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Picomonas judraskeda gen. et sp. nov.: the first identified member of the Picozoa phylum nov., a widespread group of picoeukaryotes, formerly known as 'picobiliphytes'.

ABSTRACT: In 2007, a novel, putatively photosynthetic picoeukaryotic lineage, the 'picobiliphytes', with no known close eukaryotic relatives, was reported from 18S environmental clone library sequences and fluorescence in situ hybridization. Although single cell genomics later showed these organisms to be heterotrophic rather than photosynthetic, until now this apparently widespread group of pico-(or nano-)eukaryotes has remained uncultured and the organisms could not be formally recognized. Here, we describe Picomonas judraskeda gen. et sp. nov., from marine coastal surface waters, which has a 'picobiliphyte' 18S rDNA signature. Using vital mitochondrial staining and cell sorting by flow cytometry, a single cell-derived culture was established. The cells are biflagellate, 2.5-3.8×2-2.5 µm in size, lack plastids and display a novel stereotypic cycle of cell motility (described as the "jump, drag, and skedaddle"-cycle). They consist of two hemispherical parts separated by a deep cleft, an anterior part that contains all major cell organelles including the flagellar apparatus, and a posterior part housing vacuoles/vesicles and the feeding apparatus, both parts separated by a large vacuolar cisterna. From serial section analyses of cells, fixed at putative stages of the feeding cycle, it is concluded that cells are not bacterivorous, but feed on small marine colloids of less than 150 nm diameter by fluid-phase, bulk flow endocytosis. Based on the novel features of cell motility, ultrastructure and feeding, and their isolated phylogenetic position, we establish a new phylum, Picozoa, for Picomonas judraskeda, representing an apparently widespread and ecologically important group of heterotrophic picoeukaryotes, formerly known as 'picobiliphytes'.

SUBMITTER: Seenivasan R

PROVIDER: S-EPMC3608682 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Picomonas judraskeda gen. et sp. nov.: the first identified member of the Picozoa phylum nov., a widespread group of picoeukaryotes, formerly known as 'picobiliphytes'.

Seenivasan Ramkumar R Sausen Nicole N Medlin Linda K LK Melkonian Michael M

PloS one 20130326 3

In 2007, a novel, putatively photosynthetic picoeukaryotic lineage, the 'picobiliphytes', with no known close eukaryotic relatives, was reported from 18S environmental clone library sequences and fluorescence in situ hybridization. Although single cell genomics later showed these organisms to be heterotrophic rather than photosynthetic, until now this apparently widespread group of pico-(or nano-)eukaryotes has remained uncultured and the organisms could not be formally recognized. Here, we desc ...[more]

PMID: 23555709

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Project description:Members of the phylum Planctomycetes are ubiquitous bacteria that dwell in aquatic and terrestrial habitats. While planctomycetal species are important players in the global carbon and nitrogen cycle, this phylum is still undersampled and only few genome sequences are available. Here we describe strain NH11T, a novel planctomycete obtained from a crustacean shell (Wadden Sea, Germany). The phylogenetically closest related cultivated species is Gimesia maris, sharing only 87% 16S rRNA sequence identity. Previous isolation attempts have mostly yielded members of the genus Rhodopirellula from water of the German North Sea. On the other hand, only one axenic culture of the genus Pirellula was obtained from a crustacean thus far. However, the 16S rRNA gene sequence of strain NH11T shares only 80% sequence identity with the closest relative of both genera, Rhodopirellula and Pirellula. Thus, strain NH11T is unique in terms of origin and phylogeny. While the pear to ovoid shaped cells of strain NH11T are typical planctomycetal, light-, and electron microscopic observations point toward an unusual variation of cell division through budding: during the division process daughter- and mother cells are connected by an unseen thin tubular-like structure. Furthermore, the periplasmic space of strain NH11T was unusually enlarged and differed from previously known planctomycetes. The complete genome of strain NH11T, with almost 9 Mb in size, is among the largest planctomycetal genomes sequenced thus far, but harbors only 6645 protein-coding genes. The acquisition of genomic components by horizontal gene transfer is indicated by the presence of numerous putative genomic islands. Strikingly, 45 "giant genes" were found within the genome of NH11T. Subsequent analysis of all available planctomycetal genomes revealed that Planctomycetes as such are especially rich in "giant genes". Furthermore, Multilocus Sequence Analysis (MLSA) tree reconstruction support the phylogenetic distance of strain NH11T from other cultivated Planctomycetes of the same phylogenetic cluster. Thus, based on our findings, we propose to classify strain NH11T as Fuerstia marisgermanicae gen. nov., sp. nov., with the type strain NH11T, within the phylum Planctomycetes.

Dataset Information

Picomonas judraskeda gen. et sp. nov.: the first identified member of the Picozoa phylum nov., a widespread group of picoeukaryotes, formerly known as 'picobiliphytes'.

Publications

Picomonas judraskeda gen. et sp. nov.: the first identified member of the Picozoa phylum nov., a widespread group of picoeukaryotes, formerly known as 'picobiliphytes'.

Similar Datasets

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