Congruent downy mildew-associated microbiomes reduce plant disease and function as transferable resistobiomes

Root-associated microbiota can protect plants against severe disease outbreaks. In the model-plant Arabidopsis thaliana, leaf infection with the obligate downy mildew pathogen Hyaloperonospora arabidopsidis (Hpa) results in a shift in the root exudation profile, therewith promoting the growth of a selective root microbiome that induces a systemic resistance against Hpa in the above-ground plant parts. Here we show that, additionally, a conserved subcommunity of the recruited soil microbiota becomes part of a pathogen-associated microbiome in the phyllosphere that is vertically transmitted with the spores of the pathogen to consecutively infected host plants. This subcommunity of Hpa-associated microbiota (HAM) limits pathogen infection and is therefore coined a “resistobiome”. The HAM resistobiome consists of a small number of bacterial species and was first found in our routinely maintained laboratory cultures of independent Hpa strains. When co-inoculated with Hpa spores, the HAM rapidly dominates the phyllosphere of infected plants, negatively impacting Hpa spore formation. Remarkably, isogenic bacterial isolates of the abundantly-present HAM species were also found in strictly separated Hpa cultures across Europe, and even in early published genomes of this obligate biotroph. Our results highlight that pathogen-infected plants can recruit protective microbiota via their roots to the shoots where they become part of a pathogen-associated resistobiome that helps the plant to fight pathogen infection. Understanding the mechanisms by which pathogen-associated resistobiomes are formed will enable the development of microbiome-assisted crop varieties that rely less on chemical crop protection

Dry bubble disease of the white button mushroom. Ecology and control of Lecanicillium fungicola

Dry bubble disease is a persistent problem in the cultivation of the white button mushroom, A. bisporus. There is a pressing need for innovative ways to control spread and development of L. fungicola in mushroom cultivation as currently disease management relies heavily on one chemical (Sporgon) for which a reduced sensitivity of the pathogen has been reported. The research described in this thesis aims to supply targets for such innovative ways. In order to develop effective control of L. fungicola, a thorough understanding of its ecology is crucial. Therefore in chapter 2, current knowledge about this mycopathogen is reviewed. The ecology of the pathogen is discussed with emphasis on host range, dispersal and primary source of infection. In addition, insights in the infection process and mushroom defense mechanisms are reviewed. In chapter 3, the ecology of L. fungicola in the casing is investigated. It was found that Lecanicillium spores remain dormant until A. bisporus colonizes the casing. It was shown that the casing microflora is involved in this dormancy and mechanisms were investigated. It appears that the casing microflora produce antifungal compounds that impose a nutrient dependency on L. fungicola spores that otherwise germinate independent of nutrients. Chapter 4 describes the search for antagonists that effectively suppress dry bubble disease. Possible mechanisms of antagonisms towards L. fungicola were investigated in vitro using well characterized Pseudomonas strains. Subsequently, a collection of bacteria that were isolated from colonized casing was screened for in vitro antagonism. In vitro, L. fungicola was inhibited by certain isolates through competition for iron and antibiosis. However, these isolates could not effectively suppress dry bubble disease. We conclude that biological control of dry bubble disease is not feasible. Control of plant pathogens often functions not only through direct antagonism of the biocontrol agent on the pathogen, but also through induction of systemic resistance in plants. Induced resistance in both plants and animals is mostly triggered upon pathogenic attack. As both plants and animals have developed functionally similar systems of induced defence, it was hypothesized that fungi too could have evolved mechanisms to respond systemically upon microbial attack. In chapter 5, however, it is shown that mushrooms of A. bisporus do not exhibit induced systemic resistance upon attack by L. fungicola. In chapter 6 application of 1-octen-3-ol to control dry bubble disease is investigated. 1-octen-3-ol is produced by A. bisporus and a principle component of the mushroom’s aroma. It was found that 1-octen-3-ol treatment reduced dry bubble disease in inoculated mushroom cultures. Under conditions that resembled the commercial production of mushrooms, 1-octen-3-ol was as effective as Sporgon. This demonstrates that 1-octen-3-ol has potential for disease management in the mushroom industry. Furthermore, preliminary results indicate that other plant pathogenic fungi are also sensitive to 1-octen-3-ol, which broadens the opportunities for 1-octen-3-ol’s application. Finally, in chapter 7, the results described in this thesis are discussed in view of possibilities to control dry bubble disease

The rhizosphere microbiome and plant health

The diversity of microbes associated with plant roots is enormous, in the order of tens of thousands of species. This complex plant-associated microbial community, also referred to as the second genome of the plant, is crucial for plant health. Recent advances in plant–microbe interactions research revealed that plants are able to shape their rhizosphere microbiome, as evidenced by the fact that different plant species host specific microbial communities when grown on the same soil. In this review, we discuss evidence that upon pathogen or insect attack, plants are able to recruit protective microorganisms, and enhance microbial activity to suppress pathogens in the rhizosphere. A comprehensive understanding of the mechanisms that govern selection and activity of microbial communities by plant roots will provide new opportunities to increase crop production

Unified multiple‐feature color display for MR images

A display method is proposed in which the spin‐lattice relaxation time T 1, the spinspin relaxation time T 2, and the proton density ρ of each pixel in a MR image are simultaneously expressed in color features in a unified way that allows international standardization. MR images were made from a phantom, a healthy volunteer, and patients in such a way that T 1 and T 2 and proton density images could be derived. T 1 and T 2 data were compared with accurate relaxation time measurements of the phantom content. Color images were computed from the acquired T 1 and T 2 images using matrix multiplication on a pixel base. In this way the color combination in each pixel represents the properties of that particular pixel by a unique mixing of the elementary colors red, green, and blue. Color resolution could be modified using different choices of the reference triangle in which the color combinations were defined. This method of representation offers a means for displaying multiple features as T 1, and T 2 in one directly interpretable image, independent of instrumental settings. © 1989 Academic Press, In

The rhizosphere revisited: root microbiomics

The rhizosphere was defined over 100 years ago as the zone around the root where microorganisms and processes important for plant growth and health are located. Recent studies show that the diversity of microorganisms associated with the root system is enormous. This rhizosphere microbiome extends the functional repertoire of the plant beyond imagination. The rhizosphere microbiome of Arabidopsis thaliana is currently being studied for the Obvious reason that it allows the use of the extensive toolbox that comes with this model plant. Deciphering plant traits that drive selection and activities of the microbiome is now a major challenge in which Arabidopsis will undoubtedly be a major research object. Here we review recent microbiome studies and discuss future research directions and applicability of the generated knowledge

Blaaskatheterisatie in historisch perspectief

ThisDit artikel geeft een overzicht van blaaskatheterisatie in Nederland tussen 1997 en 2018. Voor het maken van het overzicht is gebruikgemaakt van een databank met declaratie-informatie over extramurale hulpmiddelenzorg onder de verzekerde bevolking. Het aantal gebruikers wordt weergegeven per 100.000 personen. Het gebruik van verblijfskatheters is toegenomen van 159 (24.734 gebruikers) in 1997 naar 315 gebruikers per 100.000 personen (54.106 gebruikers) in 2018. Het gebruik van wegwerpkatheters verdrievoudigde van 92 (14.258 gebruikers) in 1997 naar 267 per 100.000 personen (45.909 gebruikers) in 2018. In 2018 had 20,7% van de gebruikers een neurogeen en 44,9% een niet-neurogeen onderliggend lijden. De totale kosten stegen van 27,7 naar 84,4 miljoen euro. De kosten voor intermitterende katheterisatie stegen het meest: van 16,4 naar 74,6 miljoen euro. Uit dit onderzoek blijkt dat in de afgelopen 21 jaar het gebruik van ve