Temperature-stress tolerance of the fungal strain Aspergillus niger 26: physiological and ultrastructural changes |
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Authors: | Radoslav Abrashev Stoyanka Stoitsova Ekaterina Krumova Svetlana Pashova Tsvetelina Paunova-Krasteva Spassen Vassilev Pavlina Dolashka-Angelova Maria Angelova |
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Affiliation: | 1. The Stephan Angeloff Institute of Microbiology, Bulgarian Academy of Sciences, 26 Acad. Georgi Bonchev Str., 1113, Sofia, Bulgaria 2. Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, 9 Acad. Georgi Bonchev Str., 1113, Sofia, Bulgaria
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Abstract: | The study focuses on the morphological and physiological cell responses to oxidative stress induced by high temperature treatment in the industrially relevant fungus Aspergillus niger 26. Temperatures above 30 °C lead to growth suppression and changes in morphological characteristics: decrease in the size of hyphal elements and increase in “active length” by switching from slightly branched long filaments to a multitude of branched forms containing active cytoplasm. Transmission electron microscopy of fungal cultures heated at 40 °C demonstrated abnormal wavy septation with reduced amount of chitin (as shown by WGA-gold labelling), intrahyphal hyphae development, disintegration of mitochondria and extensive autolysis. Temperature-dependent decrease in the total intracellular protein content and a sharp increase (six to tenfold) in oxidatively damaged proteins were also demonstrated. Elevated temperatures caused a two and threefold increase in catalase and superoxide dismutase activities, respectively. |
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