bioRxiv preprint doi: https://doi.org/10.1101/2021.03.15.435355; this version posted March 15, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. An ecological basis for dual genetic code expansion in marine deltaproteobacteria 1 Veronika Kivenson1, Blair G. Paul2, David L. Valentine2* 2 1Interdepartmental Graduate Program in Marine Science, University of California, Santa Barbara, CA 3 93106, USA 4 2Department of Earth Science and Marine Science Institute, University of California, Santa Barbara, 5 CA 93106, USA 6 * Correspondence: 7 David L. Valentine 8
[email protected] 9 Present Address 10 VK: Oregon State University, Corvallis, OR 97331 11 BGP: Marine Biological Laboratory, Woods Hole, MA 02543 12 13 Keywords: microbiome, pyrrolysine, selenocysteine, metabolism, metagenomics 14 15 Abstract 16 Marine benthic environments may be shaped by anthropogenic and other localized events, leading to 17 changes in microbial community composition evident decades after a disturbance. Marine sediments 18 in particular harbor exceptional taxonomic diversity and can shed light on distinctive evolutionary 19 strategies. Genetic code expansion may increase the structural and functional diversity of proteins in 20 cells, by repurposing stop codons to encode noncanonical amino acids: pyrrolysine (Pyl) and 21 selenocysteine (Sec). Here, we show that the genomes of abundant Deltaproteobacteria from the 22 sediments of a deep-ocean chemical waste dump site, have undergone genetic code expansion. Pyl 23 and Sec in these organisms appear to augment trimethylamine (TMA) and one-carbon metabolism, 24 representing key drivers of their ecology.