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Penicillin G oversecretion by Penicillium chrysogenum PQ96 is associated with a strictly adjusted cellular organization of the mature and senescent mycelial cells. Abundant vacuolar phagy and extended cellular vacuolization combined with vacuolar budding resulting in the formation of vacuolar vesicles that fuse with the cell membrane are the most important characteristic features of those cells. We suggest as follows: if the peroxisomes are integrated into vacuoles, the penicillin G formed in peroxisomes might be transferred to vacuoles and later secreted out of the cells by an exocytosis process. The peroxisomal cells of the mycelium are privileged in penicillin G secretion.
A modified method of glutaraldeyde-osmium tetroxide fixation was adjusted to characterize the ultrastructure of Candida albicans pleomorphic forms, using phase-contrast microscopy, scanning electron microscopy and transmission electron microscopy. &e discovered morphological criteria defining the individual morphotypes are discussed in terms of mycological and histopathological diagnostics of candidiasis. &e relations are discussed between fungal pleomorphism, virulence and susceptibility of di!erent morphotypes to fungicides.
The arrangement of organelles in the sub-apical productive non-growing vacuolated hyphal cells of the high- and the low-penicillin-producing strains Penicillium chrysogenum was compared using transmission electron microscopy. In the productive cells of the high-yielding strain the endoplasmic reticulum and the polyribosomes with associated peroxisomes are frequently arranged at the periphery of the cytoplasm and around the vacuoles. At the high activity of penicillin G biosynthesis the immuno-label of the cytosolic isopenicillin N synthase is concentrated at the polyribosomes arranged in the peripheral cytoplasm and along the tonoplast as well as around the peroxisomes. On the basis of the obtained results the compartmentalization of the pathway of penicillin G biosymthesis is discussed. The obtained results support the phenylacetic acid detoxification hypothesis of penicillin G biosynthesis.
The different members of the secreted aspartyl proteinase (Sap) family of the human pathogenic yeast Candida albicans are proposed to play different roles during infection and are differentially expressed at various body sites. In recent reports, expression analysis has focused on the genes SAP1-6, while the expression pattern of SAP7-10 was less well studied. We analyzed the SAP7-SAP10 expression profile of C. albicans under human serum influence that may be elucidated in the course of blood infection in humans and how this in vitro expression profile is associated with hyphal formation. The phenotypes of strains were examined under scanning electron microscopy. Quantitative RT-PCR (2–ΔΔCT) was used to monitor SAP expression of C. albicans wild type cells and mutants lacking SAP9 and/or SAP10. Of the four analyzed SAP genes, only SAP7 was detectably induced in the double mutant and in the wild type strains in the model that mimics bloodstream infections. On the other hand, in the wild types (isolate 83 and CAF2-1), SAP7 was expressed 0.8- or 0.4-fold less than SAP10, respectively. Our findings suggest that Sap7 may respond to the challenge of the human blood environment. Furthermore, the results support the notion that compensatory upregulation of SAP7 and SAP8 in the Δsap9/Δsap10 mutant occurs in these conditions. SAP7-10 expression was strain-specific. Our findings point to a link between morphogenesis and expression of SAP9 in serum, where these conditions induce both hyphae and SAP9, but temporal gene expression patterns might be controlled by other factors.
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