Guo, Jinqiang, Achterberg, Eric P. , Shen, Yuan, Yuan, Huamao, Song, Jinming, Liu, Jin, Li, Xuegang and Duan, Liqin (2023) Stable carbon isotopic composition of amino sugars in heterotrophic bacteria and phytoplankton: Implications for assessment of marine organic matter degradation. Limnology and Oceanography, 68 (12). pp. 2414-2825. DOI 10.1002/lno.12468.

	Text lno12468-sup-0001-figures1.docx - Supplemental Material Available under License Creative Commons: Attribution-Noncommercial-No Derivative Works 4.0. Download (36kB)
Preview	Text Limnology Oceanography - 2023 - Guo - Stable carbon isotopic composition of amino sugars in heterotrophic bacteria and-1.pdf - Published Version Available under License Creative Commons: Attribution-Noncommercial-No Derivative Works 4.0. Download (1MB) | Preview

Abstract

Compound‐specific isotope analysis has opened up a new realm for resolving the sources and transformation processes of marine organic matter. However, the stable carbon isotope patterns of amino sugars remain unknown. We examined δ 13 C of amino sugars in marine phytoplankton and heterotrophic bacteria, and the variations in amino sugar δ 13 C during 66‐d planktonic organic matter degradation experiments, to investigate the metabolic sources and transformations of amino sugars by bacterial reworking. The δ 13 C values of glucosamine (GlcN) and galactosamine (GalN) were comparable in heterotrophic bacteria (difference Δδ 13 C GlcN–GalN = 0.4–4.0‰) but pronouncedly different in phytoplankton (Δδ 13 C GlcN–GalN = 4.3–16.6‰), suggesting similar synthesis pathways of GlcN and GalN in bacteria that differed from phytoplankton. Compared to GlcN and GalN, bacteria preferentially use isotopically light organic compounds for muramic acid (MurA) synthesis. During simulated microbial degradation of organic matter, the δ 13 C difference between GlcN and GalN decreased from 5.8‰ on the initial day to 1‰ at a late stage in the experiment, but the difference between GlcN and MurA remained at 5.3‰. This difference is consistent with the pattern in cultured phytoplankton (average Δδ 13 C GlcN–GalN = 5.9‰ ± 1.4‰) and heterotrophic bacteria (average Δδ 13 C GlcN–MurA = 4.6‰ ± 3.4‰), indicating enhanced bacterial resynthesis as degradation proceeded. Based on the difference in δ 13 C among GlcN, GalN, and MurA, we propose a novel index of variation in amino sugar δ 13 C, representing amino sugar resynthesis, to describe the diagenetic state of organic matter. Together, these findings suggest that amino sugar δ 13 C can be used as a new tool to track heterotrophic processes of marine organic matter.

Actions (login required)

View Item