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The Non-Photosynthetic Algae Helicosporidium spp.: Emergence of a Novel Group of Insect Pathogens.

Tartar A - Insects (2013)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Division of Math, Science, and Technology, Nova Southeastern University, 3301 College Avenue, Fort Lauderdale, FL 33314, USA. aurelien@nova.edu.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus

Scanning electron micrograph of the gut content of insect hosts challenged with Helicosporidium cysts, demonstrating that filamentous cells are released in the gut lumen.
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insects-04-00375-f003: Scanning electron micrograph of the gut content of insect hosts challenged with Helicosporidium cysts, demonstrating that filamentous cells are released in the gut lumen.

Mentions: The pathogenicity process of Helicosporidium spp. has been inferred principally from two long‑term studies that detailed the infection sequence in heterologous lepidopteran hosts maintained in laboratories [8,14,15,16,20]. A Helicosporidium originally isolated from larvae and adults of Carpophilus mutilatus (Coleoptera, Nitidulidae) was tracked in the navel orangeworm Paramyelois transitella [14,15]. Later, Helicosporidium Sj-1 was used to obtain infections in common laboratory insects such as the corn earworm Helicoverpa zea, the tobacco hornworm Manduca sexta, or the beet armyworm Spodoptera exigua [8,16,20]. Both studies established that cysts are the infective propagules and that infection occurs per os, when cysts are ingested by susceptible hosts. During insect bioassays, significant infection rates have routinely be obtained after per os challenge, even though a significant portion of intact cysts may be retrieved in the animal’s feces [20]. Gut dissections clearly demonstrated that cyst dehiscence was induced in the gut lumen [8,14,20]. The impact of insect gut on cysts was confirmed in vitro, as cysts incubated in midgut fluids were induced to rupture and release the filamentous cells [8]. Ovoid cells contained in the cysts were observed to lyse in the midgut [8,20]. In vivo cyst dehiscence is illustrated in Figure 3, complementing additional micrographs of insect gut lumen that demonstrated the infection process [8,20].


The Non-Photosynthetic Algae Helicosporidium spp.: Emergence of a Novel Group of Insect Pathogens.

Tartar A - Insects (2013)

Scanning electron micrograph of the gut content of insect hosts challenged with Helicosporidium cysts, demonstrating that filamentous cells are released in the gut lumen.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4553470&req=5

insects-04-00375-f003: Scanning electron micrograph of the gut content of insect hosts challenged with Helicosporidium cysts, demonstrating that filamentous cells are released in the gut lumen.
Mentions: The pathogenicity process of Helicosporidium spp. has been inferred principally from two long‑term studies that detailed the infection sequence in heterologous lepidopteran hosts maintained in laboratories [8,14,15,16,20]. A Helicosporidium originally isolated from larvae and adults of Carpophilus mutilatus (Coleoptera, Nitidulidae) was tracked in the navel orangeworm Paramyelois transitella [14,15]. Later, Helicosporidium Sj-1 was used to obtain infections in common laboratory insects such as the corn earworm Helicoverpa zea, the tobacco hornworm Manduca sexta, or the beet armyworm Spodoptera exigua [8,16,20]. Both studies established that cysts are the infective propagules and that infection occurs per os, when cysts are ingested by susceptible hosts. During insect bioassays, significant infection rates have routinely be obtained after per os challenge, even though a significant portion of intact cysts may be retrieved in the animal’s feces [20]. Gut dissections clearly demonstrated that cyst dehiscence was induced in the gut lumen [8,14,20]. The impact of insect gut on cysts was confirmed in vitro, as cysts incubated in midgut fluids were induced to rupture and release the filamentous cells [8]. Ovoid cells contained in the cysts were observed to lyse in the midgut [8,20]. In vivo cyst dehiscence is illustrated in Figure 3, complementing additional micrographs of insect gut lumen that demonstrated the infection process [8,20].

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Division of Math, Science, and Technology, Nova Southeastern University, 3301 College Avenue, Fort Lauderdale, FL 33314, USA. aurelien@nova.edu.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus