Drouetiella Mai, Johansen et Pietrasiak, 2018

Mai, Truc, Johansen, Jeffrey R., Pietrasiak, Nicole, Bohunická, Markéta & Martin, Michael P., 2018, Revision of the Synechococcales (Cyanobacteria) through recognition of four families including Oculatellaceae fam. nov. and Trichocoleaceae fam. nov. and six new genera containing 14 species, Phytotaxa 365 (1), pp. 1-59 : 27-28

Drouetiella Mai, Johansen et Pietrasiak gen. nov.

Description:— Filaments mostly solitary, at times consolidated into fascicles, with infrequent single false branching. Sheath clear, thin, and firm, occasionally widened. Trichomes untapered, straight, flexuous, or spirally coiled, but not in nodules, slightly constricted at the crosswalls. Cells mostly longer than wide, becoming isodiametric to slightly shorter than wide in dividing trichomes, without aerotopes, rarely with a central granule in the cytoplasm; with parietal thylakoids. Apical cells cylindrical, untapered, rounded, without calyptra. Reproduction by trichome fragmentation via disintegration without necridia.

Etymology:— Drouetiella : named in honor of Francis Drouet, a prominent North American phycologist of the late 20 th century whose monographic works still serve as a primary bibliographic reference into the nomenclature of the cyanobacteria.

Type species:— Drouetiella lurida (Gomont) Mai, Johansen et Pietrasiak comb. nov.

Taxonomic notes:— The genus Drouetiella currently contains three named species: D. lurida , D. fasciculata , and D. hepatica . This genus is most closely related to the cluster containing both Cartusia and Pegethrix ( Fig. 2 ). Genetic identity analysis of the 16S rRNA of these species separated three species at the 98.8 % threshold ( Table 9). However, their percent dissimilarity in the ITS regions strongly supported their separation into four different lineages ( Table 10). There are also diagnosable differences among the species in their morphology ( Figs. 14‒16 ) and secondary structures of the ITS.

Figures

FIGURE 2. 16S rRNA Bayesian Inference analysis of the filamentous group of Synechococcales cyanobacteria, showing Oculatellaceae. Black polygons represent genera that have been validly described or are named in provision (e.g., “Trichotorquatus”), with length corresponding to the distance from the most basal OTU to the most diverged OTU of the genus. Posterior probabilities for the BI analysis are given above the nodes. Taxa which we consider to be incorrectly named in NCBI or requiring revisionary work are in quotation marks.

FIGURE 14. Drouetiella lurida. A. Olive-greenish trichome coloration of mature culture. B. Liver-brown filament coloration in healthy culture. C–D. Filaments with thin, attached sheath, indistinct with no diacritical characters. Scale bar 10μm in 400X (A) and 1000X magnification (B–D).

FIGURE 15. Drouetiella fasciculata. A. Fasiculated filaments with individual sheath. B. Mature trichomes with one to two large central granules. B–C. Different coiling patterns of filaments. D. Hormogonia. E–G. Cells barrel-shaped, not constricted and separated by somewhat translucent cross-walls. Scale bar 10μm in 400X (A) and 1000X magnification (B–J).

FIGURE 16. Drouetiella hepatica. A.Heterogeneity in trichome width between young and mature filaments, young filaments isodiametric to slightly cylindrical. B–C. False-branching very rare in young trichomes, only single false-branches observered. D–F. Sheath sometimes elongated and lamellate as in (E). G. Rapid cell division in meristematic zones sometimes caused twisted trichomes. H. Frequent necridia occur along actively dividing trichomes. Scale bar 10μm in 1000X magnification.