Phaseolotoxin (N-sulphodiaminophosphinyl-ornithyl-alanyl-homoarginine) is a phytotoxic secondary metabolite produced by Pseudomonas syringae pv. phaseolicola. The production of the phytotoxin is strongly regulated by temperature. The optimal temperature for phaseolotoxin production is 18 degrees C. Temperatures in the range between 18 degrees C and 30 degrees C inhibit the production of phaseolotoxin in an increasing manner. By temperature shift experiments and the inhibition of protein synthesis by chloramphenicol it was demonstrated, that the synthesis of enzymes related to toxin synthesis and not the regulation of the activity of the responsible enzyme system is affected by higher temperatures.