Single-cell genomics reveals pyrrolysine-encoding potential in members of uncultivated archaeal candidate division MSBL1.

Pyrrolysine (Pyl), the 22nd canonical amino acid, is only decoded and synthesized by a limited number of organisms in the domains Archaea and Bacteria. Pyl is encoded by the amber codon UAG, typically a stop codon. To date, all known Pyl-decoding archaea are able to carry out methylotrophic methanogenesis. The functionality of methylamine methyltransferases, an important component of corrinoid-dependent methyltransfer reactions, depends on the presence of Pyl. Here, we present a putative pyl gene cluster obtained from single-cell genomes of the archaeal Mediterranean Sea Brine Lakes group 1 (MSBL1) from the Red Sea. Functional annotation of the MSBL1 single cell amplified genomes (SAGs) also revealed a complete corrinoid-dependent methyl-transfer pathway suggesting that members of MSBL1 may possibly be capable of synthesizing Pyl and metabolizing methylated amines.