Two new Pseudanabaena (Cyanobacteria, Synechococcales) species from Japan, Pseudanabaena cinerea and Pseudanabaena yagii , which produce 2‐methylisoborneol

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 rbc L, and by the secondary structures of the ITS regions of the rRNA operon.