INTERACTIONS AMONG VARIANT AND WILD-TYPE STRAINS OF CELLULAR SLIME MOLDS ACROSS THIN AGAR MEMBRANES

Open Access
Publisher Website
Google Scholar
Abstract
A wild stock of Dictyo-stelium mucoroides, strain S -2, and both wild and variant stocks of D. discoideum, strain NC-4, were grown on glucose-peptone agar in association with Aerobacter aerogenes for 48 hours at 22[degree]C. The myxamoebae were separated from the bacteria by differential centrifuga tion. Washed cell suspensions of morphologically deficient stocks were mixed in paired combinations and in varying cell ratios, and gave synergistic development on a washed agar-distilled water substratum. Dilutions of each of such stocks were prepared and .01-cc aliquots were placed on washed agar-distilled water membranes. When the cells had lodged upon the agar surface the excess fluid was drained away, and a 2d deficient stock was treated similarly on the opposite side of the membrane. Tests of synergistic strains in pairs in all possible cell ratios and against wild type NC -4 gave no synergistic development with one exception, indicating that diffusible materials are usually not exchanged. The ability of chemotactic agents associated with aggregation to pass through membranes was tested by dispensing . 1-cc aliquots of myxamoebae on both sides of membranes of varied thicknesses, and classifying the attraction between aggregates as strong, weak, or none. For both D. discoideum and D mucoroides wild stocks and interspecific appositions between them, strong attraction was observed at distances up to 140[mu], weak attraction up to 205[mu] and none beyond 230[mu]. Attraction occurred between any 2 fruitless strains or between a fruitless strain and wild type across membranes of 30-100u[mu] in thickness. Aggregateless myxamoebae clustered within a diameter of .2 mm directly above or below the centers of aggregations of fruitless or wild-type cells across thin membranes. The aggregate-less cells were believed to be sensitive to a chemotactic agent but incapable of producing it.