Detection of the new cosmopolitan genus Thermoleptolyngbya (Cyanobacteria, Leptolyngbyaceae) using the 16S rRNA gene and 16S–23S ITS region

• A new taxon of filamentous cyanobacteria is erected, the genus Thermoleptolyngbya.
• Thermoleptolyngbya is one of the most widespread taxa in thermal environments.
• Two species of Thermoleptolyngbya are described: T. albertanoae and T. oregonensis.
• A number of new 16S rRNA and 16S–23S ITS secondary structures are produced.
• 16S rRNA phylogenies + ITS secondary structures are useful to detect cryptic taxa.

Cyanobacteria are widespread prokaryotes that are able to live in extreme conditions such as thermal springs. Strains attributable to the genus Leptolyngbya are among the most common cyanobacteria sampled from thermal environments. Leptolyngbya is a character-poor taxon that was demonstrated to be polyphyletic based on molecular analyses. The recent joining of 16S rRNA gene phylogenies with 16S–23S ITS secondary structure analysis is a useful approach to detect new cryptic taxa and has led to the separation of new genera from Leptolyngbya and to the description of new species inside this genus and in other related groups.In this study, phylogenetic investigations based on both the 16S rRNA gene and the 16S–23S ITS region were performed alongside 16S rRNA and 16S–23S ITS secondary structure analyses on cyanobacteria of the family Leptolyngbyaceae. These analyses focused on filamentous strains sampled from thermal springs with a morphology ascribable to the genus Leptolyngbya. The phylogenetic reconstructions showed that the Leptolyngbya-like thermal strains grouped into a monophyletic lineage that was distinct from Leptolyngbya. The 16S–23S ITS secondary structure results supported the separation of this cluster. A new genus named Thermoleptolyngbya was erected to encompass these strains, and two species were described inside this new taxon: T. albertanoae and T. oregonensis.

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