Gloeothece guizhouensis J.Chen et F.Cai, 2024

Chen, Jiaxin, Li, Shuheng, Li, Renhui, Yu, Gongliang & Cai, Fangfang, 2024, The description of a novel Gloeothece species (Chroococcales, Cyanobacteria) from China, based on a polyphasic approach, Phytotaxa 662 (1), pp. 53-66 : 56-61

Gloeothece guizhouensis J.Chen et F.Cai sp. nov. ( Fig. 1 )

Description: Coccoid cyanobacteria. Colonies macroscopic, being made up with small cell clusters into a gray-green or olive-green smooth gelatinous mass covering the substrate, 15–35 μm long and 10–26 μm wide. Mucilaginous wide, colorless, with 1–2 diffluent, often scarcely visible, concentric lamellations around small clusters of cells. Cells oval to cylindrical, mostly 2–8 cells forming a small population, rarely single, 7–11 μm long, 4–6 μm wide, with dividing cells 10–12 μm long. Cell contents weakly pigmented, grayish olive to yellowish olive colored, mostly homogenous, sometimes minutely granular. Morphological comparison of the studied strain Gloeothece guizhouensis CHAB 5847 and several typical Gloeothece species are displayed in Table 2.

Holotype (here designated):Dry specimen of the strain CHAB5847 stored in the FreshwaterAlgal Herbarium( HBI), Institute of Hydrobiology , Chinese Academy of Science, Wuhan, China, with specimen number of GZLB1005.

Reference strain: G. guizhouensis CHAB 5847, culture maintained at Wuhan Polytechnic University, Wuhan, China.

Type locality: In Xiaoqikong Scenic Spot, Libo County, Guizhou Province, China (25°12′– 25°34′N, 107°39′– 107°95′E).

Etymology: G guizhouensis refers to Guizhou Province, where the strains were collected, transliterated into Latin.

Habitat: Wet soil.

Molecular and Phylogenetic Analysis. The total length of the obtained 16S rRNA gene sequences of two clones of CHAB 5847 were 1484 bp. The results manifested that the similarity between the two clones was 100%. And the 16S rRNA gene sequences of the studied strain shared 93.1%–98.1% similarity with other Gloeothece species ( Table 3).

In total, 103 cyanobacterial taxa sequences, including the studied strain, were applied to construct phylogenetic trees. The 16S rRNA gene phylogeny was constructed based on neighbor-joining (NJ), maximum likelihood (ML), and Bayesian inference (BI). The Bayesian tree revealed that the studied strain, together with other Gloeothece species, shaped a separate and unique cluster. In the big Gloeothece cluster, two clones of 16S rRNA gene sequences of the studied strain CHAB 5847 formed an independent clade, and were close to Gloeothece aequatorialis with high bootstrap values of 100%, 100%, and 1.00 (NJ, ML, BI approaches), correspondingly ( Fig. 2A ).

The percent dissimilarity among 16S–23S ITS region between our strain and other Gloeothece species varied from 22.2%–56.0% ( Table 4). The 16S–23S ITS phylogenetic tree was constructed based on neighbor-joining (NJ) and maximum likelihood (ML). The ML tree showed that two clones of ITS sequences of the studied strain shaped a single cluster, and was supported by NJ, ML approaches with high bootstrap values of 100%, 100% ( Fig. 2B ).

The 16S–23S ITS secondary structures. The ITS rRNA regions of the strain in this study, as well as sequences derived from GenBank, were used to construct the ITS rRNA region secondary structures. The ITS secondary structure of the strain G. guizhouensis CHAB 5847 was compared to infer its relationship with other several representative

Gloeothece species ( Table 5). The full-length of the ITS sequence of the isolated G. guizhouensis CHAB 5847 was 348 bp. The D1-D1’ helices of Gloeothece were identical at the basal part of the helix (except G. citriformis ), but were diverse in the nucleotides and patterns. The D1-D1’ helix analysis showed that G. guizhouensis CHAB 5847 ( Fig. 3A ) consist of a base stem of 4-bp helix, followed by a 2:9-bp bilateral bulge, followed by one 2:2-bp bilateral bulge, and the terminal loop contained 13-bp bases (CUUUAAUUUUUAC).

Shown in Fig. 4 , the Box-B helices of Gloeothece were all very similar at the basal part of the helix, but the sequences and structure at the end are disparate. The Box-B helices of Gloeothece species were divided into several different types. The base stem of the Box-B helix of CHAB 5847 ( Fig. 4A ) composed of a 4-bp helix, followed by a 3- bp bilateral ring structure, a 7-bp helix, and the terminal loop with 6-bp bases (AAAAAA). The V3 helices were mostly various in sequence, the base part, structure and length ( Fig. 5 ). The V3 helix of the studied stain was completely different from that of other Gloeothece species. The base stem of G. guizhouensis CHAB 5847 ( Fig. 5A ) was made up of a 6-bp helix, followed by a 2:2-bp bilateral bulge, and the terminal loop contained 6-bp bases (AAUCGA).

Figures

FIGURE 1. Micrographs of G. guizhouensis CHAB 5847 under the light microscopy (LM): (i,j) G. guizhouensis CHAB 5847 in liquid BG11 medium. (a–h) Colonies at different magnification. Scale bars: (a, b) 100 μm, (c, d) 50 μm, (e, f) 20 μm, (g, h) 10 μm.

FIGURE 2. Phylogenies based on rRNA data. (A) Bayesian Inference (BI) phylogenetic tree of G. guizhouensis CHAB 5847 based on 16S rRNA gene sequences. * Indicates that bootstrap values are 100,—indicates that Bootstrap values lower than 50% with distance/parsimony methods are not displayed at the nodes in this form: NJ/ML/Bayes. The novel species are in bold font. (B) Maximum Likelihood (ML) tree of Gloeothece based on the 16S–23S ITS region of the operon containing the tRNAIle gene.Branch support values are given at nodes in this order: NJ/ML, supports> 99% from both analyses are indicated by an asterisk. Bold font indicates sequences obtained in this study.

FIGURE 3. Secondary structure of D1–D1’ helix: (A) G. guizhouensis CHAB 5847; (B) G. aequatorialis SAG 36.87; (C) G. aurea CCALA 1111; (D) G. bryophila HA4964-KK2; (E) G. citriformis PCC 7424; (F) G. membranacea SAG 26.84; (G) G. reniformis CCALA 1113; (H) G. tepidariorum PCC 6909 (=ACOI 604) and CCAP 1430/3; (I) G. tepidariorum CCALA 1112 (=CCALA 1114); (J) G. tonkinensis Vict Nam 01; (K) G. verrucosa PCC 7822.

FIGURE 4. Secondary structure of Box-B helix: (A) G. guizhouensis CHAB 5847; (B) G. aequatorialis SAG 36.87; (C) G. aurea CCALA 1111; (D) G. bryophila HA4964-KK2; (E) G. citriformis PCC 7424; (F) G. membranacea SAG 26.84; (G) G. reniformis CCALA 1113; (H) G. tepidariorum PCC 6909 (=ACOI 604) and CCAP 1430/3; (I) G. tepidariorum CCALA 1112 (=CCALA 1114); (J) G. tonkinensis Vict Nam 01; (K) G. verrucosa PCC 7822.

FIGURE 5. Secondary structure of V3 helix: (A) G. guizhouensis CHAB 5847; (B) G. aequatorialis SAG 36.87; (C) G. aurea CCALA 1111; (D) G. bryophila HA4964-KK2; (E) G. citriformis PCC 7424; (F) G. membranacea SAG 26.84; (G) G. reniformis CCALA 1113; (H) G. tepidariorum PCC 6909 (=ACOI 604) and CCAP 1430/3; (I) G. tepidariorum CCALA 1112 (=CCALA 1114); (J) G. tonkinensis Vict Nam 01; (K) G. verrucosa PCC 7822.