Temperature Effects Explain Continental Scale Distribution of Cyanobacterial Toxins

Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains.Peer reviewe

Capturing biodiversity: linking a cyanobacteria culture collection to the “scratchpads” virtual research environment enhances biodiversity knowledge

Figure 1 - Preview of the "Cyanobacteria culture collection" database collection. The Taxonomy system is presented as part of the "Cyanobacteria" tab; an overview of the strain Chococcus minutus AUTH 0599 is shown as an example

Cyanobacteria of Greece: an annotated checklist

The checklist of Greek Cyanobacteria was created in the framework of the Greek Taxon Information System (GTIS), an initiative of the LifeWatchGreece Research Infrastructure (ESFRI) that has resumed efforts to compile a complete checklist of species reported from Greece. This list was created from exhaustive search of the scientific literature of the last 60 years. All records of taxa known to occur in Greece were taxonomically updated. The checklist of Greek Cyanobacteria comprises 543 species, classified in 130 genera, 41 families, and 8 orders. The orders Synechococcales and Oscillatoriales have the highest number of species (158 and 153 species, respectively), whereas these two orders along with Nostocales and Chroococcales cover 93% of the known Greek cyanobacteria species. It is worth mentioning that 18 species have been initially described from Greek habitats. The marine epilithic Ammatoidea aegea described from Saronikos Gulf is considered endemic to this area. Our bibliographic review shows that Greece hosts a high diversity of cyanobacteria, suggesting that the Mediterranean area is also a hot spot for microbes

Phylogenetic analysis of cyanobacteria based on two novel molecular markers, implicated in the nitrogenase biosynthesis

The characterization of bloom cyanobacteria communities remains challenging, as taxonomy of several cyanobacterial genera is still unresolved, especially within Nostocales taxa. Nostocales cyanobacteria are capable of nitrogen fixation; nitrogenase genes are grouped into operons and are located in the same genetic locus. Previous studies demonstrated, that the divergence rate of nitrogenase structural gene (nifH) in cyanobacteria appear to be in congruence with that of 16S rRNA. However, there is no available information regarding the phylogeny of structural genes of the nitrogenase cluster. In this context, we developed a set of degenerate PCR primers for the amplification of nifE and nifN, two understudied structural nitrogenase genes. Successful phylogenetic analyses of nifE and nifN genes were carried out on thirty (30) Nostocales cyanobacteria strains, representing the genera Anabaena, Anabaenopsis, Calothrix, Chlorogloeopsis, Desmonostoc, Dolichospermum, Komarekiella, Nodularia, Nostoc, Raphidiopsis, Sphaerospermopsis, and Trichormus. A similar phylogenetic pattern between nifE/nifN, nifH, and 16S rRNA was observed, while phylogeny based on the nitrogenase structural genes nifE/nifN showed a higher resolution between Nostocales cyanobacteria and their lifestyle. In this study, we propose the use of two novel molecular markers, which could provide better insights in the taxonomy of Nostocales

Impact of unidentified secondary metabolites from five new cyanobacterial species on aquatic plant

Cyanobacteria are a great source of bioactive secondary metabolites, exerting harmful (cyanotoxins) or beneficial (drugs) effects on other organisms. In this work, we investigated the impact of the cyanobacteria strains Jaaginema sp. and Trichormus variabilis, and the newly described species Komarekiella chia, Nodularia mediterranea, and Iphianassa zackieohae with unknown metabolome on Lemna trisulca macrophyte. The experiments were prepared in short- (cyanobacteria extracts, up to 24h) and long-term (co-cultivation in BG11, 2 weeks) periods. Co-cultivation with I. zackieohae cells initially stimulated plant growth, but after 14 days the value was close to the control, while the remaining cyanobacteria slightly inhibited the accumulation of macrophyte biomass. After 14 days of co-cultivation, K. chia, and N. mediterranea significantly increased the total amount of protein in the plant [mg·g-1 dry weight], by 33% and 44%, respectively. The extracts of all analyzed cyanobacteria significantly increased the respiration process after 24-hour exposure. The tested cyanobacteria strains, except I. zackieohae, decreased the content of chlorophylls a and b by an average of 48% and 53%, respectively. Jaaginema sp. extract temporarily inhibited plant photosynthesis just within 7 minutes. The above effects on photosynthesis were confirmed by ultrastructural imaging of chloroplasts. Oxidative stress induced after treatments is also discussed

The Effects of Using Evogen Biogas Additive on the Microbiome and Performance of Full-Scale Biogas Plant

Biogas production from organic waste is a promising renewable energy source, but achieving optimal production and digester stability can be challenging. This study investigated the impact of the Evogen microbial additive on biogas production and digester status in two biogas plants (BG01 and BG02). Microbial abundance and physicochemical parameters were analyzed to assess the effects. The results show distinct microbial community shifts in Evogen-treated digesters, with increased abundance of methanogenic archaea and hydrolytic bacteria, indicating improved anaerobic digestion. Evogen supplementation positively influenced digester performance, as evidenced by higher alkalinity buffer capacity (FOS/TAC ratios), indicating enhanced acidification and methanogenesis, along with reductions in total solids and volatile solids, demonstrating improved organic matter degradation. Evogen-treated digesters exhibited significantly higher biogas production and improved process stability, as indicated by volatile fatty acids (VFAs) profiling. The dominance of Firmicutes, Synergistetes, Proteolytic Bacteroidetes and Actinobacteria highlighted their roles in substrate degradation and VFA production. The findings contribute to optimizing biogas production systems and understanding complex microbial interactions within anaerobic digesters. The addition of Evogen influenced microbial community composition and dynamics, potentially altering substrate utilization, metabolic interactions and overall community structure

Linking environmental heterogeneity and chemo-diversity in cyanobacteria: A culture-dependent profile based analysis

Cyanobacteria are ecologically versatile microorganisms that inhabit most environments, ranging from marine systems to arid deserts. Given their ability to survive under harsh and extreme conditions, we hypothesize that cyanobacteria could produce a wide variety of compounds in specific niches. In this context, we sampled a number of different environments, from freshwater and brackish ecosystems to terrestrial and anchialine caves, spanning from the Canary Islands and Iceland to Estonia and Greece. Forty-four (44) cyanobacteria strains were analyzed with de novo peptide fragmentation in order to detect their metabolome profile; further, their antimicrobial, cytotoxic, and enzyme inhibitory activity was investigated. Both freshwater/planktic and rock-dwelling/benthic strains exhibited different types of inhibitory activities. However, cyanopeptides were only detected in freshwater strains; microcystins, anabaenopeptins, and aeruginosins congeners from Microcystis spp., Thrichormus variabilis, and Calothrix epiphytica strains. Therefore, our results indicate a high degree of unknown chemo-diversity, as we could not link the presence/absence of any known cyanopeptides and inhibitory activities from strains derived from other habitats, in contrast with freshwater cyanobacteria strains. In this work we discuss the correlation between the cyanobacteria chemo- and lifestyle diversity providing a missing study material for profile-based analysis on cyanobacteria from under-explored environments

A Greek Raphidiopsis raciborskii strain and Microcystins: A toxic relationship

The cyanobacterium Raphidiopsis raciborskii is extensively studied for its toxicity and invasive behavior, which is presumably enhanced by global warming. The widening of its geographic distribution and the isolation of strains showing high optimum growth temperature underline its ecological heterogeneity, suggesting the existence of different ecotypes. In this study, we investigate the ecotoxicology of Raphidiopsis raciborskii TAU-MAC 1414 strain, isolated from Lake Karla, Greece. The effect of different growth conditions (temperature, light intensity, phosphorus concentration, co-culture with toxic and non-toxic Microcystis spp. extracts) on microcystin production by R. raciborskii was examined. MC-LR and MC-HilR were detected with LC-MS/MS, mainly during the cultivation of R. raciborskii with toxic or non-toxic Microcystis spp. strains’ extracts. Further, the subcellular phytotoxic effects of R. raciborskii on Oryza sativa (rice) are discussed. Our research demonstrated unambiguously for the first time that R. raciborskii is able to produce microcystins under certain conditions, shedding new light in the ecotoxicology of the species, whereas the triggering of microcystin production remains to be further investigated

Fractionation and characterization of Dunaliella microalgal biomass and extraction of carotenoids

This paper presents findings on the application of two fractionation protocols of Dunaliella microalgal biomass with the aim to separate and recover the lipid, pigment and protein fraction, leaving as “residue” the fraction that contains carbohydrates. The first protocol (LPC) is based on the initial extraction of lipids, followed by extraction of proteins, while in the second protocol (CLP), the pigments are first extracted followed by lipids extraction. With the LPC protocol the recovered lipid fraction was 34 and 32 wt%, while the recovered proteinic fraction was 46 and 50 wt% for the two samples under study, i.e. 1120 (D. granulata) and 1220 (D. minutissima). The CLP protocol led to the initial extraction of the pigment fraction with a percentage of 10–15 wt% while the subsequently recovered lipidic fraction was 16–24 wt%. The initial biomass was characterized for its moisture (<0.7 wt% for both samples), ash (approx. 45 wt% for both samples), organic matter, elemental composition and higher heating value (HHV) which was 23 and 30 MJ/kg (organic matter based-OMB). The composition of the lipid fraction was analyzed via esterification and gas chromatography (GC-FID) showing C16 and C18 as the predominant acids in the samples. The residue/carbohydrate fraction was analyzed via acid hydrolysis and analysis by high pressure liquid chromatography (HPLC) showing about 20 wt% (-OMB) content of carbohydrates. The high ash content of the biomass was found to be co-extracted during the fractionation protocols at a percentage of ≈49 % in the lipidic fraction and 45 % in the proteinic fraction. Furthermore, emphasis was given on pigment extraction and recovery using various solvents and quantification methods. Measurements of β-carotene, carotenoids, and chlorophyll content through UV and HPLC analyses is presented with chlorophyl and carotenoid content being ≈12 wt% and ≈9 wt% for samples 1120 and 1220 (-OMB). Additionally, a comparison between three solvents (THF, dichloromethane, acetone) was performed regarding their ability to extract the pigments from the microalgal biomass showing that acetone is capable of extracting pigments when concentration of the pigments is not high. The comparison of the HPLC with the UV method, suggested that UV spectroscopy is a reliable and rapid alternative for pigments determination, while HPLC enables identification and quantitative determination of specific pigments and chlorophyll species. The study provides insights for different fractionation protocols applied in two not yet fully studied Dunaliella species as well as the chlorophyl and carotenoid content

Stratification strength and light climate explain variation in chlorophyll a at the continental scale in a European multilake survey in a heatwave summer

To determine the drivers of phytoplankton biomass, we collected standardized morphometric, physical, and biological data in 230 lakes across the Mediterranean, Continental, and Boreal climatic zones of the European continent. Multilinear regression models tested on this snapshot of mostly eutrophic lakes (median total phosphorus [TP] = 0.06 and total nitrogen [TN] = 0.7 mg L-1), and its subsets (2 depth types and 3 climatic zones), show that light climate and stratification strength were the most significant explanatory variables for chlorophyll a (Chl a) variance. TN was a significant predictor for phytoplankton biomass for shallow and continental lakes, while TP never appeared as an explanatory variable, suggesting that under high TP, light, which partially controls stratification strength, becomes limiting for phytoplankton development. Mediterranean lakes were the warmest yet most weakly stratified and had significantly less Chl a than Boreal lakes, where the temperature anomaly from the long-term average, during a summer heatwave was the highest (+4 degrees C) and showed a significant, exponential relationship with stratification strength. This European survey represents a summer snapshot of phytoplankton biomass and its drivers, and lends support that light and stratification metrics, which are both affected by climate change, are better predictors for phytoplankton biomass in nutrient-rich lakes than nutrient concentrations and surface temperature.Peer reviewe