Co-production of microcystins and aeruginopeptins by natural cyanobacterial bloom

The relationship between Microcystis composition and the production of micr ocystins and nontoxic peptides in bloom cells, which was regularly collecte d in Lake Suwa, Japan, in the summer season from 1991 to 1994, was investig ated. In order to determine the structures of the nontoxic peptides, we col lected large amounts of bloom materials from the same lake on July 23, 1991 , and isolated three nontoxic peptides. They were named as aeruginopeptins 917S-A, -B, and -C, and their structures were mainly determined by a mass s pectrometry/mass spectrometry (MS/MS) technique as 19-membered cyclic depsi peptides possessing the Ahp (3-amino-6-hydroxy-2-piperidone) moiety. An ana lysis of the microcystins and aeruginopeptins in the collected bloom cells and their Microcystis composition suggested that the M. aeruginosa large ce ll size produces both microcystins and aeruginopeptins, and the production of both compounds is genetically closely related. (C) 2001 by John Wiley & Sons, Inc.