Effect of Phenyl-Acyl Compounds on the Growth, Morphology, and Toxin Production of Microcystis aeruginosa Kützing

Abstract

The proliferation of cyanobacteria and, consequently, the production of cyanotoxins is a serious public health concern; for their control, several alternatives have been proposed, including physical, chemical, and biological methods. In the search for new alternatives and a greater understanding of the biochemical process involved in the blooms’ formation, we report here the effect of eight phenyl-acyl compounds in the growth of Microcystis aeruginosa Kützing (assesed as cell density/count and Chl a fluorescence concentration) morphology, and production of the toxin microcystin-LR (MC-LR). Caffeic acid and eugenol decreased the growth of M. aeruginosa Kützing and the levels of Chl a. However, 3,5-dimethoxybenzoic acid and syringic acid caused the opposite effect in the growth; 2′and 4′only affected the Chl a. A reduction in the concentration of the MC-LR toxin was detected after treatment with syringic acid, caffeic acid, and eugenol. According to HPLC/MS (High Performance Liquid Chromatography coupled to Mass Spectrometry), a redox process possibly occurs between caffeic acid and MC-LR. The optical microscopy and Scanning Electron Microscopy analyses revealed morphological changes that had been exposed to caffeic acid and vanillin, specifically in the cell division and presence of mucilage. Finally, assays in Daphnia pulex De Geer neonates indicated that caffeic acid had a non-toxic effect at concentrations as high as 100 mg/L at 48 h.

Proof of Concept for Cell Culture-Based Coffee

“…40 Daphnia are sensitive to phenolics such as caffeic acid, too. 41 However, the investigated samples exhibit toxicity values close to previously evaluated plant cell samples. 33 The microbial load of the samples was below the threshold value (10 CFU/g or less than 1 CFU/mL), and therefore, the samples were approved for sensory evaluation.…”

Enhancement of Lipid Production by <i>Euglena gracilis</i> Using Vanillin as a Growth Stimulant

“…The effect of vanillin on the microalgae growth were reported to be controversial in the previous studies. For instance, 40 mg/L of vanillin had obvious inhibitory effect on the growth of Alexandrium tamarense 23) ; the mortality of Microcystis aeruginosa Kützing was 50% with vanillin at 50 mg/L treatment 24) . The toxic effect of vanillin at higher concentrations might be related to the increase of phenolic monomers permeability to cell membrane leading to the leakage of cytoplasmic components and the influx of toxic compounds outside the cell 25) .…”

Advancing Knowledge on Cyanobacterial Blooms in Freshwaters

“…Towards this direction, an integrated approach for the management of cyanobacterial blooms targeting the impacted ecological functions is presented by Hall et al [11]. In the fight against toxic cyanobacterial blooms, Herrera et al [9] proved experimentally the oppressive effect of eight phenyl-acyl compounds in the growth of Microcystis aeruginosa, and also the non-toxic effect of specific caffeic acid concentrations in non-target zooplankton organisms, expanding, thus, the potential use of novel substances in cyanobacterial biomass reduction.…”

“…In this direction, a deeper understanding of the mechanisms that determine cyanobacterial bloom structure and toxin production become a target for managing practices [5,6]. This Special Issue, entitled "Advancing Knowledge on Cyanobacterial Blooms in Freshwaters", includes 11 research papers [9][10][11][12][13][14][15][16][17][18][19] and aims to bring together the recent research of multiand interdisciplinary approaches from the field to the laboratory and back again, driven by working hypotheses based on any aspect from ecological theory to applied research on mitigating cyanobacterial blooms.…”