Discovery of a new phylum: from barcoding to taxonomy

One of the new way to discover cryptic diversity is to sequence environmental clone libraries. In 2007, researcher discovered a new and very deep lineage of picoeurcaryote from plankton samples using 18S. After years of survey, they could finally isolate this unicellular organism and describe it. The cell is 3.0 x 2.2 micrometers, it is biflagellate, it has a single mitochondrion and has a unique stereotypic motility. Based on these features, they decided to establish a new phylum: Picozoa. It is a nice example on how genetics helps in biodiversity survey and taxonomy. The paper was published the 26 March in Plos One (see reference below).

Figure 2. A Picomonas cell. 2A. Differential interference contrast of a chemically fixed cell. Inset shows phase contrast image of a live cell from tissue culture flask photographed with an inverted microscope (Scale bar 5 µm). 2B. Fluorescence and phase contrast overlay, nucleus (blue), mitochondrion (red). 2C. SEM image. 2D. A longitudinal section through a cell in the plane of the flagella, viewed from the cell’s left. 2E. A 3 D serial section reconstruction of the cell depicted in 2D. AF/PF (anterior−/posterior flagellum); AP/PP (anterior/posterior part of the cell); G (Golgi body); M (mitochondrion); MB (‘microbody’); N (nucleus); tr1,tr2 (distal [tr2] and proximal [tr1] flagellar transitional regions); P (posterior digestive body); Cl (cleft separating the anterior from the posterior part of the cell); vc (vacuolar cisterna). doi:10.1371/journal.pone.0059565.g002

Source: Seenivasan R, Sausen N, Medlin LK, Melkonian M (2013) Picomonas judraskeda Gen. Et Sp. Nov.: The First Identified Member of the Picozoa Phylum Nov., a Widespread Group of Picoeukaryotes, Formerly Known as ‘Picobiliphytes’. PLoS ONE 8(3): e59565. doi:10.1371/journal.pone.0059565

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0059565