Biological effect of the Planktothrix sp. FP1 cyanobacterial extract

A modelling approach to evaluate the present and future effectiveness of hypolimnetic withdrawal for the restoration of eutrophic Lake Varese (Northern Italy)

Hypolimnetic withdrawal has been applied as a restoration measure in lakes subject to eutrophication together with external load reduction, to decrease internal load by removing limiting nutrient phosphorus (P) from anoxic deep waters and contributing to the unloading of bottom sediments from previously deposited nutrients and organic matter. The aim of this study is to evaluate the effect of hypolimnetic withdrawal on Lake Varese, a 24 m-deep and 14.8 km2-large subalpine lake in North-Western Italy. The lake suffered from extended eutrophication in the second half of the 20th century due to uncontrolled delivery of untreated urban sewage. Several restoration measures have been implemented during the years, including hypolimnetic withdrawal. In 2019, a cooperative programme for the protection and management of the lake and its surroundings was launched, establishing a systematic annual hypolimnetic withdrawal in the stratified season since 2020. In this research, we calibrated a one-dimensional (1D) coupled ecological-hydrodynamic model (General Lake Model/Aquatic EcoDynamics - GLM/AED2) of Lake Varese with data surveyed in the lake in 2019-2021. Model simulations of the period 2020-2021 with and without the performed withdrawal proved the effectiveness of this measure on hypolimnetic P concentration reduction. Then, future simulations of 2023-2085 were carried out to predict the future efficiency of hypolimnetic withdrawal and of reductions in external nutrient loads under climate change scenarios. Results show that the prescribed withdrawal increases hypolimnetic temperatures. This effect, coupled with thermocline deepening due to global warming, will possibly lead to decreasing water mass stability in autumn and shorter stratification in the moderately deep Lake Varese, with an eventual decrease of P concentrations in the water column. The future effectiveness of hypolimnetic withdrawal is further discussed considering the possible role of dry periods.

A Low-FODMAP Diet Provides Benefits for Functional Gastrointestinal Symptoms but Not for Improving Stool Consistency and Mucosal Inflammation in IBD: A Systematic Review and Meta-Analysis

Background: A low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols diet (LFD) is claimed to improve functional gastrointestinal symptoms (FGSs). However, the role of LFD in inflammatory bowel disease (IBD) patients with FGSs remains unclear. Objective: To systematically assess the efficacy of LFD in IBD patients with FGSs. Methods: Six databases were searched from inception to 1 January 2022. Data were synthesized as the relative risk of symptoms improvement and normal stool consistency, mean difference of Bristol Stool Form Scale (BSFS), Short IBD Questionnaire (SIBDQ), IBS Quality of Life (IBS-QoL), Harvey-Bradshaw index (HBi), Mayo score, and fecal calprotectin (FC). Risk of bias was assessed based on study types. A funnel plot and Egger’s test were used to analyze publication bias. Results: This review screened and included nine eligible studies, including four randomized controlled trials (RCTs) and five before–after studies, involving a total of 446 participants (351 patients with LFD vs. 95 controls). LFD alleviated overall FGSs (RR: 0.47, 95% CI: 0.33–0.66, p = 0.0000) and obtained higher SIBDQ scores (MD = 11.24, 95% CI 6.61 to 15.87, p = 0.0000) and lower HBi score of Crohn’s disease (MD = −1.09, 95% CI −1.77 to −0.42, p = 0.002). However, there were no statistically significant differences in normal stool consistency, BSFS, IBS-QoL, Mayo score of ulcerative colitis, and FC. No publication bias was found. Conclusions: LFD provides a benefit in FGSs and QoL but not for improving stool consistency and mucosal inflammation in IBD patients. Further well-designed RCTs are needed to develop the optimal LFD strategy for IBD.

Are known cyanotoxins involved in the toxicity of picoplanktonic and filamentous North Atlantic marine cyanobacteria?

Eight marine cyanobacteria strains of the genera Cyanobium, Leptolyngbya, Oscillatoria, Phormidium, and Synechococcus were isolated from rocky beaches along the Atlantic Portuguese central coast and tested for ecotoxicity. Strains were identified by morphological characteristics and by the amplification and sequentiation of the 16S rDNA. Bioactivity of dichloromethane, methanol and aqueous extracts was assessed by the Artemia salina bioassay. Peptide toxin production was screened by matrix assisted laser desorption/ionization time of flight mass spectrometry. Molecular analysis of the genes involved in the production of known cyanotoxins such as microcystins, nodularins and cylindrospermopsin was also performed. Strains were toxic to the brine shrimp A. salina nauplii with aqueous extracts being more toxic than the organic ones. Although mass spectrometry analysis did not reveal the production of microcystins or other known toxic peptides, a positive result for the presence of mcyE gene was found in one Leptolyngbya strain and one Oscillatoria strain. The extensive brine shrimp mortality points to the involvement of other unknown toxins, and the presence of a fragment of genes involved in the cyanotoxin production highlight the potential risk of cyanobacteria occurrence on the Atlantic coast.

Cyanotoxins from black band disease of corals and from other coral reef environments

Many cyanobacteria produce cyanotoxins, which has been well documented from freshwater environments but not investigated to the same extent in marine environments. Cyanobacteria are an obligate component of the polymicrobial disease of corals known as black band disease (BBD). Cyanotoxins were previously shown to be present in field samples of BBD and in a limited number of BBD cyanobacterial cultures. These toxins were suggested as one of the mechanisms contributing to BBD-associated coral tissue lysis and death. In this work, we tested nine cyanobacterial isolates from BBD and additionally nine isolated from non-BBD marine sources for their ability to produce toxins. The presence of toxins was determined using cell extracts of laboratory grown cyanobacterial cultures using ELISA and the PP2A assay. Based on these tests, it was shown that cyanobacterial toxins belonging to the microcystin/nodularin group were produced by cyanobacteria originating from both BBD and non-BBD sources. Several environmental factors that can be encountered in the highly dynamic microenvironment of BBD were tested for their effect on both cyanobacterial growth yield and rate of toxin production using two of the BBD isolates of the genera Leptolyngbya and Geitlerinema. While toxin production was the highest under mixotrophic conditions (light and glucose) for the Leptolyngbya isolate, it was highest under photoautotrophic conditions for the Geitlerinema isolate. Our results show that toxin production among marine cyanobacteria is more widespread than previously documented, and we present data showing three marine cyanobacterial genera (Phormidium, Pseudanabaena, and Spirulina) are newly identified as cyanotoxin producers. We also show that cyanotoxin production by BBD cyanobacteria can be affected by environmental factors that are present in the microenvironment associated with this coral disease.

Toxicological effects of marine palytoxin evaluated by FETAX assay

The FETAX (frog embryo teratogenesis assay Xenopus) is considered a useful bioassay to detect health hazard substances. In the study of the marine toxin palytoxin (PTX), FETAX has revealed evident impacts on embryo mortality, teratogenesis and growth at the two highest (370 and 37nM) concentrations used. Significant mortality rates, peaks in the number of malformed embryos and delays in growth were found, while the total sample number fell by about 80% at the end of the assay with the concentrated dose. The histological analysis to evaluate the morpho-functional induced modifications demonstrated damage to the nervous and muscle tissue, a general reduction in the size of the main inner visceral organs and severe injury to the heart structure in some specimens. No inflammatory response was observed.

Evaluation of the effects of the marine toxin okadaic acid by using FETAX assay

The Frog Embryo Teratogenesis Assay Xenopus (FETAX), is a screening assay using embryos at gastrula stage of the anuran Xenopus laevis to identify substances that may pose a developmental hazard in humans. The FETAX assay evaluates three parameters, i.e. mortality, delayed growth and embryo malformation. In the present investigation, the FETAX protocol was applied to the marine toxin okadaic acid (OA) and the experiments show that OA affects the above parameters in a dose-correlated manner. The morpho-functional modifications induced in embryo organs by OA were also studied. The nervous system, tail skeletal musculature, intestine and kidney appeared particularly damaged, with the former being the most sensitive. On the whole, various advantages emerge from using the FETAX assay: different parameters can be tested simultaneously, the indication of the presence of a potentially dangerous substance is rapid and the assay is a valid alternative to mammalian systems.

Toxicity of complex cyanobacterial samples and their fractions in Xenopus laevis embryos and the role of microcystins

This work evaluated the effects of various cyanobacterial fractions in Frog Embryo Teratogenesis Assay Xenopus (FETAX) with African clawed frog embryos. Fractions were prepared from five biomasses with different dominant genera (Microcystis, Aphanizomenon, Anabaena, Planktothrix) and different microcystin content. Effects of following fractions were investigated: (I) homogenate of complex cyanobacterial biomass, (II) cell debris (pellet) after centrifugation of complex biomass, (III) supernatant after centrifugation of complex biomass (= crude aqueous extract), (IV) permeate after passing of crude extract through C-18 column (fraction devoid of microcystins), and (V) eluate from C-18 column (containing microcystins, if present). Besides classical parameters evaluated in 96 h FETAX (mortality, growth inhibition, malformations), we have also assessed the effects on biochemical markers of oxidative stress and detoxification (glutathione pool, GSH; activity of glutathione peroxidase, GPx; glutathione reductase, GR; activity of glutathione-S-transferase, GST). Complex biomass (I) and aqueous extract (III) were generally the most toxic fractions in terms of mortality and growth inhibition, whereas eluates containing microcystins (V) were generally less toxic. On the other hand, the same fraction (eluates) induced significant malformations in low concentrations but the effects were not related to the content of microcystins. Biomarkers were affected in variable manner but no significant effect or clear relation to microcystin content was observed. Our data support the hypothesis that microcystins are not the only or major toxic compounds in the complex cyanobacterial samples (at least for some species) and that more attention should be paid to other components of complex cyanobacterial biomass including non-specific parameters such as oxygen content or toxic ammonia released during bacterial decay of organic material.

Toxicity of culturable cyanobacteria strains isolated from the Portuguese coast

Cyanobacteria are common inhabitants of terrestrial and aquatic ecosystems. In the aquatic environments their success is particularly well documented in fresh and brackish waters. References related to the occurrence of these organisms in marine habitats and especially in what concerns to toxicology are scarce. Reports of cyanotoxins in marine habitats are restricted to the warmer temperate and tropical regions. In this study, cyanobacteria strains belonging to the genera Cyanobacterium, Oscillatoria, Synechocystis and Synechococcus were isolated from rocky beaches along the Portuguese coast and were cultured and screened for toxicological properties. The toxicity to mice was observed after intraperitoneal injection of centrifuged and non-centrifuged extracts. The results showed a wide range of responses with strains showing no signs of poisoning and strains producing protracted or slightly protracted toxic effects. Neurotoxic symptoms and effects in liver, kidney, small intestine and lungs are reported. The identity of the toxic compounds is thus far unknown but the implication drawn from the present data is that more than one toxic compound is produced. There was a clear discrepancy between the toxicity of centrifuged and non-centrifuged extracts. In most cases the pellet was toxic indicating that toxicity can be associated with compounds tightly bound to the cell walls.

Intracellular and dissolved microcystin in reservoirs of the river Segura basin, Murcia, SE Spain

The seasonal sampling of irrigation or drinking water reservoirs in the province of Murcia (SE Spain) in the hydrological year 2000-2001 revealed the presence of intracellular microcystins in the benthic cyanophyte communities throughout the year. The total microcystin levels, as measured by HPLC, were relatively high but lower than others published for planktonic communities of the European continent or certain African countries. The diversity of forms was also very high and comparable to those found for other European countries. The concentrations of microcystins dissolved in the water were always below limits recommended by the WHO for drinking water and, during most of the year, undetectable by immunological methods. We discuss the need for setting up a control network for detecting benthic cyanobacteria growth to prevent long-term undesirable effects in the human population in small towns (through drinking water or the consumption of vegetables) and in wild animals. In the particular case of the Iberian Peninsula, a joint strategy between Portugal and Spain is recommendable.