significant function. Retinal architecture was preserved in infected TLR2-/- eyes, with limited retinal and vitreal cellular infiltration compared to that of infected wild type eyes. Ocular myeloperoxidase activities corroborated these results. In general, TNFα, IFNγ, IL6, and KC were detected in greater concentrations in infected wild type eyes than in infected TLR2-/- eyes. The absence of TLR2 resulted in decreased intraocular proinflammatory cytokine/chemokine levels and altered recruitment of inflammatory cells into the eye, resulting in less intraocular inflammation and preservation of retinal architecture, and a slightly greater degree of retinal function. These results demonstrate TLR2 is an important component of the initial ocular response to B. cereus endophthalmitis

Legacy of Amazonian Dark Earth soils on forest structure and species composition

This is the final version. Available from the publisher via the DOI in this record.Aim: Amazonian forests predominantly grow on highly weathered and nutrient poor soils. Anthropogenically enriched Amazonian Dark Earths (ADE), traditionally known as Terra Preta de Índio, were formed by pre-Columbian populations. ADE soils are characterized by increased fertility and have continued to be exploited following European colonization. Here, we evaluated the legacy of land-use and soil enrichment on the composition and structure in ADE and non-ADE (NDE) forests. Location: Eastern and southern Amazonia. Time period: Pre-Columbia – 2014. Methods: We sampled nine pairs of ADE and adjacent NDE forest plots in eastern and southern Amazonia. In each plot, we collected soil samples at 0–10 and 10–20 cm depth and measured stem diameter, height, and identified all individual woody plants (palms, trees and lianas) with diameter ≥ 10 cm. We compared soil physicochemical properties, vegetation diversity, floristic composition, aboveground biomass, and percentage of useful species. Results: In the nine paired plots, soil fertility was significantly higher in ADE soil. We sampled 4,191 individual woody plants representing 404 species and 65 families. The floristic composition of ADE and NDE forests differed significantly at both local and regional levels. In southern Amazonia, ADE forests had, on average, higher aboveground biomass than other forests of the region, while in eastern Amazonia, biomass was similar to that of NDE forests. Species richness of both forest types did not differ and was within the range of existing regional studies. The differences in composition between large and small diameter tree recruits may indicate long-term recovery and residual effects from historical land-use. Additionally, the proportion of edible species tended to be higher in the ADE forests of eastern and southern Amazonia. Main conclusions: The marked differences in soil fertility, floristic composition and aboveground biomass between ADE and NDE forests are consistent with a small-scale long-term land-use legacy and a regional increase in tree diversity

Survival and conjugation of Bacillus thuringiensis in a soil microcosm

The survival and conjugation ability of sporogenic and asporogenic Bacillus thuringiensis strains were investigated in broth, in non-amended sterile clay soil monoculture and in mixed soil culture. The 75 kb pHT73 plasmid carrying an erythromycin resistance determinant and a cry1Ac gene was transferred in mating broth and soil microcosm. Survival of strains was assessed in soil monoculture and in mixed soil culture for up to 20 days. Sporogenic strains rapidly formed viable spores which were maintained until the end of the experiment. The asporogenic strains were no longer recovered after 8 days of incubation. This study shows that the environmental impact of asporogenic B. thuringiensis strains is lower than that of sporogenic B. thuringiensis strains. Thus, the use of asporogenic strains may significantly reduce any potential risk (gene transfer, soil and plant contamination) due to the dissemination of B. thuringiensis-based biopesticides in the environment. Copyright (C) 2000 Federation of European Microbiological Societies