Cephalothrix lacustris Malone et al. (2015: 3004)

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 : 278

Cephalothrix lacustris Malone et al. (2015: 3004) ( Figs 2D, 2I, 2J )

Strains:— LEGE 15487 (MF629804), LEGE 15492 (MF629809) and LEGE 15493 (MF629810).

Description:— In culture, the trichomes start growing at the bottom of the culture flask, forming a thin biofilm towards the top, at the air-medium interface. Groups of filaments may float on the surface of the culture medium or may stay attached to air bubbles at the bottom of the flask. Trichomes are straight or flexuous, slightly constricted at the cell-cell joints and exhibit gliding motility and biconcave necridia. The trichomes are pale to olive-green and are solitary or grouped in mats. In addition, the trichomes have facultative hyaline and firm sheaths that are either attached to the trichome or are at a slight distance ( Fig. 2D, 2I, 2J ). Cells are wider (4.2–7.5 μm) than long (1.4–3.8 μm) and have facultative gas vesicles. Apical cells might be rounded or capitate and have facultative calyptra.

Phylogeny and polyphasic identification:— The 16S rRNA gene sequences of LEGE 15487, LEGE 15493 and LEGE 15492 showed similarity values equal or higher than 98.8% ( Table 4) with the sequences from Cephalothrix lacustris Malone et al. (2015: 3004) CCIBt 3261 (98.8–99.5%) and C. lacustris CMAA 1561 (98.9–99.5%). Concerning the phylogenetic tree, only the ML method was able to give support to a subgroup formed by the abovementioned strains plus C. komarekiana Malone et al. (2015: 3003) CMAA 1558 and Phormidium sp. KS ( Fig. 3 , see also Fig. S1 and Fig. S2 ). Still, the three inference methods support a major clade (ML/BI/MP = 100/1.00/97) that encloses the abovementioned group of sequences and also the sequence of Cephalothrix komarekiana CCIBt 3277, the type strain of the genus ( Fig. 3 ). Based on the morphology, ecology and molecular data, these LEGE strains can be identified as Cephalothrix lacustris .

Figures

FIGURE 1. Map of the study area with an aerial view of the sampling sites: raw and treated water. Coordinate System: UTM zone 22N, SIRGAS 2000.

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).