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Two cyanobacterial strains morphologically identified to the genus Nostoc were isolated from a wet rocky wall in a mid-subtropical region in China, and they were taxonomically and phylogenetically characterized based on the polyphasic approach combining morphological and genetic characteristics. 16S rRNA gene sequence analysis showed that the two strains containing six clones were all >99.6% similar to each other, but had < 94.3% similarities to the existing cyanobacterial genera. The phylogenies based on 16S rRNA and rpoC1 gene sequences indicated that their sequences grouped into a unique and robust cluster with high bootstrap values. This unique cluster was separated from the clade of the 'Nostoc sensu stricto' and the respective clades formed by the morphologically similar genera Mojavia, Desmonostoc, Aliinostoc, Komarekiella and Halotia. The 16S-23S rRNA ITS secondary structure of the both strains exhibited the unique pattern of D1-D1´, Box-B and V3 helix, distinguishing it from the other heterocytous genera. Such a clear cluster leads to the establishment of Minunostoc gen. nov., with the type species as Minunostoc cylindricum sp. nov.

Desertifilum, a filamentous cyanobacterial genus, was initially described from biological crusts in Thar crusts in India. In this study, we isolated a novel cyanobacterial strain (CHAB7200) from a alkaline pool in Zhejiang province, China. The strain showed an identical 16S rRNA gene sequence to Desertifilum tharense, but was distinctly different in cellular morphology, ultrastructure and ecology. In addition, the strain exhibited growth ability at different alkalinities during 4.5 ~ 54 g/L, and the optimum growth was shown at 1% salinity, indicating its stronger tolerance to wider range of alkalinities and salinities than D. tharense. Ecological niche is an important criterion used to separate and define cyanobacterial species. In this case, the strain was proposed as a novel cyanobacterial species, Desertifilum salkalinema. sp. nov.

Cyanobacterial blooms that form in response to climate warming and nutrient enrichment in freshwater lakes have become a global environmental challenge. Historical legacy effects and the mechanisms underlying cyanobacterial community succession are not well understood, especially for plateau lakes that are important global freshwater resources. This study investigated the temporal dynamics of cyanobacterial communities over centuries in response to nutrient enrichment and climate warming in low-latitude plateau lakes using high-throughput DNA sequencing of sedimentary DNA combined with traditional paleolimnological analyses. Our results confirmed that nutrients and climate warming drive shifts in cyanobacterial communities over time. Cyanobacterial community turnover was pronounced with regime shifts toward new ecological states, occurring after exceeding a tipping point of aquatic total phosphorus (TP). The inferred species interactions, niche differentiation, and identity of keystone taxa significantly changed after crossing the aquatic TP ecological threshold, as demonstrated by network analysis of cyanobacterial taxa. Further, the contribution of aquatic TP to cyanobacterial community dynamics was greater than that of air temperature when lakes were in an oligotrophic state. In contrast, as the aquatic TP threshold was exceeded, the contribution to community dynamics by air temperature increased and potentially surpassed that of aquatic TP. Overall, these results provide new evidence for how past nutrient levels in lacustrine ecosystems influence contemporary cyanobacterial community responses to global warming in low-latitude plateau lakes.

Six Limnothrix strains, isolated for the first time from a shallow eutrophic lake in central China, were taxonomically and phylogenetically evaluated by investigating their polyphasic characteristics, including morphological features, cellular ultrastructures, and 16S rRNA gene sequences. All the six strains were morphologically similar, and their trichomes were in average 1.7 lm wide and cells 4.0 lm long, and having small gas vesicles within cells, and therefore identified as Limnothrix planctonica (Woloszynska) Meffert. Cellular ultrastructures of them showed that peripheral thylakoids with 3-5 parallel layers were parietally distributed in the cells. The phylogenetic results based on the 16S rRNA gene sequences showed that all the Limnothrix strains, including the six in this study and those from the Genbank, formed two distinct clusters. The similarity in 16S rDNA sequences between these two clusters was lower than 90%, indicating that these Limnothrix strains belong to different genera. This is the first report on the morphology and phylogeny of L. planctonica strains, providing the new information on taxonomy of the genus Limnothrix.

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Five strains that were morphologically identified as Planktolyngbya circumcreta were isolated from three geographical regions in China. The strains were phylogenetically and taxonomically characterised based on a polyphasic approach that merged morphological and genetic characteristics, as well as ultrastructure. The ultrastructure of these strains showed a similar arrangement of thylakoids, with four to eight parallel layers that were parietally distributed, suggesting that they belonged to the order Synechococcales, family Leptolyngbyaceae. As inferred from 16S rRNA gene sequence analysis, these pure cultures share ! 98.5% similarity and were grouped into a unique and robust cluster with high bootstrap values. This unique cluster was separated from a clade composed of two strains of Planktolyngbya limnetica, which belonged to the type species of the genus Planktolyngbya. Thus, we transferred these five P. circumcreta strains to the new genus Limnolyngbya. The species Limnolyngbya circumcreta nov. comb. was designated as the type of the genus.