The non-protein amino acid β-N-methylamino-L-alanine in Portuguese cyanobacterial isolates

A systematic review on analytical methods of the neurotoxin β-N-methylamino-L-alanine (BMAA), and its causative microalgae and distribution in the environment

β-N-Methylamino-L-alanine (BMAA), a neurotoxin produced by various microalgal groups, is associated with neurodegenerative diseases and is considered a major environmental factor potentially linked to sporadic amyotrophic lateral sclerosis. This study systematically reviews the analytical methods used to study BMAA in publications from 2019 to the present. It also investigates the causative microalgae of BMAA and its geographical distributions in aquatic ecosystems based on studies conducted since 2003. A comprehensive search using the Web of Science database revealed that hydrolysis for extraction (67%), followed by quantification using LC-MS/MS (LC: 84%; MS/MS: 88%), is the most commonly employed method in BMAA analysis. Among analytical methods, RPLC-MS/MS had the highest percentage (88%) of BMAA-positive results and included a high number of quality control (QC) assessments. Various genera of cyanobacteria and diatoms have been reported to produce BMAA. The widespread geographical distribution of BMAA across diverse ecosystems highlights significant environmental and public health concerns. Notably, BMAA accumulation and biomagnification are likely more potent in marine or brackish water ecosystems than in freshwater ecosystems, potentially amplifying its ecological impacts. Future research should prioritize advanced, sensitive methods, particularly LC-MS/MS with as many QC assessments as possible, and should expand investigations to identify novel microalgal producers and previously uncharted geographical areas, with a special focus on marine or brackish water ecosystems. This effort will enhance our understanding of the environmental distribution and impacts of BMAA.

Spatiotemporal distribution of neurotoxin β-N-methylamino-L-alanine and 2,4-diaminobutyric acid in offshore aquaculture area of Shandong province, China

The neurotoxin β-N-methylamino-L-alanine (BMAA) has been widely detected in aquatic environments and got the public's attention due to its potential risk to human neurodegenerative diseases. Three cruises in spring, summer and autumn seasons were carried out in Laizhou Bay (LZB), Sishili Bay (SSLB), Sanggou Bay (SGB), Jiaozhou Bay (JZB) and Haizhou Bay (HZB) in 2023. Results showed that the temporal distribution pattern of BMAA in plankton varied in the survey bays. In LZB, the highest average concentration of BMAA in phytoplankton occurred in spring. The highest average concentration of BMAA in phytoplankton was detected in summer in SSLB, JZB and HZB. However, BMAA was only detected in phytoplankton at the R2 station in SGB in spring. The highest average concentration of BMAA in zooplankton was observed in spring in LZB, SSLB and SGB. Zooplankton accumulated the highest average concentration of BMAA in JZB and HZB in summer and autumn, respectively. The BMAA was widely detected in marine mollusks throughout the investigative period. In addition, Mantel test and RDA analysis results indicated that DIN/DIP strongly impacted on the spatiotemporal distribution of BMAA in phytoplankton, in JZB and SSLB. The spatiotemporal distribution of BMAA in plankton was correlated with temperature and DO in JZB. More field cruises should be conducted to explore the environmental drivers of the neurotoxin BMAA in marine ecosystems in future studies.

Present and future potential role of toxin-producing Synechococcus in the tropical region

As anthropogenic induced temperature rises and nutrient loadings increase in fresh and brackish environments, the ecological function of the phytoplankton community is expected to favour the picocyanobacteria, of the genus Synechococcus. Synechococcus is already a ubiquitous cyanobacterium found in both freshwater and marine environments, notwithstanding that the toxigenic species still remains unexplored in many freshwaters. Their fast growth rate and their ability to produce toxins make Synechococcus a potential dominant player in harmful algal blooms under climate change scenarios. This study examines the responses of a novel toxin-producing Synechococcus (i.e., one belonging to a freshwater clade; the other belonging to a brackish clade) to environmental changes that reflect climate change effects. We conducted a series of controlled experiments under present and predicted future temperatures, as well as under various N and P nutrients loadings. Our findings highlight how Synechococcus can be altered by the differing reactions to increasing temperature and nutrients, which resulted in considerable variations in cell abundance, growth rate, death rate, cellular stoichiometry and toxin production. Synechococcus had the highest growth observed at 28 °C, and further increases in temperature resulted in a decline for both fresh and brackish waters. Cellular stoichiometry was also altered, where more nitrogen (N) per cell was required, and the plasticity of N:P was more severe for the brackish clade. However, Synechococcus become more toxic under future scenario. Anatoxin-a (ATX) saw the greatest spike when temperature was at 34 °C especially under P-enrichment conditions. In contrast, Cylindrospermopsin (CYN) was promoted at the lowest tested temperature (25 °C) and under N-limitation. Overall, both temperature and external nutrients are the dominant control over Synechococcus toxins production. A model was also created to assess Synechococcus toxicity to zooplankton grazing. Zooplankton grazing was reduced by two folds under nutrient limitation, but temperature accounted for very insignificant change.

Environmental Neurotoxin β-N-Methylamino-L-alanine (BMAA) as a Widely Occurring Putative Pathogenic Factor in Neurodegenerative Diseases

In the present review we have discussed the occurrence of β-N-methylamino-L-alanine (BMAA) and its natural isomers, and the organisms and sample types in which the toxin(s) have been detected. Further, the review discusses general pathogenic mechanisms of neurodegenerative diseases, and how modes of action of BMAA fit in those mechanisms. The biogeography of BMAA occurrence presented here contributes to the planning of epidemiological research based on the geographical distribution of BMAA and human exposure. Analysis of BMAA mechanisms in relation to pathogenic processes of neurodegeneration is used to critically assess the potential significance of the amino acid as well as to identify gaps in our understanding. Taken together, these two approaches provide the basis for the discussion on the potential role of BMAA as a secondary factor in neurodegenerative diseases, the rationale for further research and possible directions the research can take, which are outlined in the conclusions.

Non-Proteinogenic Amino Acid β-N-Methylamino-L-Alanine (BMAA): Bioactivity and Ecological Significance

Research interest in a non-protein amino acid β-N-methylamino-L-alanine (BMAA) arose due to the discovery of a connection between exposure to BMAA and the occurrence of neurodegenerative diseases. Previous reviews on this topic either considered BMAA as a risk factor for neurodegenerative diseases or focused on the problems of detecting BMAA in various environmental samples. Our review is devoted to a wide range of fundamental biological problems related to BMAA, including the molecular mechanisms of biological activity of BMAA and the complex relationships between producers of BMAA and the environment in various natural ecosystems. At the beginning, we briefly recall the most important facts about the producers of BMAA (cyanobacteria, microalgae, and bacteria), the pathways of BMAA biosynthesis, and reliable methods of identification of BMAA. The main distinctive feature of our review is a detailed examination of the molecular mechanisms underlying the toxicity of BMAA to living cells. A brand new aspect, not previously discussed in any reviews, is the effect of BMAA on cyanobacterial cells. These recent studies, conducted using transcriptomics and proteomics, revealed potent regulatory effects of BMAA on the basic metabolism and cell development of these ancient photoautotrophic prokaryotes. Exogenous BMAA strongly influences cell differentiation and primary metabolic processes in cyanobacteria, such as nitrogen fixation, photosynthesis, carbon fixation, and various biosynthetic processes involving 2-oxoglutarate and glutamate. Cyanobacteria were found to be more sensitive to exogenous BMAA under nitrogen-limited growth conditions. We suggest a hypothesis that this toxic diaminoacid can be used by phytoplankton organisms as a possible allelopathic tool for controlling the population of cyanobacterial cells during a period of intense competition for nitrogen and other resources in various ecosystems.

Anthropogenic activities and geographic locations regulate microbial diversity, community assembly and species sorting in Canadian and Indian freshwater lakes

Freshwater lakes are important reservoirs and sources of drinking water globally. However, the microbiota, which supports the functionality of these ecosystems is threatened by the influx of nutrients, heavy metals and other toxic chemical substances from anthropogenic activities. The influence of these factors on the diversity, assembly mechanisms and co-occurrence patterns of bacterial communities in freshwater lakes is not clearly understood. Hence, samples were collected from six different impacted lakes in Canada and India and examined by 454-pyrosequencing technology. The trophic status of these lakes was determined using specific chemical parameters. Our results revealed that bacterial diversity and community composition was altered by both the lake water chemistry and geographic distance. Anthropogenic activities pervasively influenced species distribution. Dispersal limitation (32.3%), homogenous selection (31.8%) and drift (20%) accounted for the largest proportions of the bacterial community assembly mechanisms. Homogenous selection increased in lakes with higher nutrient concentration, while stochasticity reduced. Community functional profiles revealed that deterministic processes dominated the assembly mechanisms of phylotypes with higher potential for biodegradation, while stochasticity dominated the assembly of phylotypes with potential for antimicrobial resistance. Bacteroidota (44%) and Proteobacteria (34%) were the most abundant phyla. Co-occurrence network analysis revealed that complexity increased in more impacted lakes, while competition and the nature of anthropogenic activity contributed to species sorting. Overall, this study demonstrates that bacterial community changes in freshwater lakes are linked to anthropogenic activities, with corresponding consequences on the distribution of phylotypes of environmental and human health interest.

Bioactive Potential of Two Marine Picocyanobacteria Belonging to Cyanobium and Synechococcus Genera

Coccoid cyanobacteria produce a great variety of secondary metabolites, which may have useful properties, such as antibacterial, antiviral, anticoagulant or anticancer activities. These cyanobacterial metabolites have high ecological significance, and they could be considered responsible for the widespread occurrence of these microorganisms. Considering the great benefit derived from the identification of competent cyanobacteria for the extraction of bioactive compounds, two strains of picocyanobacteria (coccoid cyanobacteria < 3 µm) (Cyanobium sp. ITAC108 and Synechococcus sp. ITAC107) isolated from the Mediterranean sponge Petrosia ficiformis were analyzed. The biological effects of organic and aqueous extracts from these picocyanobacteria toward the nauplii of Artemia salina, sea urchin embryos and human cancer lines (HeLa cells) were evaluated. Methanolic and aqueous extracts from the two strains strongly inhibited larval development; on the contrary, in ethyl acetate and hexane extracts, the percentage of anomalous embryos was low. Moreover, all the extracts of the two strains inhibited HeLa cell proliferation, but methanol extracts exerted the highest activity. Gas chromatography–mass spectrometry analysis evidenced for the first time the presence of β-N-methylamino-l-alanine and microcystin in these picocyanobacteria. The strong cytotoxic activity observed for aqueous and methanolic extracts of these two cyanobacteria laid the foundation for the production of bioactive compounds of pharmacological interest.

Is Exposure to BMAA a Risk Factor for Neurodegenerative Diseases? A Response to a Critical Review of the BMAA Hypothesis

In a literature survey, Chernoff et al. (2017) dismissed the hypothesis that chronic exposure to β-N-methylamino-L-alanine (BMAA) may be a risk factor for progressive neurodegenerative disease. They question the growing scientific literature that suggests the following: (1) BMAA exposure causes ALS/PDC among the indigenous Chamorro people of Guam; (2) Guamanian ALS/PDC shares clinical and neuropathological features with Alzheimer's disease, Parkinson's disease, and ALS; (3) one possible mechanism for protein misfolds is misincorporation of BMAA into proteins as a substitute for L-serine; and (4) chronic exposure to BMAA through diet or environmental exposures to cyanobacterial blooms can cause neurodegenerative disease. We here identify multiple errors in their critique including the following: (1) their review selectively cites the published literature; (2) the authors reported favorably on HILIC methods of BMAA detection while the literature shows significant matrix effects and peak coelution in HILIC that may prevent detection and quantification of BMAA in cyanobacteria; (3) the authors build alternative arguments to the BMAA hypothesis, rather than explain the published literature which, to date, has been unable to refute the BMAA hypothesis; and (4) the authors erroneously attribute methods to incorrect studies, indicative of a failure to carefully consider all relevant publications. The lack of attention to BMAA research begins with the review's title which incorrectly refers to BMAA as a "non-essential" amino acid. Research regarding chronic exposure to BMAA as a cause of human neurodegenerative diseases is emerging and requires additional resources, validation, and research. Here, we propose strategies for improvement in the execution and reporting of analytical methods and the need for additional and well-executed inter-lab comparisons for BMAA quantitation. We emphasize the need for optimization and validation of analytical methods to ensure that they are fit-for-purpose. Although there remain gaps in the literature, an increasingly large body of data from multiple independent labs using orthogonal methods provides increasing evidence that chronic exposure to BMAA may be a risk factor for neurological illness.

Evaluating amino acids as protectants against β-N-methylamino-l-alanine-induced developmental neurotoxicity in a rat model

With accumulating evidence that supports the role of β-N-methylamino-l-alanine (BMAA) in neurodegeneration, it is necessary to elucidate the mechanisms and modes of BMAA toxicity so as to facilitate the search for potential preventative/therapeutic strategies. Daily supplementation with l-serine was suggested as a possible therapy to treat BMAA-induced neurotoxicity, based on the hypothesized mechanism of BMAA misincorporation into proteins for l-serine. As an alternative to misincorporation, it was hypothesized that BMAA toxicity may, in part, be due to its high affinity for associating with hydroxyl group-containing amino acids, and that a dietary excess of the hydroxyl-containing l-serine might offer protection by binding to BMAA and reducing its toxicity. Additionally, l-serine can also reduce the uptake of BMAA into human cells by competitive uptake at ASCT2, and l-phenylalanine, by competitive uptake at LAT1, and l-alanine, by competitive uptake at SNAT2, can also reduce BMAA uptake into human cells. The aim of this study was therefore to determine the protective value of l-serine, l-phenylalanine and l-alanine in reducing the effects of neonatal exposure to BMAA in a Sprague Dawley rat model. Pre-treatment with l-phenylalanine reduced the observed behavioral abnormalities and neuropathologies by 60-70% in most cases. l-serine was also effective in reducing some of the behavioral abnormalities and neuropathologies, most markedly spinal cord neuronal loss. However, the protective effect of l-serine was obfuscated by neuropathies that were observed in l-serine-treated control male rats. l-alanine had no effect in protecting against BMAA-induced neurotoxicity, suggesting that competitive amino acid uptake plays a minor role in protecting against BMAA-induced neurotoxicity.

Impact factors on the production of β-methylamino-L-alanine (BMAA) by cyanobacteria

Cyanobacteria produce a series of secondary metabolites, one of which is beta-N-methylamino-l-alanine (BMAA). BMAA is considered to be the cause of human neurodegeneration. Compared with other cyanotoxins, the role of BMAA in cyanobacteria remains unclear. To investigate this question, six strains of cyanobacteria were cultured and tested in this experiment with an optimized and validated BMAA determination method. The results show that four strains can produce BMAA. The effects of nutrient levels on the production of BMAA by Anabaena sp. FACHB-418 were studied by changing the initial concentrations of nitrate (NaNO₃) and phosphate (K₂HPO₄) in mediums. Bound BMAA was detected in all samples and the concentrations were within 50-100 ng/g. Free BMAA was presence when the concentration of nitrogen was lower than 1.7 mg/L (121.43 μM). Free BMAA was released from the dead and ruptured cells during the cell decline period, so dissolved BMAA cannot be detectable in the adaptation and logarithmic periods, but could be abundant in the decline periods. Statistical analyses show that free BMAA concentrations were negatively correlated with nitrogen strongly (p = 2.334 × 10^-10 and r = -0.842), but positively correlated with phosphorus weakly (p = 0.016 and r = 0.405). Moreover, the results of culture experiments indicated that exogenous BMAA could inhibit the growth of cyanobacteria that cannot produce BMAA, and the effect was enhanced as the concentration of exogenous BMAA increased. This phenomenon implies that the production of BMAA may be the stress response by some cyanobacteria to low nitrogen conditions to kill other cyanobacteria, i.e., their competitors.

Production of the neurotoxin beta-N-methylamino-l-alanine may be triggered by agricultural nutrients: An emerging public health issue

Diverse taxa of cyanobacteria, dinoflagellates and diatoms produce β-N-methylamino-l-alanine (BMAA), a non-lipophilic, non-protein amino acid. BMAA is a neurotoxin in mammals. Its ingestion may be linked to human neurodegenerative diseases, namely the Amyotrophic lateral sclerosis/Parkinsonism dementia complex, based on epidemiological evidence from regions where cyanobacterial harmful algal blooms occur frequently. In controlled environments, cyanobacteria produce BMAA in response to ecophysiological cues such as nutrient availability, which may explain the elevated BMAA concentrations in freshwater environments that receive nutrient-rich agricultural runoff. This critical review paper summarizes what is known about how BMAA supports ecophysiological functions like nitrogen metabolism, photosyntheis and provides a competitive advantage to cyanobacteria in controlled and natural environments. We explain how BMAA production affected competitive interactions among the N₂-fixing and non-N₂-fixing populations in a freshwater cyanobacterial bloom that was stimulated by nutrient loading from the surrounding agricultural landscape. Better control of nutrients in agricultural fields is an excellent strategy to avoid the negative environmental consequences and public health concerns related to BMAA production.

A systematic review of analytical methods for the detection and quantification of β-N-methylamino-l-alanine (BMAA)

Neurodegenerative diseases are influenced by environmental factors such as exposure to toxins including the cyanotoxin β-N-methylamino-l-alanine (BMAA) that can bioaccumulate in common food sources such as fish, mussels and crabs. Accurate and precise analytical methods are needed to detect and quantify BMAA to minimize human health risks. The objective of this review is to provide a comprehensive overview of the methods used for BMAA analysis from 2003 to 2019 and to evaluate the reported performance characteristics for each method to determine the consensus data for each analytical approach and different sample matrices. Detailed searches of the database Web of Science™ (WoS) were performed between August 21st, 2018 and April 5th, 2019. Eligible studies included analytical methods for the detection and quantification of BMAA in cyanobacteria and bioaccumulated BMAA in higher trophic levels, in phytoplankton and zooplankton and in human tissues and fluids. This systematic review has limitations in that only the English language literature is included and it did not include standard operating protocols nor any method validation data that have not been made public. We identified 148 eligible studies, of which a positive result for BMAA in one or more samples analyzed was reported in 84% (125 out of 148) of total studies, 57% of HILIC studies, 92% of RPLC studies and 71% of other studies. The largest discrepancy between different methods arose from the analysis of cyanobacteria samples, where BMAA was detected in 95% of RPLC studies but only in 25% of HILIC studies. Without sufficient published validation of each method's performance characteristics, it is difficult to establish each method as fit for purpose for each sample matrix. The importance of establishing methods as appropriate for their intended use is evidenced by the inconsistent reporting of BMAA across environmental samples, despite its prevalence in diverse ecosystems and food webs.

Production of β-methylamino-L-alanine (BMAA) and Its Isomers by Freshwater Diatoms

β-methylamino-L-alanine (BMAA) is a non-protein amino acid that has been implicated as a risk factor for motor neurone disease (MND). BMAA is produced by a wide range of cyanobacteria globally and by a small number of marine diatoms. BMAA is commonly found with two of its constitutional isomers: 2,4-diaminobutyric acid (2,4-DAB), and N-(2-aminoethyl)glycine (AEG). The isomer 2,4-DAB, like BMAA, has neurotoxic properties. While many studies have shown BMAA production by cyanobacteria, few studies have looked at other algal groups. Several studies have shown BMAA production by marine diatoms; however, there are no studies examining freshwater diatoms. This study aimed to determine if some freshwater diatoms produced BMAA, and which diatom taxa are capable of BMAA, 2,4-DAB and AEG production. Five axenic diatom cultures were established from river and lake sites across eastern Australia. Cultures were harvested during the stationary growth phase and intracellular amino acids were extracted. Using liquid chromatography triple quadrupole mass spectrometry (LC-MS/MS), diatom extracts were analysed for the presence of both free and protein-associated BMAA, 2,4-DAB and AEG. Of the five diatom cultures analysed, four were found to have detectable BMAA and AEG, while 2,4-DAB was found in all cultures. These results show that BMAA production by diatoms is not confined to marine genera and that the prevalence of these non-protein amino acids in Australian freshwater environments cannot be solely attributed to cyanobacteria.

Prevalence of β-methylamino-L-alanine (BMAA) and its isomers in freshwater cyanobacteria isolated from eastern Australia

Environmental exposure to the amino acid β-methylamino-L-alanine (BMAA) was linked to the high incidence of neurodegenerative disease first reported on the island of Guam in the 1940s and has more recently been implicated in an increased incidence of amyotrophic lateral sclerosis (ALS) in parts of the USA. BMAA has been shown to be produced by a range of cyanobacteria and some marine diatoms and dinoflagellates in different parts of the world. BMAA is commonly found with two of its constitutional isomers: 2,4- diaminobutyric acid (2,4-DAB) and N-(2-aminoethyl) glycine (AEG). These isomers are thought to be co-produced by the same organisms that produce BMAA and MS/MS analysis following LC separation can add an additional level of specificity over LC-FL. Although the presence of BMAA and 2,4-DAB in surface scum samples from several sites in Australia has been reported, which Australian cyanobacterial species are capable of BMAA, 2,4-DAB and AEG production remains unknown. The aims of the present studies were to identify some of the cyanobacterial genera or species that can produce BMAA, 2,4-DAB and AEG in freshwater cyanobacteria blooms in eastern Australia. Eleven freshwater sites were sampled and from these, 19 single-species cyanobacterial cultures were established. Amino acids were extracted from cyanobacterial cultures and analysed using liquid chromatography-tandem mass spectrometry. BMAA was detected in 17 of the 19 isolates, 2,4-DAB was detected in all isolates, and AEG was detected in 18 of the 19 isolates, showing the prevalence of these amino acids in Australian freshwater cyanobacteria. Concentrations of all three isomers in Australian cyanobacteria were generally higher than the concentrations reported elsewhere. This study confirmed the presence of BMAA and its isomers in cyanobacteria isolated from eastern Australian freshwater systems, and determined which Australian cyanobacterial genera or species were capable of producing them when cultured under laboratory conditions.

Neurotoxin BMAA and its isomeric amino acids in cyanobacteria and cyanobacteria-based food supplements

Cyanobacteria are photosynthetic microorganisms distributed globally in aquatic and terrestrial environments. They are also industrially cultivated to be used as dietary supplements, as they have a high nutritional value; however, they are also known to produce a wide range of toxic secondary metabolites, called cyanotoxins. BMAA (β-methylamino-l-alanine) and its most common structural isomers, DAB (2,4-diaminobutyric acid) and AEG (N-2-aminoethylglycine) produced by cyanobacteria, are non-proteinogenic amino acids that have been associated with neurodegenerative diseases. A possible route of exposure to those amino acids is through consumption of food supplements based on cyanobacteria. The review critically discusses existing reports regarding the occurrence of BMAA, DAB and AEG in cyanobacteria and cyanobacteria-based food supplements. It is shown that inconsistencies in reported results could be attributed to performance of different methods of extraction and analysis applied and in ambiguities regarding determination of soluble and bound fractions of the compounds. The critical aspect of this review aims to grow awareness of human intake of neurotoxic amino acids, while results presented in literature concerning dietary supplements aim to promote further research, quality control as well as development of guidelines for cyanotoxins in food products.

Stress effects of cyanotoxin β-methylamino-L-alanine (BMAA) on cyanobacterial heterocyst formation and functionality

Various species of cyanobacteria, diatoms and dinoflagellates are capable of synthesizing the non-proteinogenic neurotoxic amino acid β-N-methylamino-L-alanine (BMAA), which is known to be a causative agent of human neurodegeneration. Similar to most cyanotoxins, the biological and ecological functions of BMAA in cyanobacteria are unknown. In this study, we show for the first time that BMAA, in micromolar amounts, inhibits the formation of heterocysts (specialized nitrogen-fixing cells) in heterocystous, diazotrophic cyanobacteria [Anabaena sp. PCC 7120, Nostoc punctiforme PCC 73102 (ATCC 29133), Nostoc sp. strain 8963] under conditions of nitrogen starvation. The inhibitory effect of BMAA is abolished by the addition of glutamate. To understand the genetic reason for the observed phenomenon, we used qPCR to study the expression of key genes involved in cell differentiation and nitrogen metabolism in the model cyanobacterium Anabaena sp. PCC 7120. We observed that in the presence of BMAA, Anabaena sp. PCC 7120 does not express two essential genes associated with heterocyst differentiation, namely, hetR and hepA. We also found that addition of BMAA to cyanobacterial cultures with mature heterocysts inhibits nifH gene expression and nitrogenase activity.

Allelopathic and Bloom-Forming Picocyanobacteria in a Changing World

Picocyanobacteria are extremely important organisms in the world's oceans and freshwater ecosystems. They play an essential role in primary production and their domination in phytoplankton biomass is common in both oligotrophic and eutrophic waters. Their role is expected to become even more relevant with the effect of climate change. However, this group of photoautotrophic organisms still remains insufficiently recognized. Only a few works have focused in detail on the occurrence of massive blooms of picocyanobacteria, their toxicity and allelopathic activity. Filling the gap in our knowledge about the mechanisms involved in the proliferation of these organisms could provide a better understanding of aquatic environments. In this review, we gathered and described recent information about allelopathic activity of picocyanobacteria and occurrence of their massive blooms in many aquatic ecosystems. We also examined the relationships between climate change and representative picocyanobacterial genera from freshwater, brackish and marine ecosystems. This work emphasizes the importance of studying the smallest picoplanktonic fractions of cyanobacteria.

Cyanobacterial diversity held in microbial biological resource centers as a biotechnological asset: the case study of the newly established LEGE culture collection

Cyanobacteria are a well-known source of bioproducts which renders culturable strains a valuable resource for biotechnology purposes. We describe here the establishment of a cyanobacterial culture collection (CC) and present the first version of the strain catalog and its online database (http://lege.ciimar.up.pt/). The LEGE CC holds 386 strains, mainly collected in coastal (48%), estuarine (11%), and fresh (34%) water bodies, for the most part from Portugal (84%). By following the most recent taxonomic classification, LEGE CC strains were classified into at least 46 genera from six orders (41% belong to the Synechococcales), several of them are unique among the phylogenetic diversity of the cyanobacteria. For all strains, primary data were obtained and secondary data were surveyed and reviewed, which can be reached through the strain sheets either in the catalog or in the online database. An overview on the notable biodiversity of LEGE CC strains is showcased, including a searchable phylogenetic tree and images for all strains. With this work, 80% of the LEGE CC strains have now their 16S rRNA gene sequences deposited in GenBank. Also, based in primary data, it is demonstrated that several LEGE CC strains are a promising source of extracellular polymeric substances (EPS). Through a review of previously published data, it is exposed that LEGE CC strains have the potential or actual capacity to produce a variety of biotechnologically interesting compounds, including common cyanotoxins or unprecedented bioactive molecules. Phylogenetic diversity of LEGE CC strains does not entirely reflect chemodiversity. Further bioprospecting should, therefore, account for strain specificity of the valuable cyanobacterial holdings of LEGE CC.

Aerosol Health Effects from Molecular to Global Scales

Poor air quality is globally the largest environmental health risk. Epidemiological studies have uncovered clear relationships of gaseous pollutants and particulate matter (PM) with adverse health outcomes, including mortality by cardiovascular and respiratory diseases. Studies of health impacts by aerosols are highly multidisciplinary with a broad range of scales in space and time. We assess recent advances and future challenges regarding aerosol effects on health from molecular to global scales through epidemiological studies, field measurements, health-related properties of PM, and multiphase interactions of oxidants and PM upon respiratory deposition. Global modeling combined with epidemiological exposure-response functions indicates that ambient air pollution causes more than four million premature deaths per year. Epidemiological studies usually refer to PM mass concentrations, but some health effects may relate to specific constituents such as bioaerosols, polycyclic aromatic compounds, and transition metals. Various analytical techniques and cellular and molecular assays are applied to assess the redox activity of PM and the formation of reactive oxygen species. Multiphase chemical interactions of lung antioxidants with atmospheric pollutants are crucial to the mechanistic and molecular understanding of oxidative stress upon respiratory deposition. The role of distinct PM components in health impacts and mortality needs to be clarified by integrated research on various spatiotemporal scales for better evaluation and mitigation of aerosol effects on public health in the Anthropocene.

A critical review of the postulated role of the non-essential amino acid, β-N-methylamino-L-alanine, in neurodegenerative disease in humans

The compound BMAA (β-N-methylamino-L-alanine) has been postulated to play a significant role in four serious neurological human diseases: Amyotrophic Lateral Sclerosis/Parkinsonism Dementia Complex (ALS/PDC) found on Guam, and ALS, Parkinsonism, and dementia that occur globally. ALS/PDC with symptoms of all three diseases first came to the attention of the scientific community during and after World War II. It was initially associated with cycad flour used for food because BMAA is a product of symbiotic cycad root-dwelling cyanobacteria. Human consumption of flying foxes that fed on cycad seeds was later suggested as a source of BMAA on Guam and a cause of ALS/PDC. Subsequently, the hypothesis was expanded to include a causative role for BMAA in other neurodegenerative diseases including Alzheimer's disease (AD) through exposures attributed to proximity to freshwaters and/or consumption of seafood due to its purported production by most species of cyanobacteria. The hypothesis that BMAA is the critical factor in the genesis of these neurodegenerative diseases received considerable attention in the medical, scientific, and public arenas. This review examines the history of ALS/PDC and the BMAA-human disease hypotheses; similarities and differences between ALS/PDC and the other diseases with similar symptomologies; the relationship of ALS/PDC to other similar diseases, studies of BMAA-mediated effects in lab animals, inconsistencies and data gaps in the hypothesis; and other compounds and agents that were suggested as the cause of ALS/PDC on Guam. The review concludes that the hypothesis of a causal BMAA neurodegenerative disease relationship is not supported by existing data.

Neurotoxic Non-proteinogenic Amino Acid β-N-Methylamino-L-alanine and Its Role in Biological Systems

Secondary metabolites of photoautotrophic organisms have attracted considerable interest in recent years. In particular, molecules of non-proteinogenic amino acids participating in various physiological processes and capable of producing adverse ecological effects have been actively investigated. For example, the non-proteinogenic amino acid β-N-methylamino-L-alanine (BMAA) is neurotoxic to animals including humans. It is known that BMAA accumulation via the food chain can lead to development of neurodegenerative diseases in humans such as Alzheimer's and Parkinson's diseases as well as amyotrophic lateral sclerosis. Moreover, BMAA can be mistakenly incorporated into a protein molecule instead of serine. Natural sources of BMAA and methods for its detection are discussed in this review, as well as the role of BMAA in metabolism of its producers and possible mechanisms of toxicity of this amino acid in different living organisms.

New Typical Vector of Neurotoxin β-N-Methylamino-l-Alanine (BMAA) in the Marine Benthic Ecosystem

The neurotoxin β-N-methylamino-l-alanine (BMAA) has been identified as an environmental factor triggering neurodegenerative diseases such as Amyotrophic Lateral Sclerosis (ALS) and Alzheimer's disease (AD). We investigated the possible vectors of BMAA and its isomers 2,4-diaminobutyric acid (DAB) and N-2(aminoethyl)glycine (AEG) in marine mollusks collected from the Chinese coast. Sixty-eight samples of marine mollusks were collected along the Chinese coast in 2016, and were analyzed by an HILIC-MS/MS (hydrophilic interaction liquid chromatography with tandem quadrupole mass spectrometer) method without derivatization. BMAA was detected in a total of five samples from three species: Neverita didyma, Solen strictus, and Mytilus coruscus. The top three concentrations of free-form BMAA (0.99~3.97 μg·g^-1 wet weight) were detected in N. didyma. DAB was universally detected in most of the mollusk samples (53/68) with no species-specific or regional differences (0.051~2.65 μg·g^-1 wet weight). No AEG was detected in any mollusk samples tested here. The results indicate that the gastropod N. didyma might be an important vector of the neurotoxin BMAA in the Chinese marine ecosystem. The neurotoxin DAB was universally present in marine bivalve and gastropod mollusks. Since N. didyma is consumed by humans, we suggest that the origin and risk of BMAA and DAB toxins in the marine ecosystem should be further investigated in the future.

Assessment of the non-protein amino acid BMAA in Mediterranean mussel Mytilus galloprovincialis after feeding with estuarine cyanobacteria

To determine whether 2-amino-3-methylaminopropanoic acid (BMAA) could be taken up by marine organisms from seawater or their diet mussels Mytilus galloprovincialis, collected from the North Atlantic Portuguese shore, were exposed to seawater doped with BMAA standard (for up to 48 h) or fed with cyanobacteria (for up to 15 days). Mussels were able to uptake BMAA when exposed to seawater. Mussels fed with cyanobacteria Synechocystis salina showed a rise in BMAA concentration during feeding and a decline in concentration during the subsequent depuration period. Cells from the gills and hepatopancreas of mussels fed with S. salina showed lessened metabolic activity in mussels fed for longer periods of time. A hot acidic digestion (considered to account for total BMAA) was compared with a proteolytic digestion, using pepsin, trypsin and chymotrypsin. The latter was able to extract from mussels approximately 30% of total BMAA. Implications for BMAA trophic transfers in marine ecosystems are discussed.

BMAA in shellfish from two Portuguese transitional water bodies suggests the marine dinoflagellate Gymnodinium catenatum as a potential BMAA source

The neurotoxin β-N-methylamino-l-alanine (BMAA) and its putative role in multiple neurodegenerative diseases have been intensely studied since 2005 when the toxin was discovered to be produced by worldwide-distributed cyanobacterial species inhabiting terrestrial, marine, brackish, and freshwater ecosystems. Recently, BMAA production was also associated with one eukaryotic group, namely, diatoms, raising questions about its production by other phytoplanktonic groups. To test for BMAA bioavailability in ecosystems where abundant phytoplanktonic blooms regularly occur, samples of filter-feeding shellfish were collected in two Portuguese transitional water bodies. BMAA content in cockles (Cerastoderma edule) collected weekly between September and November 2009 from Ria de Aveiro and at least once a month from May to November from Ria Formosa, fluctuated from 0.079±0.055 to 0.354±0.066μg/g DW and from below the limit of detection to 0.434±0.110μg/g DW, respectively. Simultaneously to BMAA occurrence in cockles, paralytic shellfish toxins were detected in shellfish as a result of Gymnodinium catenatum blooms indicating a possible link between this marine dinoflagellate and BMAA production. Moreover, considerable high BMAA levels, 0.457±0.186μg/g DW, were then determined in a laboratory grown culture of G. catenatum. This work reveals for the first time the presence of BMAA in shellfish from Atlantic transitional water bodies and consubstantiate evidences of G. catenatum as one of the main sources of BMAA in these ecosystems.

Uptake of a cyanotoxin, β-N-methylamino-L-alanine, by wheat (Triticum aestivum)

In order to study the uptake of the cyanobacterial neurotoxin β-N-methylamino-l-alanine (BMAA) into the crop plant Triticum aestivum during germination and primary growth imbibed grains and 7-day-old seedlings were irrigated with 100 and 1000µg l(-1) BMAA for 4 days and 100µg l(-1) BMAA for 28 days. Content of derivatized free and protein-associated BMAA in seedlings, root and shoot tissue, respectively, were analyzed by LC-MS/MS. Free BMAA was only detected in seedlings exposed to 1000µg l(-1) BMAA, whereas protein-associated BMAA was found at both exposure concentrations. Irrigation with 100µgl(-1) BMAA led to an uptake of the neurotoxin into roots and shoots and to immediate protein-association. In roots, protein-associated BMAA was detectable after 5 days with peaking amounts after 14 days. Longer exposure did not cause further accumulation in roots. In contrast, protein-associated BMAA was detected in shoot samples after only 1 day. In shoots the highest amounts of protein-associated BMAA were found after 28 days. In turn, in both plant compartments free BMAA was below the measurable concentration.

Presence of the neurotoxin BMAA in aquatic ecosystems: what do we really know?

The neurotoxin β-N-methylamino-l-alanine (BMAA) is suspected to play a role in the neurological diseases amyotrophic lateral sclerosis, Alzheimer’s disease, and Parkinson’s disease. BMAA production by cyanobacteria has been reported and contact with cyanobacteria infested waters or consumption of aquatic organisms are possible pathways to human exposure. However, there is little consensus regarding whether BMAA is present in cyanobacteria or not, and if so, at what concentrations. The aim of this review is to indicate the current state of knowledge on the presence of BMAA in aquatic ecosystems. Some studies have convincingly shown that BMAA can be present in aquatic samples at the µg/g dry weight level, which is around the detection limit of some equally credible studies in which no BMAA was detected. However, for the majority of the reviewed articles, it was unclear whether BMAA was correctly identified, either because inadequate analytical methods were used, or because poor reporting of analyses made it impossible to verify the results. Poor analysis, reporting and prolific errors have shaken the foundations of BMAA research. First steps towards estimation of human BMAA exposure are to develop and use selective, inter-laboratory validated methods and to correctly report the analytical work.

Evaluation of a commercial enzyme linked immunosorbent assay (ELISA) for the determination of the neurotoxin BMAA in surface waters

The neurotoxin β-N-methylamino-L-alanine (BMAA) is suspected to play a role in Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis. Because BMAA seems to be produced by cyanobacteria, surface waters are screened for BMAA. However, reliable analysis of BMAA requires specialized and expensive equipment. In 2012, a commercial enzyme-linked immunosorbent assay (ELISA) for determination of BMAA in surface waters was released. This kit could enable fast and relatively cheap screening of surface waters for BMAA. The objective of this study was to determine whether the BMAA ELISA kit was suitable for the determination of BMAA concentrations in surface waters. We hypothesised that the recovery of spiked samples was close to 100% and that the results of unspiked sample analysis were comparable between ELISA and liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. However, we found that recovery was higher than 100% in most spiked samples, highest determined recovery was over 400%. Furthermore, the ELISA gave a positive signal for nearly each tested sample while no BMAA could be detected by LC-MS/MS. We therefore conclude that in its current state, the kit is not suitable for screening surface waters for BMAA.

The cyanobacterial neurotoxin β-N-methylamino-l-alanine (BMAA) induces neuronal and behavioral changes in honeybees

The cyanobacterially produced neurotoxin beta-N-methylamino-l-alanine (BMAA) is thought to induce amyotrophic lateral sclerosis/Parkinsonism dementia complex (ALS/PDC)-like symptoms. However, its mechanism of action and its pathway of intoxication are yet unknown. In vivo animal models suitable for investigating the neurotoxic effect of BMAA with applicability to the human are scarce. Hence, we used the honeybee (Apis mellifera) since its nervous system is relatively simple, yet having cognitive capabilities. Bees fed with BMAA-spiked sugar water had an increased mortality rate and a reduced ability to learn odors in a classical conditioning paradigm. Using (14)C-BMAA we demonstrated that BMAA is biologically available to the bee, and is found in the head, thorax and abdomen with little to no excretion. BMAA is also transferred from one bee to the next via trophallaxis resulting in an exposure of the whole beehive. BMAA bath application directly onto the brain leads to an altered Ca(2+) homeostasis and to generation of reactive oxygen species. These behavioral and physiological observations suggest that BMAA may have effects on bee brains similar to those assumed to occur in humans. Therefore the bee could serve as a surrogate model system for investigating the neurological effects of BMAA.