Effects of Cylindrospermopsin Producing Cyanobacterium and Its Crude Extracts on a Benthic Green Alga—Competition or Allelopathy?

Abstract

Cylindrospermopsin (CYN) is a toxic secondary metabolite produced by filamentous cyanobacteria which could work as an allelopathic substance, although its ecological role in cyanobacterial-algal assemblages is mostly unclear. The competition between the CYN-producing cyanobacterium Chrysosporum (Aphanizomenon) ovalisporum, and the benthic green alga Chlorococcum sp. was investigated in mixed cultures, and the effects of CYN-containing cyanobacterial crude extract on Chlorococcum sp. were tested by treatments with crude extracts containing total cell debris, and with cell debris free crude extracts, modelling the collapse of a cyanobacterial water bloom. The growth inhibition of Chlorococcum sp. increased with the increasing ratio of the cyanobacterium in mixed cultures (inhibition ranged from 26% to 87% compared to control). Interestingly, inhibition of the cyanobacterium growth also occurred in mixed cultures, and it was more pronounced than it was expected. The inhibitory effects of cyanobacterial crude extracts on Chlorococcum cultures were concentration-dependent. The presence of C. ovalisporum in mixed cultures did not cause significant differences in nutrient content compared to Chlorococcum control culture, so the growth inhibition of the green alga could be linked to the presence of CYN and/or other bioactive compounds.

Toxic cyanobacteria and cyanotoxins in European waters – recent progress achieved through the CYANOCOST Action and challenges for further research

“…The latter observation however is disputable N o n -c o m m e r c i a l u s e o n l y as no studies on isolated cultures of this cyanobacterium were performed. Complementary studies have been recently conducted on the toxicity of CYN (Guzmán-Guillén et al, 2015;Sierosławska et al, 2015;), mechanisms of toxicity , biodegradation (Dziga et al, 2016) and biological role and allelopathy (B-Béres et al, 2015). These works have contributed valuable knowledge on these aspects but at the same time have revealed many gaps in understanding of the role(s) of CYN in aquatic ecosystems and its impact on their functioning (Sukenik et al, 2015).…”

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

“…CYN-producing A. ovalisporum inhibited the benthic Chlorococcum sp. green alga [ 177 ]. In mixed culture treatments (green alga to cyanobacterium ratios: 1:1, 1:2 and 1:4), a higher initial cell number of the cyanobacterium had a more significant inhibitory effect on the growth of green alga.…”

Molecular characterizations of Thai <i>Raphidiopsis raciborskii</i> (Nostocales, Cyanobacteria) based on 16S rDNA, <i>rbcLX</i>, and cylindrospermopsin synthetase genes

“…For the preparation of crude extract, 1 mL of a culture containing Thai R. raciborskii cells at the exponential growth phase was frozen and thawed at least twice, as described by B-Béres et al (2015). To confirm the presence of CYN and its analogues in the Thai strains, CYN and 7-deoxy-CYN concentrations were determined in the aqueous extract (intracellular and extracellular) by liquid chromatography-mass spectrometry analysis on a Triple Quadrupole Varian 320 MS (LC/MS/MS) (Varian, Palo Alto, CA, USA); 20 µL of each aqueous extract was in-jected onto a Pursuit XRs 3 C18 column (150 4.6 mm; Agilent Technologies, Waldbronn, Germany) coupled to a double mass spectrometer in tandem (Varian 320MS-MS) at 50°C and a flow rate of 0.3 mL/min (solvent A: 0.1% formic acid/deionized water, solvent B 0.1% formic acid/acetonitrile).…”