No abstract

Modern, mainly sustainability-driven trends, such as low-temperature washing or bleach-free liquid detergents, facilitate microbial survival of the laundry processes. Favourable growth conditions like humidity, warmth and sufficient nutrients also contribute to microbial colonization of washing machines. Such colonization might lead to negatively perceived staining, corrosion of washing machine parts and surfaces, as well as machine and laundry malodour. In this study, we characterized the bacterial community of 13 domestic washing machines at four different sampling sites (detergent drawer, door seal, sump and fibres collected from the washing solution) using 16S rRNA gene pyrosequencing and statistically analysed associations with environmental and user-dependent factors. Across 50 investigated samples, the bacterial community turned out to be significantly site-dependent with the highest alpha diversity found inside the detergent drawer, followed by sump, textile fibres isolated from the washing solution, and door seal. Surprisingly, out of all other investigated factors only the monthly number of wash cycles at temperatures ≥ 60 • C showed a significant influence on the community structure. A higher number of hot wash cycles per month increased microbial diversity, especially inside the detergent drawer. Potential reasons and the hygienic relevance of this finding need to be assessed in future studies.

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.

No abstract

A model for transepithelial migration of human fungal pathogens was established, in which Candida albicans was shown to migrate across a monolayer of Caco-2 intestinal cells in a two-chamber system. Electron microscopy revealed typical stages of epithelial penetration by C. albicans including phagocytosis at the apical side, intra- and intercellular migration and exit on the basolateral side of the monolayer. Hyphal growth forms appeared particularly involved in penetration of the Caco-2 monolayer. The model was examined using defined C. albicans mutants defective in hyphal development (efg1/efg1) or growth (ura3/ura3). Transmigration of the efg1/efg1 mutant strain was reduced, while transmigration of the ura3/ura3 strain was blocked completely in the absence of uridine. Because these results parallel virulence characteristics of the mutants the Caco-2 monolayer system appears a useful model for the study of fungal-human host cell interactions.