Cephalothrix lacustris Malone et al., 2015

Song, Ji-Ho, Kim, Do-Hyun, Lee, Nam-Ju, Kim, So-Won & Lee, Hye-Ryeung Wang and Ok-Min, 2022, Four newly recorded species of planktonic cyanobacteria (Oscillatoriales, Cyanobacteria) in Korea, Journal of Species Research 11 (4), pp. 321-329 : 325-328

Cephalothrix lacustris Malone et al., 2015 ( Fig. 4 )

Filaments fasciculated, blue-green in color. Trichomes cylindrical, straight, slightly attenuated towards ends, sometimes bent at the end, constricted at the cross-walls. Sheaths hyaline and firm. Apical cells strongly capitate, sometimes with conical calyptra. Cells shorter than wide, with facultative aerotopes, 2.12-3.43 μm long, 4.92-6.12 μm wide. Hormogonia formation by necridic cells.

Ecology. This species appeared in freshwater ponds ( Malone et al., 2015) and was isolated from freshwater in this study.

Distribution. Brazil ( Malone et al., 2015).

Site of collection. 472, Woongjin-dong, Gongju-si , Chungcheongnam-do (36°27′47.9″N, 127°06′05.4″E). Date of collection. August 26, 2019 .

Specimen deposit No. FBCC-A1473.

16S rRNA and phylogenetic affiliation

In this study, ML and Bayesian phylogenetic analysis were performed for more accurate phylogenetic analysis. In addition, if the 16S rRNA gene sequence similarity is 98.65% or more, it can be determined as the same species ( Kim et al., 2014), so the 16S rRNA gene sequence similarity and genetic distance were also analyzed.

In Laspinema thermale (FBCC-A1475), a phylogenetic analysis was performed by comparing L. thermale , L. etoshii , L. lumbricale , and other species, previously reported in NCBI, and as a result, all trees showed similar branching patterns. Also, L. thermale (FBCC-A1475) was tied to the same cluster as previously reported L. thermale (two strains including HK S5), and it was confirmed that it formed a cluster distinctly different from L. etoshii and L. lumbricale included in the genus Laspinema ( Fig. 5 ). Additionally, as a result of analyzing the 16S rRNA gene sequence similarity and genetic distance, it showed a similarity of 99.30-99.50% and a genetic distance of 0.42- 0.63% with the previously reported L. thermale ( Table 2).

For Planktothricoides raciborskii (FBCC-A1472), analysis was performed on P. raciborskii and other species, previously reported in NCBI. All trees showed similar branching patterns, and P. raciborskii (FBCC-A1472) was tied to the same cluster as previously reported P. raciborskii (six strains including NIES-207), forming a cluster distinctly different from other species ( Fig. 5 ). In the case of P. attenuata belonging to the same genus as P. raciborskii , there was no previously reported genetic information, so it was excluded from the phylogenetic analysis. However, P. raciborskii exhibits narrowing from apical cell of trichome, whereas P. attenuata showed a distinct morphological difference because trichome gradually narrowed from the central part to apical cell ( Komárek and Komárková-Legnerová, 2007). Additionally, as a result of analyzing the 16S rRNA gene sequence similarity and genetic distance, it showed a similarity of 98.80-99.50% and a genetic distance of 0.38-1.08% with the previously reported P. raciborskii ( Table 2).

The phylogenetic analysis of Planktothrix spiroides (SJH-1) was performed by comparing P. spiroides , P. agardhii , P. mougeotii , P. pseudagardhii , P. rubescens , and other species, previously reported in NCBI, and as a result, all trees showed similar branching patterns. Also, P. spiroides (SJH-1) was tied to the same cluster as previously reported P. spiroides (three strains including fs1), and it was confirmed that it formed a cluster distinctly different from P. agardhii , P. mougeotii , P. pseudagardhii , and P. rubescens included in the genus Planktothrix ( Fig. 5 ). Additionally, as a result of analyzing the 16S rRNA gene sequence similarity and genetic distance, it showed a similarity of 99.80-99.90% and a genetic distance of 0.08- 0.15% with the previously reported P. spiroides ( Table 2).

For Cephalothrix lacustris (FBCC-A1473), a phylogenetic analysis was performed by comparing C. lacustris , C. alaskaensis , C. komarekiana , and other species, previously reported in NCBI. As a result, all trees showed similar branching patterns, and C. lacustris (FBCC-A1473) was tied to the same cluster as previously reported C. lacustris (three strains including CCIBt 3261), forming a cluster distinctly different from C. alaskaensis and C. komarekiana included in the genus Cephalothrix ( Fig. 5 ). Additionally, as a result of analyzing the 16S rRNA gene sequence similarity and genetic distance, it showed a similarity of 99.80-99.90% and a genetic distance of 0.1-0.19% with the previously reported C. lacustris ( Table 2).

Through the above results, Laspinema thermale , Planktothricoides raciborskii , Planktothrix spiroides , and Cephalothrix lacustris are proposed as unrecorded species of cyanobacteria in Korea.

Figures

Fig. 4. Microscopic photographs of Cephalothrix lacustris FBCC-A1473. (A, B) Arrangement of filament in the colony, (C-H) Apical cell of trichomes, (C, D, H, I, L) Aerotopes, (F-H, J-L) Apical cell strongly capitate with calyptra, (K) Necridic cell. Scale bars (A) 50 μm, (B) 20 μm, (C-L) 10 μm.

Fig. 5. Maximum-Likelihood (ML) phylogenetic tree based on 16S rRNA gene sequences of Laspinema thermale, Planktothricoides raciborskii, Planktothrix spiroides, Cephalothrix lacustris, and other cyanobacterial strains. A 16S rRNA gene sequences of Gloeobacter violaceus (Gloeobacteraceae), Pseudanabaena catenata (Pseudanabaenaceae) were included as the outgroups. The support values at the nodes are written as follows: ML/Bayesian. Support values are displayed at nodes for>50% ML bootstrap proportions and>0.5 Bayesian posterior probability. The branch lengths are proportional to the scale given. Bold represents data obtained in this study.