Cytotoxic activities of P. fluorescens MF37 treated with cyclic nucleotide analogues. Effect of dibutyryl cyclic AMP (dbcAMP) and 8-bromo cyclic GMP (8BcGMP) (10-5 M) on the apoptotic (A) and necrotic (B) activities of Pseudomonas fluorescens MF37. The apoptotic effect of the bacterium was determined by measuring the accumulation of NO2- in the medium resulting from the activation of inducible NO synthase activity in glial cells. The necrotic activity of the bacterium was assessed by measuring the accumulation of lactate dehydrogenase (LDH) in the medium resulting from rupture of the cytoplasmic membrane of glial cells. Values are expressed as mean concentrations of NO2- or LDH in the culture medium after 24 h of incubation with untreated (n = 32) or treated (n = 24 for dbcAMP, and n = 22 for 8BcGMP) bacteria. Data are means for four independent experiments. *** : Significantly different (P < 0.001).