Effects of pH on genes involved in oxalic acid production in the brown rot fungus Postia placenta

• Published in: Phytopathology Vol. 100; no. 6; p. S21
• Main Authors: Carlson, B, Jellison, J
• Format: Journal Article
• Language: English
• Published: 01.06.2010
• ISSN: 0031-949X

Brown rot fungi are the organisms primarily responsible for the biodegradation of soft, in-service wood. During the decay process, brown rot decay fungi such as Postia placenta release large amounts oxalic acid (pKa1 = 1.27, pKa2 = 4.28) which rapidly dissociates into H+ and oxalate (C sub(2)O super(2) sub(4) super(-)). To characterize the relationship between glucose consumption, oxalic acid production and pH, a time course study was run over 21 days on P. placenta grown in 50 ml of modified Highley's media. Shake cultures with 1 mM asparagine and ammonium-L-tartrate and 5% glucose were harvested after 1, 3, 5, 7, 13, 17, 19, 22 days following inoculation and were analyzed for glucose, oxalic acid, pH, and biomass. As available glucose in culture decreased, pH decreased from 4.73 c 0.03 to 2.81 c 0.06 and oxalic acid increased from below detection limits to 0.51 c 0.10 mg/ml. To determine the effect pH has on gene expression of enzymes involved in oxalic acid synthesis, static cultures were grown and pH was adjusted to 7 with 2M NaOH. 17 hours after treatment, the pH of the treated culture dropped and mycelia were harvested for real time PCR. Preliminary results (n = 1) show a 9.4 fold increase in glyoxylate oxidase but no significant change in oxalate decarboxylase, oxaloacetase, isocitrate lyase gene expression.