Microcystin-LR, a Cyanobacterial Toxin, Induces DNA Strand Breaks Correlated with Changes in Specific Nuclease and Protease Activities in White Mustard (Sinapis alba) Seedlings

There is increasing evidence for the induction of programmed cell death (PCD) in vascular plants by the cyanobacterial toxin microcystin-LR (MC-LR). Our aim was to detect the occurrence of PCD-related DNA strand breaks and their possible connections to specific nuclease and protease activities. DNA breaks were studied by the deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) method in the photoperiodically grown dicot model of white mustard (Sinapis alba). In-gel nuclease and protease activity assays showed changes in the activities of specific isoenzymes during treatments with MC-LR. Strand breaks occurred both in the developing root epidermis and cortex. Several isoenzyme activities were related to these breaks, for example: an increase in the activity of neutral 80–75 kDa, acidic high MW (100–120 kDa) and, most importantly, an increase in the activity of neutral 26–20 kDa nucleases, all of them having single-stranded DNA cleaving (SSP nuclease) activities. Increases in the activities of alkaline proteases in the 61–41 kDa range were also detected and proved to be in relation with MC-LR-induced PCD. This is one of the first pieces of evidence on the correlation of PCD-related DNA strand breaks with specific hydrolase activities in a model dicot treated with a cyanobacterial toxin known to have environmental importance.

Cyanobacteria Microcystis aeruginosa Contributes to the Severity of Fish Diseases: A Study on Spring Viraemia of Carp

Fish are exposed to numerous stressors in the environment including pollution, bacterial and viral agents, and toxic substances. Our study with common carps leveraged an integrated approach (i.e., histology, biochemical and hematological measurements, and analytical chemistry) to understand how cyanobacteria interfere with the impact of a model viral agent, Carp sprivivirus (SVCV), on fish. In addition to the specific effects of a single stressor (SVCV or cyanobacteria), the combination of both stressors worsens markers related to the immune system and liver health. Solely combined exposure resulted in the rise in the production of immunoglobulins, changes in glucose and cholesterol levels, and an elevated marker of impaired liver, alanine aminotransferase (ALT). Analytical determination of the cyanobacterial toxin microcystin-LR (MC-LR) and its structurally similar congener MC-RR and their conjugates showed that SVCV affects neither the levels of MC in the liver nor the detoxification capacity of the liver. MC-LR and MC-RR were depurated from liver mostly in the form of cysteine conjugates (MC-LR-Cys, MC-RR-Cys) in comparison to glutathione conjugates (LR-GSH, RR-GSH). Our study brought new evidence that cyanobacteria worsen the effect of viral agents. Such inclusion of multiple stressor concept helps us to understand how and to what extent the relevant environmental stressors co-influence the health of the fish population.

Effects of a Cyanobacterial Toxin and Macrophyte composition on Amphibian Parasitism

Amphibians are experiencing global declines with habitat loss and degradation, and infectious diseases as major contributors. Environmental changes such as eutrophication and climate alterations can cause the proliferation of primary producers, including cyanobacteria, and both native and invasive macrophytes. Cyanobacterial blooms can be toxic due to the production of microcystins such as MC-LR, and invasive macrophytes can alter the structural complexity of aquatic habitats – both can affect host-parasite dynamics. I examined the effects of MC-LR on larval amphibian susceptibility to infection by a trematode parasite as well as host growth and anti-parasite behaviour, finding increased susceptibility to infection at low concentrations. I also investigated how MC-LR affected the longevity and activity of trematode infectious stages (cercariae), and demonstrated variable effects among species. Lastly, I examined how environmental structural complexity, modeled as macrophyte complexity and density, affected tadpole infection by a trematode parasite and host anti-parasite behaviour but found no impact.

Effects of a Cyanobacterial Toxin and Macrophyte composition on Amphibian Parasitism

Amphibians are experiencing global declines with habitat loss and degradation, and infectious diseases as major contributors. Environmental changes such as eutrophication and climate alterations can cause the proliferation of primary producers, including cyanobacteria, and both native and invasive macrophytes. Cyanobacterial blooms can be toxic due to the production of microcystins such as MC-LR, and invasive macrophytes can alter the structural complexity of aquatic habitats – both can affect host-parasite dynamics. I examined the effects of MC-LR on larval amphibian susceptibility to infection by a trematode parasite as well as host growth and anti-parasite behaviour, finding increased susceptibility to infection at low concentrations. I also investigated how MC-LR affected the longevity and activity of trematode infectious stages (cercariae), and demonstrated variable effects among species. Lastly, I examined how environmental structural complexity, modeled as macrophyte complexity and density, affected tadpole infection by a trematode parasite and host anti-parasite behaviour but found no impact.

Whole-Genome Sequencing of Bacterial Isolates That Degrade the Cyanobacterial Toxin Microcystin-LR

ABSTRACT We previously demonstrated that 13 bacterial isolates from Lake Erie, when grown in groups of four to five isolates per group, degraded the cyanobacterial toxin microcystin-LR (MC-LR) into nontoxic fragments. Whole-genome sequencing of these bacteria was performed to provide genus and species information and to predict putative MC-LR-degrading genes.