The Fungal Ecology of the Activated Sludge Process
A thesis submitted to the
faculty of the Graduate College
in partial fulfillment of the
requirements for the degree of
Master of Arts
Biology
in Western Michigan University
1984
by
Douglas William Jacques
Committee Members: Clarence Goodnight, Joseph Engemann, Marjory Spradling
ABSTRACT
Examination of wastewater secondary influent and activated sludge reveal that bacteria and fungi may exist in a negative correlation. Activated sludge may support a resident population of microfungi. All fungi isolated from secondary influent and activated sludge belong to the form-class Deuteromycetes. The density of geofungi in activated sludge may exceed that of bacterial chemolithotrophs and rival that of bacterial heterotrophs.
General Remarkes Concerning Fungal Isolates Pictured in Plates One and Two
Geotrichum candidum (Plate 1) is a saprophyte commonly found in nature. The mold is associated with lactic acid fermentation of sugars present in plant materials such as sillage, pickles and sauerkraut. G. candidum is also used to ripen soft cheeses (i.e., Brie, Limburger) through processes of protein and fat decomposition (proteolysis and lipolysis). In addition,this fungus lives as a commensal in the mouth, gastrointestinal tract and genitourinary tract of humans. On rare occasions, G. candidum, can cause a lung infection, pulmonary geotrichosis, of which the symptoms approximate those of tuberculosis.
Aspergillus sp. (Plate 2) is primarily a saprophytic mold. The molds of this genus are nearly omnipresent components of both soil biota and air spora. They are a common comtaninant in mycological laboratories, they colonize the surfaces of shoes, clothes and other apparel, especially in humid tropical climates, and they readily cause decay of exposed foodstuffs.
Aspergillus flavus, a common plant saprophyte, produces toxic substances called aflatoxins. A. flavus colonizes ground nuts (i.e. peanuts), tree nuts (i.e., walnuts), grains and oil seeds, and unless cumulated aflatoxin residues are removed, products made from such materials, when ingested, can cause serious illness. In poultry and laboratory animals, aflatoxins are proven liver carcinogens. To date, no direct link has been established between aflatoxins and liver cancer in humans.
However, several species of Aspergillus (i.e., A. flavus, A. fumigatus, A. niger) are known to cause a variety of human pathologies, such as intermittent bronchial plugging, pneumonia and auditory canal infection (otomycosis), collectively identified as aspergillosis. Infections are occasioned by inhalation of airborne spores. Although aspergillosis is an uncommon diease, when it does occur, it is often associated with other medical conditions, such as asthma and allergy to Aspergillus spp. Patients who are immunosuppressed are more likelty to develop aspergillosis than people with relatively healthy immune systems.