Streaming defect in gxcDD- cells. (A) AX2 and gxcDD- cells were allowed to starve on plastic plates. Images were continuously recorded. Streams formed in gxcDD- cells broke down to aggregates. (B) Streaming was also recorded in wild type and gxcDD- cells using an exogenous source of cAMP in a capillary chemotaxis assay. gxcDD- cells did migrate towards the cAMP source but did not form streams. (C) gxcDD- and AX2 cells were allowed to starve in Soerensen buffer at a density of 1 × 107 cells/ml and samples were withdrawn at the indicated times. The percentage of aggregated cells was determined by measuring the OD600. The data represent the average of three independent experiments.