Patterns of fungal diversity and composition along a salinity gradient

Estuarine salinity gradients are known to influence plant, bacterial and archaeal community structure. We sequenced 18S rRNA genes to investigate patterns in sediment fungal diversity (richness and evenness of taxa) and composition (taxonomic and phylogenetic) along an estuarine salinity gradient. We sampled three marshes—a salt, brackish and freshwater marsh—in Rhode Island. To compare the relative effect of the salinity gradient with that of plants, we sampled fungi in plots with Spartina patens and in plots from which plants were removed 2 years prior to sampling. The fungal sediment community was unique compared with previously sampled fungal communities; we detected more Ascomycota (78%), fewer Basidiomycota (6%) and more fungi from basal lineages (16%) (Chytridiomycota, Glomeromycota and four additional groups) than typically found in soil. Across marshes, fungal composition changed substantially, whereas fungal diversity differed only at the finest level of genetic resolution, and was highest in the intermediate, brackish marsh. In contrast, the presence of plants had a highly significant effect on fungal diversity at all levels of genetic resolution, but less of an effect on fungal composition. These results suggest that salinity (or other covarying parameters) selects for a distinctive fungal composition, and plants provide additional niches upon which taxa within these communities can specialize and coexist. Given the number of sequences from basal fungal lineages, the study also suggests that further sampling of estuarine sediments may help in understanding early fungal evolution

Potential environmental, ecological and health effects of soil antibiotics and ARGs

Antibiotics are biologically active compounds and are widely used in humans and animals to prevent or treat microbial diseases. Antibiotic resistance is a direct result of antibiotic use. The occurrence and dissemination of antimicrobial-resistant bacteria (ARB) and antimicrobial resistance genes (ARGs) are recognized as a major public health concern. The effect of clinically relevant ARGs and ARB that are released from anthropogenic sources, along with the excessive use of antibiotics in both human and veterinary settings, is currently considered to be a serious environmental and ecological hazard. The resistant bacteria in the environment can lead to structural changes in the microbial cell, with potential toxic effects on the balance of natural ecosystems. Soil environment is primary media, declared as recipient/reservoir and source of antimicrobial-resistant bacteria of clinical concern. The antimicrobial resistance genes interacted within these bacterial contaminants can multiply in their hosts, then transfer to other bacterial populations and be subject to further development and progression in the bacterial community. Therefore, antimicrobial-resistant bacteria that occur in the environment represent serious risks for human health