Fungal food spoilage often starts with a contamination with spores. Experimental data strongly indicate the existence of subpopulations of spores with different levels of resistance to preservation... Show moreFungal food spoilage often starts with a contamination with spores. Experimental data strongly indicate the existence of subpopulations of spores with different levels of resistance to preservation methods. In this thesis, the extent of this heterogeneity and the underlying mechanisms using fungal model systems is studied. The role of the genetic background, environmental conditions and the developmental state of the spores were studied, using quantitative imaging, genome and RNA/protein sequencing as well as functional gene analysis. The role of transcription factors in weak acid stress resistance of Aspergillus niger is described. Next, heat resistance of fungal spores of three food spoilage species was quantified and compared. The genomes of Aspergillus niger strains were sequenced and compared revealing the existence of a possible sexual cycle. Melanin of fungal spores impacts UV-C resistance, but not heat resistance and a functional CRISPR/Cas9 genome editing system for Paecilomyces variotii and Penicillium roqueforti is described. Older spores are more heat resistant than younger spores, which can be contributed to differences in compatible solute composition. Additionally, a high cultivation temperature results in fungal spores with high heat resistance, possibly due to heat shock proteins. Show less
