Desmodesmus subspicatus co-cultured with microcystin producing (PCC 7806) and the non-producing (PCC 7005) strains of Microcystis aeruginosa

Abstract

Although microcystins (MCs) are the most commonly studied cyanotoxins, their significance to the producing organisms remains unclear. MCs are known as endotoxins, but they can be found in the surrounding environment due to cell lysis, designated as extracellular MCs. In the present study, the interactions between MC producing and the non-producing strains of Microcystis aeruginosa , PCC 7806 and PCC 7005, respectively, and a green alga, Desmodesmus subspicatus , were studied to better understand the probable ecological importance of MCs at the collapse phase of cyanobacterial blooms. We applied a dialysis co-cultivation system where M. aeruginosa was grown inside dialysis tubing for one month. Then, D. subspicatus was added to the culture system on the outside of the membrane. Consequently, the growth of D. subspicatus and MC contents were measured over a 14-day co-exposure period. The results showed that Microcystis negatively affected the green alga as the growth of D. subspicatus was significantly inhibited in co-cultivation with both the MC-producing and -deficient strains. However, the inhibitory effect of the MC-producing strain was greater and observed earlier compared to the MC-deficient strain. Thus, MCs might be considered as an assistant factor that, in combination with other secondary metabolites of Microcystis , reinforce the ability to outcompete co-existing species.

Reviewing Interspecies Interactions as a Driving Force Affecting the Community Structure in Lakes via Cyanotoxins

“…However, a toxic M. aeruginosa strain caused a stronger growth inhibition on C. vulgaris than did a non-toxic strain [ 92 ]. The same was observed for the growth of Desmodesmus subspicatus co-cultured with stationary phase cultures of both toxic (PCC 7806) and non-toxic (PCC 7005) strains of M. aeruginosa, i.e., faster and stronger inhibition observed with the toxic strain [ 91 ]. It is important to repeat such experiments using log phase grown cells since there are many indications that those respond differently to biotic and abiotic conditions [ 93 ].…”

“…Metabolic profiles also were different among the species grown in mono- versus co-cultures [ 220 ]. Direct co-cultivation approaches, such as membrane-separated technique [ 91 , 94 ], as a more realistic, practical method that mimics natural conditions, are needed to study the molecular basis for cell-cell interactions and advance our knowledge of the subject interspecies interactions in detail but with less interference. Finally, a better understanding of the biotic interactions may help to improve the current approaches towards the mitigation of toxic blooms [ 35 ].…”

“…Exposure of natural Planktothrix agardhii population to the MC-containing extracts of two Planktothrix agardhii -predominated bloom samples excluded the bioactive role of MCs, but not the other biogenic compounds in the increased biomass as well as MC and chlorophyll a content of the target species [ 90 ]. Several studies concerning the interactions between green algae and MC-producing Microcystis reported that in addition to MCs, other secondary metabolites influence the phytoplankton community, explaining growth inhibition observed with exposure to non-toxic strains [ 91 , 92 ]. However, a toxic M. aeruginosa strain caused a stronger growth inhibition on C. vulgaris than did a non-toxic strain [ 92 ].…”

Phosphate Limitation Increases Content of Protease Inhibitors in the Cyanobacterium Microcystis aeruginosa

“…However, we cannot exclude that, depending on culture conditions, release of PIs into the medium has occurred. For MCs, which are known as endotoxins, it is known that they can be found in the surrounding environment due to cell lysis as it occurs during collapse of cyanobacterial blooms [61]. Cell lysis would be associated with the release of cell content into the medium and should thus lead to lower POC values.…”

Cyanobacterial Harmful Algal Blooms in Aquatic Ecosystems: A Comprehensive Outlook on Current and Emerging Mitigation and Control Approaches

“…Here, we highlight an emerging venue based on intra- and inter-species communication/competition/allopathic interactions that take place between toxic cyanobacteria, non-toxic cyanobacteria (mainly Microcystis sp. ), and other organisms, mainly (but not only) green algae, that may ultimately lead to the development of mitigation protocols (see [ 66 , 75 , 89 , 117 , 118 , 119 , 120 , 121 , 122 , 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 , 140 , 141 , 142 , 143 , 144 , 145 ] and references therein). An emerging example is the reduction of cyanoHAB populations that enables the persistence dominance of various non-toxic algae.…”