Marine Bacteroidetes enzymatically digest xylans from terrestrial plants

Area of Science:

• Marine microbiology
• Biogeochemical cycling
• Enzymology

Background:

• Marine Bacteroidetes are crucial for ocean carbon cycling through polysaccharide degradation.
• Terrestrial plant organic matter enters oceans via rivers, raising questions about marine bacteria's ability to utilize diverse glycans.

Purpose of the Study:

• To investigate if marine bacteria can degrade structurally similar glycans from both terrestrial and marine sources.
• To characterize the xylan-degrading capabilities of the marine bacterium Flavimarina sp. Hel_I_48.

Main Methods:

• Genomic analysis to identify polysaccharide utilization loci (PULs).
• Biochemical assays to determine xylanase activity and specificity.
• Proteomics to analyze genomic region responses to specific xylan substrates.
• Growth curve analysis to correlate enzyme activity with bacterial growth.

Main Results:

• Flavimarina sp. Hel_I_48 possesses two PULs capable of degrading xylans from terrestrial plants and marine algae.
• Biochemical experiments confirmed the activity and specificity of encoded xylanases and associated enzymes.
• Proteomics revealed that PULs respond to glucuronoxylans and arabinoxylans, with key enzymes showing broad activity on conserved xylan structures.
• Enzyme activity correlated with bacterial growth on diverse xylan substrates.

Conclusions:

• Flavimarina sp. Hel_I_48 exhibits genetic and biochemical flexibility to utilize structurally diverse xylans from multiple sources.
• The prevalence of similar enzyme repertoires in other marine Bacteroidetes suggests widespread xylan degradation capabilities in the ocean.
• These findings expand our understanding of marine bacteria's role in processing complex organic matter in marine ecosystems.