Saturday 5 February 2022

Thainema salinarum: A new species of Cyanobacterium from Thailand.

Cyanobacteria are simple Prokaryotic photosynthesising micro-organisms found in practically all photic environments on Earth. They can be singular and free-living, but many form filamentous chains, which in turn come together to for microbial mats. Cyanobacteria are thought to have been the first photosynthetic organisms to have produced oxygen, starting from about 2.5 billion years ago, and are still important ecosystem formers today, particularly in extreme environments such as salterns (pools which are periodically flooded by marine waters which are then lost to evaporation, creating a high-salinity environment), where they lack predators or competitors. Due to their importance, Cyanobacteria have been studied by biologists for a long time, althouth their taxonomy remains somewhat confused, at least in part because many described species were originally based upon morphological descriptions, which are of, at best, limited use in Prokaryote taxonomy, as well as general shortage of studies of these organisms outside of temperate regions.

In a paper published in the journal PLoS One on 7 January 2022, Somayeh Rasouli-Dogaheh and Jiří Komárek of the Department of Botany at the University of South Bohemia, Thomrat Chatchawan of the Department of Biology at Chiang Mai University, and Tomáš Hauer, also of the Department of Botany at the University of South Bohemia, describe a new species of Cyanobacterium from a manmade solar saltern environment in Petchaburi Province, central Thailand.

The new species is named Thainema salinarum, where 'Thainema' means 'Thai-thread' and 'salinarum' refers to the environment where it was found. The colony appeared as a pale to bright blue-green mat on the salt-saturated soil of the saltern. It was originally thought to be a member of the genus Halomicronema, but genetic analysis based upon the structure of the 16S rRNA sequence showed that it is the sister species to all members curently assigned to the Family Leptolyngbyaceae, including Halomicronema (that is to say, all curent members of the Family Leptolyngbyaceae are more closely related to one-another than to Thainema salinarum, but that Thainema salinarum and all curent members of the Family Leptolyngbyaceae are more closely related to one-another than either is to anything else). To avoid any further confusion given the large number of single species groups within the Cyanobacteria, Thainema salinarum is added to the Family Leptolyngbyaceae, as an outlying species.

 
Light microscope view of Thainema salinarum. The golden granules at cross-walls and sheaths are observed. Scale bar is 10 μm. Rasouli-Dogaheh et al. (2022).

Filaments of Thainema salinarum are 1–3 μm wide, with trichomes (elongate hair-like structures on the the terminal cells) in a sheath with no branching, mostly straight and slightly constricted, or not constricted at the cross-walls. The Bacterial cells are 2–3.5 μm long, and not as wide as their length. The terminal cells typically rounded, without calyptra

 
Micrographs of Thainema salinarum obtained with a transmission electron microscope. (A), (B) Cells with parietal thylakoids, granules, and sheath. Scale bar is 0.5 μm. (C) Longitudinal section of filaments showing the presence of parietal thylakoids. Scale bar is 1 μm. (D) Short filament showing a round apical cell. Scale bar is 5 μm. Rasouli-Dogaheh et al. (2022).

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