Conidium

Asexual reproduction in ascomycetes (the phylum Ascomycota) is by the formation of conidia, which are borne on specialized stalks called conidiophores.

Aspergillus is not only a familiar fungus found across various different settings in the world, but it poses a danger for immunocompromised individuals, as inhaled Aspergillus conidia could germinate inside the respiratory tract and cause aspergillosis, a form of pulmonary infection, and continual developments of aspergillosis such as new risk groups and the resistance against antifungal drugs.

The dormant conidia are able to germinate even after an year of remaining at room temperature, due to their resilient intracellular and extracellular characteristics, which enable them to undergo harsh conditions like dehydration, variation in osmotic pressure, oxidation, and temperature, and change in UV exposure and acidity levels.

In the polarized growth stage, upregulated and overexpressed proteins and transcripts included ones involved in synthesis of chitin (a major component of the fungal cell wall), mitosis and DNA processing, remodeling of cell morphology, and ones in germ tube formation pertaining to infection and virulence factors.

In some cases, specialized macroscopic fruiting structures perhaps 1 mm or so in diameter containing masses of conidia are formed under the skin of the host plant and then erupt through the surface, allowing the spores to be distributed by wind and rain.

Acervular conidiomata, or acervuli, are cushion-like structures that form within the tissues of a host organism: Mostly they develop a flat layer of relatively short conidiophores which then produce masses of spores.

The increasing pressure leads to the splitting of the epidermis and cuticle and allows release of the conidia from the tissue.

[12] Exposure to conidia from certain species, such as those of Cryptostroma corticale, is known to cause hypersensitivity pneumonitis, an occupational hazard for forest workers and paper mill employees.

[15] Especially with species of the Aspergillus genus, germination in the respiratory tract can lead to aspergillosis, which is quite common, can vary in severity, and has shown signs of developing new risk groups and antifungal drug resistance.