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Gromochytrium mamkaevae gen. & sp. nov. and two new orders: Gromochytriales and Mesochytriales (Chytridiomycetes).

Karpov SA, Kobseva AA, Mamkaeva MA, Mamkaeva KA, Mikhailov KV, Mirzaeva GS, Aleoshin VV - Persoonia (2014)

Bottom Line: During the last decade several new orders were established in the class Chytridiomycetes on the basis of zoospore ultrastructure and molecular phylogeny.Detailed investigation revealed that the zoospore ultrastructure of this strain has unique characters not found in any order of Chytridiomycetes: posterior ribosomal core unbounded by the endoplasmic reticulum and detached from the nucleus or microbody-lipid complex, and kinetosome composed of microtubular doublets.An isolated phylogenetic position of x-51 is further confirmed by the analysis of 18S and 28S rRNA sequences, and motivates the description of a new genus and species Gromochytrium mamkaevae.

View Article: PubMed Central - PubMed

Affiliation: Zoological Institute, Russian Academy of Sciences, St. Petersburg 198904, Russian Federation; ; Biological Faculty, St. Petersburg State University, St. Petersburg 198904, Russian Federation.

ABSTRACT
During the last decade several new orders were established in the class Chytridiomycetes on the basis of zoospore ultrastructure and molecular phylogeny. Here we present the ultrastructure and molecular phylogeny of strain x-51 CALU - a parasite of the alga Tribonema gayanum, originally described as Rhizophydium sp. based on light microscopy. Detailed investigation revealed that the zoospore ultrastructure of this strain has unique characters not found in any order of Chytridiomycetes: posterior ribosomal core unbounded by the endoplasmic reticulum and detached from the nucleus or microbody-lipid complex, and kinetosome composed of microtubular doublets. An isolated phylogenetic position of x-51 is further confirmed by the analysis of 18S and 28S rRNA sequences, and motivates the description of a new genus and species Gromochytrium mamkaevae. The sister position of G. mamkaevae branch relative to Mesochytrium and a cluster of environmental sequences, as well as the ultrastructural differences between Gromochytrium and Mesochytrium zoospores prompted us to establish two new orders: Gromochytriales and Mesochytriales.

No MeSH data available.


Related in: MedlinePlus

Stages of the life cycle of Gromochytrium mamkaevae (x-51 CALU) on the host Tribonema gayanum. — a–c: LM images of living parasite on filament of host Tribonema, phase contrast. – a. Two cysts with a lipid globule; b. young sporangium with 3 lipid globules; c. mature sporangium contains zoospores. – d. Rhizoid in the host cell in TEM. – e. Drawing of the life cycle. — Abbreviations: cy = cyst; l = lipid globule; msp = mature sporangium; rh = rhizoid; sp = sporangium; spw = sporangium wall; ysp = young sporangium; zs = zoospores. — Scale bars: a–c = 10 μm; d = 2 μm.
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Figure 1: Stages of the life cycle of Gromochytrium mamkaevae (x-51 CALU) on the host Tribonema gayanum. — a–c: LM images of living parasite on filament of host Tribonema, phase contrast. – a. Two cysts with a lipid globule; b. young sporangium with 3 lipid globules; c. mature sporangium contains zoospores. – d. Rhizoid in the host cell in TEM. – e. Drawing of the life cycle. — Abbreviations: cy = cyst; l = lipid globule; msp = mature sporangium; rh = rhizoid; sp = sporangium; spw = sporangium wall; ysp = young sporangium; zs = zoospores. — Scale bars: a–c = 10 μm; d = 2 μm.

Mentions: The parasite has a typical chytrid endogenous life cycle with tiny (~ 2 μm diam) zoospores that attach to the host cell surface, retract the flagellum and encyst. After the germ tube enters the host the zoospore cyst enlarges; a prominent lipid globule is clearly visible at this early stage (Fig. 1a). The young sporangium has homogenous contents with few lipid globules of different size (Fig. 1b), and the mature sporangium contains zoospores, which are released through an apical pore. The inoperculate sporangium is long ovoid (~ 18 × 10 μm diam) without a differentiated apical papilla (Fig. 1c). The apical pore varies in its dimensions: from narrow to as broad as the diameter of the sporangium or even broader (Fig. 1e). The delicate rhizoidal system is poorly visible, but can be estimated as weakly branched with short rhizoids emerging from a slender main axis (Fig. 1d, e). According to this description the fungus could be identified as Rhizophydium mammillatum (A. Braun) A. Fish. (1892) or, less likely, R. melosirae (1952) (Sparrow 1960, Letcher & Powell 2012), and therefore it was identified as R. mammillatum (Mamkaeva et al. 2006).


Gromochytrium mamkaevae gen. & sp. nov. and two new orders: Gromochytriales and Mesochytriales (Chytridiomycetes).

Karpov SA, Kobseva AA, Mamkaeva MA, Mamkaeva KA, Mikhailov KV, Mirzaeva GS, Aleoshin VV - Persoonia (2014)

Stages of the life cycle of Gromochytrium mamkaevae (x-51 CALU) on the host Tribonema gayanum. — a–c: LM images of living parasite on filament of host Tribonema, phase contrast. – a. Two cysts with a lipid globule; b. young sporangium with 3 lipid globules; c. mature sporangium contains zoospores. – d. Rhizoid in the host cell in TEM. – e. Drawing of the life cycle. — Abbreviations: cy = cyst; l = lipid globule; msp = mature sporangium; rh = rhizoid; sp = sporangium; spw = sporangium wall; ysp = young sporangium; zs = zoospores. — Scale bars: a–c = 10 μm; d = 2 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4150072&req=5

Figure 1: Stages of the life cycle of Gromochytrium mamkaevae (x-51 CALU) on the host Tribonema gayanum. — a–c: LM images of living parasite on filament of host Tribonema, phase contrast. – a. Two cysts with a lipid globule; b. young sporangium with 3 lipid globules; c. mature sporangium contains zoospores. – d. Rhizoid in the host cell in TEM. – e. Drawing of the life cycle. — Abbreviations: cy = cyst; l = lipid globule; msp = mature sporangium; rh = rhizoid; sp = sporangium; spw = sporangium wall; ysp = young sporangium; zs = zoospores. — Scale bars: a–c = 10 μm; d = 2 μm.
Mentions: The parasite has a typical chytrid endogenous life cycle with tiny (~ 2 μm diam) zoospores that attach to the host cell surface, retract the flagellum and encyst. After the germ tube enters the host the zoospore cyst enlarges; a prominent lipid globule is clearly visible at this early stage (Fig. 1a). The young sporangium has homogenous contents with few lipid globules of different size (Fig. 1b), and the mature sporangium contains zoospores, which are released through an apical pore. The inoperculate sporangium is long ovoid (~ 18 × 10 μm diam) without a differentiated apical papilla (Fig. 1c). The apical pore varies in its dimensions: from narrow to as broad as the diameter of the sporangium or even broader (Fig. 1e). The delicate rhizoidal system is poorly visible, but can be estimated as weakly branched with short rhizoids emerging from a slender main axis (Fig. 1d, e). According to this description the fungus could be identified as Rhizophydium mammillatum (A. Braun) A. Fish. (1892) or, less likely, R. melosirae (1952) (Sparrow 1960, Letcher & Powell 2012), and therefore it was identified as R. mammillatum (Mamkaeva et al. 2006).

Bottom Line: During the last decade several new orders were established in the class Chytridiomycetes on the basis of zoospore ultrastructure and molecular phylogeny.Detailed investigation revealed that the zoospore ultrastructure of this strain has unique characters not found in any order of Chytridiomycetes: posterior ribosomal core unbounded by the endoplasmic reticulum and detached from the nucleus or microbody-lipid complex, and kinetosome composed of microtubular doublets.An isolated phylogenetic position of x-51 is further confirmed by the analysis of 18S and 28S rRNA sequences, and motivates the description of a new genus and species Gromochytrium mamkaevae.

View Article: PubMed Central - PubMed

Affiliation: Zoological Institute, Russian Academy of Sciences, St. Petersburg 198904, Russian Federation; ; Biological Faculty, St. Petersburg State University, St. Petersburg 198904, Russian Federation.

ABSTRACT
During the last decade several new orders were established in the class Chytridiomycetes on the basis of zoospore ultrastructure and molecular phylogeny. Here we present the ultrastructure and molecular phylogeny of strain x-51 CALU - a parasite of the alga Tribonema gayanum, originally described as Rhizophydium sp. based on light microscopy. Detailed investigation revealed that the zoospore ultrastructure of this strain has unique characters not found in any order of Chytridiomycetes: posterior ribosomal core unbounded by the endoplasmic reticulum and detached from the nucleus or microbody-lipid complex, and kinetosome composed of microtubular doublets. An isolated phylogenetic position of x-51 is further confirmed by the analysis of 18S and 28S rRNA sequences, and motivates the description of a new genus and species Gromochytrium mamkaevae. The sister position of G. mamkaevae branch relative to Mesochytrium and a cluster of environmental sequences, as well as the ultrastructural differences between Gromochytrium and Mesochytrium zoospores prompted us to establish two new orders: Gromochytriales and Mesochytriales.

No MeSH data available.


Related in: MedlinePlus