Class Cariacotrichea, a novel ciliate taxon from the anoxic Cariaco Basin, Venezuela

Abstract

The majority of environmental micro-organisms identified with the rRNA approach have never been visualized. Thus, their reliable classification and taxonomic assignment is often difficult or even impossible. In our preliminary 18S rRNA gene sequencing work from the world’s largest anoxic marine environment, the Cariaco Basin (Caribbean Sea, Venezuela), we detected a ciliate clade, designated previously as CAR_H [Stoeck, S., Taylor, G. T. & Epstein, S. S. (2003). Appl Environ Microbiol 63, 5656–5663]. Here, we combine the traditional rRNA detection method of fluorescent in situ hybridization (FISH) with scanning electron microscopy (SEM) and confirm the phylogenetic separation of the CAR_H sequences from all other ciliate classes by showing an outstanding morphological feature of this group: a unique, archway-shaped kinety surrounding the oral apparatus and extending to the posterior body end in CAR_H cells. Based on this specific feature and the molecular phylogenies, we propose a novel ciliate class, Cariacotrichea nov. cl.

Large-scale phylogenomic analysis reveals the phylogenetic position of the problematic taxon Protocruzia and unravels the deep phylogenetic affinities of the ciliate lineages

“…Beyond this deep division, it is generally agreed that there are 11 major ciliate lineages or classes and a twelfth single species clade of Cariacotrichea (Adl et al, 2012;Lynn, 2008;Orsi et al, 2012;Stoeck et al, 2003). Most of these classes are strongly supported by morphology, with the exception of the ''riboclasses'' -the Armophorea and Plagiopylea, which are identified only by sequences of the 18S rRNA genes, as included taxa lack any morphological synapomorphies (Bernhard et al, 1995(Bernhard et al, , 2001Cameron et al, 2001;Embley et al, 1995;Greenwood et al, 1991;Leipe et al, 1994;Lynn, 2008;Lynn et al, 1999;Lynn and Strüder-Kypke, 2002;Snoeyenbos-West et al, 2004;Stechmann et al, 1998).…”

Prevalence of partnerships between bacteria and ciliates in oxygen-depleted marine water columns

“…These works revealed the presence of many uncultured ciliate lineages distantly related to cultured representatives known to harbor symbiotic prokaryotic partners. Recently, efforts have been made to visualize and describe the cellular morphologies of novel ciliate clades (Orsi et al, 2012a), and their functional roles within ecosystems (Orsi et al, 2012b). …”

Microbial Eukaryotes in Marine Oxygen Minimum Zones

“…C. aureus has a cortex that is completely covered by bacteria belonging to the bacterial genus Arcobacter , a group capable of performing chemoautotrophy and chemoorganotrophy coupled to nitrate reduction and sul fi de oxidization (Bernhard et al, 2000 ;Edgcomb et al, 2010 ;Yubuki et al, 2009 ) . Phylogenetic analyses of ciliate-af fi liated sequences recovered from both oxygen-depleted waters of the Cariaco Basin and Saanich Inlet (Orsi et al, 2012a ) reveal a high diversity of the novel ciliate class Cariacotrichea (Orsi et al, 2012b ) and suggest that this new taxon is restricted to oxygen-depleted marine habitats.…”