The Fate of Marine Bacterial Exopolysaccharide in Natural Marine Microbial Communities

Abstract

Most marine bacteria produce exopolysaccharides (EPS), and bacterial EPS represent an important source of dissolved organic carbon in marine ecosystems. It was proposed that bacterial EPS rich in uronic acid is resistant to mineralization by microbes and thus has a long residence time in global oceans. To confirm this hypothesis, bacterial EPS rich in galacturonic acid was isolated from Alteromonas sp. JL2810. The EPS was used to amend natural seawater to investigate the bioavailability of this EPS by native populations, in the presence and absence of ammonium and phosphate amendment. The data indicated that the bacterial EPS could not be completely consumed during the cultivation period and that the bioavailability of EPS was not only determined by its intrinsic properties, but was also determined by other factors such as the availability of inorganic nutrients. During the experiment, the humic-like component of fluorescent dissolved organic matter (FDOM) was freshly produced. Bacterial community structure analysis indicated that the class Flavobacteria of the phylum Bacteroidetes was the major contributor for the utilization of EPS. This report is the first to indicate that Flavobacteria are a major contributor to bacterial EPS degradation. The fraction of EPS that could not be completely utilized and the FDOM (e.g., humic acid-like substances) produced de novo may be refractory and may contribute to the carbon storage in the oceans.

A Novel Exopolysaccharide with Metal Adsorption Capacity Produced by a Marine Bacterium Alteromonas sp. JL2810

“…It was indicated that JL2810 EPS contained a large amount of GalA (42%) [32]. Similarly, it was indicated that the EPS produced by Alteromonas isolated from deep-sea hydrothermal vents also contained relatively large amount of acidic sugars such as GlcA and GalA [13,28,33,34].…”

Mini‐review: Phytoplankton‐derived polysaccharides in the marine environment and their interactions with heterotrophic bacteria

“…However, phytoplankton is not the only source of polysaccharides, because bacteria exude polysaccharides themselves (Thornton, 2014;Zhang et al, 2015). Mostly, bacterial polysaccharides consist of mannose, rhamnose, glucose, galactose and galacturonic acid, and are characterized by their high proportion of uronic acid (20%-50%), which tend to form complexes with transition metals due to its negative charge (Zhang et al, 2015). Compared with phytoplankton polysaccharides, polysaccharides of bacterial origin have a higher resistence against mineralization by microbes and thus longer residence times.…”

“…Compared with phytoplankton polysaccharides, polysaccharides of bacterial origin have a higher resistence against mineralization by microbes and thus longer residence times. Nevertheless, bacterial polysaccharides can also be utilized by dinstinct bacteria, which mostly belong to the Bacteroidetes (Zhang et al, 2015). Such secondary usage of polysaccharides (after the primary utilization of phytoplankton-derived polysaccharides) yields humic-like components that contribute to the formation of refractory DOC in the oceans.…”

“…The ability of marine microorganisms to utilize polysaccharides may reflect the conflict posed by the metabolic costs of its uptake versus the energy gained from its metabolism (Arrieta et al, 2015). However, based on the frequent clustering of the bacterial community into preferential consumers of either LMW-or HMW-DOM (e.g., Fernández-Gómez et al, 2013), it is likely that phytoplankton-derived polysaccharides are almost completely remineralized and that heterotrophic bacteria are generators of recalcitrant DOM in the ocean (e.g., Jiao et al, 2010;Zhang et al, 2015). DOM of bacterial origin is especially rich in uronic acid and humic-like components, which increases its resistance against mineralization by microbes (Zhang et al, 2015).…”

“…However, based on the frequent clustering of the bacterial community into preferential consumers of either LMW-or HMW-DOM (e.g., Fernández-Gómez et al, 2013), it is likely that phytoplankton-derived polysaccharides are almost completely remineralized and that heterotrophic bacteria are generators of recalcitrant DOM in the ocean (e.g., Jiao et al, 2010;Zhang et al, 2015). DOM of bacterial origin is especially rich in uronic acid and humic-like components, which increases its resistance against mineralization by microbes (Zhang et al, 2015). Nevertheless, some of the bacterial EPS can be consumed, for example, by Flavobacteria, and phytoplankten are themselves a source of partly recalcitrant DOM (Landa et al, 2014).…”