Canopy openness in gaps determines the influence of herbaceous climbers and insect folivory on the survival of a tropical pioneer tree,Neoboutonia macrocalyx Pax

Gaps created 10 years ago by clearing of conifer plantations in Kibale National Park, Uganda, still experience very little tree regeneration. We studied the arrested succession by examining the survival of Neoboutonia macrocalyx Pax in different sized canopy gaps. We examined whether Neoboutonia seedlings can survive in gaps, which the tree rarely colonizes naturally and whether survival is limited by the size of the canopy opening, herbaceous climbers or insect folivory. A total of 384 seedlings were planted in 24 gaps, and survival was monitored for 19 months. Survival was dependent on canopy openness, being lowest in small gaps and highest in large gaps. We found a significant negative relationship between survival and folivory and a positive relationship between survival and climber infestation. Because 53% of the seedlings survived, regeneration could be limited by seed dispersal, rather than high seedling mortality. However, considering its high survival rate in arrested succession gaps, Neoboutonia seems to have good potential for forest restoration.     

Fungal fragments as indoor air biocontaminants

The aerosolization process of fungal propagules of three species (Aspergillus versicolor, Penicillium melinii, and Cladosporium cladosporioides) was studied by using a newly designed and constructed aerosolization chamber. We discovered that fungal fragments are aerosolized simultaneously with spores from contaminated agar and ceiling tile surfaces. Concentration measurements with an optical particle counter showed that the fragments are released in higher numbers (up to 320 times) than the spores. The release of fungal propagules varied depending on the fungal species, the air velocity above the contaminated surface, and the texture and vibration of the contaminated material. In contrast to spores, the release of fragments from smooth surfaces was not affected by air velocity, indicating a different release mechanism. Correlation analysis showed that the number of released fragments cannot be predicted on the basis of the number of spores. Enzyme-linked immunosorbent assays with monoclonal antibodies produced against Aspergillus and Penicillium fungal species showed that fragments and spores share common antigens, which not only confirmed the fungal origin of the fragments but also established their potential biological relevance. The considerable immunological reactivity, the high number, and the small particle size of the fungal fragments may contribute to human health effects that have been detected in buildings with mold problems but had no scientific explanation until now. This study suggests that future fungal spore investigations in buildings with mold problems should include the quantitation of fungal fragments.     

Effect of electrical charges and fields on injury and viability of airborne bacteria

In this study, the effects of the electric charges and fields on the viability of airborne microorganisms were investigated. The electric charges of different magnitude and polarity were imparted on airborne microbial cells by a means of induction charging. The airborne microorganisms carrying different electric charge levels were then extracted by an electric mobility analyzer and collected using a microbial sampler. It was found that the viability of Pseudomonas fluorescens bacteria, used as a model for sensitive bacteria, carrying a net charge from 4100 negative to 30 positive elementary charges ranged between 40% and 60%; the viability of the cells carrying >2700 positive charges was below 1.5%. In contrast, the viability of the stress-resistant spores of Bacillus subtilis var. niger (used as simulant of anthrax-causing Bacillus anthracis spores when testing bioaerosol sensors in various studies), was not affected by the amount of electric charges on the spores. Because bacterial cells depend on their membrane potential for basic metabolic activities, drastic changes occurring in the membrane potential during aerosolization and the local electric fields induced by the imposed charges appeared to affect the sensitive cells' viability. These findings facilitate applications of electric charging for environmental control purposes involving sterilization of bacterial cells by imposing high electric charges on them. The findings from this study can also be used in the development of new bioaerosol sampling methods based on electrostatic principles.     

Riedel's thyroiditis in a patient with multiple sclerosis

Our patient developed Riedel's thyroiditis soon after having an exacerbation of multiple sclerosis (MS). MS has been associated with other autoimmune diseases, including thyroiditis, and both Hashimoto's thyroiditis and subacute thyroiditis have been described in connection with MS. Yet, we are not aware of any other patient reported to have concomitant MS and Riedel's thyroiditis. The association between MS and Riedel's thyroiditis remains obscure but may reflect an autoimmune disorder common to both diseases.     

Modelling Nutrient Uptake by Individual Hyphae of Arbuscular Mycorrhizal Fungi: Temporal and Spatial Scales for an Experimental Design

Arbuscular mycorrhizas, associations between plant roots and soil fungi, are ubiquitous among land plants. Arbuscular mycorrhizas can be beneficial for plants by overcoming limitations in nutrient supply. Hyphae, which are long and thin fungal filaments extending from the root surface into the soil, increase the volume of soil accessible for plant nutrient uptake. However, no models so far specifically consider individual hyphae. We developed a mathematical model for nutrient uptake by individual fungal hyphae in order to assess suitable temporal and spatial scales for a new experimental design where fungal uptake parameters are measured on the single hyphal scale. The model was developed based on the conservation of nutrients in an artificial cylindrical soil pore (capillary tube) with adsorbing wall, and analysed based on parameter estimation and non-dimensionalisation. An approximate analytical solution was derived using matched asymptotic expansion. Results show that nutrient influx into a hypha from a small capillary tube is characterized by three phases: Firstly, uptake rapidly decreases as the hypha takes up nutrients, secondly, the depletion zone reaches the capillary wall and thus uptake is sustained by desorption of nutrients from the capillary wall, and finally, uptake goes to zero after nutrients held on the capillary wall have been completely depleted. Simulating different parameter regimes resulted in recommending the use of capillaries filled with hydrogel instead of water in order to design an experiment operating over measurable time scales.