Effects of the Secondary Metabolite Producing Pseudomonas fluorescens CHA0 on Soil Protozoa and Bacteria

Bacteria producing secondary metabolites with antagonistic effects on fungal pathogens have received attention during the last decades as an alternative to chemical pesticides. They, however, might also have effects on indigenous soil organisms like bacteria and protozoa, the latter ones being among the most important grazers of bacteria in soil. The present study reports on the effect of the potential biocontrol agent Pseudomonas fluorescens CHA0 and its genetically modified derivative CHA0/pME3424 on indigenous soil bacteria and protozoa in a soil system. CHA0/pME3424 overproduces two of the secondary metabolites produced by CHA0: the polyketide antibiotics pyoluteorin (Plt) and 2,4-diacetylphloroglucinol (DAPG). P. fluorescens CHA0/gfp1 and CHA0/pME3424 both negatively affected the abundance of soil bacteria and protozoa and the genetic community structure of Kinetoplastida studied by PCR-DGGE. The negative effects were detectable after 14 days but were decreasing and are expected to be temporary. The overproducer of secondary metabolites did not differ in effect from the wild type. The soil respiration and bacterial genetic community structure were not significantly affected. The study shows the soil bacteria and protozoa to be temporary affected by bacteria producing secondary metabolites, which can have implications for nutrient-cycling in soil and environmental risks of biocontrol agents

Factors Affecting Vegetable Growers’ Exposure to Fungal Bioaerosols and Airborne Dust

We have quantified vegetable growers’ exposure to fungal bioaerosol components including (1→3)-β-d-glucan (β-glucan), total fungal spores, and culturable fungal units. Furthermore, we have evaluated factors that might affect vegetable growers’ exposure to fungal bioaerosols and airborne dust. Investigated environments included greenhouses producing cucumbers and tomatoes, open fields producing cabbage, broccoli, and celery, and packing facilities. Measurements were performed at different times during the growth season and during execution of different work tasks. Bioaerosols were collected with personal and stationary filter samplers. Selected fungal species (Beauveria spp., Trichoderma spp., Penicillium olsonii, and Penicillium brevicompactum) were identified using different polymerase chain reaction-based methods and sequencing. We found that the factors (i) work task, (ii) crop, including growth stage of handled plant material, and (iii) open field versus greenhouse significantly affected the workers’ exposure to bioaerosols. Packing of vegetables and working in open fields caused significantly lower exposure to bioaerosols, e.g. mesophilic fungi and dust, than harvesting in greenhouses and clearing of senescent greenhouse plants. Also removing strings in cucumber greenhouses caused a lower exposure to bioaerosols than harvest of cucumbers while removal of old plants caused the highest exposure. In general, the exposure was higher in greenhouses than in open fields. The exposures to β-glucan during harvest and clearing of senescent greenhouse plants were very high (median values ranging between 50 and 1500 ng m−3) compared to exposures reported from other occupational environments. In conclusion, vegetable growers’ exposure to bioaerosols was related to the environment, in which they worked, the investigated work tasks, and the vegetable crop

Transmission of mycoviruses: new possibilities

Mycoviruses are viruses that infect fungi. In recent years, an increasing number of mycoviruses have been reported in a wide array of fungi. With the growing interest of scientists and society in reducing the use of agrochemicals, the debate about mycoviruses as an effective next-generation biocontrol has regained momentum. Mycoviruses can have profound effects on the host phenotype, although most viruses have neutral or no effect. We speculate that understanding multiple transmission modes of mycoviruses is central to unraveling the viral ecology and their function in regulating fungal populations. Unlike plant virus transmission via vegetative plant parts, seeds, pollen, or vectors, a widely held view is that mycoviruses are transmitted via vertical routes and only under special circumstances horizontally via hyphal contact depending on the vegetative compatibility groups (i.e., the ability of different fungal strains to undergo hyphal fusion). However, this view has been challenged over the past decades, as new possible transmission routes of mycoviruses are beginning to unravel. In this perspective, we discuss emerging studies with evidence suggesting that such novel routes of mycovirus transmission exist and are pertinent to understanding the full picture of mycovirus ecology and evolution

State of Knowledge of Soil Biodiversity: Status, Challenges, and Potentialities

This report presents the threats to soil biodiversity and the solutions that soil biodiversity can provide to problems in different fields, including agriculture, environmental conservation, climate change adaptation and mitigation, nutrition, medicine and pharmaceuticals, remediation of polluted sites, and many others. There is increasing attention on the importance of biodiversity for food security and nutrition, especially above-ground biodiversity such as plants and animals. Less attention is being paid to the biodiversity beneath our feet: soil biodiversity. Yet the rich diversity of soil organisms drives many processes that produce food, regenerate soil or purify water. This report is the result of an inclusive process involving more than 300 scientists from around the world under the auspices of FAO's Global Soil Partnership and its Intergovernmental Technical Panel on Soils, the Convention on Biological Diversity, the Global Soil Biodiversity Initiative, and the European Commission