title: Gromochytrium mamkaevae gen. & sp. nov. and two new orders: Gromochytriales and Mesochytriales (Chytridiomycetes).
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.
authors.affiliation: Zoological Institute, Russian Academy of Sciences, St. Petersburg 198904, Russian Federation; ; Biological Faculty, St. Petersburg State University, St. Petersburg 198904, Russian Federation.
authors.forename: S A
authors.initials: SA
authors.lastname: Karpov
authors.affiliation: Biological Faculty, St. Petersburg State University, St. Petersburg 198904, Russian Federation.
authors.forename: A A
authors.initials: AA
authors.lastname: Kobseva
authors.affiliation: Biological Faculty, St. Petersburg State University, St. Petersburg 198904, Russian Federation.
authors.forename: M A
authors.initials: MA
authors.lastname: Mamkaeva
authors.affiliation: Biological Faculty, St. Petersburg State University, St. Petersburg 198904, Russian Federation.
authors.forename: K A
authors.initials: KA
authors.lastname: Mamkaeva
authors.affiliation: A.N. Belozersky Institute for Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119991, Russian Federation. ; A.A. Kharkevich Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow 127994, Russian Federation.
authors.forename: K V
authors.initials: KV
authors.lastname: Mikhailov
authors.affiliation: Institute of Gene Pool of Plants and Animals, Uzbek Academy of Sciences, 32 Durmon-yuli str., Tashkent 100125, Republic of Uzbekistan.
authors.forename: G S
authors.initials: GS
authors.lastname: Mirzaeva
authors.affiliation: A.N. Belozersky Institute for Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119991, Russian Federation. ; A.A. Kharkevich Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow 127994, Russian Federation. ; National Research Institute of Physiology, Biochemistry, and Nutrition of Farm Animals, Russian Academy of Agricultural Sciences, Borovsk 249013, Kaluga region, Russian Federation.
authors.forename: V V
authors.initials: VV
authors.lastname: Aleoshin
keywords: Gromochytriales; Gromochytrium mamkaevae; Mesochytriales; Rhizophydium; chytridiomycetes; strain x-51 CALU