Salileptolyngbya diazotrophicum Zhou, 2018

Zhou, Wei-Guo, Ding, De-Wen, Yang, Qing-Song, Ahmad, Manzoor, Zhang, Yuan-Zhou, Lin, Xian-Cheng, Zhang, Yan-Ying, Ling, Juan & Dong, Jun-De, 2018, Marileptolyngbya sina gen. nov., sp. nov. and Salileptolyngbya diazotrophicum gen. nov., sp. nov. (Synechococcales, Cyanobacteria), species of cyanobacteria isolated from a marine ecosystem, Phytotaxa 383 (1), pp. 75-92 : 80-81

Salileptolyngbya diazotrophicum Zhou sp. nov. ( Fig. 1 d–f , Fig. 2 f–i , Fig. 3 e–i )

Description: —Thallus blue-green. Filaments not branched, straight or curved to floating mats, 1.49–2.27 μm wide. Sheaths firm, thick, covered the trichomes. Trichomes not attenuated at the end. Distinctly constricted at the cross walls. Cells longer than wide, 1.53–2.37 μm in length and 0.93–1.44 μm in width. Apical cell 1.38–2.43 μm in length, 0.79–1.48 μm in width, and without calyptra. Thylakoids in parietal arrangement, varying from four to five. Gas vesicles absent. No heterocytes. Reproduction via hormogonia.

Etymology: — “diazotrophicum ” means the special ability of the species to fix nitrogen

Habitat: —from plankton-trawled 200-m deep seawater.

Type locality: — CHINA, northern South China Sea , 22°0.169’N, 118°59.876’E, 16 August 2015. (Ecology: temperature 29.45°C; pH 8.96; salinity 33.46‰; silicate 0.16 mg /L; phosphate 0.02 mg /L; ammonium 0.02 mg /L; nitrate 0.04 mg /L; nitrite 0.006 mg /L)

Holotype: A monospecific-dried sample in liquid nitrogen has been deposited in the China Center For Type Culture Collection ( CCTCC); accession number M 2017362

Observation: —Trichomes formed a cyanobacterial mat when cultivated in liquid BG-11 medium. Ultrastructure in a cross-section view showed cell walls surrounded by a fibrous multilayered sheath separated by an extensive electron-transparent layer ( Fig. 3e ). In a longitudinal orientation, cells were linked with intercellular space ( Fig. 3 h-i). Thylakoids were parietal, varying from four to five, and gas vesicles absent ( Figs. 3f–i ).

The morphological features of SCSIO T- 2, SCSIO 43686, and their phylogenetic closest taxa are summarized in Table 1. Both strains presented similar morphological structures with filaments, sheaths and cross walls, but SCSIO T- 2 had a longer cell size and higher length-width ratio than that of SCSIO 43686. Nodosilinea nodulosa UTEX2910 , the representative of Nodosilinea , was also isolated from a marine environment and is able to fix nitrogen ( Perkerson et al. 2011); Compared with our studied strains, it had lower length-width ratio, unique characteristics of flattened filaments and nodules at low light intensity. Leptolyngbya boryana UTEX 485 was representative of Leptolyngbya sensu stricto; it had similar morphological characteristics to our studied strains but with smaller cells. Phormidesmis priestleyi ANT.LPR 2.6 belongs to the genus Phormidesmis ; it had longer trichome width than our strains and cells shorter than wide.

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Figures

FIGURE 1. Light micrographs of Marileptolyngbya sina SCSIO T-2 and Salileptolyngbya diazotrophicum SCSIO 43686 (100X). a–c: SCSIO T-2; d–f: SCSIO 43686. a. unbranched and breakage of filaments. b. rounded terminal cell, sometimes extended. c. entangled filements. d. wavy filaments. e. firm sheath contained uniseriate and unbranched trichome. f. filaments reproducing by hormogonia. Scale bars= 10 μm.

FIGURE 2. Scanning electron micrographs of Marileptolyngbya sina SCSIO T-2 and Salileptolyngbya diazotrophicum SCSIO 43686. a–e: SCSIO T-2; f–i: SCSIO 43686. Scale bars: a, g=10 μm; b–f, i= 5μm; h=1μm.

FIGURE 3. Transmission electron micrographs of Marileptolyngbya sina SCSIO T-2 and Salileptolyngbya diazotrophicum SCSIO 43686. a–b. Cross section view of SCSIO T-2. c–d. Longitudinal section view of SCSIO T-2. e–g. Cross section view of SCSIO 43686. h–i. Longitudinal section view of SCSIO 43686. Scale bars: a–b, e–f, h–i= 200μm; c–d= 500 μm; f= 100μm.