EXPLORING THE NATURAL ROLE OF MICROCYSTINS—A REVIEW OF EFFECTS ON PHOTOAUTOTROPHIC ORGANISMS¹

Abstract

Cyanobacterial blooms and the production of cyanotoxins represent a serious global problem. Although the effects of a group of important cyanotoxins, microcystins (MCs), have been studied intensively in various organisms, little is known about the natural functions of these cyclic heptapeptides. MCs may have allelopathic effects. This paper summarizes the information from the studies that have investigated the effects of MCs on photoautotrophs in vitro and in vivo. Interactions with terrestrial plants, macrophytes, macroalgae, and planktonic microalgae are reported in detail with respect to the ecological relevancy of experimental conditions related to allelopathy. Our review shows that only a limited number of studies described harmful effects of MCs at concentrations that are typical for the environment. Consequently, the ability of MCs to act as general allelopathic compounds against photoautotrophs seems unlikely. However, further research is needed for definitive confirmation or rejection of the allelopathic hypothesis as well as, an explanation of the crucial question of MC function in the context of new information from evolutionary and molecular biology.

A review of neurotoxicity of microcystins

“…The progeny of Swiss Albino mice treated with MCs extracted from cyanobacterial bloom were reported to have a brain size reduction (Babica et al 2006). A sparse structure, distention of endoplasmic reticulum, and swelling mitochondria of cerebrum ultrastructure were shown in the brains of rat offspring after pregnant SD rats were exposed to MC-LR at 10 μg/kg body weight (BW)/day from gestational day 8 (GD8) to postnatal day 15 (PD15) of lactation (Zhao et al 2015a).…”

Hydrogen peroxide induces apoptotic-like cell death inMicrocystis aeruginosa(Chroococcales, Cyanobacteria) in a dose-dependent manner

“…Among the toxic cyanobacteria, M. aeruginosa commonly occurs in highly eutrophic lakes, and it often dominates the phytoplankton in eutrophic lakes and ponds (Yamamoto & Nakahara 2009). Microcystis aeruginosa produces the hepatotoxin microcystin, which is a threat to human and environmental health (Babica et al 2006). Recently, it has been reported that M. aeruginosa NIES 843 and PCC 7806 harbour genes for PCD that may be related to the rapid collapse of Microcystis blooms (Kaneko et al 2007;Frangeul et al 2008).…”

Effects of microcystin-producing and microcystin-free strains ofPlanktothrix agardhiion long-term population dynamics ofDaphnia magna

“…Indeed, the production of toxic metabolites is suspected to alter biotic communities through allelopathic interactions. Several hypotheses have been proposed concerning the role of such metabolites at several trophic levels (for reviews, see Vasconcelos and Pereira, 2001;Gross, 2003;Wiegand and Pflugmacher, 2005;Babica et al, 2006;Leflaive and TenHage, 2007;Schatz et al, 2007). However, such a toxic activity is difficult to characterize because of (i) the presence of other molecules that may modify the effect of toxins (Rohrlack et al, 1999b;Buryskova et al, 2006), (ii) the adaptation of target organisms (Wilson and Hay, 2007) and (iii) the appearance of avoidance behaviour in some species of zooplankton (Kurmayer and Ju¨ttner, 1999).…”