Scytolyngbya timoleontis, Song & Jiang & Li, 2015

Song, Gao-Fei, Jiang, Yong-Guang & Li, Ren-Hui, 2015, Scytolyngbya timoleontis, gen. et sp. nov. (Leptolyngbyaceae, Cyanobacteria): a novel false branching Cyanobacteria from China, Phytotaxa 224 (1), pp. 72-84 : 74-77

Scytolyngbya timoleontis Song et Li, sp. nov. ( Figs 1, 1S)

Thallus pale bluish green to yellow-brown. Filaments bent, entangled. Sheaths initially thin, colourless, later yellow-brown, widened. Filaments 6.0–8.4 μm (=7.2 μm) wide, richly repeated false branching. Branches 3.2–6.1 μm (=4.4μm) wide. Trichomes 1.9–2.6 μm (=2.3 μm) wide, distinctly constricted at cross-walls, not attenuated at the ends. Cells longer than wide, cylindrical, non-granular, 3.5–10.8 (32.1) μm (=6.6 μm) long. Apical cells rounded.

Type:— CHINA. Hubei Province. Growing epilithically on well’s stones in a water treatment facility, G. F. Song, 6 June 2012 (holotype CHCB! XS 20120601).

Etymology:— The name of the species “ Scytolyngbya timoleontis ” was chosen due the thick sheaths, which resemble the plant Poa timoleontis .

Occurrence:— epilithically on well’s stones (with dim light) in a water treatment facility with high Fe and Mn contents.

Life cycle:— ( Fig. 2) Mature filaments bent, hard, yellow-brown, sheath thick. When the young branch appears, only 5–10 cells remain attached to the old filament. The young branches were observed to be not attenuated towards ends, with trichomes 1.9–2.6 μm in diameter, obviously constricted at the cross-walls, initially enveloped by a thin, hyaline mucilage (sometimes not easily visible), later the sheath becomes yellow-brownish to black, 2.0–3.2 μm wide and rigid. If the filaments are long enough, the rigid sheath begins to break somewhere, thereby maintaining their flexibility.

Phylogenetic analysis:— the Bayesian analysis, Maximum Likelihood (ML) and Neighbor-Joining (NJ) algorithms produced similar tree topologies. The phylogenetic tree from the 16S rRNA gene analyses ( Fig. 3) showed that Scytolyngbya timoleontis clustered together in a robust clade, separating from Leptolyngbya sensu stricto (A1).

Two distinct large clades were marked in the phylogenetic reconstruction, here named clades A and B. The new species Scytolyngbya timoleontis was placed in Clade A7. Clade A can be divided into seven subclades (A1–A7). Subclade A1 corresponds to Leptolyngbya sensu stricto, and contained the type species of this genus, Leptolyngbya boryana . Subclades A2,A4, and A5gathered the Plectolyngbya , Planktolyngbya , and Phormidesmis species respectively. Subclade A3 was formed by a group of Alkalinema Vaz et Fiore in Vaz et al. (2015: 298) species. Subclade A6 just included one Leptolyngbya species, and subclade A7 consisted of the new species Scytolyngbya timoleontis . Clade B can be divided into two subcaldes (B1 and B2), subclade B1 included three Leptolyngbya species and subclade B2 was formed by the recently described genus Pantanalinema Vaz et Fiore in Vaz et al. (2015: 298).

Direct PCR without routine extraction of DNA resulted in obtaining four 16S rRNA gene sequences. The four 16S rRNA gene sequences from the Scytolyngbya timoleontis population showed more than 99.6% similarity, and these four sequences shared from 89.6% to 93.3% similarities with other Leptolyngbya species. Table 1 lists the 16S rRNA gene sequence similarities among species of the genus Leptolyngbya and those from the other Pseudanabaenales species.

Secondary structure of the 16S-23S ITS:— Table 2 compares the 16S-23S rRNA ITS sequences among Scytolyngbya timoleontis and the five related taxa. These sequences ranged in length from 424 to 794 bp. One or two tRNAs (Ile and Ala) were contained except Pantanalinema rosaneae KF 246503 without tRNA ( Table2). The ITS region of Scytolyngbya timoleontis was different from the other strains both in nucleotide sequence and lengths of some regions. The D1-D1’ helix exhibited six distinct patterns within these six taxa ( Fig 4). All the outgroups differed from Scytolyngbya timoleontis in the absence of a terminal loop separated by only two base pairs from a subterminal bilateral bulge, and in the number of unilateral and bilateral bulges. Within this group, the strain Geitlerinema splendidum (Grevile ex Gomont 1892: 224) Anagnostidis (1989: 129) had a very different structure in the base of helix, which was held together by only four bp instead of the typical five bp in most cyanobacteria ( Fig. 4D). The Box-B helix was the relatively conserved helix represented in Scytolyngbya timoleontis ( Fig. 5). This structure of Scytolyngbya timoleontis differed from all other five taxa Box-B structures, although all of the helical structures had very similar basal sequences. The V3 region of ITS was the most variable helix within all these six taxa which have six different secondary structures ( Fig. 6 A–F).