Limnothrix cf. planctonica (Woloszynska) Meffert (1988: 269)

Cunha De Oliveira, Elane D., Da Cunha, Alan C., Da Silva, Natalina B., Castelo-Branco, Raquel, Morais, João, Schneider, Maria Paula C., Faustino, Silvia M. M., Ramos, Vitor & Vasconcelos, Vitor, 2019, Morphological and molecular characterization of cyanobacterial isolates from the mouth of the Amazon River, Phytotaxa 387 (4), pp. 269-288 : 276

Limnothrix cf. planctonica (Woloszynska) Meffert (1988: 269) ( Figs 2B, 2N )

Strains:— LEGE 15485 (MF629802) and LEGE 15497 (MF629814).

Description:— In culture, groups of trichomes might float, indicating gas-vesicle - driven buoyancy. Trichomes are arranged in fascicles, which are bright blue-green in color and may form thin to thick biofilms at the air-medium interface on the walls and at the bottom of the culture flask. If detached from the bottom, the culture becomes a floating mass. Long trichomes, almost-straight, non-constricted and non-attenuated with facultative, fine, diffluent mucilagevisible in the apical cells ( Fig. 2B, 2N ). The trichomes exhibited a slow gliding motility. The cells are cylindrical, pale blue-green, 1.6–2.6 μm wide and 2.9–8.6 μm long with small facultative gas vesicles localized to the cell poles and with facultative granules. The morphology of these strains resembles those of Limnothrix redekei ( Goor 1918: 258) Meffert (1988: 274) and Limnothrix planctonica (Woloszynska 1912: 530) Meffert 1988: 269 . However, the LEGE strains share more morphological attributes with the latter than with the former ( Komárek & Anagnostidis, 2005).

Phylogeny and polyphasic identification:— The 16S rRNA gene sequences of the Limnothrix Meffert (1988: 274) LEGE isolates share more than 99% of identity with the sequences from Limnothrix sp. CENA545 and from other strains identified as L. planctonica or Limnothrix sp. ( Table 4 and Table S1). These sequences form a clade highly supported by ML and BI methods, and exclusively composed by strains from the Limnothrix genus ( Fig. 3 ). However, this clade is placed distantly from that of the type strain L. redekei NIVA-CYA 227/1 ( Suda et al. 2002), which shows to be phylogenetically more related to Pseudanabaena Lauterborn (1915: 437) strains ( Fig. 3 ). Based on all the data, the strains LEGE 15497 and LEGE 15485 were identified as Limnothrix cf. planctonica ( Meffert, 1988; Komárek & Anagnostidis, 2005).

Figures

FIGURE 2 Microphotographs of the Amazonian cyanobacterial strains: A) Alkalinema aff. pantanalense LEGE 15484, B) Limnothrix cf. planctonica LEGE 15485, C) Leptolyngbya boryana LEGE 15486, D) Cephalothrix lacustris LEGE 15487, E) Phormidium sp. LEGE 15488, F) Pseudanabaena cf. galeata LEGE 15489, G) P. cf. galeata LEGE 15490, H) P. cf. galeata LEGE 15491, I) Cephalothrix lacustris LEGE 15492, J) C. lacustris LEGE 15493; K) unidentified Nostocales LEGE 15494, L) unidentified Nostocales LEGE 15495, M) unidentified Nostocales LEGE 15496, and N) Limnothrix cf. planctonica LEGE 15497.

FIGURE 3. ML phylogenetic tree based on 16S rRNA gene sequences showing the placement of the Amazonian cyanobacterial strains (in bold). Bootstrap values>70% or Posterior Probabilities>0.90 are indicated below the clade nodes (ML/BI/MP). Each strain sequence is identified by its accession number. The tree was rooted with the outgroup Chloroflexus aurantiacus J-10-fl (NR_074263), which was pruned from the tree for clarity. (T)refers to type strains according to CyanoType (Ramos et al. 2017).