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Two filamentous cyanobacterial strains were isolated from the mats attached to rock surfaces in the Ganfu Channel, Jiangxi Province, China. A polyphasic approach based on the combination of morphological and molecular features was used to characterize the two strains. Both strains showed the Lyngbya-like morphology under the light microscopy, and had the highest similarity range of 16S rRNA gene sequences as 95.00-96.01% to clones of Microseira wollei, exceeding the cutoff for species delimitation in cyanobacteria. Phylogenetic analyses based on both 16S rRNA and nifH genes and smaller sizes of trichomes in the two Lyngbya-like strains supported them to be proposed as a new species in the genus Microseira as Microseira minor, which is the second species of the genus Microseira. The difference of the 16S-23S ITS region between the two Microseira minor strains and its implication for the evaluation on cyanobacterial diversity and species differentiation were also discussed.

长孢藻是具有产多种蓝藻毒素及异味物质潜在能力的丝状异形胞蓝藻.为了探究长孢藻的生物学特性，我们从江西柘林湖分离24株长孢藻，经形态鉴定分成4个种类，分别为浮游长孢藻（Dolichospermum planctonicum）、近亲长孢藻（D.affine）、卷曲长孢藻（D.circinale）、螺旋长孢藻（D.spiroides）.16S rRNA基因序列表明柘林湖长孢藻与日本等地区的长孢藻高度相似，但只有近亲长孢藻与日本近亲长孢藻在分子系统进化树上聚为一支.基于16S-23S rRNA之间高变异性的ITS序列分析，4种长孢藻的D1-D1'螺旋结构相同，藻丝为直型的浮游长孢藻、近亲长孢藻与藻丝为弯型的卷曲长孢藻、螺旋长孢藻的Box-B、V3螺旋结构差异较大.通过对毒素和异味的分子生物学检测显示24株长孢藻均不产毒，但是4株浮游长孢藻及1株卷曲长孢藻含有土腥素合成基因.本研究不仅对柘林湖水华蓝藻的多样性以及潜在生态风险提供科学的基础资料，也在流域层面上为鄱阳湖的水生态系统研究和保护提供了一定的科学基础.

Microseira minor Geng et Yu sp. nov. (Fig. 1) Diagnosis: ���This species is morphologically similar to the genus Microseira but differs from M. wollei in the lack of false branching, much narrower filaments and trichomes, smaller ratio of cell length and width under the light microscopy. The phylogenetic analysis based on 16S rRNA gene, partial 16S-23S rRNA operon and nifH gene showed that this species was formed a well-supported clade, closest to other Microseira species, far away from other close genera. In addition, the non-producing of neurotoxins and hepatotoxins is also a major difference. Description: ���Filaments unbranched, long, 13.73���(16.04)���18.58 ��m broad, forming densely aggregations, blueblack, brown-black, yellowed when old, straight or slightly flexuous. Trichomes cylindrical, isopolar, not attenuated to the ends, not or slightly constricted at the cross-walls. Cells discoid, 3.12���(5.03)���7.70 ��m long, 9.02���(11.05)���13.33 ��m broad, 2���3 �� broader than long, with granular content, not aerotopes. Apical cells rounded, without calyptra or thickened outer cell wall. Sheath usually present, colorless, hyaline, firm, lamellated when old, and open at the apex. Reproduction by motile hormogonia formed by help of necridia. Thylakoids irregularly arranged. Etymology: ���The name of species ��� minor ��� was chosen because of its small and thin discoid cells. Type locality: ��� In the Ganfu Channel, Jiangxi Province, China. (August 2019, site one 28��11���8.2��� N, 116��10���2.56��� E and October 2019, site two 28��14���7.70��� N, 116��6���38.21��� E). Holotype here designated: ���Dry material of strain CHAB 4136 was stored at the Freshwater Algae Biology Herbarium (HBI), Institute of Hydrobiology, Chinese Academy of Science, Wuhan, Hubei Province, China, as specimen No. JXGF201901. Reference strain: ��� CHAB 4136 and CHAB 4163 (the additional strain) were deposited at the CHAB, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China. Habitat: ���Rock surface in freshwater rivers and channels in subtropical region. Molecular and phylogeny analyses: ���The 16S rRNA gene sequences of Microseira minor strains CHAB 4136 and CHAB 4163 obtained in this study shared 98.90%���99.92% similarities among all six clones by calculating p-distance with pairwise deletion of gaps using MEGA software v7.0. These clones shared 95.00%���96.01% with other Microseira species, less than 97% which was regarded as the cutoff for bacterial species delimitation. These clones had a maximum similarity of 16S rRNA gene sequences as 95.50% with their closest filamentous genera (sharing similarities to Potamosiphon, Aerosakkonema, Phormidium, Potamolinea and Oscillatoria as 93.98%���95.50%, 92.78%���92.95%, 92.28%���92.44%, 92.11%���92.44% and 91.92%���92.60%, respectively) (Table 1). The 16S rRNA gene phylogenetic trees based on ML and BI methods showed that the six clones of Microseira minor clustered a unique clade (cluster A) together with other Microseira species (Fig. 3 and Fig. 4), supported by ML and BI calculations with high bootstrap values of 100% and 1.000. In the nifH phylogeny (Fig. 5 and Fig. 6), the eight clones obtained from the two strains of Microseira minor in this study formed a well-supported freshwater clade together with all environmental clones of Microseira wollei (cluster M, cluster N and cluster L). The nifH gene sequences of CHAB 4136 (cluster S1) and CHAB 4163 (cluster S2) divided into two distinct sub-groups with cluster M and cluster N, and sequence similarities were 94.28%���95.96% and 96.97%���98.32%, respectively (Table 2). The whole clade formed by Microseira clones including the two strains of Microseira minor were supported by ML and BI methods with high bootstrap values of 85% and 0.90, supporting the two strains as a new species Microseira minor within the genus Microseira. Genes associated with four types of toxins of microcystins, cylindrospermopsin, paralytic shellfish toxins and anatoxin were not detected in any of these Microseira minor strains. Analyses of ITS between 16S and 23S rRNA gene: ���The ITS sequences of the six clones from the two strains of Microseira minor, shared 96.05-96.26% similarities with each other, and contained both tRNA Ile and tRNA Ala, ranging from 485 to 499 bp., Published as part of Geng, Ruozhen, Wen, Qianzhi, Wang, Yilang, Yang, Ping, Dai, Guofei, Li, Renhui & Yu, Gongliang, 2021, A novel filamentous cyanobacterium Microseira minor sp. nov. (Oscillatoriaceae, Cyanobacteria) from the Ganfu Channel, Jiangxi, China, pp. 178-190 in Phytotaxa 524 (3) on pages 180-183, DOI: 10.11646/phytotaxa.524.3.2, http://zenodo.org/record/5649286

Metals can react with microcystin (MC), which is released from cyanobacterial blooms through various mechanisms; these reactions may mitigate the environmental and health risks of MCs but may also cause harm to aquatic ecosystems and humans. Several studies were conducted, including laboratory tests, ecological simulations, and a field investigation of Poyang Lake. The laboratory studies showed that Fe3+, Cu2+, and Pb2+ stimulated MC photodegradation under high light intensity at the water-sediment interface, which reduced the MC accumulation in the sediment. In the laboratory studies involving the addition of metal ions to lake sediment containing adsorbed MC, MC biodegradation was inhibited by supplementing with high levels of Fe3+, Cu2+, or Pb2+. Fe3+ and Pb2+ promoted MC accumulation in the hydrophyte Eichhornia crassipes at relatively low concentrations, but this effect decreased with increasing high metal concentrations. An ecological survey in Poyang Lake during the dry season demonstrated that high Fe levels can reduce MC accumulation in the sediment, which could be the result of Fe-mediated photodegradation. The results indicate that metals involved in MC transportation and degradation may play an important role in the environmental fate of MC.

The uses of laccase in the degradation and removal of antibiotics have recently been reported because of the high efficiency and environmental friendliness of laccase. However, these removal studies mostly refer to a limited number of antibiotics. In this study, soil adsorption was introduced into the laccase-oxidation system to assist the simultaneous removal of 14 kinds of sulfonamide, tetracycline, and quinolone antibiotics, which differed in structures and chemical properties. The complementary effects of laccase-mediated oxidation and soil adsorption enabled the simultaneous removal. Removal characteristics were determined by a comprehensive consideration of the separate optimum conditions for laccase oxidation and soil adsorption removal experiments. With concentrations of laccase, syringaldehyde (SA), and soil of 0.5mg/mL, 0.5mmol/L, and 50g/L, respectively, and at pH 6 and 25°C, the removal rates of each antibiotic exceeded 70% in 15min and were close to 100% in 180min. Sulfonamide antibiotics (SAs) were removed mainly by laccase oxidation and quinolone antibiotics (QUs) mainly by soil adsorption. Tetracycline antibiotics (TCs) were removed by both treatments in the coupled system, but laccase oxidation dominated. Electrostatic adsorption was speculated to be one of the adsorption mechanisms in soil adsorption with QUs and TCs.