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Drion G. Boucias - One of the best experts on this subject based on the ideXlab platform.
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a lack of parasitic reduction in the obligate parasitic green alga Helicosporidium
PLOS Genetics, 2014Co-Authors: Jean-françois Pombert, Drion G. Boucias, Nicolas A Blouin, Christopher E Lane, Patrick J. KeelingAbstract:The evolution of an obligate parasitic lifestyle is often associated with genomic reduction, in particular with the loss of functions associated with increasing host-dependence. This is evident in many parasites, but perhaps the most extreme transitions are from free-living autotrophic algae to obligate parasites. The best-known examples of this are the apicomplexans such as Plasmodium, which evolved from algae with red secondary plastids. However, an analogous transition also took place independently in the Helicosporidia, where an obligate parasite of animals with an intracellular infection mechanism evolved from algae with green primary plastids. We characterised the nuclear genome of Helicosporidium to compare its transition to parasitism with that of apicomplexans. The Helicosporidium genome is small and compact, even by comparison with the relatively small genomes of the closely related green algae Chlorella and Coccomyxa, but at the functional level we find almost no evidence for reduction. Nearly all ancestral metabolic functions are retained, with the single major exception of photosynthesis, and even here reduction is not complete. The great majority of genes for light-harvesting complexes, photosystems, and pigment biosynthesis have been lost, but those for other photosynthesis-related functions, such as Calvin cycle, are retained. Rather than loss of whole function categories, the predominant reductive force in the Helicosporidium genome is a contraction of gene family complexity, but even here most losses affect families associated with genome maintenance and expression, not functions associated with host-dependence. Other gene families appear to have expanded in response to parasitism, in particular chitinases, including those predicted to digest the chitinous barriers of the insect host or remodel the cell wall of Helicosporidium. Overall, the Helicosporidium genome presents a fascinating picture of the early stages of a transition from free-living autotroph to parasitic heterotroph where host-independence has been unexpectedly preserved.
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host age and pathogen dosage impact cyst morphogenesis in the invertebrate pathogenic alga Helicosporidium sp chlorophyta trebouxiophyceae
Journal of Invertebrate Pathology, 2009Co-Authors: John S S Denton, Verenaulrike Lietze, Drion G. BouciasAbstract:Helicosporidium sp. is a pathogenic alga that replicates in the hemolymph of various invertebrate hosts. Morphogenesis of the infectious life stage, the cyst, occurs in the infected host, but to date cannot be induced in vitro. Using larvae of the heterologous host Helicoverpa zea, we examined potential factors influencing pathogenicity and in vivo cyst production of the alga and the impact of infection on host survival. Factors tested were cyst dosage administered per os (ranging from 10(2) to 10(5) cysts per larva) and host age at exposure (third, fourth, and fifth larval instar). Cyst production occurred between 7 and 13days after treatment, regardless of host age at treatment. Increasing dosage increased both percent infection and mortality, but cyst production did not track the total infection response. Increasing host age at exposure mitigated dosage effects on infection and mortality and also elevated cyst production in later-treated larvae. Only the highest dosage produced a significant decrease in the overall time to death. Moderate cyst dosages and later host ages were most effective at regenerating Helicosporidium cysts.
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development of the insect pathogenic alga Helicosporidium
Journal of Eukaryotic Microbiology, 2006Co-Authors: Verenaulrike Blaskelietze, James J Becnel, John S S Denton, Alexandra M Shapiro, Michael Botts, Drion G. BouciasAbstract:This study examined the morphogenesis and replication dynamics of the different life stages (cysts, filamentous cells, vegetative cells) of Helicosporidium sp., a non-photosynthetic, entomopathogenic alga. The isolate (SjHe) used originated from an in- fected black fly larva. Filamentous cell transformation into vegetative cells and autosporulation during vegetative cell replication were observed under controlled in vitro conditions. The transformation process was initiated by a partial swelling of the filamentous cell along with the reorganization of the nuclear material. Two subsequent nuclear and cell divisions resulted in the release of 4 rod-shaped daughter cells, which divided into oval to spherical vegetative cells. These underwent several cycles of autosporogenic cell division. Multiple- passaged vegetative cell cultures formed non-motile, adherent cell clusters (palmelloid colonies). Vegetative replication dynamics were also observed in 2 experimental noctuid hosts, Spodoptera exigua and Helicoverpa zea. The average density of helicosporidial cells produced per microliter hemolymph exceeded cell concentrations obtained in vitro by 15- and 46-fold in S. exigua and H. zea, respec- tively. Cyst morphogenesis was only observed in the hemolymph, whereas no cysts differentiated at various in vitro conditions.
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infectivity of two isolates of Helicosporidium spp chlorophyta trebouxiophyceae in heterologous host insects
Florida Entomologist, 2005Co-Authors: Tracy Conklin, James J Becnel, Verenaulrike Blaskelietze, Drion G. BouciasAbstract:Abstract Members of the genus Helicosporidium are the first described algal insect pathogens. They have a close affinity to the non-photosynthetic algae of the genus Prototheca, and have a wide host range, infecting many species of aquatic and terrestrial insects. In this study the infectivity of two Helicosporidium spp. isolates, originating from a black fly (SjHe) and an aquatic weevil (CsHe), was tested against a weevil Diaprepes abbreviatus (L.) and three mosquito species Anopheles quadrimaculatus Say, Culex quinquefasciatus Say, and Aedes aegypti (L.). The weevil constitutes a new experimental host record for helicosporidia. The CsHe isolate was more virulent than the SjHe isolate in D. abbreviatus. Anopheles quadrimaculatus was the most susceptible mosquito species measured by infection rate and mortality. The infectivity and virulence of SjHe and CsHe isolates did not differ in any of the mosquito species.
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pathogenesis of Helicosporidium sp chlorophyta trebouxiophyceae in susceptible noctuid larvae
Journal of Invertebrate Pathology, 2005Co-Authors: Verenaulrike Blaskelietze, Drion G. BouciasAbstract:Helicosporidium sp. is a unique, achlorophyllous green alga that has been reported to infect various insect orders, including Lepidoptera, Diptera, and Coleoptera. The infectious cyst stage is ingested by the host, ruptures in the midgut lumen, and releases a Wlamentous cell. Histopathological examinations using larvae of a susceptible noctuid host, Spodoptera exigua, showed both cysts and Wlamentous cells aYliated with the microvillar lining of the midgut epithelium. A considerable proportion of the ingested cysts (22–39%) were recovered in feces collected 24 h after ingestion. A small number of Wlamentous cells passed the midgut epithelium and entered the hemocoel within 4–24 h after cyst ingestion. After 48 h, vegetative cell stages were detected in the hemolymph, followed by a 4- to 5-day period of increasing multiplication. Cyst diVerentiation in the colonized hemolymph began 6–7 days after the treatment.
Patrick J. Keeling - One of the best experts on this subject based on the ideXlab platform.
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A Lack of Parasitic Reduction in the Obligate Parasitic Green Alga Helicosporidium
2016Co-Authors: Nicolas Achille Blouin, Chris Lane, Drion Boucias, Patrick J. KeelingAbstract:The evolution of an obligate parasitic lifestyle is often associated with genomic reduction, in particular with the loss of functions associated with increasing host-dependence. This is evident in many parasites, but perhaps the most extreme transitions are from free-living autotrophic algae to obligate parasites. The best-known examples of this are the apicomplexans such as Plasmodium, which evolved from algae with red secondary plastids. However, an analogous transition also took place independently in the Helicosporidia, where an obligate parasite of animals with an intracellular infection mechanism evolved from algae with green primary plastids. We characterised the nuclear genome of Helicosporidium to compare its transition to parasitism with that of apicomplexans. The Helicosporidium genome is small and compact, even by comparison with the relatively small genomes of the closely related green algae Chlorella and Coccomyxa, but at the functional level we find almost no evidence for reduction. Nearly all ancestral metabolic functions are retained, with the single major exception of photosynthesis, and even here reduction is not complete. The great majority of genes for light-harvesting complexes, photosystems, and pigment biosynthesis have been lost, but those for other photosynthesis-related functions, such as Calvin cycle, are retained. Rather than loss of whole function categories, the predominant reductive force in the Helicosporidium genome is a contraction of gene family complexity, but even here most losses affect families associated with genome maintenance and expression, not functions associated with host-dependence
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a lack of parasitic reduction in the obligate parasitic green alga Helicosporidium
PLOS Genetics, 2014Co-Authors: Jean-françois Pombert, Drion G. Boucias, Nicolas A Blouin, Christopher E Lane, Patrick J. KeelingAbstract:The evolution of an obligate parasitic lifestyle is often associated with genomic reduction, in particular with the loss of functions associated with increasing host-dependence. This is evident in many parasites, but perhaps the most extreme transitions are from free-living autotrophic algae to obligate parasites. The best-known examples of this are the apicomplexans such as Plasmodium, which evolved from algae with red secondary plastids. However, an analogous transition also took place independently in the Helicosporidia, where an obligate parasite of animals with an intracellular infection mechanism evolved from algae with green primary plastids. We characterised the nuclear genome of Helicosporidium to compare its transition to parasitism with that of apicomplexans. The Helicosporidium genome is small and compact, even by comparison with the relatively small genomes of the closely related green algae Chlorella and Coccomyxa, but at the functional level we find almost no evidence for reduction. Nearly all ancestral metabolic functions are retained, with the single major exception of photosynthesis, and even here reduction is not complete. The great majority of genes for light-harvesting complexes, photosystems, and pigment biosynthesis have been lost, but those for other photosynthesis-related functions, such as Calvin cycle, are retained. Rather than loss of whole function categories, the predominant reductive force in the Helicosporidium genome is a contraction of gene family complexity, but even here most losses affect families associated with genome maintenance and expression, not functions associated with host-dependence. Other gene families appear to have expanded in response to parasitism, in particular chitinases, including those predicted to digest the chitinous barriers of the insect host or remodel the cell wall of Helicosporidium. Overall, the Helicosporidium genome presents a fascinating picture of the early stages of a transition from free-living autotroph to parasitic heterotroph where host-independence has been unexpectedly preserved.
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Conserved gene clusters between the Helicosporidium and Chlorella genomes.
2014Co-Authors: Jean-françois Pombert, Nicolas Achille Blouin, Chris Lane, Drion Boucias, Patrick J. KeelingAbstract:Only syntenic clusters from the ten largest Helicosporidium contigs are shown. Genes from Helicosporidium are shown on top; Chlorella genes are shown below. Locus_tag prefixes (Helicosporidium, H632_; Chlorella, CHLNDRAFT_) were omitted for clarity (see Data S2 for PFAM product names). The corresponding contigs (Helicosporidium) or scaffolds (Chlorella) are indicated on the left; in the Chlorella scaffolds, adjacent genes are not always labelled incrementally. Genes that are absent from the other genome are colored in light gray. Genes that have been relocated are shown in dark gray. Partial genes are indicated by double daggers (‡). In Helicosporidium the c9p0 gene, indicated by an asterisk, is predicted as a single entity encompassing the Chlorella 32522 and 36846 genes.
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Summary statistics for predicted chitinase proteins in Helicosporidium genome.
2014Co-Authors: Jean-françois Pombert, Nicolas Achille Blouin, Chris Lane, Drion Boucias, Patrick J. KeelingAbstract:Summary statistics for predicted chitinase proteins in Helicosporidium genome.
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Evolutionary gene network analysis showing functional contractions in Helicosporidium relative to Chlorella and Coccomyxa.
2014Co-Authors: Jean-françois Pombert, Nicolas Achille Blouin, Chris Lane, Drion Boucias, Patrick J. KeelingAbstract:The connected components depicted here represent a small portion of the genes involved in each of these functional categories. Helicosporidium, Coccomyxa and Chlorella are represented by orange, blue and green nodes, respectively. Interactions between the different components are denoted by gray lines connecting the nodes.
Mustafa Yaman - One of the best experts on this subject based on the ideXlab platform.
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Distribution and occurrence of the insect pathogenic alga Helicosporidium sp. (Chlorophyta: Trebouxiophyceae) in the predator beetle Rhizophagus grandis G: yll. (Coleoptera: Rhizophagidae)-rearing laboratories.
Folia microbiologica, 2011Co-Authors: Mustafa Yaman, Onur Tosun, Cicek Aydin, Ömer ErtürkAbstract:The distribution and occurrence of the insect pathogenic algae Helicosporidium sp. (Chlorophyta: Trebouxiophyceae) in the predator beetle Rhizophagus grandis (Coleoptera: Rhizophagidae)-rearing laboratories were studied and reported here for the first time. The insect pathogenic alga Helicosporidium sp. infection was observed in all R. grandis-rearing laboratories. The infection rate reached more than 20% which is significant among the samples in some R. grandis-rearing laboratories. The infection rates of the examined beetles showed noticeable differences between localities and years. There was no significant difference in the infection levels of male and female beetles. These results showed that Helicosporidium sp. is one of the factors that decrease efficiency of the R. grandis-rearing laboratories.
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First record of the insect pathogenic alga Helicosporidium sp. (Chlorophyta: Trebouxiophyceae) infection in larvae and pupae of Rhizophagus grandis Gyll. (Coleoptera, Rhizophaginae) from Turkey
Journal of invertebrate pathology, 2009Co-Authors: Mustafa Yaman, Renate Radek, Onur Tosun, Cicek Aydin, Ömer ErtürkAbstract:The predator beetle Rhizophagus grandis Gyll. (Coleoptera, Rhizophaginae) is one of the most important biological control agents, mass-bred and used to suppress populations of an important pest: the great spruce bark beetle, Dendroctonus micans. The achlorophyllous alga Helicosporidium sp. was first discovered in the pest. Later it was also found in the predator, but only in the adults. In this study, the pathogenic alga Helicosporidium sp. was discovered in larvae and early pupae of R. grandis for the first time. The morphological characteristics of the pathogenic alga were revealed by light and electron microscopy. Infection rates of Helicosporidium sp. in the larvae and pupae of R. grandis were 23.5% and 6.25%, respectively.
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first results on distribution and occurrence of the insect pathogenic alga Helicosporidium sp chlorophyta trebouxiophyceae in the populations of the great spruce bark beetle dendroctonus micans kugelann coleoptera curculionidae scolytinae
2008Co-Authors: Mustafa YamanAbstract:This is the first study on the distribution and occurrence of Helicosporidium sp. in the populations of the great spruce bark beetle Dendroctonus micans (Coleoptera: Curculionidae, Scolytinae) from different localities. Two hundred and eight of 2300 examined beetles were infected by Helicosporidium sp. In total infection rate was 9.04%. The infection reached 71.7%. The prevalence of Helicosporidium sp. infections in the examined beetles considerably differed between localities and years. The male beetles were infected to higher degree than female beetles in all investigated localities. These results revealed that Helicosporidium sp. is distributed by the infected host adults in the host populations among the localities during the flying period.
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Infection of the predator beetle Rhizophagus grandis Gyll. (Coleoptera, Rhizophagidae) with the insect pathogenic alga Helicosporidium sp. (Chlorophyta: Trebouxiophyceae)
Biological Control, 2007Co-Authors: Mustafa Yaman, Renate RadekAbstract:Abstract This report is the first description of a pathogen or parasite in the predator beetle Rhizophagus grandis (Coleoptera, Rhizophagidae) and the first report of a naturally infected beetle from the family Rhizophagidae (Coleoptera). The hemolymph of the beetle was infected by the parasitic green alga Helicosporidium . The typical cysts of Helicosporidium contain three ovoid cells and one helical, filamentous cell. The morphological characteristics are revealed by light and electron microscopy. In total, 6.8% of the beetles were infected by the parasite. The infection was observed at two of five Turkish laboratories which rear Rhizophagus grandis . The infection was 23.6% at the laboratories in Artvin and 9.8% in Ordu.
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Helicosporidium infection of the great european spruce bark beetle dendroctonus micans coleoptera scolytidae
European Journal of Protistology, 2005Co-Authors: Mustafa Yaman, Renate RadekAbstract:Abstract An infection of the great European spruce bark beetle Dendroctonus micans (from Turkey) by the parasitic green alga Helicosporidium is described. This is the first time that Helicosporidium has been found to infect a bark beetle (Scolytidae) and the first time that a naturally infected beetle has been reported for the Eurasian continent. The typical cysts of Helicosporidium contain three ovoid cells and one helical, filamentous cell. The morphological characteristics are revealed by light and electron microscopy. Distinct electron-dense inclusions with a peculiar ultrastructure may represent pyrenoids. Since D. micans is an important pest, the discovery of a natural pathogen may offer a chance for biological control.
Renate Radek - One of the best experts on this subject based on the ideXlab platform.
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First record of the insect pathogenic alga Helicosporidium sp. (Chlorophyta: Trebouxiophyceae) infection in larvae and pupae of Rhizophagus grandis Gyll. (Coleoptera, Rhizophaginae) from Turkey
Journal of invertebrate pathology, 2009Co-Authors: Mustafa Yaman, Renate Radek, Onur Tosun, Cicek Aydin, Ömer ErtürkAbstract:The predator beetle Rhizophagus grandis Gyll. (Coleoptera, Rhizophaginae) is one of the most important biological control agents, mass-bred and used to suppress populations of an important pest: the great spruce bark beetle, Dendroctonus micans. The achlorophyllous alga Helicosporidium sp. was first discovered in the pest. Later it was also found in the predator, but only in the adults. In this study, the pathogenic alga Helicosporidium sp. was discovered in larvae and early pupae of R. grandis for the first time. The morphological characteristics of the pathogenic alga were revealed by light and electron microscopy. Infection rates of Helicosporidium sp. in the larvae and pupae of R. grandis were 23.5% and 6.25%, respectively.
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Infection of the predator beetle Rhizophagus grandis Gyll. (Coleoptera, Rhizophagidae) with the insect pathogenic alga Helicosporidium sp. (Chlorophyta: Trebouxiophyceae)
Biological Control, 2007Co-Authors: Mustafa Yaman, Renate RadekAbstract:Abstract This report is the first description of a pathogen or parasite in the predator beetle Rhizophagus grandis (Coleoptera, Rhizophagidae) and the first report of a naturally infected beetle from the family Rhizophagidae (Coleoptera). The hemolymph of the beetle was infected by the parasitic green alga Helicosporidium . The typical cysts of Helicosporidium contain three ovoid cells and one helical, filamentous cell. The morphological characteristics are revealed by light and electron microscopy. In total, 6.8% of the beetles were infected by the parasite. The infection was observed at two of five Turkish laboratories which rear Rhizophagus grandis . The infection was 23.6% at the laboratories in Artvin and 9.8% in Ordu.
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Helicosporidium infection of the great european spruce bark beetle dendroctonus micans coleoptera scolytidae
European Journal of Protistology, 2005Co-Authors: Mustafa Yaman, Renate RadekAbstract:Abstract An infection of the great European spruce bark beetle Dendroctonus micans (from Turkey) by the parasitic green alga Helicosporidium is described. This is the first time that Helicosporidium has been found to infect a bark beetle (Scolytidae) and the first time that a naturally infected beetle has been reported for the Eurasian continent. The typical cysts of Helicosporidium contain three ovoid cells and one helical, filamentous cell. The morphological characteristics are revealed by light and electron microscopy. Distinct electron-dense inclusions with a peculiar ultrastructure may represent pyrenoids. Since D. micans is an important pest, the discovery of a natural pathogen may offer a chance for biological control.
Aurélien Tartar - One of the best experts on this subject based on the ideXlab platform.
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the non photosynthetic algae Helicosporidium spp emergence of a novel group of insect pathogens
Insects, 2013Co-Authors: Aurélien TartarAbstract:Since the original description of Helicosporidium parasiticum in 1921, members of the genus Helicosporidium have been reported to infect a wide variety of invertebrates, but their characterization has remained dependent on occasional reports of infection. Recently, several new Helicosporidium isolates have been successfully maintained in axenic cultures. The ability to produce large quantity of biological material has led to very significant advances in the understanding of Helicosporidium biology and its interactions with insect hosts. In particular, the unique infectious process has been well documented; the highly characteristic cyst and its included filamentous cell have been shown to play a central role during host infection and have been the focus of detailed morphological and developmental studies. In addition, phylogenetic analyses inferred from a multitude of molecular sequences have demonstrated that Helicosporidium are highly specialized non-photosynthetic algae (Chlorophyta: Trebouxiophyceae), and represent the first described entomopathogenic algae. This review provides an overview of (i) the morphology of Helicosporidium cell types, (ii) the Helicosporidium life cycle, including the entire infectious sequence and its impact on insect hosts, (iii) the phylogenetic analyses that have prompted the taxonomic classification of Helicosporidium as green algae, and (iv) the documented host range for this novel group of entomopathogens.
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expressed sequence tag est survey of the highly adapted green algal parasite Helicosporidium
Protist, 2005Co-Authors: Audrey P. De Koning, Drion G. Boucias, Aurélien Tartar, Patrick J. KeelingAbstract:Helicosporidia are obligate invertebrate pathogens with a unique and highly adapted mode of infection. The evolutionary history of Helicosporidia has been uncertain, but several recent molecular phylogenetic studies have shown an unexpectedly close relationship to green algae, and specifically to the opportunistic pathogen Prototheca. To date, molecular sequences from Helicosporidia are restricted to those genes used for phylogenetic reconstruction and genes related to the existence and function of its cryptic plastid. We have therefore conducted a small expressed sequence tag (EST) project on Helicosporidium sp., yielding about 700 unique sequences. We have examined the functional distribution of known genes, the distribution of EST abundance, and the prevalence of previously unknown gene sequences. To demonstrate the potential utility of large amounts of data, we have used ribosomal proteins to test whether the phylogenetic position of Helicosporidium inferred from a small number of genes is broadly supported by a large number of genes. We conducted phylogenetic analyses on 69 ribosomal proteins and found that 98% supported the green algal origin of Helicosporidia and 80% support a specific relationship with Prototheca. Overall, these data multiply the available molecular information from Helicosporidium 100-fold, which should provide the basis for new insights into these unusual but interesting parasites.
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comparison of plastid 16s rrna rrn16 genes from Helicosporidium spp evidence supporting the reclassification of helicosporidia as green algae chlorophyta
International Journal of Systematic and Evolutionary Microbiology, 2003Co-Authors: Aurélien Tartar, Drion G. Boucias, James J Becnel, Byron J AdamsAbstract:The Helicosporidia are invertebrate pathogens that have recently been identified as non-photosynthetic green algae (Chlorophyta). In order to confirm the algal nature of the genus Helicosporidium, the presence of a retained chloroplast genome in Helicosporidia cells was investigated. Fragments homologous to plastid 16S rRNA (rrn16) genes were amplified successfully from cellular DNA extracted from two different Helicosporidium isolates. The fragment sequences are 1269 and 1266 bp long, are very AT-rich (60.7 %) and are similar to homologous genes sequenced from non-photosynthetic green algae. Maximum-parsimony, maximum-likelihood and neighbour-joining methods were used to infer phylogenetic trees from an rrn16 sequence alignment. All trees depicted the Helicosporidia as sister taxa to the non-photosynthetic, pathogenic alga Prototheca zopfii. Moreover, the trees identified Helicosporidium spp. as members of a clade that included the heterotrophic species Prototheca spp. and the mesotrophic species Chlorella protothecoides. The clade is always strongly supported by bootstrap values, suggesting that all these organisms share a most recent common ancestor. Phylogenetic analyses inferred from plastid 16S rRNA genes confirmed that the Helicosporidia are non-photosynthetic green algae, close relatives of the genus Prototheca (Chlorophyta, Trebouxiophyceae). Such phylogenetic affinities suggest that Helicosporidium spp. are likely to possess Prototheca-like organelles and organelle genomes.
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Phylogenetic analysis identifies the invertebrate pathogen Helicosporidium sp. as a green alga (Chlorophyta).
International journal of systematic and evolutionary microbiology, 2002Co-Authors: Aurélien Tartar, Drion G. Boucias, Byron J Adams, James J BecnelAbstract:Historically, the invertebrate pathogens of the genus Helicosporidium were considered to be either protozoa or fungi, but the taxonomic position of this group has not been considered since 1931. Recently, a Helicosporidium sp., isolated from the blackfly Simulium jonesi Stone & Snoddy (Diptera: Simuliidae), has been amplified in the heterologous host Helicoverpa zea. Genomic DNA has been extracted from gradient-purified cysts. The 185, 28S and 5.8S regions of the Helicosporidium rDNA, as well as partial sequences of the actin and beta-tubulin genes, were amplified by PCR and sequenced. Comparative analysis of these nucleotide sequences was performed using neighbour-joining and maximum-parsimony methods. All inferred phylogenetic trees placed Helicosporidium sp. among the green algae (Chlorophyta), and this association was supported by bootstrap and parsimony jackknife values. Phylogenetic analysis focused on the green algae depicted Helicosporidium sp. as a close relative of Prototheca wickerhamii and Prototheca zopfii (Chlorophyta, Trebouxiophyceae), two achlorophylous, pathogenic green algae. On the basis of this phylogenetic analysis, Helicosporidium sp. is clearly neither a protist nor a fungus, but appears to be the first described algal invertebrate pathogen. These conclusions lead us to propose the transfer of the genus Helicosporidium to Chlorophyta, Trebouxiophyceae.