In vitro toxicity of isolated strains and cyanobacterial bloom biomasses over Paramecium caudatum (ciliophora): Lessons from a non-metazoan model organism

Toxicological impacts and likely protein targets of bisphenol a in Paramecium caudatum

Bisphenol A (BPA) is a widely used plasticizer agent and a well-known ubiquitous endocrine disruptor, which is frequently associated with a series of reproductive, developmental, and transgenerational effects over wildlife, livestocks, and humans. Although extensive toxicological data is available for metazoans, the impact of BPA over unicellular eukaryotes, which represents a considerable proportion of eukaryotic diversity, remains largely overlooked. Here, we used acute end-point toxicological assay and an inverted virtual-screening (IVS) approach to evaluate cellular impairments infringed by BPA over the cosmopolitan ciliated protist, Paramecium caudatum. Our data indicate a clear time-dependent effect over P. caudatum survival, which seems to be a consequence of disruptions to multiple core cellular functions, such as DNA and cell replication, transcription, translation and signaling pathways. Finally, the use of this ciliate as a biosensor to monitor BPA within environments and the relevance of bioinformatic methods to leverage our current knowledge on the impacts of emerging contaminants to biological systems are discussed.

Evaluation of the Toxicity of Microcyclamide Produced by Microcystis aeruginosa in Danio rerio Embryos

The genus of cyanobacteria Microcystis is one of the most recurrent in blooms and is associated with the hepatotoxin microcystin production. In addition to cyanotoxins, these bacteria produce a wide range of secondary metabolites with a wide repertoire of activities. The co-occurrence of cyanotoxins and other cyanopeptides during blooming is quite common, and the negative effects are not always limited to one class of toxins, which makes it essential to investigate the toxicity of the other compounds individually. The objective of this study was to isolate the cyanopeptide microcyclamide produced by the strain Microcystis aeruginosa LTPNA 08 by liquid chromatography coupled to high-resolution mass spectrometry with a quadrupole-time-of-flight analyzer (LC-HR-QTOF-MS/MS) and to evaluate its acute toxicity in embryos of Danio rerio through the Fish Embryo Acute Toxicity (FET) assay. The fraction containing microcyclamide (95% purity) caused lethality in 62% of the embryos after 96 h exposure (50 µg mL^-1), with evidence of cardiotoxicity (cardiac edema). The calculated LC₅₀ value was 42.98 µg mL^-1 (with a concentration range of 37.79-48.89 µg mL^-1). The characterization of the secondary metabolites produced by cyanobacteria and the investigation of the toxicity of these compounds individually are essential for the identification of the substances responsible for negative effects on living organisms and on the ecosystem, in addition to assisting in the development of risk management policies.