PMC

(A) A schematic of methylamine metabolism using the methylamine dehydrogenase (encoded by the mau gene cluster) for methylamine oxidation (orange). During methylamine growth mediated by methylamine dehydrogenase, formate is the branch point of C₁ metabolism and the tetrahydrofolate (H₄F) dependent pathway is essential for C₁ assimilation. (B) A schematic of methylamine metabolism using the N-methylglutamate pathway for methylamine oxidation (blue). During methylamine growth mediated by the N-methylglutamate (NMG) pathway, formaldehyde is the branch point of C₁ metabolism and the H₄F dependent pathway is not used at all for C₁ assimilation.

Growth of P. tricornutum and in cocultures with Donghicola sp. strain KarMa under photoautotrophic conditions (A,C,E) in the absence and (B,D,F) in the presence of additional carbon and energy sources. Algal and bacterial abundance were determined by chlorophyll fluorescence and CFU counts, respectively, the methylamine mixture contained 0.66 mM of each monomethylamine (MMA), dimethylamine (DMA), and trimethylamine (TMA). (A) Abundance of P. tricornutum with 2 mM MMA (△), DMA (⋄), TMA (◻), the methylamine mixture (◼), and 0.66 mM MMA (×) as nitrogen sources. (B) Abundance of P. tricornutum with 2 mM succinate and either 2 mM MMA (△) or the methylamine mixture (◼) or with 2 mM GBT (○) as nitrogen and carbon source. (C) Abundance of strain KarMa with 2 mM MMA (△), DMA (⋄), TMA (◻), the methylamine mixture (◼), and 0.66 mM MMA (×) as nitrogen sources. (D) Abundance of strain KarMa with 2 mM succinate and either 2 mM MMA (△) or the methylamine mixture (◼) or with 2 mM GBT (○) as nitrogen and carbon source. (E) Ammonium concentrations of cocultures with 2 mM MMA (△), DMA (⋄), TMA (◻), the methylamine mixture (◼), and 0.66 mM MMA (×) as nitrogen sources. (F) Ammonium concentrations of cocultures with 2 mM succinate and 2 mM MMA (△) or methylamine mixture (◼) as nitrogen sources and with 2 mM GBT (○) as carbon and nitrogen source. (G) MMA concentrations of cocultures with 2 mM nitrogen sources in form of MMA (△), DMA (⋄), TMA (◻), and methylamine mixture (◼) as well as 0.66 mM MMA (×). (H) MMA concentrations of cocultures with 2 mM succinate and either 2 mM MMA (△) or 2 mM methylamine mixture (◼) or with 2 mM GBT (○) as nitrogen and carbon source. (I) DMA concentrations of cocultures with 2 mM nitrogen sources in form of DMA (⋄), TMA (◻), and methylamine mixture (◼). (J) DMA concentrations of cocultures with 2 mM succinate and 2 mM methylamine mixture (◼). Error bars indicate standard deviation for diatom abundance (n = 3) and standard error of the mean for bacterial abundance (n = 3).

The root-mean-square deviations (RMSD) of the atoms of His318 relative to their initial structure as a function of simulation time from the trajectories of methylamine (A) and ammonia (B) through H168A AmtB. C, Frequency distribution for the location of methylamine along the Z-axis of the channel in H168A AmtB (trajectory B1, data were collected in the whole trajectory). D, The residues of H168A AmtB involved in hydrogen bonds with methylamine versus simulation time in the trajectory B1. E, Side views of three snapshots (at 20750, 23140, and 23160 ps, respectively) showing the trap of methylamine at site z≈0 nm by forming hydrophobic contacts with residues around A168 and at z≈−0.6 nm by forming a hydrogen bond with H318 respectively. Hydrogen bonds are shown as red dashed lines.