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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

(A) Helicosporidium cyst dehiscence observed under light microscopy, showing groups of three ovoid cells (O), diagnostic filamentous cells (F) and empty pellicles (E). (B) Scanning electron micrograph detailing the filamentous cell and its barbs (pointing away from the core of ovoid cells).
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insects-04-00375-f002: (A) Helicosporidium cyst dehiscence observed under light microscopy, showing groups of three ovoid cells (O), diagnostic filamentous cells (F) and empty pellicles (E). (B) Scanning electron micrograph detailing the filamentous cell and its barbs (pointing away from the core of ovoid cells).

Mentions: In addition to TEM pictures, a recent study presented scanning electron microscopes pictures of cysts that were purified using Ludox gradient centrifugation, as well as light microscopy and SEM pictures of the filamentous cell being liberated from the cyst and separated from the remaining three ovoid cells [8]. This process is known as dehiscence (Figure 2). It has been observed both in vitro, by applying pressure to the microscope slide [8], and in vivo, in the gut lumen of susceptible hosts [14], and in the host hemolymph, after a series of desiccation events [1]. Significantly, dehisced cysts were used to single out the filamentous cells and highlight the presence of barbs [8] (Figure 2). Purified filamentous cells range in length from 37 to 62 μm [1,4,8,10,14]. It remains unclear if these ultrastructural differences can be related to the hosts from which these Helicosporidium were isolated.


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

Tartar A - Insects (2013)

(A) Helicosporidium cyst dehiscence observed under light microscopy, showing groups of three ovoid cells (O), diagnostic filamentous cells (F) and empty pellicles (E). (B) Scanning electron micrograph detailing the filamentous cell and its barbs (pointing away from the core of ovoid cells).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

insects-04-00375-f002: (A) Helicosporidium cyst dehiscence observed under light microscopy, showing groups of three ovoid cells (O), diagnostic filamentous cells (F) and empty pellicles (E). (B) Scanning electron micrograph detailing the filamentous cell and its barbs (pointing away from the core of ovoid cells).
Mentions: In addition to TEM pictures, a recent study presented scanning electron microscopes pictures of cysts that were purified using Ludox gradient centrifugation, as well as light microscopy and SEM pictures of the filamentous cell being liberated from the cyst and separated from the remaining three ovoid cells [8]. This process is known as dehiscence (Figure 2). It has been observed both in vitro, by applying pressure to the microscope slide [8], and in vivo, in the gut lumen of susceptible hosts [14], and in the host hemolymph, after a series of desiccation events [1]. Significantly, dehisced cysts were used to single out the filamentous cells and highlight the presence of barbs [8] (Figure 2). Purified filamentous cells range in length from 37 to 62 μm [1,4,8,10,14]. It remains unclear if these ultrastructural differences can be related to the hosts from which these Helicosporidium were isolated.

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