Effects of chitosan and oligochitosan on development and mitochondrial function of Rhizopus stolonifer

Abstract

The antifungal activities of chitosan and oligochitosan have been used to control postharvest decay of the fruits. The effect of chitosan and oligochitosan on mycelium growth, spore germination, and mitochondrial function of Rhizopus stolonifer was evaluated in order to establish a connection between fungus development and the main organelle in charge to provide energy to the cell. The mycelium growth of R. stolonifer was significantly reduced on minimum media amended with chitosan or oligochitosan. The highest antifungal indexes were obtained on media containing chitosan or oligochitosan at 2.0 mg ml(-1). Microscopic observation showed that chitosan and oligochitosan affected the spore germination and hyphae morphology. Both polymers increased oxygen consumption of R. stolonifer. Respiratory activity was restored with NADH in permeabilized treated and untreated cells, and was inhibited with rotenone and flavones. Complex III and IV were inhibited by antimycin A and cyanide, respectively, in treated and untreated cells. Chitosan and oligochitosan increased NADH dehydrogenase activity in isolated mitochondria. However, there were not changes in the cytochrome c oxidase and ATPase activities by effect of these polymers. These results suggest that both chitosan and oligochitosan affect the development of R. stolonifer and might be implicated in the mitochondrial dysfunction.

Proteomic analysis of the inhibitory effect of oligochitosan on the fungal pathogen, Botrytis cinerea

“…The rate of germination rate was > 90% in the non‐treated control after 8 h of incubation in potato dextrose broth at 25 °C, whereas the germination rate of oligochitosan‐treated spores was approximately 50%. These results confirm previous reports demonstrating that oligochitosan inhibited the spore germination of other postharvest fungal pathogens, including A. kikuchiana , P. piricola , M. fructicola , P. expansum and R. stolonifer …”

“…Oligochitosan has been suggested as a potential, eco‐friendly alternative to the use of synthetic fungicides for controlling postharvest diseases, and several studies have demonstrated that it can be effective for controlling fungal diseases of plant hosts, including those of economically important horticultural crops . In addition to inducing systemic resistance, oligochitosan has been shown to have a direct inhibitory effect on spore germination, germ tube elongation, and mycelial growth and development of several fungal pathogens, including Alternaria alternata , Alternaria kikuchiana , Physalospora piricola , Monilinia fructicola , Penicillium expansum , Rhizopus stolonifer and Colletotrichum gloeosporioides . A comprehensive understanding of the mode of action by which oligochitosan inhibits fungal pathogens, however, is lacking.…”

Influence of chitosan and its derivatives on cell development and physiology of Ustilago maydis

“…Control cells and oligochitosan-treated cells showed an increase in the oxygen consumption rate at 12 h. Oligochitosan induced faster consumption of oxygen in the cells incubated for 24 h. After 48 h in culture, oligochitosan induced faster consumption of oxygen by cells, while glycol chitosan provoked slower oxygen consumption. A previous report showed that oligochitosan at 1 mg/mL raised oxygen consumption in Rhizopus stolonifer cells [10]. Therefore, the cells required more energy to repair moderate damages caused by the polymer.…”

“…Cells were weighed, diluted to 50% (w/v) with sterile distilled water, and 50 L (25 mg wet weight) of each suspension was used for the assay. The oxymetric traces were recorded, and the initial oxygen consumption rates were expressed in nmol O 2 min −1 mg −1 [10].…”

“…molecules. Besides, it was demonstrated that oligochitosan also affected the endomembrane system [9] and caused an increase in NADH dehydrogenase activity in mitochondria, therefore it might be implicated in the mitochondrial dysfunction [10]. On the other hand, glycol chitosan is a chitosan derivative soluble in water over a wide range of pH values and possessing potentially useful biological properties [11].…”