Umezakia natans M.WaTaN. was described by Dr. M. Watanabe in 1987 as a new species in the family of Stigonemataceae, following the rules of the Botanical Code. According to the original description, this planktonic filamentous species grows well in a growth media with pH being 7 to 9, and with a smaller proportion of sea water. Both heterocytes and akinetes were observed, as well as true branches developing perpendicular to the original trichomes in cultures older than one month. Watanabe concluded that Umezakia was a monotypic and only planktonic genus belonging to the family of Stigonemataceae. Unfortunately, the type culture has been lost. In 2008, we successfully isolated a new strain of Umezakia natans from a sample collected from Lake Suga. This lake is situated very close to the type locality, Lake Mikata in Fukui Prefecture, Japan. We examined the morphology of this U. natans strain, and conducted a DNA analysis using 16S rDNA regions. Morphological characters of the newly isolated strain were in a good agreement with the original description of U. natans. Furthermore, results of the DNA analysis showed that U. natans appeared in a cluster containing Aphanizomenon ovalisporum and Anabaena bergii. Therefore we conclude that Umezakia natans belongs to the family of Nostocaceae, not to Stigonemataceae.
Nasty smell of tap water supplied from Lake Biwa caused a great trouble. Then many researches have been conducted from the point of view of water supply management or water quality in Japan. The matter of this bad smell was identified as 2-methylisoborneol (2-MIB) and the source organism of this bad odor was then reported as Phormidium tenue and later two different cultured strains were established. One of these strains shows green color, produce 2-MIB, and is marked PTG. The other shows brown color, does not produce 2-MIB and is marked PTB. However their nomenclatural description has not been done yet and, in fact, they have morphological characters of genus Pseudanabaena rather than Phormidium. Pseudanabaena species are also observed in Lake Kasumigaura. PS1306 produces 2-MIB and other strain PS1303 has no smell. This study focuses on morphological and genetical (16S rRNA) comparison of strains from both lakes. In addition, the ultrastructure of cells of PTB and PTG are demonstrated. On the basis of this comparison we propose description of two new planktic species producing 2-MIB: Pseudanabaena foetida Niiyama, Tuji et ichise sp. nov. and P. subfoetida Niiyama et Tuji sp. nov.
Our environmental DNA analysis identified Annamia-like operational taxonomic units (OTUs) from Lake Kasumigaura, Japan every summer season during the period from June 2012-May 2015. A strain from Lake Kasumigaura that agreed with an Annamia-like OTU (NIES-4383) was established with a cell-sorting machine. Based on the differences in morphology and 16S rRNA sequences, a new taxon is described: Annamia dubia Tuji, Yamaguchi et Niiyama sp. nov. A. dubia produces a microcystins that is also produced by A. toxica. Our 16S rRNA phylogenetical analysis reveals that the genus Annamia makes a monophyletic clade with the genera Geminocystis, Geminobacterium, and 'Cyanobacterium.' Although this clade agrees with Cyanobacteriaceae Komárek et al. (2014), this family is invalid based on the invalid genus Cyanobacterium and the type species Cyanobacterium stanieri. We propose the alternative name Geminocystaceae Tuji, Yamaguchi et Niiyama fam. nov. based on the genus Geminocystis.
SUMMARY
Two new Pseudanabaena species, Pseudanabaena cinerea and Pseudanabaena yagii, were described. Both species are members of taxa that produce 2‐methylisoborneol and have a musty odor. P. cinerea was found at the Serikawa reservoir and in Lake Ogawara in Japan. P. cinerea is morphologically similar to P. subfoetida Niiyama et Tuji, but its cell color is different. The cell color of the former is greenish‐gray to gray, and that of the latter is bright blue‐green. P. yagii was described using an old strain, NIVA‐CYA 111, which was isolated from Lake Biwa in 1982. P. yagii can be distinguished from other 2‐MIB‐producing taxa by its thinner cell width and by the absence of small granules in its cells. The putative secondary structures of the internal transcribed spacer (ITS) regions of the ribosomal RNA operon were predicted for 2‐MIB‐producing Pseudanabaena species including the two new taxa. Both new taxa are also distinguished by their molecular phylogenies using 16S rRNA and rbcL, and by the secondary structures of the ITS regions of the rRNA operon.
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