Leptolyngbya nodulosa sp. nov. (Oscillatoriaceae), a subtropical marine cyanobacterium that produces a unique multicellular structure

Abstract

Z. Li and J. Brand. 2007. Leptolyngbya nodulosa sp. nov. (Oscillatoriaceae), a subtropical marine cyanobacterium that produces a unique multicellular structure. Phycologia 46: 396–401. DOI: 10.2216/06-89.1A previously undescribed, filamentous, nonheterocystous cyanobacterium was isolated from the South China Sea. The nonbranching and nonmotile filaments had well-defined sheaths of variable thickness. Trichomes were 1.1–1.5 µm in diameter, while individual cells ranged from 1.2 to 2.4 µm in length under culturing conditions. Thylakoids within individual cells were peripheral and appeared to become confluent at one end of the cell. Cells did not contain gas vacuoles. Cultures grew under a wide range of conditions, including salinities ranging from freshwater to 60 ppt of sodium chloride. Nonaxenic cultures could be grown indefinitely (for at least 2 years) in media devoid of any combined nitrogen source but grew much more rapidly in the presence of ammonium or nitrate ions. A unique feature of this organism was the presence, under dim light, of well-defined multicellular structures (nodules), distributed at irregular intervals along the filaments. Nodules were highly variable in shape and size, with each nodule constructed of a region of a filament tightly folded and wrapped into a discrete unit and surrounded by a firm common sheath. The internal structure of cells within nodules appeared identical to the structures of cells occurring along other portions of the filament. Comparisons of 16S rDNA, the 16S–23S internal transcribed spacer (ITS) sequence, and morphological characteristics of this strain to corresponding features of other cyanobacteria indicate that it is a member of the genus Leptolyngbya. Differences in DNA sequences and isolation habitat of this organism, along with the occurrence of nodules, indicate that it is not closely related to the type species, L. boryana, and should be assigned a distinct specific epithet. We propose the name Leptolyngbya nodulosa for this organism.