Soil Saprobic Fungi Differ in Their Response to Gradually and Abruptly Delivered Copper

Towards establishing a fungal economics spectrum in soil saprobic fungi

Trait-based frameworks are promising tools to understand the functional consequences of community shifts in response to environmental change. The applicability of these tools to soil microbes is limited by a lack of functional trait data and a focus on categorical traits. To address this gap for an important group of soil microorganisms, we identify trade-offs underlying a fungal economics spectrum based on a large trait collection in 28 saprobic fungal isolates, derived from a common grassland soil and grown in culture plates. In this dataset, ecologically relevant trait variation is best captured by a three-dimensional fungal economics space. The primary explanatory axis represents a dense-fast continuum, resembling dominant life-history trade-offs in other taxa. A second significant axis reflects mycelial flexibility, and a third one carbon acquisition traits. All three axes correlate with traits involved in soil carbon cycling. Since stress tolerance and fundamental niche gradients are primarily related to the dense-fast continuum, traits of the 2nd (carbon-use efficiency) and especially the 3rd (decomposition) orthogonal axes are independent of tested environmental stressors. These findings suggest a fungal economics space which can now be tested at broader scales.

Combined application of up to ten pesticides decreases key soil processes

Natural systems are under increasing pressure by a range of anthropogenic global change factors. Pesticides represent a nearly ubiquitously occurring global change factor and have the potential to affect soil functions. Currently the use of synthetic pesticides is at an all-time high with over 400 active ingredients being utilized in the EU alone, with dozens of these pesticides occurring concurrently in soil. However, we presently do not understand the impacts of the potential interaction of multiple pesticides when applied simultaneously. Using soil collected from a local grassland, we utilize soil microcosms to examine the role of both rate of change and number of a selection of ten currently used pesticides on soil processes, including litter decomposition, water stable aggregates, aggregate size, soil pH, and EC. Additionally, we used null models to enrich our analyses to examine potential patterns caused by interactions between pesticide treatments. We find that both gradual and abrupt pesticide application have negative consequences for soil processes. Notably, pesticide number plays a significant role in affecting soil health. Null models also reveal potential synergistic behavior between pesticides which can further their consequences on soil processes. Our research highlights the complex impacts of pesticides, and the need for environmental policy to address the threats posed by pesticides.

Multi-site fungicides suppress banana Panama disease, caused by Fusarium oxysporum f. sp. cubense Tropical Race 4

Global banana production is currently challenged by Panama disease, caused by Fusarium oxysporum f.sp. cubense Tropical Race 4 (FocTR4). There are no effective fungicide-based strategies to control this soil-borne pathogen. This could be due to insensitivity of the pathogen to fungicides and/or soil application per se. Here, we test the effect of 12 single-site and 9 multi-site fungicides against FocTR4 and Foc Race1 (FocR1) in quantitative colony growth, and cell survival assays in purified FocTR4 macroconidia, microconidia and chlamydospores. We demonstrate that these FocTR4 morphotypes all cause Panama disease in bananas. These experiments reveal innate resistance of FocTR4 to all single-site fungicides, with neither azoles, nor succinate dehydrogenase inhibitors (SDHIs), strobilurins or benzimidazoles killing these spore forms. We show in fungicide-treated hyphae that this innate resistance occurs in a subpopulation of "persister" cells and is not genetically inherited. FocTR4 persisters respond to 3 μg ml-1 azoles or 1000 μg ml-1 strobilurins or SDHIs by strong up-regulation of genes encoding target enzymes (up to 660-fold), genes for putative efflux pumps and transporters (up to 230-fold) and xenobiotic detoxification enzymes (up to 200-fold). Comparison of gene expression in FocTR4 and Zymoseptoria tritici, grown under identical conditions, reveals that this response is only observed in FocTR4. In contrast, FocTR4 shows little innate resistance to most multi-site fungicides. However, quantitative virulence assays, in soil-grown bananas, reveals that only captan (20 μg ml-1) and all lipophilic cations (200 μg ml-1) suppress Panama disease effectively. These fungicides could help protect bananas from future yield losses by FocTR4.

Latent Benefits and Toxicity Risks Transmission Chain of High Dietary Copper along the Livestock-Environment-Plant-Human Health Axis and Microbial Homeostasis: A Review

The extensive use of high-concentration copper (Cu) in feed additives, fertilizers, pesticides, and nanoparticles (NPs) inevitably causes significant pollution in the ecological environment. This type of chain pollution begins with animal husbandry: first, Cu accumulation in animals poisons them; second, high Cu enters the soil and water sources with the feces and urine to cause toxicity, which may further lead to crop and plant pollution; third, this process ultimately endangers human health through consumption of livestock products, aquatic foods, plants, and even drinking water. High Cu potentially alters the antibiotic resistance of soil and water sources and further aggravates human disease risks. Thus, it is necessary to formulate reasonable Cu emission regulations because the benefits of Cu for livestock and plants cannot be ignored. The present review evaluates the potential hazards and benefits of high Cu in livestock, the environment, the plant industry, and human health. We also discuss aspects related to bacterial and fungal resistance and homeostasis and perspectives on the application of Cu-NPs and microbial high-Cu removal technology to reduce the spread of toxicity risks to humans.

Fungal response to abruptly or gradually delivered antifungal agent amphotericin B is growth stage dependent

Anthropogenic disturbances pose a multitude of novel challenges to ecosystems. While many experiments have tested effects using abrupt treatment applications, most environmental changes in fact are gradual. Since ecosystem responses might be highly dependent on the temporal nature of stressors, it is crucial to differentiate the effects of abrupt vs gradual treatment application. Antifungal agents, which are widely used in disease control both for humans and in agriculture, are becoming a new class of environmental contaminants. In this study, we examined the effect of a sub-lethal application of one antifungal agent, amphotericin B. We applied different rates of delivery, e.g. gradual and abrupt, and monitored biomass and sporulation of the model fungus Neurospora crassa in a batch culture. Our results demonstrate that: (i) the effect size difference between abrupt and gradual treatments is fungal growth stage dependent and (ii) the gradual treatment clearly had a higher sporulation level compared with all types of abrupt treatments. Our findings highlight the importance of considering the rate of change in environmental change research and point to a new research direction for future global change studies. Furthermore, our results also have important implications for avoiding treatment-induced spore production in agriculture and medical practise.