Variability of Aspergillus nidulans antigens with media and time and temperature of growth

Abstract

The influence of culture medium and time and temperature of growth on the appearance of Aspergillus nidulans antigens was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, followed by silver staining or Western blot (immunoblot), of the proteins present in total cellular extracts or culture supernatants. Samples in the exponential, deceleration, and stationary growth phases were selected by biochemical, morphological, and ultrastructural criteria. Protein and antigen patterns (detected with rabbit antibodies) from total extracts were very similar in all cases, and the major differences observed seemed to depend on the age of the cultures. Culture supernatant patterns were highly dependent on the type of medium (complex or defined) and the age of the culture. Temperature did not significantly influence these results. The reproducible reactivity of selected human sera from aspergilloma-affected individuals was strictly associated with the use of defined media, especially Czapek Dox-AOAC, in both total extracts and culture supernatants. Extended growth times were necessary in the case of metabolic antigens (those obtained from culture supernatants). Screening of a battery of 10 selected human serum samples from patients with aspergilloma or invasive aspergillosis demonstrated that two of the antigens (96 to 98 and 45 kDa) from stationary-phase culture supernatants in Czapek Dox-AOAC medium were consistently reactive. When considered together as one unit, both antigens reacted with more than 50% of the sera, and at least one or the other of the antigens reacted with more than 90% of the sera. Less consistent results were obtained for two somatic antigens (from total cell extracts) of 45 to 50 and 20 to 22 kDa.