A NEW APPROACH TO THE PROBLEM OF AGGREGATION IN THE CELLULAR SLIME MOLDS

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Abstract
1. It has been shown that there is a substance (or substances) given off by the cellular slime mold amoebae that both orients aggregating cells ( e. g. in the Shaffer test) and increases the rate of movement of the cells. A simple, quantitative assay has been developed to test the rate of cell movement. Using both types of test in conjunction, we have been able to show that the substance(s) is produced before the aggregation of the amoebae and is even present in large amounts in the food source, E. coli. 2. The substance(s) is not species-specific; it induces adhesiveness in cells approaching aggregation; it does not affect center formation or center inhibition (territory size); nor is it related to the phenomenon of cell repulsion. 3. It is quite possible that there are many substances involved and the rate-increasing substance (s) is separate from orientation substance(s). Another possibility is that they are all one substance, which has hitherto been called acrasin. If this is the case then aggregation can no longer be considered the moment of first acrasin secretion, but one would have to assume that it is the moment of first acute sensitivity to acrasin, a sensitivity sufficient to override the cell repulsion phenomenon. It is hoped that if the chemical identification of the rate substance is achieved, then many of these important questions will be answered.