Microbial metabolism of methanol and methylamine in the Gulf of Mexico: insight into marine carbon and nitrogen cycling

Abstract

One carbon (C1) metabolism plays an important role in marine carbon cycling but the dynamics and modes of C1 transformations are not fully understood. We made contemporaneous measurements of methylamine and methanol metabolism to elucidate the role of C1 compounds as sources of carbon, energy and nitrogen. Methanol and methylamine were predominantly used as an energy source in offshore waters (oxidation rate constant: k : 0.02-0.10 day ; k : 0.01-0.18 day ), but were also important sources of biomass carbon in coastal waters (assimilation rate constant: k : 0.04-0.10 day ; k : 0.01-0.05 day ). The relative extent of assimilation versus oxidation for these substrates correlated positively with chlorophyll, nutrients and heterotrophic bacterial production. Methanol oxidation and assimilation were stimulated significantly by nutrient addition. In contrast, methylamine metabolism was inhibited by ammonium or nitrate, suggesting that methylamine served as a nitrogen source. A preliminary metagenomic survey revealed a diverse population of putative C1-utilizing microorganisms. These results show that the remineralization of methylamine could provide both C and N sources for microbes. Both methanol and methylamine contribute to microbial energetic and carbon substrate demands with a distinctly different signature in nearshore versus offshore environments.

Communal metabolism by Methylococcaceae and Methylophilaceae is driving rapid aerobic methane oxidation in sediments of a shallow seep near Elba, Italy

“…Hence, methylotrophs that degrade these compounds are commonly found in marine habitats. These methylotrophs, however, are distinctly different from those present at methane seeps and are typically dominated by members of the Roseobacter clade, the Methylophilaceae group OM43 or the SAR11 clade (Giovannoni et al ., ; Sun et al ., ; Zhuang et al ., ). In our microcosms, we found members of the Roseobacter clade and other Alphaproteobacteria with the genetic potential for C 1 utilization.…”

Significance of Acetate as a Microbial Carbon and Energy Source in the Water Column of Gulf of Mexico: Implications for Marine Carbon Cycling

“…A number of facultative methylotrophs (e.g., Rhodobacter sphaeroides ; Methylobacterium extorquens AM1) are also able to incorporate acetate via the ethylmalonyl‐CoA pathway in place of the glyoxylate cycle (Alber et al, ; Ensign, ; Schneider et al, ). In our samples, facultative methylotrophs including R. sphaeroides , Rhodobacter capsulatus , Paracoccus versutus were present across the sites (Zhuang et al, ). These organisms may grow on acetate via the ethylmalonyl‐CoA pathway (Alber et al, ; Gottschal & Kuenen, ; Petushkova & Tsygankov, ).…”

“…The large portion of assimilation suggests acetate could serve as an important carbon source for microbes. This is in contrast to other low molecular weight organic compounds such as methanol and methylamine, which are used predominantly for microbial energy production (Zhuang et al, ). Intriguingly, the amount of assimilated carbon from acetate at the coastal Taylor Energy sites constituted 44.4–58.0% of total acetate uptake, a value that far exceeded that observed at most of the oceanic sites.…”

“…= below the detection limit. Nutrients data were also shown in Zhuang et al (2018). DOC = dissolved organic carbon.…”

“…Depth profile of (a, f) chlorophyll and oxygen, (b, g) nitrate and phosphate, (c, h) DOC and POC, (d, i) acetate assimilation and oxidation, and (e, j) bacterial production at GC600 (a-e) and OC26 (f-j) in the northern Gulf of Mexico. Bacteria production data were also shown in Zhuang et al (2018). DOC = dissolved organic carbon; POC = particulate organic carbon.…”