Neosynechococcus sphagnicola Dvořák, Hindák, Hašler & Hindáková, 2014

Dvořák, Petr, Hindák, František, Hašler, Petr, Hindáková, Alica & Poulíčková, Aloisie, 2014, Morphological and molecular studies of Neosynechococcus sphagnicola, gen. et sp. nov. (Cyanobacteria, Synechococcales), Phytotaxa 170 (1), pp. 24-34 : 26-28

Neosynechococcus sphagnicola Dvořák, Hindák, Hašler & Hindáková , sp. nov. ( Fig. 1 )

Cells solitary or grouped in short pseudofilaments or irregularly clusters. Cells Synechococcus -like, i.e. short to long cylindrical or cylindrically oval, several times longer than wide, (1.5)–3–10–(70) × (0.8)–1.5–1.8–(2) µm. Protoplasm homogenous, blue-green, cytoplasm with a conspicuous row of central granules. Cells are known to be motile by a slow gliding. Cells divide by binary fission, transversely in one plane in successive generations, perpendicular to longitudinal axis into two isomorphic or different (after asymmetric binary fission) daughter cells, which occasionally remain joined for some period in pairs or up to 5 cells.

Type: — SLOVAKIA. Peat bog Klin near Námestovo, 49º 25’ N, 19º 29’ E, coll. F . Hindák, 12 September 2010 (holotype OLM! Botany 24: Lichenes and others No. 9217, dried sample is deposited in Regional Museum in Olomouc , Czech Republic. Type strain: Culture Collection of Algae of Charles University in Prague, Czech Republic, number CAUP A 1101 ) .

Etymology:—The generic name Neosynechococcus expresses a new genus among Synechococcu s-like cyanobacteria. The Latin species epithet is derived from the typical endophytic mode of life in acidic Sphagnum peat bog.

Habitat:—Facultatively endophytic inside hyaline cells of Sphagnum , sheaths of cyanobacteria, dead cells of desmids, carapaces of dead crustaceans, and solitary.

Ultrastructure:—( Fig. 1 ) Cell wall does not contain conspicuous mucilage layer. Thylakoids possess parietal arrangement. Centroplasm includes row of granules (probably polyhydroxybutyrate), glycogen, polyphosphate granules and carboxyzomes. Especially old cells exhibit invagination of cell wall at both ends, which are visible on TEM as bright spherical or hemispherical areas.

Observations:—Morphological features of N. sphagnicola were consistent in both natural and cultured material except maximum cell length, which varied from 20 µm in natural samples to 70 µm in culture and subcultures. Moreover, growth of N. sphagnicola in culture with Sphagnum was demonstrated by inoculation of culture on dried Sphagnum sp. (peat moss) biomass. Neosynechococcus sphagnicola was observed growing inside the hyaline cells ( Fig. 1 ). However, N. sphagnicola grows also freely in the liquid medium and on the peat moss biomass. Thus, N. sphagnicola is able to actively penetrate into the hyaline cells, while also able to occupy a wider spectrum of habitats as was observed in the natural samples. 16S rRNA, 16S-23S ITS and rbc L sequences ( Figs 2–4 ) were used for a reconstruction of the evolutionary history of the studied strain. Neosynechococcus consistently forms a distinctive lineage in all phylogenetic trees, with only the 16S rRNA phylogeny showing significant bootstrap support ( Fig. 2 ). The 16S rRNA and 16S-23S ITS sequences clustered together with filamentous cyanobacteria of the genus Leptolyngbya Komárek et Anagnostidis (1988: 390) . However, using the rbc L phylogeny ( Fig. 4 ), Neosynechococcus shared a clade with Synechococcus and Thermosynechococcus Katoh et al. (2001: 604) , but with no bootstrap support. The closest BLAST (http://blast.ncbi.nlm.nih.gov/Blast.cgi) hit for the 16S rRNA sequence of the studied strain was Leptolyngbya frigida Komárek et Anagnostidis (1988: 390) , ANT.L52B.3 ( AY493612 ) with 97% similarity. An exact sequence similarity with the closest BLAST hit was calculated from the pairwise sequence alignment (96.6%). 16S rRNA phylogeny showed the overall polyphyletic origin of the Synechococcus -like morphotypes. They formed eight independent lineages. Six of these included filamentous cyanobacteria. Strain Hindák 2010/8 formed novel unicellular lineage related to filamentous cyanobacteria of the genus Leptolyngbya ( Fig. 2 ) and was a sister group to a clades containing Synechococcus , Leptolyngbya and other filamentous cyanobacteria. However, these clades were connected with no bootstrap support.

Figures

FIGURE 1. Morphological variability of Neosynechococcus sphagnicola. A–B. Population living inside Sphagnum sp. hyalocytes, + pseudofilament formation, arrow shows formation of the cell wall invagination. C–D. TEM (cross-sections), * parietal arrangement of thylakoids, ** granule of polyhydroxybutyrate, *** invaginations of cell wall, X polyphosphate body, XX cyanophycin granule, arrow shows cyanophycean starch. E–F. Microphotograph of N. sphagnicola strain. F. Extremely elongated cells. G. Line drawings showing cell differentiation and pseudofilament formation of N. sphagnicola. Scale bars: 5 µm (A, B, E–G), 2 µm (C), 1 µm (D).

FIGURE 2. Phylogenetic tree of the Synechococcus-like cyanobacteria and other reference taxa from orders Chroococcales and Oscillatoriales based on 16S rRNA using maximum likelihood topology. The bootstrap support values are at the nodes in order – maximum likelihood, neighbour joining, maximum parsimony.Only values higher than 50% are presented, asterisk represents 99 and 100% bootstrap value. Studied strain is printed in bold and arrows represent polyphyletic lineages of the polyphyletic genus Synechococcus sensu lato.

FIGURE 3. Phylogenetic analysis based on complete sequence of the 16S-23S ITS region of the closest relatives identified by BLAST and available sequences of Leptolyngbya and Synechococcus It is based on maximum likelihood topology and support values at the nodes are in following order: maximum likelihood, neighbour joining, maximum parsimony. Studied strain is printed in bold.

FIGURE 4. Phylogenetic analysis based on complete sequence of the rbcL gene of the closest relatives identified by BLAST. It is based on maximum likelihood topology and support values at the nodes are in following order: maximum likelihood, neighbour joining, maximum parsimony. Studied strain is printed in bold.