title: A novel rhythm of microcystin biosynthesis is described in the cyanobacterium Microcystis panniformis Komárek et al.
abstract: The presence of microcystins (MCY) in the cyanobacteria Microcystis panniformis Komárek et al. is reported for the first time. This strain of cyanobacterium has been isolated from Barra Bonita, an eutrophicated water reservoir in São Paulo state, Brazil. The identification of M. panniformis was confirmed by both traditional morphological analysis and the phycocyanin intergenic spacer sequences. MCY-LR and [Asp(3)]-MCY-LR were identified in this strain after HPLC purification and extensive ESI-MS/MS analysis. Their levels in this strain were determined by HPLC and ranged from 0.25 to 2.75 and 0.08 to 0.75 fmol/cell, respectively. Analyzing the levels of MCY-LR and [Asp(3)]-MCY-LR in different times during the light:dark (L:D) cycle, it was found that levels of MCYs per cell were at least threefold as high during the day-phase than during the night-phase. This may be associated to the biological clock since prokaryotic cyanobacteria express robust circadian (daily) rhythms under the control of a timing mechanism that is independent of the cell division cycle. Our findings also showed the same pattern under light:light (L:L) cycle.
authors.affiliation: Departamento de Ciências Biológicas, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Piracicaba, SP, Brazil.
authors.forename: Maria do Carmo
authors.initials: Mdo C
authors.lastname: Bittencourt-Oliveira
authors.forename: Paula
authors.initials: P
authors.lastname: Kujbida
authors.forename: Karina Helena Morais
authors.initials: KH
authors.lastname: Cardozo
authors.forename: Valdemir Melechco
authors.initials: VM
authors.lastname: Carvalho
authors.forename: Ariadne do Nascimento
authors.initials: Ado N
authors.lastname: Moura
authors.forename: Pio
authors.initials: P
authors.lastname: Colepicolo
authors.forename: Ernani
authors.initials: E
authors.lastname: Pinto
mesh_terms: D002940:Circadian Rhythm / Q000502:physiology*; D008029:Lighting; D052998:Microcystins; D046931:Microcystis / Q000302:isolation & purification / Q000378:metabolism*; D010456:Peptides, Cyclic / Q000096:biosynthesis*; D010802:Phylogeny; D021241:Spectrometry, Mass, Electrospray Ionization; D013997:Time Factors
chemical_list: D052998:Microcystins; D010456:Peptides, Cyclic; C078588:microcystin