Bioactive lipopeptides of ice-nucleating snow bacterium Pseudomonas syringae strain 31R1

The production of secondary metabolite lipopeptides by ice-nucleating Pseudomonas syringae strain 31R1 was investigated. Pseudomonas syringae strain 31R1 is a rifampicin-resistant derivative of P. syringae no. 31 used for the commercial production of snow. It is shown that P. syringae strain 31R1 produces antifungal lipodepsipeptides, syringomycins E and G, and, in addition, a novel and unique lipopeptide, peptin31. Spectroscopic and spectrometric analyses revealed that peptin31 is a linear undecalipopeptide with sequence identities to N- and C-terminal portions but lacking 11 amino acids of known lipodepsipeptide syringopeptin SPPhv. Peptin31 displayed antifungal activities against Rhodotorula pilimanae, Rhizoctonia solani, and Trichoderma harzianum and also hemolytic and antibacterial activities. Extracts of P. syringae strain 31R1 grown in medium with chloride were fungicidal, but not when grown without chloride. The latter extracts lacked peptin 31 and contained des-chloro forms of syringomycins E and G with low antifungal activities. Thus, the three lipopeptides account for the fungicidal properties of P. syringae 31R1 extracts. The occurrence of these bioactive metabolites should be considered when P. syringae no. 31 and its derivatives are used in products for making artificial snow.