Fig. 2. Spore formation in wild type and grlE^– strains. Early culminants of the wild-type strain AX4 (white columns) and the grlE^– null strain (hatched columns) were disaggregated, washed and deposited at 10⁵ cells per well in 2 ml buffer. GABA (100 nM); 10 pM SDF2; 100 nM GABA and 10 µM glutamate; or 10 pM SDF-2 and 10 µM glutamate were then added to the wells as indicated. The proportion of spores was determined 1 hour later and compared with cells that received no additions. Each experiment was repeated three to five times; the error bars represent 1 s.d.