Role of bacteria in the production and degradation of Microcystis cyanopeptides

Abstract

The freshwater cyanobacteria, Microcystis sp., commonly form large colonies with bacteria embedded in their mucilage. Positive and negative interactions between Microcystis species and their associated bacteria have been reported. However, the potential role of bacteria in the production and degradation of cyanobacterial secondary metabolites has not been investigated. In this study, a Microcystis‐associated bacterial community was isolated and added to the axenic M. aeruginosa PCC7806 liquid culture. After 3 years of cocultivation, we studied the bacterial genetic diversity adapted to the PCC7806 strain and compared the intra‐ and extracellular concentration of major cyanopeptides produced by the cyanobacterial strain under xenic and axenic conditions. Mass spectrometric analyses showed that the intracellular concentration of peptides was not affected by the presence of bacteria. Interestingly, the produced peptides were detected in the axenic media but could not be found in the xenic media. This investigation revealed that a natural bacterial community, dominated by Alpha‐proteobacteria, was able to degrade a wide panel of structurally varying cyclic cyanopeptides.

Global metabolomic characterizations of Microcystis spp. highlights clonal diversity in natural bloom-forming populations and expands metabolite structural diversity

“…Although, the strains used in this study were not cultured in stringent axenic conditions, no noticeable contamination by fungi or heterotroph bacteria could have been detected during the systematic screening of all strains under light microscope prior to the experiment. In addition, a previous metabolome analyses in PCC 7806 grown under axenic or non-axenic condition do not detected any variation in the metabolite produced by the cyanobacteria (Briand et al, 2016b). We assume that the metabolite profiles observed here for the 24 strains are characteristic of the cyanobacteria them self and that the different metabolite observed in this study, comprising the unknown metabolite clusters highlighted by the network analysis, are genuine produced by the cyanobacteria themselves.…”

A Mini Review on Microcystins and Bacterial Degradation

“…isolated from the mucilage of M. aeruginosa colonies during a bloom in a French pond completely degraded MC-LR and Des-MCLR. It is of interest that the bacterial community also degraded cyanobacterial secondary metabolites such as cyanopeptolins and aerucyclamides [131]. The findings of this study suggest that, bacterial community may possess the ability not only to degrade MC but also other cyanobacterial secondary metabolites.…”

Microbial diversity and metabolic potential in cyanotoxin producing cyanobacterial mats throughout a river network

“…With the exception of samples 9 and 10, the other sample assemblages containing Cyanobacteria with the anatoxin-a operon had relatively more Sphingomonadales, an order with many known microcystin degrading species (Kormas and Lymperopoulou, 2013;Mou et al, 2013;Briand et al, 2016). However, anatoxin-a and microcystin have different molecular structures.…”