Aspergillus fungus conidiophores. Computer illustration of conidiophores from Aspergillus fumigatus fungus. Conidiophores contain the conidia (spores, small, round) of a fungus. Aspergillus is widespread in nature and is typically found in soil and decaying organic matter, where it plays an essential role in carbon and nitrogen recycling. It is one of the most common species to cause disease in individuals with an immunodeficiency, such as organ transplant recipients and people with AIDS or leukaemia. In these people, the fungus is more likely to become pathogenic, over-running the host's weakened defences and causing a range of diseases generally termed aspergillosis.