Tabtoxin, also known as wildfire toxin, is a simple monobactam phytotoxin produced by Pseudomonas syringae. It is the precursor to the antibiotic tabtoxinine β-lactam. Tabtoxin is a monocyclic β-lactam produced by P. syringae pv. tabaci, coronafaciens, and garcae. Pseudomonas syringae pv. tabaci, the causal agent of the wildfire of tobacco, produces the phytotoxin tabtoxin. tabtoxin-producing bacterium, P. syringae BR2, causes a disease of bean (Phaseolus vulgaris) similar to tobacco wildfire. This organism is closely related to P. syringae pv. tabaci but cannot be classified in the pathovar tabaci because it is not pathogenic on tobacco. Tabtoxin has been shown to be a dipeptide precursor that must undergo hydrolysis by a peptidase to yield the biologically active form, tabtoxinine-p-lact