Release LTP_12_2020, featuring a new ARB alignment and improved 16S rRNA tree for prokaryotic type strains

The new release of the All-Species Living Tree Project (LTP) represents an important step forward in the reconstruction of 16S rRNA gene phylogenies, since we not only provide an updated set of type strain sequences until December 2020, but also a series of improvements that increase the quality of the database. An improved universal alignment has been introduced that is implemented in the ARB format. In addition, all low-quality sequences present in the previous releases have been substituted by new entries with higher quality, many of them as a result of whole genome sequencing. Altogether, the improvements in the dataset and 16S rRNA sequence alignment allowed us to reconstruct robust phylogenies. The trees made available through this current LTP release feature the best topologies currently achievable. The given nomenclature and taxonomic hierarchy reflect all the changes available up to December 2020. The aim is to regularly update the validly published nomenclatural classification changes and new taxa proposals. The new release can be found at the following URL: https://imedea.uib-csic.es/mmg/ltp/.