Temperature-stress tolerance of the fungal strain Aspergillus niger 26: physiological and ultrastructural changes
2014
Abrashev, Radoslav | Stoitsova, Stoyanka | Krumova, Ekaterina | Pashova, Svetlana | Paunova-Krasteva, Tsvetelina | Vassilev, Spassen | Dolashka-Angelova, Pavlina | Angelova, Maria
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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