642 Journal of Basic Microbiology 2012, 52, 642 – 652 © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.jbm-journal.com Research Paper Effect of the fungal mycotoxin patulin on the chromatin structure of fission yeast Schizosaccharomyces pombe Eszter Horvath 1 , Gabor Nagy 2 , Melinda Turani 2 , Eniko Balogh 2 , Gabor Papp 1 , Edit Pollak 3 , Istvan Pocsi 2 , Miklos Pesti 1 and Gaspar Banfalvi 2 1 Department of General and Environmental Microbiology, University of Pecs, Pecs, Hungary 2 Department of Microbial Biotechnology and Cell Biology, University of Debrecen, Debrecen, Hungary 3 Department of General Zoology, University of Pecs, Pecs, Hungary The fungal mycotoxin patulin is produced by several molds, especially by Aspergillus and Penicillium. The aim of this study was to clarify whether patulin causes alterations in plasma membrane permeability of Schizosaccharomyces pombe lead to cellular shrinkage charateristic to apoptosis or increases cell size indicating necrosis in cells. Transmission and scanning electronmicroscopy revealed that lower concentrations of patulin induced cellular shrinkage and blebbing, higher concentration caused expansion without cellular disruption. Large-scale morphological changes of individual cells were followed by time lapse video microscopy. Patulin caused the elongation and stickiness of cells or rounded up their shapes. To visualize chromatin structures of S. pombe nuclei upon patulin treatment, protoplasts were isolated from S. pombe and subjected to fluorescent microscopy. Chromatin changes in the presence of 50 μM patulin concentration were characterized by elongated nuclei containing sticky fibrillary chro- matin and enlarged round shaped nuclei trapped at the fibrillary stage of chromatin conden- sation. Short (60 min) incubation of S. pombe cells in the presence of high (500 μM) patulin concentration generated patches of condensed chromatin bodies inside the nucleus and caused nuclear expansion, with the rest of chromatin remaining in fibrillary form. Longer (90 min, 500 μM) incubation resulted in fewer highly condensed chromatin patches and in nuclear fragmentation. Although, high patulin concentration increased the size of S. pombe size, it did not lead to necrotic explosion of cells, neither did the fragmented nuclei resemble apoptotic bodies that would have indicated programmed cell death. All these morphological changes and the high rate of cell survival point to rapid adaptation and mixed type of fungistatic effects. Keywords: Protoplast / Transmission electronmicroscopy / Scanning electronmicroscopy / Fluorescence microscopy / Long-term scanning / Chromatin structure; cell death Received: October 12, 2011; accepted: November 03, 2011 DOI 10.1002/jobm.201100515 Introduction * Patulin is a water soluble broad-spectrum antibiotic against a wide range of disease-causing bacteria. This lactone mycotoxin is produced by several molds, espe- cially by Aspergillus and Penicillium and is commonly found in rotting apples. It exerts antibacterial, carcino- Correspondence: Prof. Gaspar Banfalvi, University of Debrecen, Depart- ment of Microbial Biotechnology and Cell Biology, Life Sciences Building 1.102, 1 Egyetem tér, Debrecen 4010, Hungary E-mail: bgaspar@unideb.hu Phone: (36) 52 512 900 ext. 62319 Fax: (36) 52 512 925 genic and mutagenic activities [1, 2]. The cytostatic effect of patulin is related to its potential to reduce the barrier properties of tight junctions [3], inhibiting the potassium uptake [4] and activation of p38 kinase [5]. This notion was confirmed in cells exposed to 50 μM patulin treatment, resulting in lipid peroxidation, abrupt calcium influx, extensive blebbing, and total LDH release suggesting the loss of structural integrity of the plasma membrane. Although, the cytotoxicity of patulin was prevented by indole tetramic acids, it was doubted, that this antioxidant potential was responsible for the preventive effect against patulin. Consequently