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Rhizarian ‘Novel Clade 10& Title Rhizarian ‘Novel Clade 10’ Revealed as Abundant and Diverse Planktonic and Terrestrial Flagellates, including Aquavolon n. gen. Authors Bass, D; Tikhonenkov, DV; Foster, R; Dyal, P; Janouškovec, J; Keeling, PJ; Gardner, M; Neuhauser, S; Hartikainen, H; Mylnikov, AP; Berney, C Description 0000-0002-6719-5565 Date Submitted 2018-05-30 Journal of Eukaryotic Microbiology ISSN 1066-5234 ORIGINAL ARTICLE Rhizarian ‘Novel Clade 10’ Revealed as Abundant and Diverse Planktonic and Terrestrial Flagellates, including Aquavolon n. gen. David Bassa,b , Denis Victorovich Tikhonenkovc,d, Rachel Fostera, Patricia Dyala, Jan Janouskovec d,e , Patrick J. Keelingd, Michelle Gardnera, Sigrid Neuhauserf, Hanna Hartikainena, Alexandre P. Mylnikovc & Cedric Berneya,1 a Department of Life Sciences, The Natural History Museum, Cromwell Road, London, SW7 5BD, UK b Centre for Environment, Fisheries and Aquaculture Science (Cefas), Barrack Road, The Nothe, Weymouth, DT4 8UB, UK c Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, 152742, Russia d Botany Department, University of British Columbia, Vancouver, BC, V6T1Z4, Canada e Department of Genetics, Evolution and Environment, University College London, Gower Street, London, WC1E 6BT, UK f Institute of Microbiology, University of Innsbruck, Technikerstraße 25, Innsbruck, 6020, Austria Keywords ABSTRACT 18S rRNA; Aquavolon dientrani; Aquavolon hoantrani; Aquavolonida; Cercozoa; environ- Rhizarian ‘Novel Clade 10’ (NC10) is frequently detected by 18S rRNA gene mental sequencing; Rhizaria; Tremula. sequencing studies in freshwater planktonic samples. We describe a new genus and two species of eukaryovorous biflagellate protists, Aquavolon hoan- Correspondence trani n. gen. n. sp. and A. dientrani n. gen. n. sp., which represent the first D. Bass, Department of Life Sciences, The morphologically characterized members of NC10, here named Aquavolonida Natural History Museum, Cromwell Road, ord. nov. The slightly metabolic cells possess naked heterodynamic flagella, London SW7 5BD, UK whose kinetosomes lie at a right angle to each other and are connected by at Telephone number: +44 207 942 5387; least one fibril. Unlike their closest known relative Tremula longifila, they rotate e-mail: [email protected] around their longitudinal axis when swimming and only very rarely glide on sur- faces. Screening of a wide range of environmental DNA extractions with lin- Received: 10 November 2017; revised 19 eage-specific PCR primers reveals that Aquavolonida consists of a large March 2018; accepted March 28, 2018. radiation of protists, which are most diversified in freshwater planktonic habi- tats and as yet undetected in marine environments. Earlier-branching lineages in Aquavolonida include less frequently detected organisms from soils and doi:10.1111/jeu.12524 freshwater sediments. The 18S rRNA gene phylogeny suggests that Aqua- volonida forms a common evolutionary lineage with tremulids and uncharacter- ized ‘Novel Clade 12’, which likely represents one of the deepest lineages in the Rhizaria, separate from Cercozoa (Filosa), Endomyxa, and Retaria. SEQUENCING of the 18S rRNA gene from environmental infer anything about their biology; they have since been samples has revealed a large diversity of undescribed pro- referred to as cercozoan Novel Clades (NCs) and num- tists in the vast majority of habitat types sampled bered 1 to 9. (Richards and Bass 2005). Some of these are regularly Since 2004 several of these initial NCs have been identi- detected and acquire their own quasi-taxonomic status, fied by cell isolation or culturing efforts: the order Mari- e.g. the various MAST (marine stramenopiles; Massana monadida (Howe et al. 2011) accounts for most of NC1, et al. 2004) and MALV (marine alveolates; Lopez Garcıa including genera Pseudopirsonia (Kuhn€ et al. 2004), Auran- et al. 2001) lineages, and the LKM11 group related to ticordis (Chantangsi et al. 2008), and Abollifer (Shiratori fungi (Lara et al. 2010; Jones et al. 2011). Likewise, the et al. 2014); NC2 has recently been shown to include the first environmental sequencing survey of the phylum Cer- heterotrophic flagellate Quadricilia (Yabuki and Ishida cozoa (Bass and Cavalier-Smith 2004) revealed novel lin- 2018), the first member of NC4 was shown to be eages that were too distantly related to known taxa to Trachyrhizium (Shiratori and Ishida 2016), which forms a © 2018 The Authors Journal of Eukaryotic Microbiology published by Wiley Periodicals, Inc. on behalf of International Society of Protistologists Journal of Eukaryotic Microbiology 2018, 0, 1–15 1 This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Aquavolon are Freshwater and Soil Rhizarian Protists Bass et al. clade with Lecythium and Diaphoropodon (Dumack et al. samples, as well as fluorescent in situ hybridization (FISH). 2018); NC6 belongs to a group including Metopion, Metro- Furthermore, phylogenetic analysis of 18S rRNA gene monas, and Micrometromonas (Howe et al. 2011; this sequences of flagellates isolated from a reservoir and wet- study); NC7 includes Pansomonadida (Aurigamonas and land in Vietnam showed them to belong to NC10. These Agitata; Bass et al. 2009b); and NC8 is part of Vampyrell- were described using light and transmission electron ida (Bass et al. 2009a; Hess et al. 2012; Berney et al. microscopy (TEM) as two new species within the new 2013). NCs 3 and 5 remain uncharacterized, although Bass genus Aquavolon. In the light of 18S rRNA gene sequence et al. (2009a) showed that NC5 is a subclade of Gra- signatures shared by all NC10 lineages presented in this nofilosea, a class of filose amoebae. More data availability study, morphological observations on our isolates, and the and improved phylogenetic methods have also shown that habitat and likely phenotype of other NC10 members, we ‘Basal Group T’ in Bass and Cavalier-Smith (2004) is more formally rename the group Aquavolonida, ord. nov. morphologically and phylogenetically diverse than that label suggests, including the flagellate Discomonas (Chan- MATERIALS AND METHODS tangsi and Leander 2010) and the testate amoeba Penardeugenia (Dumack et al. 2017). Environmental DNA screening and NC10 clone library Further NCs were defined in Bass et al. (2009a), the sequencing most relevant here being NCs 10, 11, and 12. These lin- eages sometimes group together with moderate support. DNA samples from filtered lake water from the English Their exact phylogenetic position within Rhizaria remains Lake District (< 2 lm and 2–20 lm size fractions), river unresolved, but they typically appear distinct from both core biofilms, and soils that were used for the study of Gross- Cercozoa (previously Filosa) and Endomyxa (Bass et al. mann et al. (2016) were also used for this study: DNA 2009a; Howe et al. 2011). On the basis of recent phyloge- was extracted from filtered water using the Qiagen Blood nomic analyses placing the root of the rhizarian radiation & Tissue DNA Extraction Kit (Qiagen, Hilden, Germany). between Cercozoa (Filosa) and Endomyxa + Retaria (Sierra DNA was extracted from biofilms newly formed on cera- et al. 2016; Krabberød et al. 2017), this group may there- mic tiles placed in the River Lambourn, UK by a standard fore form one of the deepest branching rhizarian lineages. CTAB/phenol-chloroform extraction method, and from soils NC11 was shown by Howe et al. (2011) to contain Tremula using the FastDNA SPIN Kit for Soil (MP Biomedicals LLC, longifila, a biflagellate gliding cell (ATCC 50530), which UK). Marine environmental DNA extractions previously along with its direct relatives inhabits freshwater sediments used in other studies (Bass and Cavalier-Smith 2004; Bass and soil. Cellular information for NC12 is still lacking, et al. 2009a; Berney et al. 2013; Hartikainen et al. 2014a, despite its frequency and diversity in a wide range of envi- b; Logares et al. 2014) were also used for screening. ronments. NC12 was originally defined on the basis of Two PCR strategies with distinct levels of specificity to sequences analyzed in Bass et al. 2009a. Since then a lar- NC10 were used for environmental DNA screening, both ger diversity of related environmental sequences has been based on a two-step, nested PCR approach using distinct revealed, analysis of which suggests the original NC12 may sets of PCR primers (see Results for the rationale and correspond to two separate, strongly supported clades plus specificity of these PCR strategies). Strategy I: first PCR some unaffiliated, single-sequence lineages. with primers C7f-NC10 and sB2n, nested PCR with pri- Likewise, NC10 has so far remained uncharacterized. It mers V8f-NC10 and EndoR1. Strategy II: first PCR with is, however, remarkable for being very frequently and primers V2f-NC and C9r-NC, nested PCR with primers almost exclusively detected in freshwater planktonic sam- C5f-NC and V8r-NC. Construction of Endomyxa-enriched ples, from the Antarctic to subtropical lakes. Table S1 pro- clone libraries was achieved using a two-step, semi- vides a list of all NC10 environmental clones we identified nested PCR approach: first PCR with primers s1259F and in GenBank at the onset of this work, with information sB2n, semi-nested PCR with primers s1259F and EndoR1. about their provenance. Key examples of these are as fol- PCR primers corresponding to the NC10-specific FISH lows: LG21-01 and LG01-12 in Richards et al. (2005), A50 probes we designed were used to verify their strict speci- in Lefranc et al. (2005) (not A51, which is a vampyrellid; ficity to a subset of NC10 using the following semi-nested Berney et al. 2013), ‘Novel clade I’ in Lefevre et al. (2007, PCR approach: first PCR with primers V4f-NC10 and C7r- 2008) (except PCC4AU2004, which belongs to NC12), all NC10, semi-nested PCR with primers V4f-NC10 and C6r- of the cercozoan sequences in Fig. 4 of Lepere et al. NC10. Table S2 provides the sequence and position of (2008) (except Cercomonas and PCC4AU2004), the ‘Cer- these primers. cozoa freshwater clade’ in Taib et al.
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