Aliterella shaanxiensis Q. Zhang
Creators: name: Zhang, Qi
name: Zheng, Lingling
name: Li, Tianli
name: Li, Renhui
name: Song, Lirong
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Bacteria
Cyanobacteria
Cyanobacteriia
Cyanobacteriales
Chroococcidiopsidaceae
Aliterella
Aliterella shaanxiensis

description: Aliterella shaanxiensis Q. Zhang et L.R. Song sp. nov. (Figs. 1–2)   
Solitary cells or, more commonly, microscopic irregular or rounded colonies with variable number of cells (up to 32–64 cells or more), usually aggregated into forming irregular, extended, compact multicolonial groups. Mucilage unstratified, colourless and firm surrounding cells and colonies. Cells cylindrical with rounded ends, measuring 2.8–3.7 μm long, 2.0–2.7 μm in diameter, 1.3 to 1.7 × longer than wide (mean, 1.5 ×). Cell contents blue-green, slightly granulated, or sometimes homogeneous. Thylakoids parietal. Reproduction by simple binary cell division in three or more planes.  
 Type: — CHINA. Shaanxi Province: Hongsi Lake, Hanzhong, elev. 629 m, N 32° 54’ 12”, E 106° 52’ 45”, collected by Qi Zhang on 17 Augest 2013 (holotype HBI! HZ 20130817). The authentic strain FACHB –2293 is also available in Freshwater Algae Culture Collection at the Institute of Hydrobiology (FACHB-collection), Chinese Academy of Sciences, Wuhan, Hubei, China, from which the holotype is derived. The holotype material was the source of 16S–23S rRNA gene sequence deposited as GenBank accession numbers MH 023997.   
 Habitat: —This taxon occurred in freshwater lakes.   
 Etymology: —The species epithet ‘ shaanxiensis ’ is derived from the type locality Shaanxi Province.   
 Light and electron microscopy: —The thallus was composed of solitary cells or, more commonly, microscopic colonies, forming extended and compact multicolonial groups (Fig. 1 A–B). Colonies were mostly irregular, sometimes rounded, with several cells (up to 32–64 cells or more) (Fig. 1 C–D). Cells were cylindrical with rounded ends when isolate (Fig. 1 F–G), sometimes irregular by mutual extrusion when in dense colonies (Fig. 1 C–D). Cells were 2.8–3.7 μm long (mean = 3.3 ± 0.3 μm, n = 40), 2.0–2.7 μm in diameter (mean = 2.2 ± 0.2 μm, n = 40), 1.3 to 1.7 × longer than wide (mean, 1.5 ×) (Fig. 1 F–G). With pressure cells were easily removed from colonies while the mucilaginous envelope remained (Fig. 1 E). The chromatoplasm and centroplasm were usually recognizable under light microscopy (Fig. 1 E–G).   
TEM showed that the cells were enveloped by firm and compacted mucilaginous sheath (Fig. 2 A–B). The cell wall consisted of three layers measured about 40 nm width, in which the electron-dense peptidoglycan layer (Fig. 2 C, E). The centroplasm and chromatoplasm were usually recognizable. DNA fibrils and spherical polyphosphate bodies were seen in centroplasm via TEM (Fig. 2 C, F). The chromatoplasm was composed of phycobilisomes, glycogen granules, thylakoids and their associated structures (Fig. 2 E–F). The ultrastructure showed that three to five parietal thylakoids could be parallel to the cell wall (Fig. 2 C, E–F). Binary fission occurred via a constrictive pinching mechanism in which all cell wall layers were involved (Fig. 2 D).  
 Molecular phylogeny and sequence analyses: —A total of 75 sequences of representative taxa were included in the phylogenetic analyses to assess the placement of the Aliterella clade in the Cyanobacteria. ML and Bayesian inference analyses produced similar tree topologies in our phylogenies. ML tree with indication of Bayesian posterior probabilities was shown in Fig. 3. All Aliterella species, including A. atlantica, A. antarctica and A. shaanxiensis, clustered into a monophyletic group in our phylogenies. A. shaanxiensis affiliated closely to A. atlantica with significant support values (BP = 0.85 and PP = 0.98). Three strains of uncultured bacteria were closely related to Aliterella clade.   
 16S rRNA gene sequence similarity between A. antarctica CENA 408 T and A. atlantica CENA 595 T was 97.4% (Table 1). Molecular data confirmed the distinctiveness of our strain that show 16S rRNA gene sequence similarity values of 98.2% with A. antarctica CENA 408 T and 98.3% with A. atlantica CENA 595 T (Table 1). The terminal loop and basal portion of the D1–D1′ helix was relatively conserved among the three strains (Fig. 4). The basal part consisted of a 4 bp helix, followed by a bilateral bulge of 9 bases and a side loop with single unpaired base. The terminal loop was conserved with 5 bp bases. Two bilateral bubbles were observed in the middle portion of D1–D1′ helix from A. atlantica CENA 595 T and A. antarctica CENA 408 T (Fig. 4a, b); however, one bilateral bubble and two minor loops with 2 bases were observed in in the middle portion from strain FACHB–2293 (Fig. 4c). In our predicted models, there were 9 base exchanges with one compensatory base change and two hemi-compensatory base changes in the D1–D1′ helix between strain FACHB–2293 and A. antarctica CENA 408 T, and 5 base exchanges with one hemi-compensatory base in the D1–D1′ helix between strain FACHB–2293 and A. atlantica CENA 595 T. The Box-B helix was quite variable in structure (Fig. 5). The base of the stem consisted of a 6 or 7 bp helix in A. atlantica CENA 595 T and strain FACHB–2293 (Fig. 5b, c). A single unpaired base was observed in the base of the stem form A. antarctica CENA 408 T (Fig. 5a). Two loops with 6 bases were presented in the middle portion from A. atlantica CENA 595 T and A. antarctica (Fig. 5a, b), whereas a loop with 8 bases, a side loop with 3 bases and a single unpaired base were presented in the middle portion from strain FACHB–2293 (Fig. 5c).
description: Published as part of Zhang, Qi, Zheng, Lingling, Li, Tianli, Li, Renhui & Song, Lirong, 2018, Aliterella shaanxiensis (Aliterellaceae), a new coccoid cyanobacterial species from China, pp. 211-220 in Phytotaxa 374 (3) on pages 213-215, DOI: 10.11646/phytotaxa.374.3.2, http://zenodo.org/record/13727229