Morphological, ultrastructural, and chemical changes induced in Cunninghamella blakesleeana by copper and cobalt

Summary

Scanning and transmission electron microscopy of Cunninghamella blakesleeana grown in the presence of toxic concentrations of copper and cobalt indicated that copper, but not cobalt, induced both morphological and ultrastructural changes. In contrast to the control or cobalt-grown cultures, the hyphae of copper-grown cultures (called “blue mycelia”) were larger in diameter, had a rough and granular surface, and the cell wall was thicker. The cytoplasm of the blue mycelia was also abnormal and was in a compressed state. X-Ray microprobe analysis indicated a lower content of magnesium and calcium in the blue mycelia and an elevated content of sulphur in both the blue and cobalt-grown mycelia. The protein composition of the cell walls of the blue mycelia, fractionated on a Sepharose-4B column saturated with copper, was different from that of control or cobalt-grown cultures, as shown by their amino acid composition. Hydroxyproline was present only in the cell wall proteins of the blue mycelia, citrulline and cystathionine were present only in the proteins of cobalt-grown cultures, and proline was absent in the cell wall protiens of the control cultures.