title: Racemization in reverse: evidence that D-amino acid toxicity on Earth is controlled by bacteria with racemases.
abstract: D-amino acids are toxic for life on Earth. Yet, they form constantly due to geochemical racemization and bacterial growth (the cell walls of which contain D-amino acids), raising the fundamental question of how they ultimately are recycled. This study provides evidence that bacteria use D-amino acids as a source of nitrogen by running enzymatic racemization in reverse. Consequently, when soils are inundated with racemic amino acids, resident bacteria consume D- as well as L-enantiomers, either simultaneously or sequentially depending on the level of their racemase activity. Bacteria thus protect life on Earth by keeping environments D-amino acid free.
authors.affiliation: Division of Earth and Ecosystem Sciences, Desert Research Institute, Las Vegas, Nevada, United States of America.
authors.forename: Gaosen
authors.initials: G
authors.lastname: Zhang
authors.affiliation: Division of Earth and Ecosystem Sciences, Desert Research Institute, Las Vegas, Nevada, United States of America.
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Sun
mesh_terms: D000596:Amino Acids / Q000633:toxicity*; D001173:Arthrobacter / Q000187:drug effects* / Q000378:metabolism; D003889:Desert Climate; D018534:Earth, Planet; D008954:Models, Biological; D019998:Racemases and Epimerases / Q000378:metabolism*; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D019998:Racemases and Epimerases