Conidial head of Aspergillus niger showing double row of sterigmata. Conidial heads of Aspergillus niger are large, globose, and dark brown, and contain the fungal spores, facilitating propagation of the organism. Aspergillosis is an opportunistic fungal infection affecting mostly those individuals whose immune state has been compromised, and may be confined to a single locality, or be disseminated throughout the body. This is one of the most common species associated with invasive "pulmonary aspergillosis."