The species was then transferred to the genus Pseudallescheria in 1982 when examination of the type specimens of Petriellidium and Pseudallescheria revealed that they were the same genus. Ecology
An ability to tolerate minimal aeration and high osmotic pressure enables P. boydii to grow on soil, polluted and stagnant water and manure. Although this fungus is commonly found in temperate climates, it is thermotolerant and can survive in tropical climates and in environments with low oxygen pressure. Growth of P. boydii  can be seen in environments where nitrogen-containing compounds are common, usually due to human pollution. Its ability to use natural gas and other volatile organic compounds suggests a capacity for bioremediation. Growth and morphology
Pseudallescheria boydii is a saprotrophic fungus with broad hyphae growing up to 2–5 μm in width. Colonies change in colour from white to pale brown and develop a cottony texture with maturity. After a 2–3 week incubation period, cleistothecia may form containing asci filled with eight fusiform, one-celled ascospores measuring 12–18 × 9–13 μm in diameter. This fungus grows on most standard media, maturing in 7 days. Its primary nutrients are the sugars xylose, arabinose, glucose, sucrose, ribitol, xylitol and L-arabinitol. It cannot assimilate maltose or lactose; however, it is able to assimilate urea, asparagine, potassium nitrate and ammonium nitrate. The optimal temperature for growth is 25 °C (77 °F) and the fungus is generally considered to be mesophilic, although it can grow at higher temperatures (up to 37 °C (99 °F)) as well.
Infections in the CNS, which are rare, present as neutrophilic meningitis or multiple brain abscesses and have a mortality rate of up to 75%. Infections have also been observed in animals, notably corneal infection, abdominal mycetoma and disseminated infections in dogs and horses. Transient colonization is more likely than disease. However, invasive pseudoallescheriasis can be found in patients with prolonged neutropenia, high-dose corticosteroid therapy and allotransplantation of bone marrow. Pseudallescheria boydii has also been implicated in pneumonia subsequent to near-drowning events with infection developing anywhere between a few weeks to several months after exposure yielding high mortality. Dissemination of the organism to the central nervous system has been observed in some cases. This species is also known as a non-invasive colonist of the external ear and airways of patients with poor lung or sinus clearance, and the first documented case of human pseudallescheriasis involved the ear canal. It has also been implicated in infection of joints following traumatic injury, and these infections can progress to osteomyelitis. Infections of the skin and cornea have also been reported. Typical host-related risk factors for infection include lymphopenia, steroid treatment, serum albumin levels of < 3 mg/dL and neutropenia. Diagnosis
Detection and diagnosis of S. apiospermum is possible through isolation of the fungus in culture or through cytology and histopathology in the tissues of diseased individuals. In mycetoma-type infections, a confluence of symptoms is necessary for diagnosis, including tumefaction, draining sinuses and extrusion of grains.