Pseudanabaena cf. galeata

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 : 279

Pseudanabaena cf. galeata ( Figs 2F, 2G, 2H )

Strains:— LEGE 15489 (MF629806), LEGE 15490 (MF629807) and LEGE 15491 (MF629808).

Description:— Planktonic cyanobacteria with trichomes that are almost straight and are either solitary or form mats in culture. Thin emerald-green mats float at the air-medium interface in the culture flask and grow on the walls and bottom of the flask in clusters. The trichomes are deeply constricted at the cross-walls, are non-attenuated and have facultative granules ( Fig. 2F, 2G, 2H ). The cells are pale blue-green or bright blue-green in color, 1.3–2.8 μm wide, 1.4–5.7 μm long and cylindrical and are connected via hyaline bridges. The apical cells exhibit polar gas vesicles. The strain LEGE 15491 exhibited a space between the cells similar to gas vesicles. The trichomes move forward slowly via trembling motility. These strains are longer than Pseudanabaena mucicola (Naumann et Huber-Pestalozzi) Schwabe (1964: 32) and exhibit a morphology that matches that of P. galeata Böcher (1949: 13) ( Komárek & Anagnostidis, 2005).

Phylogeny and polyphasic identification:— The BLAST search results for the sequences from strains LEGE 15489 and LEGE 15490 were very similar, while the BLAST results for the sequence from LEGE 15491 was comparable, although slightly different ( Table S1). Despite this, Pseudanabaena LEGE strains share high similarity values between themselves (99.1–100%), and between themselves and the strains retrieved from the BLAST searches: Pseudanabaena sp. CMAA1555 (99–99.8%) and P. galeata CHAB 732 (98.8–99.9%) ( Table 4). LEGE 15489 and LEGE 15490 are clustered with Pseudanabaena sp. CMAA 1555 in a clade with good support values (ML/BI/MP = 99/1.00/76), as illustrated in Fig. 3 . On the other hand, these strains form a larger clade together with LEGE 15491 and P. galeata CHAB 732, even though in this case it is better supported by BI (1.00) than by ML (80%) and MP (74%) methods. The closest branch of this clade is a cluster that includes P. galeata CHAB 2916 and P. galeata PB ( Fig. 3 ). Based on the morphological description, behavior in culture and phylogenetic information, the three LEGE strains were identified as Pseudanabaena cf. galeata (see also Komárek & Anagnostidis, 2005).

Unidentified Nostocales ( Figs 2K, 2L, 2M )

Strains:— LEGE 15494 (MF629811), LEGE 15495 (MF629812) and LEGE 15496 (MF629813).

Description:— Heterocytous cyanobacteria, typically belonging to the order Nostocales ( Komárek, 2013) . The filaments grow at the bottom and walls of the culture flask and may produce air bubbles. These bacteria show flexuous or coiled filaments with tight, diffluent, mucilaginous envelopes ( Fig. 2K, 2L, 2M ). Hormogonia are present and exhibit gliding motility. The vegetative cells are oval or highly spherical, 2.8–4.6 μm wide, and 2.0–4.0 μm long. The terminal heterocysts are 3.2 ± 0.4 μm wide and 3.3 ± 0.4 μm long. The colonies are olive-green and rounded, flattened or irregular in form.

Phylogeny and polyphasic identification:— BLAST results show that sequences from the filamentous, heterocytous LEGE strains have more than 98% identity with sequences from several strains identified as Nostoc Vaucher ex Bornet et Flahault (1888: 181) and with a sequence from an unidentified Nostocaceae cyanobacterium ( Table S1). Table 4 shows that the LEGE sequences have very high similarities to the sequence of Nostoc sp. Cam2S01 (ranging from 99.5% to 99.6%). Unlikely, LEGE strains sequences present lower similarity values when compared with that of the reference strain Nostoc punctiforme PCC 73102 (95.9–96.1%) ( Table 4). In fact, the Nostocales LEGE strains are phylogenetically apart from the Nostoc clade sensu stricto ( Genuário et al. 2015), which includes N. punctiforme PCC 73102 ( Fig. 3 ). Data from morphological, ecological, and phylogenetic analyses were not sufficient to properly identify these strains at the species or genus level. However, these strains can be classified as belonging to the order Nostocales .

Screening for cyanotoxins:—None of the genes associated with cyanotoxin production could be amplified.

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).