Some Aspects of Chemotaxis Using the Cellular Slime Molds as an Example

A conspicuous feature in the development of fungi is some form of chemotropism or chemotaxis (see the recent excellent review by Gooday, 1975). The hyphae will, in some species, go towards food or towards other hyphae (positive chemotropism) or they will go away from toxic substances, often produced by themselves (negative chemotropism). Very little is known of the molecular mechanisms involved although it is clear that the growth of the hyphae occurs generally at the tip and that somehow chemical gradients must be directly affecting the orientation of this tip growth. In some cases there is evidence for growth stimulators, in others growth inhibitors, but it is not known how the substances act. Positive chemotaxis is also found in motile zoospores and gametes in fungi, as, for instance, in the well known case of sirenin discovered by Leonard Machlis in Allomyces. Gooday makes clear there is increasing