Effect of Fatty Acids and Methyl Octanoate on Resting Mycelium of Boletus variegatus

Abstract

AbstractThe endogenous respiration of resting, submerged grown Boletus variegatus mycelium has been determined. In young cultures the intensity of the endogenous oxygen uptake was subject to great variations during the first few hours of starvation. However, by using six to eight days old mycelium the Qo2 values could be kept at a relatively low and constant level for at least nine hours.Inhibition of the endogenous respiration was found after addition of n‐saturated C‐2 to C‐12 fatty acids (2 × 10‐3M, pH 4.85). The inhibitory effect of the compound was dependent on the length of the carbon chain. Maximum effects were obtained for acids with eight to twelve carbon atoms per molecule. The inhibition was also dependent on the amount of undissociated acid present. By raising the pH so that the fatty acid dissociated the established inhibition was partly reversed. The effect of the neutral compound methyl octanoate was in essence identical to that obtained with octanoic acid.After fatty acid addition a close correspondence was found between the degree of inhibition of the oxygen uptake and the amount of UV absorbing substances leaking out from the cells. This extracellular material had an absorption maximum at 260 nm and a minimum around 240 nm. The leaking was ascribed to interaction between fatty acids or methyl octanoate and lipophilic substances of the cytoplasmic membrane. It is suggested that the inhibitory action on the endogenous respiration is due to similar effects on intracellular membrane systems.