SAR11 Cells Rely on Enzyme Multifunctionality To Metabolize a Range of Polyamine Compounds

• DOI: 10.1128/mbio.01091-21
• Publication Date: 2021-08-24T08:31:11Z
• Authors: Stephen E. Noell; Gregory E. Barrell; Christopher Suffr...; Jeff Morré; Kevin P. Gable; Jason R. Graff; Brian J. VerWey; Ferdi L. Hellweger; Stephen J. Giovan...
• Keywords: Polyamine; Agmatine; Bacterioplankton; Metabolic pathway

In the ocean surface layer and cell culture, polyamine transport protein PotD of SAR11 bacteria is often one most abundant proteins detected. Polyamines are organic cations at seawater pH produced by all living organisms thought to be an important component dissolved matter (DOM) in planktonic ecosystems. We hypothesized that cells uptake metabolize multiple polyamines use them as sources carbon nitrogen. Metabolic footprinting fingerprinting were used measure five compounds (putrescine, cadaverine, agmatine, norspermidine, spermidine) two strains represent majority environment, "Candidatus Pelagibacter" strain HTCC7211 Pelagibacter ubique" HTCC1062. Both took up concentrated micromolar or millimolar intracellular concentrations. could meet their nitrogen requirements, but did not fully substitute for requirements glycine (or related compounds) pyruvate compounds). Our data suggest potABCD transports spermidine synthase, speE, reversible, catalyzing breakdown addition its usual biosynthetic role. These findings provide support hypothesis enzyme multifunctionality enables streamlined ecosystems increase range DOM they metabolize. IMPORTANCE Genome streamlining bacterioplankton has resulted a small repertoire genes, yet paradoxically, consume substantial fraction primary production oceans. Enzyme multifunctionality, referring enzymes adapted have broader substrate catalytic than canonically defined, adaptation increases metabolized environments where selection favors genome minimization. experimental this demonstrating take propose set multifunctional catalyze metabolism. report rates can exceed metabolic rates, resulting both high concentrations these nitrogen-rich (in comparison native levels) size.