Dihydropyriculol produced by Pyricularia oryzae inhibits the growth of Streptomyces griseus.

Dihydropyriculol is a major secondary metabolite of Pyricularia oryzae. However, the biological activity of dihydropyriculol has not been reported. Here, we showed that dihydropyriculol has inhibitory activity against Streptomyces griseus. Localization analysis of dihydropyriculol revealed that dihydropyriculol could reach to S. griseus under confrontation culture. These results suggest that dihydropyriculol can be used as a chemical weapon against S. griseus.

The evolutionary dynamics of venom toxins made by insects and other animals.

Animal venoms are recognised as unique biological systems in which to study molecular evolution. Venom use has evolved numerous times among the insects, and insects today use venom to capture prey, defend themselves from predators, or to subdue and modulate host responses during parasitism. However, little is known about most insect venom toxins or the mode and tempo by which they evolve. Here, I review the evolutionary dynamics of insect venom toxins, and argue that insects offer many opportunities to examine novel aspects of toxin evolution. The key questions addressed are: How do venomous animals evolve from non-venomous animals, and how does this path effect the composition and pharmacology of the venom? What genetic processes (gene duplication, co-option, neofunctionalisation) are most important in toxin evolution? What kinds of selection pressures are acting on toxin-encoding genes and their cognate targets in envenomated animals? The emerging evidence highlights that venom composition and pharmacology adapts quickly in response to changing selection pressures resulting from new ecological interactions, and that such evolution occurs through a stunning variety of genetic mechanisms. Insects offer many opportunities to investigate the evolutionary dynamics of venom toxins due to their evolutionary history rich in venom-related adaptations, and their quick generation time and suitability for culture in the laboratory.

[Membrane protection of intestine and liver cells in the effectiveness of minimally invasive surgery for acute peritonitis]. / Otsenka effektivnosti mini-invazivnykh vmeshatel'stv pri ostrom peritonite na osnovanii izucheniya funktsional'nogo sostoyaniya pecheni i kishechnika.

OBJECTIVE: To determine the value of membrane protective effect in intestine and liver cells for the effectiveness of minimally invasive surgery for acute peritonitis. MATERIAL AND METHODS: Patients with acute peritonitis undergoing laparoscopic (n=60) and open (n=50) surgery are analyzed. Functional characteristics of liver and bowel, disorders of homeostasis were evaluated in early postoperative period. RESULTS: Reduced negative impact of surgical aggression on the state of liver and intestine is essential to improve treatment outcomes in patients with acute peritonitis undergoing minimally invasive surgery. Fast recovery of intestine inevitably results reduced release of endotoxins while restoration of liver function is associated with rapid elimination of these toxins. These processes prevent severe intoxication and facilitate accelerated recovery. Functional restoration of liver and bowel is associated with reduced oxidative stress during laparoscopic operations. It is also important because peritonitis causes activation of free-radical processes per se. Therefore, an additional source of oxidative phenomena is extremely undesirable in these cases. CONCLUSION: Laparoscopic surgery for acute peritonitis minimizes surgical aggression and is associated with more favorable recovery of liver and bowel function. Undoubtedly, these findings should be considered to choose surgical approach in this severe category of patients.

Genome of lethal Lepiota venenata and insights into the evolution of toxin-biosynthetic genes.

BACKGROUND: Genomes of lethal Amanita and Galerina mushrooms have gradually become available in the past ten years; in contrast the other known amanitin-producing genus, Lepiota, is still vacant in this aspect. A fatal mushroom poisoning case in China has led to acquisition of fresh L. venenata fruiting bodies, based on which a draft genome was obtained through PacBio and Illumina sequencing platforms. Toxin-biosynthetic MSDIN family and Porlyl oligopeptidase B (POPB) genes were mined from the genome and used for phylogenetic and statistical studies to gain insights into the evolution of the biosynthetic pathway. RESULTS: The analysis of the genome data illustrated that only one MSDIN, named LvAMA1, exits in the genome, along with a POPB gene. No POPA homolog was identified by direct homology searching, however, one additional POP gene, named LvPOPC, was cloned and the gene structure determined. Similar to ApAMA1 in A. phalloides and GmAMA1 in G. marginata, LvAMA1 directly encodes α-amanitin. The two toxin genes were mapped to the draft genome, and the structures analyzed. Furthermore, phylogenetic and statistical analyses were conducted to study the evolution history of the POPB genes. Compared to our previous report, the phylogenetic trees unambiguously showed that a monophyletic POPB lineage clearly conflicted with the species phylogeny. In contrast, phylogeny of POPA genes resembled the species phylogeny. Topology and divergence tests showed that the POPB lineage was robust and these genes exhibited significantly shorter genetic distances than those of the house-keeping rbp2, a characteristic feature of genes with horizontal gene transfer (HGT) background. Consistently, same scenario applied to the only MSDIN, LvAMA1, in the genome. CONCLUSIONS: To the best of our knowledge, this is the first reported genome of Lepiota. The analyses of the toxin genes indicate that the cyclic peptides are synthesized through a ribosomal mechanism. The toxin genes, LvAMA1 and LvPOPB, are not in the vicinity of each other. Phylogenetic and evolutionary studies suggest that HGT is the underlining cause for the occurrence of POPB and MSDIN in Amanita, Galerina and Lepiota, which are allocated in three distantly-related families.

Comparison of microbial and transient expression (tobacco plants and plant-cell packs) for the production and purification of the anticancer mistletoe lectin viscumin.

Cancer is the leading cause of death in industrialized countries. Cancer therapy often involves monoclonal antibodies or small-molecule drugs, but carbohydrate-binding lectins such as mistletoe (Viscum album) viscumin offer a potential alternative treatment strategy. Viscumin is toxic in mammalian cells, ruling them out as an efficient production system, and it forms inclusion bodies in Escherichia coli such that purification requires complex and lengthy refolding steps. We therefore investigated the transient expression of viscumin in intact Nicotiana benthamiana plants and Nicotiana tabacum Bright Yellow 2 plant-cell packs (PCPs), comparing a full-length viscumin gene construct to separate constructs for the A and B chains. As determined by capillary electrophoresis the maximum yield of purified heterodimeric viscumin in N. benthamiana was ~7 mg/kg fresh biomass with the full-length construct. The yield was about 50% higher in PCPs but reduced 10-fold when coexpressing A and B chains as individual polypeptides. Using a single-step lactosyl-Sepharose affinity resin, we purified viscumin to ~54%. The absence of refolding steps resulted in estimated cost savings of more than 80% when transient expression in tobacco was compared with E. coli. Furthermore, the plant-derived product was ~3-fold more toxic than the bacterially produced counterpart. We conclude that plants offer a suitable alternative for the production of complex biopharmaceutical proteins that are toxic to mammalian cells and that form inclusion bodies in bacteria.

Molecular physiology of chemical defenses in a poison frog.

Poison frogs sequester small molecule lipophilic alkaloids from their diet of leaf litter arthropods for use as chemical defenses against predation. Although the dietary acquisition of chemical defenses in poison frogs is well documented, the physiological mechanisms of alkaloid sequestration has not been investigated. Here, we used RNA sequencing and proteomics to determine how alkaloids impact mRNA or protein abundance in the little devil frog (Oophaga sylvatica), and compared wild-caught chemically defended frogs with laboratory frogs raised on an alkaloid-free diet. To understand how poison frogs move alkaloids from their diet to their skin granular glands, we focused on measuring gene expression in the intestines, skin and liver. Across these tissues, we found many differentially expressed transcripts involved in small molecule transport and metabolism, as well as sodium channels and other ion pumps. We then used proteomic approaches to quantify plasma proteins, where we found several protein abundance differences between wild and laboratory frogs, including the amphibian neurotoxin binding protein saxiphilin. Finally, because many blood proteins are synthesized in the liver, we used thermal proteome profiling as an untargeted screen for soluble proteins that bind the alkaloid decahydroquinoline. Using this approach, we identified several candidate proteins that interact with this alkaloid, including saxiphilin. These transcript and protein abundance patterns suggest that the presence of alkaloids influences frog physiology and that small molecule transport proteins may be involved in toxin bioaccumulation in dendrobatid poison frogs.

Worker Defensive Behavior Associated with Toxins in the Neotropical Termite Neocapritermes braziliensis (Blattaria, Isoptera, Termitidae, Termitinae).

Termite societies are abundant in the tropics, and are therefore exposed to multiple enemies and predators, especially during foraging activity. Soldiers constitute a specialized defensive caste, although workers also participate in this process, and even display suicidal behavior, which is the case with the species Neocapritermes braziliensis. Here we describe the morphology, mechanisms of action, and proteomics of the salivary weapon in workers of this species, which due to the autothysis of the salivary glands causes their body rupture, in turn releasing a defensive secretion, observed during aggressiveness bioassays. Salivary glands are paired, composed of two translucent reservoirs, ducts and a set of multicellular acini. Histological and ultrastructural techniques showed that acini are composed of two types of central cells, and small parietal cells located in the acinar periphery. Type I central cells were abundant and filled with a large amount of secretion, while type II central cells were scarce and presented smaller secretion. Parietal cells were often paired and devoid of secretion. The gel-free proteomic approach (shotgun) followed by mass spectrometry revealed 235 proteins in the defensive secretion, which were classified into functional groups: (i) toxins and defensins, (ii) folding/conformation and post-translational modifications, (iii) salivary gland detoxification, (iv) housekeeping proteins and (v) uncharacterized and hypothetical proteins. We highlight the occurrence of neurotoxins previously identified in arachnid venoms, which are novelties for termite biology, and contribute to the knowledge regarding the defense strategies developed by termite species from the Neotropical region.

Molecular characterization and toxin quantification of Microcystis panniformis: A microcystin producer in Lake Taihu, China.

Microcystis panniformis is a bloom forming species with flat panniform-like colonies. This species was recently found in Lake Taihu, China. To specifically characterize M. panniformis based on isolated strains, morphological examination on colonial transition and genetic examination are needed. Three M. panniformis strains isolated from a water bloom sample in Lake Taihu were characterized by molecular analysis and toxin quantification. Phylogenetic analysis based on both 16S rRNA gene and internal transcribed spacer (ITS) between 16S and 23S rRNA genes were performed and compared to facilitate easy identification of the species. Relatively high similarities (98%-99%) were shown in 16S rDNA sequences between the strains of M. panniformis and those of other Microcystis species, whereas the similarities for ITS sequences were 88%-95%. In the phylogenetic tree based on the 16S rDNA sequences, the M. panniformis and M. aeruginosa strains were intermixed together with no clear division, whereas all of the M. panniformis strains were clustered together in a single clade based on the ITS sequences based phylogenyetic tree. The mcyE gene was detected in all three strains, and microcystin was determined by high-performance liquid chromatography. The molecular detection and toxin production of M. panniformis strains are of great significance for the environmental risk assessment of Microcystis blooms.

Comparative genomics of Cylindrospermopsis raciborskii strains with differential toxicities.

BACKGROUND: Cylindrospermopsis raciborskii is an invasive filamentous freshwater cyanobacterium, some strains of which produce toxins. Sporadic toxicity may be the result of gene deletion events, the horizontal transfer of toxin biosynthesis gene clusters, or other genomic variables, yet the evolutionary drivers for cyanotoxin production remain a mystery. Through examining the genomes of toxic and non-toxic strains of C. raciborskii, we hoped to gain a better understanding of the degree of similarity between these strains of common geographical origin, and what the primary differences between these strains might be. Additionally, we hoped to ascertain why some cyanobacteria possess the cylindrospermopsin biosynthesis (cyr) gene cluster and produce toxin, while others do not. It has been hypothesised that toxicity or lack thereof might confer a selective advantage to cyanobacteria under certain environmental conditions. RESULTS: In order to examine the fundamental differences between toxic and non-toxic C. raciborskii strains, we sequenced the genomes of two closely related isolates, CS-506 (CYN+) and CS-509 (CYN-) sourced from different lakes in tropical Queensland, Australia. These genomes were then compared to a third (reference) genome from C. raciborskii CS-505 (CYN+). Genome sizes were similar across all three strains and their G + C contents were almost identical. At least 2,767 genes were shared among all three strains, including the taxonomically important rpoc1, ssuRNA, lsuRNA, cpcA, cpcB, nifB and nifH, which exhibited 99.8-100% nucleotide identity. Strains CS-506 and CS-509 contained at least 176 and 101 strain-specific (or non-homologous) genes, respectively, most of which were associated with DNA repair and modification, nutrient uptake and transport, or adaptive measures such as osmoregulation. However, the only significant genetic difference observed between the two strains was the presence or absence of the cylindrospermopsin biosynthesis gene cluster. Interestingly, we also identified a cryptic secondary metabolite gene cluster in strain CS-509 (CYN-) and a second cryptic cluster common to CS-509 and the reference strain, CS-505 (CYN+). CONCLUSIONS: Our results confirm that the most important factor contributing to toxicity in C. raciborskii is the presence or absence of the cyr gene cluster. We did not identify any other distally encoded genes or gene clusters that correlate with CYN production. The fact that the additional genomic differences between toxic and non-toxic strains were primarily associated with stress and adaptation genes suggests that CYN production may be linked to these physiological processes.

Hybrid biosynthesis of roseobacticides from algal and bacterial precursor molecules.

Roseobacticides regulate the symbiotic relationship between a marine bacterium (Phaeobacter inhibens) and a marine microalga (Emiliania huxleyi). This relationship can be mutualistic, when the algal host provides food for the bacteria and the bacteria produce growth hormones and antibiotics for the algae, or parasitic, when the algae senesce and release p-coumaric acid. The released p-coumaric acid causes the bacteria to synthesize roseobacticides, which are nM-µM toxins for the algae. We examined the biosynthesis of roseobacticides and report that all roseobacticide precursors play critical roles during the mutualist phase of the symbiosis. Roseobacticides are biosynthesized from the algal growth promoter, the major food molecule provided by the algal cells, and the algal senescence signal that initiates the mutualist-to-parasite switch. Thus, molecules that are beneficial during mutualism are diverted to the synthesis of toxins during parasitism. A plausible mechanism for assembling roseobacticides from these molecules is proposed.

RNAi Mediated curcin precursor gene silencing in Jatropha (Jatropha curcas L.).

Curcin, a type I ribosomal inhibiting protein-RIP, encoded by curcin precursor gene, is a phytotoxin present in Jatropha (Jatropha curcas L.). Here, we report designing of RNAi construct for the curcin precursor gene and further its genetic transformation of Jatropha to reduce its transcript expression. Curcin precursor gene was first cloned from Jatropha strain DARL-2 and part of the gene sequence was cloned in sense and antisense orientation separated by an intron sequence in plant expression binary vector pRI101 AN. The construction of the RNAi vector was confirmed by double digestion and nucleotide sequencing. The vector was then mobilized into Agrobacterium tumefaciens strain GV 3101 and used for tissue culture independent in planta transformation protocol optimized for Jatropha. Germinating seeds were injured with a needle before infection with Agrobacterium and then transferred to sterilized sand medium. The seedlings were grown for 90 days and genomic DNA was isolated from leaves for transgenic confirmation based on real time PCR with NPT II specific dual labeled probe. Result of the transgenic confirmation analysis revealed presence of the gene silencing construct in ten out of 30 tested seedlings. Further, quantitative transcript expression analysis of the curcin precursor gene revealed reduction in the transcript abundance by more than 98% to undetectable level. The transgenic plants are being grown in containment for further studies on reduction in curcin protein content in Jatropha seeds.

Osmotic stress triggers toxin production by the dinoflagellate Karenia brevis.

With the increase in frequency of harmful algal blooms (HABs) worldwide, a better understanding of the mechanisms that influence toxin production is needed. Karenia brevis, the major HAB dinoflagellate in the Gulf of Mexico, produces potent neurotoxins, known as brevetoxins. Human health is directly impacted by blooms of K. brevis through consumption of shellfish contaminated by accumulated brevetoxins (neurotoxic shellfish poisoning) or from aerosolized brevetoxins in sea spray (reduced respiratory function); however, the reason for brevetoxin production has remained a mystery. Here we show that brevetoxin production increased dramatically in response to osmotic stress in three of the four K. brevis clones examined. By rapidly changing salinity to simulate a shift from oceanic conditions to a decreased salinity typical of coastal conditions, brevetoxin production was triggered. As a result, brevetoxin cell quota increased by >14-fold, while growth rate remained unchanged. Live images of K. brevis cells were also examined to assess changes in cell volume. In the K. brevis Wilson clone, cells responded quickly to hypoosmotic stress by increasing their brevetoxin cell quota from ∼10 to 160 pg of brevetoxin per cell, while cell volume remained stable. In contrast, the K. brevis SP1 clone, which has a consistently low brevetoxin cell quota (<1 pg per cell), was unable to balance the hypoosmotic stress, and although brevetoxin production remained low, average cell volume increased. Our findings close a critical gap in knowledge regarding mechanisms for toxin production in K. brevis by providing an explanation for toxin production in this harmful dinoflagellate.

Rotaviral enterotoxin nonstructural protein 4 targets mitochondria for activation of apoptosis during infection.

Viruses have evolved to encode multifunctional proteins to control the intricate cellular signaling pathways by using very few viral proteins. Rotavirus is known to express six nonstructural and six structural proteins. Among them, NSP4 is the enterotoxin, known to disrupt cellular Ca(2+) homeostasis by translocating to endoplasmic reticulum. In this study, we have observed translocation of NSP4 to mitochondria resulting in dissipation of mitochondrial membrane potential during virus infection and NSP4 overexpression. Furthermore, transfection of the N- and C-terminal truncated NSP4 mutants followed by analyzing NSP4 localization by immunofluorescence microscopy identified the 61-83-amino acid region as the shortest mitochondrial targeting signal. NSP4 exerts its proapoptotic effect by interacting with mitochondrial proteins adenine nucleotide translocator and voltage-dependent anion channel, resulting in dissipation of mitochondrial potential, release of cytochrome c from mitochondria, and caspase activation. During early infection, apoptosis activation by NSP4 was inhibited by the activation of cellular survival pathways (PI3K/AKT), because PI3K inhibitor results in early induction of apoptosis. However, in the presence of both PI3K inhibitor and NSP4 siRNA, apoptosis was delayed suggesting that the early apoptotic signal is initiated by NSP4 expression. This proapoptotic function of NSP4 is balanced by another virus-encoded protein, NSP1, which is implicated in PI3K/AKT activation because overexpression of both NSP4 and NSP1 in cells resulted in reduced apoptosis compared with only NSP4-expressing cells. Overall, this study reports on the mechanism by which enterotoxin NSP4 exerts cytotoxicity and the mechanism by which virus counteracts it at the early stage for efficient infection.

Dozens of toxin-related genes are expressed in a nontoxic strain of the dinoflagellate Heterocapsa circularisquama.

The dinoflagellate Heterocapsa circularisquama is lethal to a variety of marine organisms, in particular, commercially important farmed bivalves. Unlike most dinoflagellate toxins, which are polyketides, the only described toxin from H. circularisquama (H2-a) is a porphyrin derivative that functions in light. It is unknown whether H2-a is produced specifically for its lytic properties. We searched for toxin-related genes in the transcriptome of a nontoxic strain of H. circularisquama, and surprisingly found the richest set of toxin-related genes yet described in dinoflagellates. There are 87 distinct expressed sequence tag contigs that encode polyketide synthases and nonribosomal peptide synthases, as well as 8 contigs that are involved in porphyrin biosynthesis. Phylogenomic analysis shows that many toxin-related genes are widely distributed among dinoflagellates. Our data likely indicate a variety of unknown metabolic functions for the toxin-related genes in H. circularisquama because they were identified in a nontoxic strain raised in unialgal culture.

Production and isolation of azaspiracid-1 and -2 from Azadinium spinosum culture in pilot scale photobioreactors.

Azaspiracid (AZA) poisoning has been reported following consumption of contaminated shellfish, and is of human health concern. Hence, it is important to have sustainable amounts of the causative toxins available for toxicological studies and for instrument calibration in monitoring programs, without having to rely on natural toxin events. Continuous pilot scale culturing was carried out to evaluate the feasibility of AZA production using Azadinium spinosum cultures. Algae were harvested using tangential flow filtration or continuous centrifugation. AZAs were extracted using solid phase extraction (SPE) procedures, and subsequently purified. When coupling two stirred photobioreactors in series, cell concentrations reached 190,000 and 210,000 cell · mL(-1) at steady state in bioreactors 1 and 2, respectively. The AZA cell quota decreased as the dilution rate increased from 0.15 to 0.3 day(-1), with optimum toxin production at 0.25 day(-1). After optimization, SPE procedures allowed for the recovery of 79 ± 9% of AZAs. The preparative isolation procedure previously developed for shellfish was optimized for algal extracts, such that only four steps were necessary to obtain purified AZA1 and -2. A purification efficiency of more than 70% was achieved, and isolation from 1200 L of culture yielded 9.3 mg of AZA1 and 2.2 mg of AZA2 of >95% purity. This work demonstrated the feasibility of sustainably producing AZA1 and -2 from A. spinosum cultures.

Evolutionary limits ameliorate the negative impact of an invasive plant.

Invasive species can quickly transform biological communities due to their high abundance and strong impacts on native species, in part because they can be released from the ecological forces that limit native populations. However, little is known about the long-term dynamics of invasions; do invaders maintain their dominant status over long time spans, or do new ecological and evolutionary forces eventually develop to limit their populations? Alliaria petiolata is a Eurasian species that aggressively invades North American forest understories, in part due to the production of toxic phytochemicals. Here we document a marked decline in its phytotoxin production and a consequent decline in their impact on three native species, across a 50+ year chronosequence of Alliaria petiolata invasion. Genetic evidence suggests that these patterns result from natural selection for decreased phytotoxin production rather than founder effects during introduction and spread. These patterns are consistent with the finding of slowing A. petiolata population growth and rebounding native species abundance across a separate chronosequence in Illinois, U.S. These results suggest that this invader is developing evolutionary limits in its introduced range and highlight the importance of understanding the long-term processes that shape species invasions and their impacts.

Short hairpin RNA-mediated silencing of bovine rotavirus NSP4 gene prevents diarrhoea in suckling mice.

While RNA interference (RNAi) has been widely used to study rotavirus gene function in vitro, the potential therapeutic role for RNAi in vivo has not been explored. To this end, we constructed two recombinant lentiviral vectors containing short hairpin RNA (shRNA) against non-structural protein-4 (NSP4) of bovine rotavirus (BRV), RNAi-351 and RNAi-492. RNAi-351 and RNAi-492 strongly suppressed the transient expression of a FLAG-tagged NSP4 fusion protein in 293T cells. In BRV-susceptible MA104 cells, RNAi-492 more potently silenced NSP4 mRNA than RNAi-351 and combination of the two shRNAs almost completely silenced viral NSP4 gene expression. While 100% of suckling mice exposed to BRV and control shRNA developed severe diarrhoea, no suckling mice exposed to BRV in the presence of RNAi-492 or a combination of RNAi-492/RNAi-351 developed severe diarrhoea, and only 20 and 3.3% developed mild diarrhoea, respectively. In addition, RNAi-492 and RNAi-351 markedly abrogated rotaviral replication in MA104 cells and significantly inhibited BRV replication in mouse pups. These results indicated that shRNAs silencing NSP4 gene had substantial antiviral properties and inhibited replication of BRV in a sequence-specific manner that may have clinical application.

Pathogenic fungus harbours endosymbiotic bacteria for toxin production.

A number of plant pathogenic fungi belonging to the genus Rhizopus are infamous for causing rice seedling blight. This plant disease is typically initiated by an abnormal swelling of the seedling roots without any sign of infection by the pathogen. This characteristic symptom is in fact caused by the macrocyclic polyketide metabolite rhizoxin that has been isolated from cultures of Rhizopus sp.. The phytotoxin exerts its destructive effect by binding to rice beta-tubulin, which results in inhibition of mitosis and cell cycle arrest. Owing to its remarkably strong antimitotic activity in most eukaryotic cells, including various human cancer cell lines, rhizoxin has attracted considerable interest as a potential antitumour drug. Here we show that rhizoxin is not biosynthesized by the fungus itself, but by endosymbiotic, that is, intracellular living, bacteria of the genus Burkholderia. Our unexpected findings unveil a remarkably complex symbiotic-pathogenic relationship that extends the fungus-plant interaction to a third, bacterial, key-player, and opens new perspectives for pest control.

Tick paralysis in Australia caused by Ixodes holocyclus Neumann.

Ticks are obligate haematophagous ectoparasites of various animals, including humans, and are abundant in temperate and tropical zones around the world. They are the most important vectors for the pathogens causing disease in livestock and second only to mosquitoes as vectors of pathogens causing human disease. Ticks are formidable arachnids, capable of not only transmitting the pathogens involved in some infectious diseases but also of inducing allergies and causing toxicoses and paralysis, with possible fatal outcomes for the host. This review focuses on tick paralysis, the role of the Australian paralysis tick Ixodes holocyclus, and the role of toxin molecules from this species in causing paralysis in the host.

[Effects of some membrane lipids on the hemolysis induced by hemolytic toxin from Karenia mikimotoi].

OBJECTIVE: To explore the effects of some membrane lipids on the hemolysis induced by hemolytic toxin from Karenia mikimotoi. METHODS: Effects of exogenous membrane lipids such as lecithin, sphingomyelin, L-alpha-phosphatidic acid,cholesterol and gangliosides on the hemolysis induced by the hemolytic toxin were observed. The sensitivities of some erythrocytes from different animals such as rabbit, rat and fish to the hemolytic toxin were evaluated. The total gangliosides in different erythrocytes membrane were detected by colorimetry. RESULTS: Only gangliosides significantly inhibited the hemolysis of the hemolytic toxin from K. mikimotoi (P <0.05). Hemolytic percentages decreased to 16.05% after 10 min addition of ganglioside, while those of control were 35.65%. The rabbit red blood cell was the most sensitive to the hemolytic toxin. The hemolytic percentages of rabbit erythrocyte were higher than those of rat (P < 0.05) and fish (P < 0.01). The amounts of lipid-bind sialic acid (LBSA) on frozen dried membrane of rabbit were 672.08 microg/g,and were higher than those of rat (585.97 microg/g) (P < 0.05) and that of fish (431.52 microg/g) (P < 0.01). CONCLUSION: Exogenous gangliosides could have a potent inhibition on the hemolysis induced by hemolytic toxin from K. mikimotoi. There was a significant correlation between the sensitivities of different erythrocytes to the hemolytic toxin and the amount of ganglioside on different erythrocytes membrane.