EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Characterization and microbial degradation of polysaccharides in high molecular weight dissolved organic matter.

Daniel J. Repeta1, Benjamin N. Granzow1, Andrew Burger2, and Edward F. DeLong2
Daniel J. Repeta et al.
  • 1Department of Chemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
  • 2Daniel K. Inouye Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, Hawaii, USA

A large fraction of marine primary production is directed towards the synthesis of polysaccharides, most of which are rapidly degraded by heterotrophs, including heterotrophic microbes. However, a novel class of polysaccharides characterized by high N-acetyl aminosugar and 6-deoxysugar content, escapes rapid degradation and accumulates as a constituent of marine dissolved organic matter (DOM). These polysaccharides, which comprise ~25% of total dissolved organic carbon, also represent a large reservoir of the potentially bioavailable organic N and P stored in DOM.   To better understand the accumulation and microbial degradation of DOM polysaccharides we used size-exclusion chromatography and diffusion-ordered NMR spectroscopy to examine the size-distribution and composition of DOM recovered from seawater by ultrafiltration. Our results show that DOM polysaccharides are relatively small, with a molecular weight range of 1.3–7.7 kD and an average molecular weight of ~6 kD in surface waters decreasing to ~3 kD at 900m. Acid hydrolysis of DOM polysaccharides releases a suite of characteristic neutral sugars (glucose, galactose, mannose, rhamnose, fucose and xylose), but most of the polysaccharide (80-90%) resists hydrolysis and undergoes Maillard-like reactions between amino- and reducing sugars. To circumvent this, we modified our hydrolysis conditions to promote sugar-sugar cleavage. With this approach, we were able to generate a suite of oligosaccharides with molecular weights between 0.3-1.8 kD that carry the same spectral characteristics as DOM polysaccharides. We are using transposon insertion sequencing (Tn-seq) of marine bacteria cultured on these oligosaccharides to identify genes and degradation pathways responsible for DOM polysaccharide degradation.


How to cite: Repeta, D. J., Granzow, B. N., Burger, A., and DeLong, E. F.: Characterization and microbial degradation of polysaccharides in high molecular weight dissolved organic matter., EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16877,, 2023.