Resistance of a fungus to its own antifungal metabolites,and the effectiveness of resistance-selection in screening for higher-yielding mutants

Summary The fungus Geotrichum flavobrunneum is markedly more resistant to the antifungal action of the azasterols which it produces than are several otherwise comparable but non-producing filamentous fungi. If mutants of G. flavobrunneum are selected for even higher resistance to azasterols, or to an antifungal which interacts with normal membrane sterols (pimaricin) a high proportion of them show significantly increased ability to produce azasterols.     

Biosynthesis of multicomponent polyhydroxyalkanoates by Wautersia eutropha

The effect of carbon supply on polyhydroxyalkanoate (PHA) synthesis by bacteria Wautersia eutropha was studied. Synthesis of multicomponent PHA composed of short- and long-chain monomers (C4-C8) by two natural strains (H16 and B5786) under mixotrophic conditions (CO2 + alkane acids as cosubstrates) was demonstrated for the first time. The PHA composition was shown to be dependent on the cosubstrate type. In the presence of odd fatty acids, four- and five-component polymers were synthesized; hydroxybutyrate, hydroxyvalerate, and hydroxyheptanoate were the major monomers, while hydroxyhexanoate and hydroxyoctanoate were minor and irregular. In the presence of even fatty acids, PHA contained not only the corresponding molecules (hydroxyhexanoate and hydroxyoctanoate), but also hydroxyvalerate; synthesis of four-component PHA which contain mainly hydroxybutyrate and hydroxyhexanoate (up to 18 mol %) is therefore possible. A series of four- and five-component PHA was synthesized and their physicochemical characteristics were determined.