Microseira wollei (Farlow ex Gomont) G.B.McGregor and Sendall ex Kennis 2017

Bae, Eun Hee, Kang, Jae-Shin & Park, Chong-Sung, 2020, New report on cyanophyte in Korea, Microseira wollei (Farlow ex Gomont) G. B. McGregor and Sendall ex Kennis (Oscillatoriaceae), Journal of Species Research 9 (3), pp. 210-217 : 213-215

Microseira wollei (Farlow ex Gomont) G.B.McGregor and Sendall ex Kennis 2017

Basionym: Plectonema wollei Farlow ex Gomont 1892 Homotypic synonym: Lyngbya wollei (Farlow ex Gomont) Speziale and Dyck 1992

Type specimen: 945406 (syntype, NY)

Habitat: The filaments of Microseira wollei were found in sublittoral habitat of a freshwater river entwined in the basal part of aquatic macrophytes or plants. Collection site: The riverside of 7 km upper stream from Gangjeong-Goryeong weir at Dalsung-gun , Daegu-city, Nakdong River (35°51 ʹ 31.6 ʺ N 128°23 ʹ 23.0 ʺ E) .

Specimens: NIBRCY0000001021 (collected by E.H. Bae, no. EHB20200513-1, 35°51 ʹ 31.6 ʺ N 128°23 ʹ 23.0 ʺ E, 13 May 2020), NIBRCY0000001022 (collected by E.H. Bae, no. EHB20200513-2, 35°51 ʹ 31.6 ʺ N 128°23 ʹ 23.0 ʺ E, 13 May 2020), NIBRCY0000001023 (collected by E.H. Bae, no. EHB20200513-3, 35°51 ʹ 31.6 ʺ N 128°23 ʹ 23.0 ʺ E, 13 May 2020), NIBRCY0000001024 (collected by E.H. Bae, no. EHB20200616-1, 35°51 ʹ 31.6 ʺ N 128°23 ʹ 23.0 ʺ E, 16 June 2020) in KB.

Habit: Microseira wollei was identified as remarkably large-celled, greenish black filamentous, mat-forming characteristics, observed with naked eyes.

Morphology

Thallus a prostrate, greenish blue-black tough mat of densely entangled filaments ( Fig. 1 ). Filaments straight to variously contorted, and infrequently false-branched. An individual filament consists of an uniseriate file of discoids to cylindrical cells. Cell division occurs throughout the length of the filament and apex is flat at immediately after trichome division. Sheath colorless, hyaline, when old distinctly thickened, roughened and colored, open at the apex. Trichomes isopolar, uniformly cylindrical, up to 70 μm wide; not or slightly constricted at the cross-walls. Cells discoid, coffee bean shaped in lateral view; contents finely granular, without aerotopes; apical cells rounded, without a calyptra and thickened outer cell wall ( Fig. 2 ).

Ultrastructures by transmission electron microscopy

(TEM)

Filaments of M. wollei were cross-sectioned to observe their ultrastructural patterns of thylakoids and intracellular contents by TEM. The trichome filaments were covered by cell wall and outer thick sheath ( Fig. 3A ). The cytoplasm was filled with numerous thylakoids ( Fig. 3B ). Membranous thylakoids were extended from near cell membrane and densely stacked as bundle ( Fig. 3C, D ). The bundles of thylakoids were located irregularly, not parietally nor radially.

Molecular phylogeny

A total of 1,267 bp of the 16S rRNA gene and 318 bp nifH (nitrogenase iron protein) gene sequences of were analyzed. All sequences of eight isolates from Korea were identical based on these two genes. Among 1,267 bp the 16S rRNA gene sequences, sequences of the Korean population were different from 0.02% (2 bp) to the Japanese population (NIES-4236), 1.2 - 1.3% to the Australian population, and 2.5 - 3.7% to USA population and other geographical populations in NCBI database. While, nucleotides of nifH gene showed distance as 8.4 - 8.7% to Australian samples and 3.5 - 3.8% to other populations. The neighbor joining trees are presented for 16S rRNA gene ( Fig. 4 ) and nifH gene ( Fig. 5 ). All trees supported our conspecific speculation of the Korean population of M. wollei .

Cyanotoxin analysis by PCR of cyr genes: The cyrF gene of 447 bp and cyrJ gene of 626 - 657 bp were not positive in all Korean samples.

Figures

Fig. 1. Collection site and specimen information of Microseira wollei. A. Collection site near Gangjeong-Goryung weir in the Nak- dong river. B. Natural form of Microseira wollei. C. Dried specimens deposited in KB, NIBRCY0000001021 (13 May 2020). D. NI- BRCY0000001024 (16 Jun 2020).

Fig. 2. Light micrographs of Microseira wollei collected in Gangjeong-Goryeong weir. A-D. Unbranched filament, showing thick sheath and trichomes. E, F. Discoid single cell released from filament.

Fig. 3. Ultrastructures of Microseira wollei by transmission electron microscopy (TEM). A. Cross-section of filament surrounded by cell wall and thickened sheath. B. Cytoplasm filled with numerous thylakoids. C. Densely stacked thylakoids. D. Magnified thylakoids. cp (cytoplasm), cw (cell wall), sh (sheath), th(thylakoid).

Fig. 4.Phylogenetic tree based on the 16S rRNA gene partial sequences aligned 1,267 bp showing the genetic position of Microseira wollei of Korea along with other geographical populations and related taxa with some taxonomic treatment of M. wollei. Numbers indicate bootstrap value (>50%) from 1,000 replicates maximum parsimony (MP), maximum likelihood (ML), neighbor-joining (NJ) analysis respectively. GenBank accession numbers are shown in parentheses (scale bar: 0.02 nucleotide substitutions per site).

Fig. 5. Phylogenetic tree based on the nifH gene partial sequences aligned 318 bp showing the genetic position of Microseira wollei of Korea along with other geographical populations. Numbers indicate bootstrap value(>50%) from 1,000 replicates maximum parsimony(MP), maximum likelihood (ML), neighbor-joining (NJ) analysis respectively. GenBank accession numbers are shown in parentheses (scale bar: 0.05 nucleotide substitutions per site).