Marileptolyngbya sina gen. nov., sp. nov. and Salileptolyngbya diazotrophicum gen. nov., sp. nov. (Synechococcales, Cyanobacteria), species of cyanobacteria isolated from a marine ecosystem Author Zhou, Wei-Guo CAS Key Laboratory of Tropical Marine Bio-resources and Ecology Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Guangzhou, 510301, China & University of Chinese Academy of Sciences, Beijing, 100049, China Author Ding, De-Wen CAS Key Laboratory of Tropical Marine Bio-resources and Ecology Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Guangzhou, 510301, China & The First Institute of Oceanography, State Oceanic Administration (SOA), Qingdao, 266061, China Author Yang, Qing-Song CAS Key Laboratory of Tropical Marine Bio-resources and Ecology Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Guangzhou, 510301, China & University of Chinese Academy of Sciences, Beijing, 100049, China Author Ahmad, Manzoor CAS Key Laboratory of Tropical Marine Bio-resources and Ecology Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Guangzhou, 510301, China & University of Chinese Academy of Sciences, Beijing, 100049, China Author Zhang, Yuan-Zhou CAS Key Laboratory of Tropical Marine Bio-resources and Ecology Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Guangzhou, 510301, China & University of Chinese Academy of Sciences, Beijing, 100049, China Author Lin, Xian-Cheng CAS Key Laboratory of Tropical Marine Bio-resources and Ecology Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Guangzhou, 510301, China & University of Chinese Academy of Sciences, Beijing, 100049, China Author Zhang, Yan-Ying CAS Key Laboratory of Tropical Marine Bio-resources and Ecology Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Guangzhou, 510301, China & Tropical Marine Biological Research Station in Hainan, Chinese Academy of Sciences, Sanya, 572000, China Author Ling, Juan CAS Key Laboratory of Tropical Marine Bio-resources and Ecology Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Guangzhou, 510301, China Author Dong, Jun-De CAS Key Laboratory of Tropical Marine Bio-resources and Ecology Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Guangzhou, 510301, China & Tropical Marine Biological Research Station in Hainan, Chinese Academy of Sciences, Sanya, 572000, China text Phytotaxa 2018 2018-12-13 383 1 75 92 http://dx.doi.org/10.11646/phytotaxa.383.1.4 journal article 10.11646/phytotaxa.383.1.4 1179-3163 13725105 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. FIGURE 4. Phylogenetic tree based on 16S rRNA gene sequences using the Bayesian algorism, showing the positions of strains Marileptolyngbya sina SCSIO T-2 and Salileptolyngbya diazotrophicum SCSIO 43686. Gloeobacter violaceus strain PCC 7421 was used as an outgroup. The studied starins were labelled in bold. Only posterior probabilities ≥ 0.50 were indicated. Bar, 0.03 substitution rate (K nuc ) units. FIGURE 5. Neighbor–joining tree based on nifH gene sequences of Marileptolyngbya sina SCSIO T-2 and Salileptolyngbya diazotrophicum SCSIO 43686. Synechocystis sp. WH8501 was used as an outgroup. The studied cyanobacterial strains were in bold font. A bootstrap test involving 1000 resamplings was performed. Bar, 0.05 substitution rate (K ) units. nuc