Monosaccharide composition of the outer membrane lipopolysaccharide and O-chain from the freshwater cyanobacterium Microcystis aeruginosa NIES-87

Cyanobacterial harmful bloom lipopolysaccharides: pro-inflammatory effects on epithelial and immune cells in vitro

Cyanobacterial harmful blooms (CyanoHABs) pose a global ecological problem, and their lipopolysaccharides (LPS) are among the bioactive compounds they release. Previous studies on CyanoHAB-LPS from single cyanobacterial species have shown varying bioactivities in different in vitro cell models. In this study, we isolated LPS from 19 CyanoHAB samples collected at 18 water bodies in the Czech Republic over two consecutive seasons. The proportions of cyanobacteria, Gram-negative bacteria (G-), and other bacteria in the biomass were determined by qPCR, while the cyanobacterial genera were identified using light microscopy. In vitro models of keratinocytes (HaCaT), the intestinal epithelium (co-culture of differentiated Caco-2 cells and peripheral blood mononuclear cells - PBMC), and PBMC alone were treated with isolated LPS at concentrations of 50, 100, and 1 µg/ml, respectively. The endotoxin activities of these concentrations were within the range measured in the aquatic environment. Approximately 85-90% of the samples displayed biological activity. However, the potency of individual LPS effects and response patterns varied across the different in vitro models. Furthermore, the observed activities did not exhibit a clear correlation with the taxonomic composition of the phytoplankton community, the relative share of microbial groups in the biomass, endotoxin activity of the LPS, or LPS migration and staining pattern in SDS-PAGE. These findings suggest that the effects of CyanoHAB-LPS depend on the specific composition and abundance of various LPS structures within the complex environmental sample and their interactions with cellular receptors.

Cyanobacterial bloom-associated lipopolysaccharides induce pro-inflammatory processes in keratinocytes in vitro

Our previous studies have shown that CyanoHAB LPS (lipopolysaccharides) and LPS from cyanobacterial cultures induce pro-inflammatory effects on intestinal epithelial and immune cells in vitro. To expand our understanding, we investigated their impact on human keratinocytes, which are targeted during water recreational activities. LPS samples were isolated from CyanoHAB biomasses dominated by Microcystis, Aphanizomenon, Planktothrix, and Dolichospermum, or from axenic cultures of these genera. We identified two CyanoHAB biomasses containing a high proportion of Gram-negative bacteria, including potentially pathogenic genera. These biomasses showed the highest induction of interleukin (IL) 8, IL-6, C-C motif chemokine ligand (CCL) 2 (also known as MCP-1), and CCL20 production by HaCaT cells. Interestingly, all CyanoHAB-derived LPS and LPS from axenic cultures (except for Microcystis) accelerated cell proliferation and migration. Our findings highlight the role of G- bacteria composition and LPS structural disparities in influencing these effects, with implications for skin health during recreational activities.

Production and composition of extracellular polymeric substances by a unicellular strain and natural colonies of Microcystis: Impact of salinity and nutrient stress

The transfer of toxic cyanobacterial Microcystis blooms from freshwater to estuaries constitutes a serious environmental problem worldwide that is expected to expand in scale and intensity with anthropogenic and climate change. The formation and maintenance of Microcystis in colonial form is conditioned to the presence of extracellular polymeric substances (EPS). In this study, we attempted to better understand how the mucilaginous colonial form of Microcystis evolves under environmental stress conditions. In particular, we studied and compared the production and the composition of EPS fractions (attached and free) from natural colonies of a Microcystis bloom and from a unicellular M. aeruginosa strain under salinity and nutrient stress (representing a land-sea continuum). Our results highlighted a greater production of EPS from the natural colonies of Microcystis than the unicellular one under nutrient and combined stress conditions dominated by the attached form. In comparison to the unicellular Microcystis, EPS produced by the colonial form were characterized by high molecular weight polysaccharides which were enriched in uronic acids and hexosamines, notably for the free fraction in response to increased salinities. This complex extracellular matrix gives the cells the ability to aggregate and allows the colonial cyanobacterial population to cope with osmotic shock.

Harmful and beneficial properties of cyanotoxins: Two sides of the same coin

Cyanotoxins are by definition "harmful agents" produced by cyanobacteria. Their toxicity has been extensively studied and reviewed over the years. Cyanotoxins have been commonly classified, based on their poisonous effects on mammals, into three main classes, neurotoxins, hepatotoxins and dermatotoxins, and, considering their chemical features, mainly identified as peptides, alkaloids and lipopolysaccharides. Here we propose a broader subdivision of cyanotoxins into eight distinct classes, taking into account their molecular structures, biosynthesis and modes of action: alkaloids, non-ribosomal peptides, polyketides, non-protein amino acids, indole alkaloids, organophosphates, lipopeptides and lipoglycans. For each class, the structures and primary mechanisms of toxicity of the main representative cyanotoxins are reported. Despite their powerful biological activities, only recently scientists have considered the biotechnological potential of cyanotoxins, and their applications both in medical and in industrial settings, even if only a few of these have reached the biotech market. In this perspective, we discuss the potential uses of cyanotoxins as anticancer, antimicrobial, and biocidal agents, as common applications for cytotoxic compounds. Furthermore, taking into account their mechanisms of action, we describe peculiar potential bioactivities for several cyanotoxin classes, such as local anaesthetics, antithrombotics, neuroplasticity promoters, immunomodulating and antifouling agents. In this review, we aim to stimulate research on the potential beneficial roles of cyanotoxins, which require interdisciplinary cooperation to facilitate the discovery of innovative biotechnologies.

β-l-Rhamnosylation and β-d-Mannosylation Mediated by 4-O-Ester Groups in a Weakly Nucleophilic Environment

eq-4-O-Acyl group directed β-rhamnosylation and β-mannosylation are achieved in a carborane or BARF anion formed weakly nucleophilic environment with the assistance of a 2,3-orthocarbonate group. The 4-O-acyl group plays a critical role in directing the β-selectivity, and the weakly coordinating anion is essential to amplify this direction. The orthocarbonate group could be readily removed with 1,3-propanediol in the presence of BF3·Et2O.

Cyanobacterial Harmful Bloom Lipopolysaccharides Induce Pro-Inflammatory Effects in Immune and Intestinal Epithelial Cells In Vitro

Freshwater cyanobacterial harmful blooms (CyanoHABs) produce a variety of toxic and bioactive compounds including lipopolysaccharides (LPSs). The gastrointestinal tract can be exposed to them via contaminated water even during recreational activities. However, there is no evidence of an effect of CyanoHAB LPSs on intestinal cells. We isolated LPSs of four CyanoHABs dominated by different cyanobacterial species and LPSs of four laboratory cultures representing the respective dominant cyanobacterial genera. Two intestinal and one macrophage cell lines were used to detect in vitro pro-inflammatory activity of the LPS. All LPSs isolated from CyanoHABs and laboratory cultures induced cytokines production in at least one in vitro model, except for LPSs from the Microcystis PCC7806 culture. LPSs isolated from cyanobacteria showed unique migration patterns in SDS-PAGE that were qualitatively distinct from those of endotoxins from Gram-negative bacteria. There was no clear relationship between the biological activity of the LPS and the share of genomic DNA of Gram-negative bacteria in the respective biomass. Thus, the total share of Gram-negative bacteria, or the presence of Escherichia coli-like LPSs, did not explain the observed pro-inflammatory activities. The pro-inflammatory properties of environmental mixtures of LPSs from CyanoHABs indicate their human health hazards, and further attention should be given to their assessment and monitoring.

Optimization of Degradation Conditions with PRG, a Polysaccharide from Phellinus ribis, by RSM and the Neuroprotective Activity in PC12 Cells Damaged by Aβ25-35

In the previous work, we found PRG, a polysaccharide from Phellinus ribis, exhibited neurotrophic activity. To obtain an active structural unit with lower molecular weight, PRG was degraded to prepare the degraded PRG (DPRG) using ascorbic acid and H₂O₂. The aim of the paper was to obtain DPRG by optimizing the degradation conditions using response surface methodology (RSM) and to study its protective effects of PC12 cells induced by Aβ_25–35. The optimum conditions were as follows; the concentration of H₂O₂-Vc was 17 mM and degradation temperature was 50 °C; when degradation time was 1.6 h, the experimental response value of PC12 cell viability was 83.4 ± 0.15%, which was in accordance with the predicted value (83.5%). We also studied the protective effects of DPRG against the Aβ_25–35-induced neurotoxicity and explored the underlying mechanism. The results showed that treatment with DPRG could attenuate PC12 cells death. The mechanism was relative to the inhibition of cell apoptosis by increasing the MMP level and decreasing the protein expression of cytochrome C (Cytc) in PC12 cells. In conclusion, DPRG with lower molecular weight was obtained successfully. It possessed neuroprotective properties and might be a candidate for neurodegenerative disease treatment.

Lipopolysaccharides from Microcystis Cyanobacteria-Dominated Water Bloom and from Laboratory Cultures Trigger Human Immune Innate Response

Massive toxic blooms of cyanobacteria represent a major threat to water supplies worldwide. Here, the biological activities of lipopolysaccharide (LPS) isolated from Microcystis aeruginosa, the most prominent cyanobacteria in water bloom, were studied. LPS was isolated from complex environmental water bloom samples dominated by M. aeruginosa, and from laboratory cultures of non-axenic as well as axenic M. aeruginosa strains PCC7806 and HAMBI/UHCC130. Employing human blood-based in vitro tests, the LPS isolated from complex water bloom revealed the priming of both major blood phagocyte population monocytes and polymorphonuclear leukocytes documented by the increased surface expression of CD11b and CD66b. This was accompanied by a water bloom LPS-mediated dose-dependent induction of tumor necrosis factor α, interleukin-1β, and interleukin-6 production. In accordance with its priming effects, water bloom LPS induced significant activation of p38 and ERK1/2 kinases, as well as NF-κB phosphorylation, in isolated polymorphonuclear leukocytes. Interestingly, the pro-inflammatory potential of LPS from the axenic strain of M. aeruginosa was not lower compared to that of LPS isolated from non-axenic strains. In contrast to the biological activity, water bloom LPS revealed almost twice higher pyrogenicity levels compared to Escherichia coli LPS, as analyzed by the PyroGene test. Moreover, LPS from the non-axenic culture exhibited higher endotoxin activity in comparison to LPS from axenic strains. Taking the above findings together, M. aeruginosa LPS can contribute to the health risks associated with contamination by complex water bloom mass.

Lectin-stimulated cellular iron uptake and toxin generation in the freshwater cyanobacterium Microcystis aeruginosa

The lectin family is composed of mono- and oligosaccharide binding proteins that could activate specific cellular activities, such as cell-cell attachment and toxin production. In the present study, the effect of the external addition of lectins to culture media containing the freshwater cyanobacterium Microcystis aeruginosa on its metabolic activities, such as iron uptake and toxin production was investigated. Among the three lectins examined in this study (concanavalin A [Con A], wheat germ agglutinin [WGA] and peanut agglutinin [PNA]), PNA substantially increased the accumulated intracellular and extracellular iron content. The binding of PNA and Con A to M. aeruginosa cells was visualized via fluorescence microscopy using a lectin adjunct with fluorescein isothiocyanate, and resulted in carbohydrate and protein accumulation in the cellular capsule. Given that the highest carbohydrate accumulation was seen in the Con A system (where iron accumulation was relatively lower), carbohydrate quality is likely important factor that influences cellular iron accumulation. Since PNA specifically binds to sugars such as galactose and N-acetylgalactosamine, these saccharide species could be important candidates for intracellular and extracellular iron accumulation and transport. Microcystin biosynthesis was stimulated in the presence of PNA and WGA, whereas cellular iron uptake increased only in the presence of PNA. Thus, the iron uptake was not necessarily congruent with the upregulation of microcystin synthesis, which suggested that the positive effect of lectin on iron uptake is probably attributable to the PNA-assisted iron accumulation around the cell surface. Overall, the present study provides insights into the interactions of lectin that influence cellular metabolic activities such as iron uptake, extracellular polymeric substance accumulation, and toxin production.

Morphophysiological and transcriptome analysis reveals a multiline defense system enabling cyanobacterium Leptolyngbya strain JSC-1 to withstand iron induced oxidative stress

Iron intoxications induce severe oxidative stress by producing reactive oxygen species (ROS) in cyanobacteria, leading to membrane lipid peroxidation, altered morphology, impaired photosynthesis and other oxidative stress injuries. Given these stresses, mitigation of ROS is a prerequisite for all aerobic organisms. Study of siderophilic cyanobacterium Leptolyngbya strain JSC-1 inhabiting iron-rich hot springs may provide insight into the mechanism of iron homeostasis and alleviation of oxidative stress. In this study, we investigated the morphophysiological and molecular mechanisms enabling this cyanobacterium to cope with iron-induced oxidative stress. Strain JSC-1 biomineralized extracellular iron via an exopolymeric sheath (acting as a first line of defense) and intracellular iron via polyphosphate inclusions (second line of defense), thus minimizing the burden of free ferric ions. Physiological parameters, SOD, CAT and POD activities, bacterioferritin and total protein contents fluctuated in response to iron elevation, displaying a third line of defense to mitigate ROS. Differential gene expression analysis of JSC-1 indicated up-regulation of 94 and 125 genes and down-regulation of 89 and 183 genes at low (4 μM) and high (400 μM) iron concentration, respectively. The differentially expressed genes (DEGs) were enriched in 100 KEGG pathways and were found to be involved in lipopolysaccharide and fatty acid biosynthesis, starch, sucrose, chlorophyll and other metabolic pathways. Together with metabolic reprogramming (fourth line of defense), JSC-1 established a unique multiline defense system that allows JSC-1 to withstand severe oxidative stress. These findings also provide insight into potential survival strategies of ancient microorganisms inhabiting similar environment present in early earth history.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2011-2012

This review is the seventh update of the original article published in 1999 on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2012. General aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, and fragmentation are covered in the first part of the review and applications to various structural types constitute the remainder. The main groups of compound are oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Much of this material is presented in tabular form. Also discussed are medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:255-422, 2017.

Mutations in Novel Lipopolysaccharide Biogenesis Genes Confer Resistance to Amoebal Grazing in Synechococcus elongatus

In natural and artificial aquatic environments, population structures and dynamics of photosynthetic microbes are heavily influenced by the grazing activity of protistan predators. Understanding the molecular factors that affect predation is critical for controlling toxic cyanobacterial blooms and maintaining cyanobacterial biomass production ponds for generating biofuels and other bioproducts. We previously demonstrated that impairment of the synthesis or transport of the O-antigen component of lipopolysaccharide (LPS) enables resistance to amoebal grazing in the model predator-prey system consisting of the heterolobosean amoeba HGG1 and the cyanobacterium Synechococcus elongates PCC 7942 (R. S. Simkovsky et al., Proc Natl Acad Sci U S A 109:16678-16683, 2012,http://dx.doi.org/10.1073/pnas.1214904109). In this study, we used this model system to identify additional gene products involved in the synthesis of O antigen, the ligation of O antigen to the lipid A-core conjugated molecule (including a novel ligase gene), the generation of GDP-fucose, and the incorporation of sugars into the lipid A core oligosaccharide ofS. elongatus Knockout of any of these genes enables resistance to HGG1, and of these, only disruption of the genes involved in synthesis or incorporation of GDP-fucose into the lipid A-core molecule impairs growth. Because these LPS synthesis genes are well conserved across the diverse range of cyanobacteria, they enable a broader understanding of the structure and synthesis of cyanobacterial LPS and represent mutational targets for generating resistance to amoebal grazers in novel biomass production strains.

Classical and Alternative Activation of Cyanobacterium Oscillatoria sp. Lipopolysaccharide-Treated Rat Microglia in vitro

The purpose of this investigation was to test the hypothesis that an in vitro exposure to cyanobacterium Oscillatoria sp. Lipopolysaccharide (LPS) might result in classical and alternative activation of rat neonatal microglia. Using Escherichia coli LPS-primed microglia as a positive control, this study revealed that treatment of rat microglia with Oscillatoria sp. LPS for 17 h in vitro resulted in both classical and alternative activation as well as concomitant pro-inflammatory and anti-inflammatory mediator release, in a concentration-dependent manner: (1) treatment with 0.1-10 000 ng/ml Oscillatoria sp. LPS resulted in minimal lactic dehydrogenase (LDH) release, induced concentration-dependent and statistically significant O2 (-) generation, matrix metalloproteinase-9 (MMP-9) release, generation of the cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), and the chemokines macrophage inflammatory protein-2 (MIP-2/CXCL2), interferon γ-induced protein 10 kDa (IP-10/CXCL-10), (MIP-1α/CCL3), monocyte chemotactic protein-1 (MCP-1/CCL2), regulated on activation, normal T cell expressed and secreted (RANTES/CCL5), and the alternative activation cytokine IL-10; (3) in contrast, treatment with 100 000 ng/ml Oscillatoria sp. LPS appeared to damage the microglia cell membrane, because it resulted in minimal O2 (-) generation, statistically significant LDH release, and a decrease in the generation of all the cytokines and chemokines investigated, with the exception of IL-1α and cytokine-induced neutrophil chemoattractant 1 (CINC-1/CXCL1) generation, which was increased. Thus, our results provide experimental support for our working hypothesis, namely that Oscillatoria sp. LPS induces classical and alternative activation of rat brain microglia in vitro in a concentration-dependent manner, namely 0.1-10 000 ng/ml Oscillatoria sp. LPS, when microglia cells were shown to be viable. Furthermore, should cyanobacterium Oscillatoria sp. LPS gain entry into the CNS, our findings suggest that classical and alternative activation of rat brain microglia in vivo, might lead to concomitant mediator release that could result in an interplay between neuroinflammation and neural repair in a concentration-dependent manner.

One-pot four-enzyme synthesis of thymidinediphosphate-l-rhamnose

A concise and effective one-pot four-enzyme synthesis of dTDP-Rha, the substrate of rhamnosyltransferases, is described.

Modulation of Biofilm Exopolysaccharides by the Streptococcus mutans vicX Gene

The cariogenic pathogen Streptococcus mutans effectively utilizes dietary sucrose for the synthesis of exopolysaccharide, which act as a scaffold for its biofilm, thus contributing to its pathogenicity, environmental stress tolerance, and antimicrobial resistance. The two-component system VicRK of S. mutans regulates a group of virulence genes that are associated with biofilm matrix synthesis. Knockout of vicX affects biofilm formation, oxidative stress tolerance, and transformation of S. mutans. However, little is known regarding the vicX-modulated structural characteristics of the exopolysaccharides underlying the biofilm formation and the phenotypes of the vicX mutants. Here, we identified the role of vicX in the structural characteristics of the exopolysaccharide matrix and biofilm physiology. The vicX mutant (SmuvicX) biofilms seemingly exhibited "desertification" with architecturally impaired exopolysaccharide-enmeshed cell clusters, compared with the UA159 strain (S. mutans wild type strain). Concomitantly, SmuvicX showed a decrease in water-insoluble glucan (WIG) synthesis and in WIG/water-soluble glucan (WSG) ratio. Gel permeation chromatography (GPC) showed that the WIG isolated from the SmuvicX biofilms had a much lower molecular weight compared with the UA159 strain indicating differences in polysaccharide chain lengths. A monosaccharide composition analysis demonstrated the importance of the vicX gene in the glucose metabolism. We performed metabolite profiling via (1)H nuclear magnetic resonance spectroscopy, which showed that several chemical shifts were absent in both WSG and WIG of SmuvicX biofilms compared with the UA159 strain. Thus, the modulation of structural characteristics of exopolysaccharide by vicX provides new insights into the interaction between the exopolysaccharide structure, gene functions, and cariogenicity. Our results suggest that vicX gene modulates the structural characteristics of exopolysaccharide associated with cariogenicity, which may be explored as a potential target that contributes to dental caries management. Furthermore, the methods used to purify the EPS of S. mutans biofilms and to analyze multiple aspects of its structure (GPC, gas chromatography-mass spectrometry, and (1)H nuclear magnetic resonance spectroscopy) may be useful approaches to determine the roles of other virulence genes for dental caries prevention.

Slr2019, lipid A transporter homolog, is essential for acidic tolerance in Synechocystis sp. PCC6803

Living organisms must defend themselves against various environmental stresses. Extracellular polysaccharide-producing cells exhibit enhanced tolerance toward adverse environmental stress. In Synechocystis sp. PCC6803 (Synechocystis), lipopolysaccharide (LPS) may play a role in this protection. To examine the relationship between stress tolerance of Synechocystis and LPS, we focused on Slr2019 because Slr2019 is homologous to MsbA in Escherichia coli, which is related to LPS synthesis. First, to obtain a defective mutant of LPS, we constructed the slr2019 insertion mutant (slr2019) strain. Sodium deoxycholate-polyacrylamide gel electrophoresis indicated that slr2019 strain did not synthesize normal LPS. Second, to clarify the participation of LPS in acid tolerance, wild type (WT) and slr2019 strain were grown under acid stress; slr2019 strain growth was significantly weaker than WT growth. Third, to examine influences on stress tolerance, slr2019 strain was grown under various stresses. Under salinity and temperature stress, slr2019 strain grew significantly slower than WT. To confirm cell morphology, cell shape and envelope of slr2019 strain were observed by transmission electron microscopy; slr2019 cells contained more electron-transparent bodies than WT cells. Finally, to confirm whether electron-transparent bodies are poly-3-hydroxybutyrate (PHB), slr2019 strain was stained with Nile Blue A, a PHB detector, and observed by fluorescence microscopy. The PHB granule content ratio of WT and slr2019 strain grown at BG-11 pH 8.0 was each 7.18 and 8.41 %. At pH 6.0, the PHB granule content ratio of WT and slr2019 strain was 2.99 and 2.60 %. However, the PHB granule content ratio of WT and slr2019 strain grown at BG-11N-reduced was 10.82 and 0.56 %. Because slr2019 strain significantly decreased PHB under BG-11N-reduced compared with WT, LPS synthesis may be related to PHB under particular conditions. These results indicated that Slr2019 is necessary for Synechocystis survival in various stresses.

Structure and Effects of Cyanobacterial Lipopolysaccharides

Lipopolysaccharide (LPS) is a component of the outer membrane of mainly Gram-negative bacteria and cyanobacteria. The LPS molecules from marine and terrestrial bacteria show structural variations, even among strains within the same species living in the same environment. Cyanobacterial LPS has a unique structure, since it lacks heptose and 3-deoxy-d-manno-octulosonic acid (also known as keto-deoxyoctulosonate (KDO)), which are present in the core region of common Gram-negative LPS. In addition, the cyanobacterial lipid A region lacks phosphates and contains odd-chain hydroxylated fatty acids. While the role of Gram-negative lipid A in the regulation of the innate immune response through Toll-like Receptor (TLR) 4 signaling is well characterized, the role of the structurally different cyanobacterial lipid A in TLR4 signaling is not well understood. The uncontrolled inflammatory response of TLR4 leads to autoimmune diseases such as sepsis, and thus the less virulent marine cyanobacterial LPS molecules can be effective to inhibit TLR4 signaling. This review highlights the structural comparison of LPS molecules from marine cyanobacteria and Gram-negative bacteria. We discuss the potential use of marine cyanobacterial LPS as a TLR4 antagonist, and the effects of cyanobacterial LPS on humans and marine organisms.

The isolation and characterization of lipopolysaccharides from Microcystis aeruginosa, a prominent toxic water bloom forming cyanobacteria

Massive toxic blooms of cyanobacteria represent a major threat to water supplies worldwide, yet serious gaps exist in understanding their complex toxic effects, including the role of lipopolysaccharides (LPS). The present comparative study focused on the levels and biological activities of LPS isolated from Microcystis aeruginosa, which is one of the most globally distributed toxic species. Using hot phenol extraction, LPS was isolated from 3 laboratory cultures and 11 natural water blooms. It formed 0.2-0.7% of the original dry biomass of the cyanobacteria, based on gravimetry. Additional analyses by commercial anti-LPS ELISA were correlated with gravimetry but showed concentrations that were about 7-times lower, which indicated either impurities in isolated LPS or the poor cross-reactivity of the antibodies used. LPS isolates from M. aeruginosa were potent pyrogens in the traditional Limulus amebocyte lysate (LAL)-test, but comparison with the PyroGene test demonstrated the limited selectivity of LAL with several interferences. The determined pyrogenicity (endotoxin units, EU) ranged from very low values in laboratory cultures (less than 0.003 up to 0.008-EU per 100 pg LPS) to higher values in complex bloom samples (0.01-0.078 EU per 100 pg of LPS), which suggested the role of bloom-associated bacteria in the overall effects. Potent pro-inflammatory effects of the studied LPS from both cultures and bloom samples were observed in a highly-relevant ex vivo human blood model by studying reactive oxygen species production in phagocytes as well as increased productions of interleukin 8, IL-8, and tumor necrosis factor α, TNF-α. LPS from M. aeruginosa seem to modulate several pathways involved in the regulation of both innate immunity and specific responses. In comparison to the standard pathogenic bacterial LPS (World Health Organization Escherichia coli O113:10 endotoxin; activity 1 EU per 100 pg), the studied cyanobacterial samples had pyrogenicity potencies that were at least 12-times lower. However, the health risks associated with LPS from M. aeruginosa should not be underestimated, especially with respect to diverse biological effects observed ex vivo and in the case of massive blooms in drinking water reservoirs, where the estimated pyrogenicity can reach up to 46,000 EU per mL of water.

N-linked glycolipids by Staudinger coupling of glycosylated alkyl diazides with fatty acids

Aiming for new glycolipids with enhanced chemical stability and close structural similarity to natural cell membrane lipids for the development of a drug delivery system, we have synthesized double amide analogs of glyco-glycerolipids. The synthesis applied a Staudinger reaction based coupling of a 1,3-diazide with fatty acid chlorides. While the concept furnished the desired glucosides in reasonable yields, the corresponding lactosides formed a tetrahydropyrimidine based 1:1 coupling product instead. This unexpected coupling result likely originates from steric hindrance at the iminophosphorane intermediate and provides an interesting core structure for potentially bioactive surfactants. The assembly behavior of both glycolipid types was investigated by optical polarizing microscopy, DSC and surface tension studies.