Drouetiella lurida (Gomont) 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 : 28-32

Drouetiella lurida (Gomont) Mai, Johansen et Pietrasiak comb. nov.

Basionym:— Phormidium luridum Gomont 1892 , Annales des Sciences Naturelles, ser. 7 16:165, plate 4, figs 17, 18.

Later Synonyms:— Leptolyngbya lurida (Gomont) Anagnostidis & Komárek 1988 : Archiv für Hydrobiologie, Supplement 80: 392

Diagnostic features: ―Dissimilar to all other Drouetiella species in the shape and sequence of D1-D1’ helix and V2 helix ( Figs. 6 , 8 ).

Description of epitype:— Colony reddish brown or brown in actively growing cultures, turning olive-green as culture senesces ( Fig. 14a ). Filaments long, without false branching, 2.0–2.6 (3.4) μm wide. Sheath firm, thin, colorless, up to 0.8 μm wide ( Fig. 14c ). Trichomes not or slightly constricted at distinct cross-walls, without necridia, lacking meristematic zones, with cell division occurring throughout the length of the trichomes, 1.7–2.1 μm wide. Hormogonia absent. Cells mostly longer than wide ( Figs. 14b, d ), rarely isodiametric after division, with parietal thylakoids, with up to three granules usually in the middle of the cell, (2.1) 2.9–3.8 (5.4) μm long. End cells untapered, rounded.

D1-D1’ helix 64 nucleotides long, with basal side loop of 7 nucleotides (5’-CAUCCCA-3’), at mid-helix with one large internal loop at position 14–17/41–44, one pair of mismatched nucleotides at position 9 on the 5’ strand (U/U) and one sub-terminal internal loop at 23–24/34–35 immediately separated from the terminal loop by a 5’-GC:GC-3’ clamp. Terminal loop of 5 nucleotides, terminal sequence 5’-AUAGU-3’ ( Fig. 6i ). Box B 34 nucleotides long, with one basal internal loop at position 5/27–28 and one unpaired adenine residue at position 9 of the 5’ strand ( Fig. 7h ). V2 helix 18 nucleotides long, unique in sequence and shape, terminal loop of 4 nucleotides, sequence 5’-UUUG-3’ ( Fig. 8f ). V3 helix was not reported as the sequence from NCBI terminated before the end of the ITS region.

Epitype:— Czech Republic: City of Most, collected in 1986 by Alena Lukesova (Epitype BRY37777!, Herbarium for Nonvascular Cryptogams, Monte L. Bean Museum, Provo, Utah).

Reference strain: ―Lukesova 1986/6, Algal Culture Collection at John Carroll University, Cleveland, USA. Found in tailings of Cainozoic clay.

Taxonomic notes:— Our strain conforms very well to the original description of Phormidium luridum Gomont , being nearly identical in filament, trichome, and cell dimensions, degree of constriction at cross-walls, and the purplish brownish color in actively growing populations, and with olive green coloration in less actively growing parts of the mat. P. luridum (subsequently Leptolyngbya lurida ) was described as having dark blue-green to dull violet or blackish mats with the subsurface layers being greyish green, which is slightly different than having cultures that have thin mats which change color with age. However, our material is so close morphologically to P. luridum , and is additionally from a European location, that we felt it could not be reasonably separated from that species. Komárek & Anagnostidis (2005) indicate that L. lurida is very widespread, and in need of revision. It clearly does not fit Leptolyngbya sensu stricto, which consistently has isodiametric cells and false branching. We have designated an epitype which we have characterized fully to help cement the concept of the species.

The 16S rRNA gene phylogeny shows that D. lurida is more closely related to the species cluster of D. hepatica and Antarctic Drouetiella than to D. fasciculata ( Fig.2 , Table 9). However, in examining the percent dissimilarity of the 16S–23S ITS region, D. lurida is>17.0% ( Table 10) different from all other species in the genus―strong evidence of separation of species.

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 6. D1-D1’ stems of species described in Oculatellaceae.The stem structures of genera described previously in other publications (Oculatella, Thermoleptolyngbya, Timaviella) or in publications under provision (Trichotorquatus) are not shown here.

FIGURE 7. Box B helices of species described in Oculatellaceae. The structures of genera described previously in other publications (Oculatella, Thermoleptolyngbya, Timaviella) or in publications under provision (Trichotorquatus) are not shown here.

FIGURE 8. V2 helices of species described in Oculatellaceae. Several species do not have this structure, including Pegethrix convoluta, P. indistincta, Antartic Pegethrix species, Cartusia fontana¸ Kaiparowitsia implicata.

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).