title: Culturing Heterotrophic Protists from the Baltic Sea: Mostly the "Usual Suspects" but a Few Novelties as Well.
abstract: The study of cultured strains has a long tradition in protistological research and has greatly contributed to establishing the morphology, taxonomy, and ecology of many protist species. However, cultivation-independent techniques, based on 18S rRNA gene sequences, have demonstrated that natural protistan assemblages mainly consist of hitherto uncultured protist lineages. This mismatch impedes the linkage of environmental diversity data with the biological features of cultured strains. Thus, novel taxa need to be obtained in culture to close this knowledge gap. In this study, traditional cultivation techniques were applied to samples from coastal surface waters and from deep oxygen-depleted waters of the Baltic Sea. Based on 18S rRNA gene sequencing, 126 monoclonal cultures of heterotrophic protists were identified. The majority of the isolated strains were affiliated with already cultured and described taxa, mainly chrysophytes and bodonids. This was likely due to "culturing bias" but also to the eutrophic nature of the Baltic Sea. Nonetheless, ~ 12% of the isolates in our culture collection showed highly divergent 18S rRNA gene sequences compared to those of known organisms and thus may represent novel taxa, either at the species level or at the genus level. Moreover, we also obtained evidence that some of the isolated taxa are ecologically relevant, under certain conditions, in the Baltic Sea.
authors.affiliation: Biological Oceanography, IOW-Leibniz Institute for Baltic Sea Research Warnemünde, Seestr. 15, Rostock, 18119, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Weber
authors.affiliation: Biological Oceanography, IOW-Leibniz Institute for Baltic Sea Research Warnemünde, Seestr. 15, Rostock, 18119, Germany.|Institute for the Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavskaya Obl., 152742, Russia.
authors.forename: Alexander P
authors.initials: AP
authors.lastname: Mylnikov
authors.affiliation: Biological Oceanography, IOW-Leibniz Institute for Baltic Sea Research Warnemünde, Seestr. 15, Rostock, 18119, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Jürgens
authors.affiliation: Biological Oceanography, IOW-Leibniz Institute for Baltic Sea Research Warnemünde, Seestr. 15, Rostock, 18119, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Wylezich
mesh_terms: D044822:Biodiversity; D018929:Cell Culture Techniques / Q000379:methods; D016054:DNA, Protozoan / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D056890:Eukaryota / Q000145:classification* / Q000235:genetics / Q000254:growth & development* / Q000302:isolation & purification; D005858:Germany; D052836:Heterotrophic Processes; D008386:Marine Biology; D010100:Oxygen / Q000737:chemistry; D010802:Phylogeny; D016053:RNA, Protozoan / Q000235:genetics; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D012623:Seawater / Q000737:chemistry / Q000469:parasitology*; D017422:Sequence Analysis, DNA
chemical_list: D016054:DNA, Protozoan; D004275:DNA, Ribosomal; D016053:RNA, Protozoan; D012337:RNA, Ribosomal, 18S; D010100:Oxygen
keywords: 
  Paraphysomonas
  ; Bodonids; chrysophytes; culturing bias; flagellates; novel taxa; traditional cultivation; unamended seawater incubation