Mirko Weide

Influence of farnesol on the morphogenesis of Aspergillus niger.

Farnesol was the first quorum‐sensing regulator to be found in eukaryotic cells. In Candida albicans, a dimorphic fungal human pathogen, farnesol blocks the yeast‐to‐filamentous growth transition. Here we show that in Aspergillus niger farnesol acts as an inhibitor of conidiation: Colonies grown on media containing farnesol were unable to develop conidia. Although farnesol treated A. niger cultures exhibited a colony morphology resembling the “fluffy” phenotype of A. nidulans, which is caused by a hyperactive G‐protein/cAMP pathway, the intracellular level of cAMP in A. niger mycelia grown in presence of farnesol is greatly diminished. Furthermore, whereas inhibiting adenylyl cyclase led to a farnesol‐like effect, the addition of external cAMP inhibited conidiation without causing a “fluffy” phenotype. This suggests that the mechanisms regulating conidiation in A. niger and A. nidulans are different. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Star‐Shaped Poly(styrene)‐block‐Poly(4‐vinyl‐N‐methylpyridiniumiodide) for Semipermanent Antimicrobial Coatings

Goal of the present work is to develop an antimicrobial coating that can be applied from an aqueous solution and resists short washing cycles, but can be rinsed off by thorough washing. To this end, a series of star-shaped polystyrene-block-poly(4-vinyl-N-methylpyridinium iodide) polymers are synthesized by anionic polymerization using a core-first approach. The optimal resulting polymers are applied as coatings on glass slides, showing high antimicrobial efficiency against Staphylococcus aureus as well as Escherichia coli. The coatings, characterized by atomic force microscopy and transmission electron microscopy, stay at the surface even after at least 20 flush-like washings with water, and retain their antimicrobial activity.

Proteome analysis of the farnesol-induced stress response in Aspergillus nidulans—The role of a putative dehydrin

The isoprenoid alcohol farnesol represents a quorum-sensing molecule in pathogenic yeasts, but was also shown to inhibit the growth of many filamentous fungi. In order to gain a deeper insight into the antifungal activity of farnesol, we performed 2D-differential gel electrophoretic analysis (2D-DIGE) of Aspergillus nidulans exposed to farnesol. We observed an increased abundance of antioxidative enzymes and proteins involved in protein folding and the ubiquitin-mediated protein degradation. A striking finding was the strong up-regulation of a dehydrin-like protein (DlpA). Expression analyses suggested the involvement of DlpA in the cellular response to oxidative, osmotic and cold stress. In line with these data, we demonstrated that dlpA expression was regulated by the MAP kinase SakA/HogA. The generation of both a dlpA Tet(on) antisense RNA-producing A. nidulans strain (dlpA-inv) and a ΔdlpA deletion mutant indicated a role of DlpA in conidiation and stress resistance of dormant conidia against heat and ROS. Furthermore, the production of the secondary metabolite sterigmatocystin was absent in both strains dlpA-inv and ΔdlpA. Our results demonstrate the complexity of the farnesol-mediated stress response in A. nidulans and describe a farnesol-inducible dehydrin-like protein that contributes to the high tolerance of resting conidia against oxidative and heat stress.

Evaluation of the virucidal performance of domestic laundry procedures

Laundering is one of the most important means to ensure a sufficient hygiene standard in the household environment. To evaluate the performance of this process, it is desirable to have methods that mimic the real-life situation as closely as possible. Although methods for the evaluation of the antibacterial and antifungal efficacy of domestic laundry procedures are available, the effect of laundering on viruses is still rather unclear. As the influence of laundry process parameters such as mechanical actions, temperature dynamics or liquor ratio cannot be simulated in vitro by suspension assays, a new in situ test method allowing virus simulation tests in washing machines has been developed. Using this in situ method we could show that conventional household washing detergents have a full virucidal efficiency at 40 degrees C also against non-enveloped surrogate viruses.

Antimicrobial Efficacy of Laundry Detergents with Regard to Time and Temperature in Domestic Washing Machines

Abstract In times of low-temperature washing, laundry hygiene gains importance, as microbial contaminations on textiles can cause infection transmission and malodour formation. This study systematically investigated the antimicrobial effect of laundry detergents (solid and liquid market detergents) with regard to time and temperature in domestic washing machines. To evaluate the microbial reduction, cotton swatches contaminated with Staph. aureus, Ent. hirae, Ps. aeruginosa, C. albicans and T. mentagrophytes were washed at 20 to 60 °C, varying the washing time, with and without detergent. All tested washing factors affected the antimicrobial effect of to a varying extend, depending on the germ. The used solid market detergent containing activated oxygen bleach provided a way to achieve high microbial reductions in low temperature washing.

Qualitative and Quantitative Analysis of Microbial Communities in Household Dishwashers in Germany

Abstract The proper cleaning of used dishes provides an essential means to maintain a sufficient hygiene level on food contact surfaces. However, little is known on the microbiological quality of domestic dishwashers themselves, especially in relation to consumer habits. This study investigated dishwashers in German households to analyse the number and composition of microbial colonisers and their putative impact on dishwashing hygiene. Although the microbiological status of dishwashers appeared to depend on multiple factors, data suggest that a trend towards lower temperatures might effect in a decreased hygiene.

Alternative Wege zu schimmelresistenten Materialien

The equipment of construction and sealing materials with biocides represents an effective way to inhibit fungal growth. However, active agents in sanitary sealants are subjected to continuous leaching. In addition, the number of available biocides declines. Alternative strategies are discussed with sanitary silicones as an example: besides the enhanced leaching stability of the fungicide, non-biocidal agents shield the surface from spore adhesion and inhibit the production of new spores.