Sensitivity of fungi to nikkomycin Z.

Nikkomycin Z inhibited colony radial extension (Kr) and hyphal density in Geotrichum candidum, Trichoderma koningii, Mucor plumbeus, and Fusarium oxysporum, although the level of inhibition varied with the fungal species and was influenced by the concentration of nutrients in the culture medium. While G. candidum and M. plumbeus were sensitive to the inhibitory effects of nikkomycin Z, T. koningii and F. oxysporum were relatively tolerant of concentrations of the antibiotic up to 100 mumol. Nikkomycin Z also caused significant decreases in rates of hyphal extension (Emax) and swelling and bursting of hyphal apices in G. candidum and M. plumbeus. The sensitivity of G. candidum and M. plumbeus to the effects of the antibiotic was due in part to their ability to remove nikkomycin from a liquid culture medium; the nikkomycin-tolerant species T. koningii and F. oxysporum were unable to transport this nucleoside dipeptide antibiotic. Although both G. candidum and F. oxysporum appeared capable of removing the di- and tripeptides, dialanine and trialanine, from a liquid medium, rate of dipeptide uptake was greater in F. oxysporum, while rate of tripeptide uptake was greater in G. candidum. However, overall rate of uptake of peptides was greater in G. candidum than in F. oxysporum.