DePasquale, D.A. and Montville, T.J. (1990) Mechanism by which ammonium bicarbonate and ammonium sulfate inhibit mycotoxigenic fungi. Applied and Environmental Microbiology, 56 (12). pp. 3711-3717.
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Abstract
The mechanism by which ammonium bicarbonate inhibits mycotoxigenic fungi was studied. Elevated extracellular pH, alone, was not responsible for the antifungal activity. Although conidia of Penicillium griseofulvum and Fusarium graminearum [Gibberella zeae] had internal pH (pHi) values as high as 8.0 in buffer at an external pH (pHo) of 9.5, their viability was not markedly affected. The pHi values from conidia equilibrated in glycine-NaOH-buffered treatments without ammonium bicarbonate or ammonium sulfate were similar to values obtained from buffered treatments containing the ammonium salts. Inhibition did not appear to be directly related to increased pHi. Ammonium sulfate in buffered media at pH≥8.7 was as inhibitory as ammonium bicarbonate, but was completely ineffective at pH≤7.8. The hypothesis that free ammonia caused the fungal inhibition was tested by using ammonium sulfate as a model for ammonium bicarbonate. Viability, expressed as log colony forming units/ml, and percent germination of P. griseofulvum and G. zeae decreased dramatically as the free ammonia concn increased. Germination rate ratios (the germination rate in buffered ammonium sulfate divided by the germination rate in buffer alone) decreased linearly as the free ammonia concn increased, further establishing NH3 as the toxic agent. It is concluded that ammonium bicarbonate inhibits fungi because the bicarbonate anion supplies the alkalinity necessary to establish an antifungal concn of free ammonia.
| Item Type: | Article |
|---|---|
| Additional Information: | This work was supported by State appropriations, US Hatch Act funds, and a grant from the Church and Dwight Co., Inc. |
| Uncontrolled Keywords: | Toxigenic fungi; Penicillium; Gibberella zeae; Inhibition; Ammonium bicarbonate; Ammonium sulfate, RP6867 |
| Author Affiliation: | Rutgers State University, New Brunswick |
| Subjects: | Soil Science and Microbiology > Microbiology |
| Divisions: | General |
| Depositing User: | Mr Daneti Raju |
| Date Deposited: | 15 Mar 2014 15:35 |
| Last Modified: | 15 Mar 2014 15:35 |
| URI: | http://eprints.icrisat.ac.in/id/eprint/12581 |
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