Algal toxins

Impact of pathogenic bacterial communities present in wastewater on aquatic organisms: Application of nanomaterials for the removal of these pathogens

Contaminated wastewater (WW) can cause severe hazards to numerous delicate ecosystems and associated life forms. In addition, human health is negatively impacted by the presence of microorganisms in water. Multiple pathogenic microorganisms in contaminated water, including bacteria, fungi, yeast, and viruses, are vectors for several contagious diseases. To avoid the negative impact of these pathogens, WW must be free from pathogens before being released into stream water or used for other reasons. In this review article, we have focused on pathogenic bacteria in WW and summarized the impact of the different types of pathogenic bacteria on marine organisms. Moreover, we presented a variety of physical and chemical techniques that have been developed to provide a pathogen-free aquatic environment. Among the techniques, membrane-based techniques for trapping hazardous biological contaminants are gaining popularity around the world. Besides, novel and recent advancements in nanotechnological science and engineering suggest that many waterborne pathogens could be inactivated using nano catalysts, bioactive nanoparticles, nanostructured catalytic membranes, nanosized photocatalytic structures, and electrospun nanofibers and processes have been thoroughly examined.

Toxic or Otherwise Harmful Algae and the Built Environment

This article gives a comprehensive overview on potentially harmful algae occurring in the built environment. Man-made structures provide diverse habitats where algae can grow, mainly aerophytic in nature. Literature reveals that algae that is potentially harmful to humans do occur in the anthropogenic environment in the air, on surfaces or in water bodies. Algae may negatively affect humans in different ways: they may be toxic, allergenic and pathogenic to humans or attack human structures. Toxin-producing alga are represented in the built environment mainly by blue green algae (Cyanoprokaryota). In special occasions, other toxic algae may also be involved. Green algae (Chlorophyta) found airborne or growing on manmade surfaces may be allergenic whereas Cyanoprokaryota and other forms may not only be toxic but also allergenic. Pathogenicity is found only in a special group of algae, especially in the genus Prototheca. In addition, rare cases with infections due to algae with green chloroplasts are reported. Algal action may be involved in the biodeterioration of buildings and works of art, which is still discussed controversially. Whereas in many cases the disfigurement of surfaces and even the corrosion of materials is encountered, in other cases a protective effect on the materials is reported. A comprehensive list of 79 taxa of potentially harmful, airborne algae supplemented with their counterparts occurring in the built environment, is given. Due to global climate change, it is not unlikely that the built environment will suffer from more and higher amounts of harmful algal species in the future. Therefore, intensified research in composition, ecophysiology and development of algal growth in the built environment is indicated.

Algal Toxic Compounds and Their Aeroterrestrial, Airborne and other Extremophilic Producers with Attention to Soil and Plant Contamination: A Review

The review summarizes the available knowledge on toxins and their producers from rather disparate algal assemblages of aeroterrestrial, airborne and other versatile extreme environments (hot springs, deserts, ice, snow, caves, etc.) and on phycotoxins as contaminants of emergent concern in soil and plants. There is a growing body of evidence that algal toxins and their producers occur in all general types of extreme habitats, and cyanobacteria/cyanoprokaryotes dominate in most of them. Altogether, 55 toxigenic algal genera (47 cyanoprokaryotes) were enlisted, and our analysis showed that besides the “standard” toxins, routinely known from different waterbodies (microcystins, nodularins, anatoxins, saxitoxins, cylindrospermopsins, BMAA, etc.), they can produce some specific toxic compounds. Whether the toxic biomolecules are related with the harsh conditions on which algae have to thrive and what is their functional role may be answered by future studies. Therefore, we outline the gaps in knowledge and provide ideas for further research, considering, from one side, the health risk from phycotoxins on the background of the global warming and eutrophication and, from the other side, the current surge of interest which phycotoxins provoke due to their potential as novel compounds in medicine, pharmacy, cosmetics, bioremediation, agriculture and all aspects of biotechnological implications in human life.

The Effect of Diet Mixing on a Nonselective Herbivore

The balanced-diet hypothesis states that a diverse prey community is beneficial to consumers due to resource complementarity among the prey species. Nonselective consumer species cannot differentiate between prey items and are therefore not able to actively regulate their diet intake. We thus wanted to test whether the balanced-diet hypothesis is applicable to nonselective consumers. We conducted a laboratory experiment in which a nonselective model grazer, the freshwater gastropod Lymnaea stagnalis, was fed benthic green algae as single species or as a multi-species mixture and quantified the snails’ somatic growth rates and shell lengths over a seven-week period. Gastropods fed the mixed diet were found to exhibit a higher somatic growth rate than the average of the snails fed single prey species. However, growth on the multi-species mixture did not exceed the growth rate obtained on the best single prey species. Similar results were obtained regarding the animals’ shell height increase over time. The mixed diet did not provide the highest growth rate, which confirms our hypothesis. We thus suggest that the balanced-diet hypothesis is less relevant for non-selective generalist consumers, which needs to be considered in estimates of secondary production.

Prymnesins: toxic metabolites of the golden alga, Prymnesium parvum Carter (Haptophyta)

Increasingly over the past century, seasonal fish kills associated with toxic blooms of Prymnesium parvum have devastated aquaculture and native fish, shellfish, and mollusk populations worldwide. Protracted blooms of P. parvum can result in major disturbances to the local ecology and extensive monetary losses. Toxicity of this alga is attributed to a collection of compounds known as prymnesins, which exhibit potent cytotoxic, hemolytic, neurotoxic and ichthyotoxic effects. These secondary metabolites are especially damaging to gill-breathing organisms and they are believed to interact directly with plasma membranes, compromising integrity by permitting ion leakage. Several factors appear to function in the activation and potency of prymnesins including salinity, pH, ion availability, and growth phase. Prymnesins may function as defense compounds to prevent herbivory and some investigations suggest that they have allelopathic roles. Since the last extensive review was published, two prymnesins have been chemically characterized and ongoing investigations are aimed at the purification and analysis of numerous other toxic metabolites from this alga. More information is needed to unravel the mechanisms of prymnesin synthesis and the significance of these metabolites. Such work should greatly improve our limited understanding of the physiology and biochemistry of P. parvum and how to mitigate its blooms.

The coastal environment and human health: microbial indicators, pathogens, sentinels and reservoirs

Innovative research relating oceans and human health is advancing our understanding of disease-causing organisms in coastal ecosystems. Novel techniques are elucidating the loading, transport and fate of pathogens in coastal ecosystems, and identifying sources of contamination. This research is facilitating improved risk assessments for seafood consumers and those who use the oceans for recreation. A number of challenges still remain and define future directions of research and public policy. Sample processing and molecular detection techniques need to be advanced to allow rapid and specific identification of microbes of public health concern from complex environmental samples. Water quality standards need to be updated to more accurately reflect health risks and to provide managers with improved tools for decision-making. Greater discrimination of virulent versus harmless microbes is needed to identify environmental reservoirs of pathogens and factors leading to human infections. Investigations must include examination of microbial community dynamics that may be important from a human health perspective. Further research is needed to evaluate the ecology of non-enteric water-transmitted diseases. Sentinels should also be established and monitored, providing early warning of dangers to ecosystem health. Taken together, this effort will provide more reliable information about public health risks associated with beaches and seafood consumption, and how human activities can affect their exposure to disease-causing organisms from the oceans.

Metal complexes and free radical toxins produced by Pfiesteria piscicida

Metal-containing organic toxins produced by Pfiesteria piscicida were characterized, for the first time, by corroborating data obtained from five distinct instrumental methods: nuclear magnetic resonance spectroscopy (NMR), inductively coupled plasma mass spectrometry (ICP-MS), liquid chromatography particle beam glow discharge mass spectrometry (LC/PB-G DMS), electron paramagnetic resonance spectroscopy (EPR), and X-ray absorption spectroscopy (XAS). The high toxicity of the metal-containing toxins is due to metal-mediated free radical production. This mode of activity explains the toxicity of Pfiesteria, as well as previously reported difficulty in observing the molecular target, due to the ephemeral nature of radical species. The toxins are highly labile in purified form, maintaining activity for only 2-5 days before all activity is lost. The multiple toxin congeners in active extracts are also susceptible to decomposition in the presence of white light, pH variations, and prolonged heat. These findings represent the first formal isolation and characterization of a radical forming toxic organic-ligated metal complex isolated from estuarine/marine dinoflagellates. These findings add to an increased understanding regarding the active role of metals interacting with biological systems in the estuarine environment, as well as their links and implications to human health.

On the annual cycle of the blue-green alga Microcystis Aeruginosa Kütz. Emend. Elenkin

A 4 year series of field, light-microscope and ultrastructural observations is presented to illustrate biological aspects of the annual cycle of natural Microcystis populations enclosed in Lund tubes. Nine morphological stati, all referable to M. aeruginosa f. aeruginosa , feature at various stages of the cycle. Summer bloom-forming populations originate from vegetative colonial stock that overwinters on the bottom sediment each year, but there is no mass transfer of these colonies to the water column: intensive growth from individual cells in the old colonies leads to the formation of new infective colonies, being stimulated when the bottom water approaches anoxia and light penetrates to the bottom sediments. Growth is slow but the developing populations sustain only minor losses through grazing and settling out, eventually becoming dominant over other species. Allelopathy possibly contributes to this effect. In postmaximal populations, several mechanisms can contribute to net buoyancy loss and a (usually) rapid recruitment of vegetative colonies to the sediments is observed. Hypotheses are advanced to account for the observed behaviour, and some of these have been tested in the laboratory. The apparent physiological flexibility of Microcystis seems well suited to growth and survival in the microenvironments encountered in eutrophic lakes.

A Mini-review of Microbial Consortia: Their Roles in Aquatic Production and Biogeochemical Cycling

Molecular oxygen (O2) is a potent inhibitor of key microbial processes, including photosynthesis, N2 fixation, denitrification, sulfate reduction, methanogenesis, iron, and metal reduction reactions. Prokaryote survival and proliferation in aquatic environments is often controlled by the ability to tolerate exposure to oxic conditions. Many prokaryotes do not have subcellular organelles for isolating O2-producing from O2-consuming processes and have developed consortial associations with other prokaryotes and eukaryotes that alleviate metabolic constraints of high O2. Nutrient transformations often rely on appropriate cellular and microenvironmental, or microzonal, redox conditions. The spatial and temporal requirements for microenvironmental overlap among microbial groups involved in nutrient transformations necessitates close proximity and diffusional exchange with other biogeochemically distinct, yet complementary, microbial groups. Microbial consortia exist at different levels of community and metabolic complexity, as shown for detrital, microbial mat, biofilm, and planktonic microalgal-bacterial assemblages. To assess the macroscale impacts of consortial interactions, studies should focus on the range of relevant temporal (minutes to hours) and spatial (microns to centimeters) scales controlling microbial production, nutrient exchange, and cycling. In this review, we discuss the utility and application of techniques suitable for determining microscale consortial activity, production, community composition, and interactions in the context of larger scale aquatic ecosystem structure and function.

Characterization of ruminal bacteria producing a toxin associated with a bovine paraplegic syndrome

We studied the ruminal population densities of bacteria in animals with and without bovine paraplegic syndrome (BPS). All bacterial counts were performed under strict anaerobiosis. Although the rumen bacterial density was around 10(9) bacteria/ml in animals, both apparently healthy or suffering from BPS, a shift towards Gram-negative strains occurred in animals with BPS. The toxin added to the cultures stimulated bacterial growth. Bacterial strains from the rumen could produce the toxin in vitro. Gram-positive bacteria differed in their ability to produce the toxin; Streptomyces bovis did not produce the toxin, while Lactobacillus vitulinum was an efficient producer. All Gram-negative bacteria tested could produce the compound.

Toxicity and toxins of natural blooms and isolated strains of Microcystis spp. (Cyanobacteria) and improved procedure for purification of cultures

All samples of cyanobacterial blooms collected from 1986 to 1989 from Lake Kasumigaura, Ibaraki Prefecture, Japan, were hepatotoxic. The 50% lethal doses (LD50s) of the blooms to mice ranged from 76 to 556 mg/kg of body weight. Sixty-eight Microcystis cell clones (67 Microcystis aeruginosa and 1 M. viridis) were isolated from the blooms. Twenty-three strains (including the M. viridis strain) were toxic. However, the ratio of toxic to nontoxic strains among the blooms varied (6 to 86%). Microcystins were examined in six toxic strains. Five toxic strains produced microcystin-RR, -YR, and -LR, with RR being the dominant toxin in these strains. Another strain produced 7-desmethylmicrocystin-LR and an unknown microcystin. This strain showed the highest toxicity. Establishment of axenic strains from the Microcystis cells exhibiting extracellularly mucilaginous materials was successful by using a combination of the agar plate technique and two-step centrifugation.

Algal biotechnology

The review gives a general outline of macro- and microalgal biotechnology. The main methods by which algae are cultivated and harvested are described. The first section deals with the environmental factors affecting mass culture and the principles governing the design and operation of mass cultivation systems. The second section gives the main current and potential uses of algae: in wastewater treatment, a source of food and feed, an energy source, and in the production of common and fine chemicals, such as polysaccharides, lipids, glycerol, pigments, and enzymes. Pharmaceutical uses of algae are described, and their potential as a source of novel biologically-active compounds is discussed. Future developments and the great potential of algae are considered.

The peptide toxin of the cyanobacterium Microcystis aeruginosa PCC 7941. Isolation and analysis by nuclear magnetic resonance and fast atom bombardment mass spectroscopy

Toxin was obtained from the cyanobacterium Microcystis aeruginosa PCC7941 by extracting freeze-dried cells with water-saturated, acidified n-butanol, diethyl ether-water distribution, reversed-phase thin-layer chromatography and silica high-performance liquid chromatography (HPLC). Two toxic peptide fractions resulted from HPLC. One of these fractions was analyzed by UV and NMR spectroscopy, amino acid analysis and fast atom bombardment mass spectroscopy. The following amino acid analysis and fast atom bombardment mass spectroscopy. The following amino acids were identified: beta-methyl-Asp, Thr, Glu, Ala, Val, Leu, Phe, Arg, N-methyldehydro-Ala and 3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid. Yet the mass spectroscopic data showed that the fraction was still composed of several, most likely cyclic peptides that did not stain with ninhydrin.

Microcystis aeruginosa toxin: cell culture toxicity, hemolysis, and mutagenicity assays

Crude toxin was prepared by lyophilization and extraction of toxic Microcystis aeruginosa from four natural sources and a unicellular laboratory culture. The responses of cultures of liver (Mahlavu and PCL/PRF/5), lung (MRC-5), cervix (HeLa), ovary (CHO-K1), and kidney (BGM, MA-104, and Vero) cell lines to these preparations did not differ significantly from one another, indicating that toxicity was not specific for liver cells. The results of a trypan blue staining test showed that the toxin disrupted cell membrane permeability within a few minutes. Human, mouse, rat, sheep, and Muscovy duck erythrocytes were also lysed within a few minutes. Hemolysis was temperature dependent, and the reaction seemed to follow first-order kinetics. Escherichia coli, Streptococcus faecalis, and Tetrahymena pyriformis were not significantly affected by the toxin. The toxin yielded negative results in Ames/Salmonella mutagenicity assays. Microtiter cell culture, trypan blue, and hemolysis assays for Microcystis toxin are described. The effect of the toxin on mammalian cell cultures was characterized by extensive disintegration of cells and was distinguishable from the effects of E. coli enterotoxin, toxic chemicals, and pesticides. A possible reason for the acute lethal effect of Microcystis toxin, based on cytolytic activity, is discussed.

Hemagglutination method for detection of freshwater cyanobacteria (blue-green algae) toxins

Strains of the freshwater cyanobacteria (blue-green algae) Anabaena flosaquae and Microcystis aeruginosa produced toxins that caused intermittent but repeated cases of livestock, waterfowl, and other animal deaths. They also caused illness, especially gastrointestinal, in humans. The most common group of toxins produced by these two species were peptide toxins termed microcystin, M. Aeruginosa type c, and anatoxin-c. A method was found to detect the toxins which utilizes their ability to cause agglutination of isolated blood cells from mice, rats, and humans. The method could detect the toxin in samples from natural algal blooms, laboratory cultures, and toxin extracts. The method consists of: (i) washing lyophilized cyanobacteria cells with physiological saline (0.9% NaCl), (ii) centrifuging the suspension and then mixing portions of the cell-free supernatant with equal volumes of saline-washed erythrocytes in V-shaped microtiter plates, (iii) allowing the mixture to stand for 3 to 4 h, and (iv) scoring the presence of the toxin as indicated by blood cell agglutination. Nontoxic strains, as determined by intraperitoneal mouse bioassay of cyanobacteria or green algae, did not produce an agglutination response.