Morphological anomalies induced by Congo red in Aspergillus niger

Area of Science:

• Mycology
• Cell Biology
• Biochemistry

Background:

• Fungal cell wall integrity is crucial for growth and survival.
• Chitin microfibril assembly is a key process in fungal cell wall formation.
• The dye Congo red is known to interfere with polysaccharide synthesis.

Purpose of the Study:

• To investigate the effects of Congo red on Aspergillus niger germ tube morphology.
• To elucidate the role of chitin assembly in maintaining hyphal tip structure and growth.
• To understand the mechanism of cell wall viscosity regulation during fungal growth.

Main Methods:

• Exposure of Aspergillus niger germ tubes to Congo red (0.15 mg/ml) for 6 hours.
• Microscopic analysis including ultraviolet light, transmission electron microscopy (TEM), and scanning electron microscopy (SEM).
• Observation of morphological alterations in hyphal tips.

Main Results:

• Congo red treatment led to significant alterations in hyphal tips, including bursting and the formation of bulges.
• New hyphal tips emerged from these bulges, followed by further conversion into bulges, creating alternating segments of isotropic and polarized growth.
• These changes indicate a disruption in the normal polarized growth pattern of the fungal hyphae.

Conclusions:

• Congo red inhibits chitin microfibril assembly, leading to aberrant fungal cell wall formation.
• The study highlights the importance of a regular gradient of wall viscosity, dependent on glycan chain aggregation, for normal hyphal extension.
• Disruption of this process results in abnormal growth patterns, such as swelling and bursting of hyphal tips in Aspergillus niger.