Alpha‐ and beta‐mannan utilization by marine Bacteroidetes

Abstract

Summary Marine microscopic algae carry out about half of the global carbon dioxide fixation into organic matter. They provide organic substrates for marine microbes such as members of the Bacteroidetes that degrade algal polysaccharides using carbohydrate‐active enzymes (CAZymes). In Bacteroidetes genomes CAZyme encoding genes are mostly grouped in distinct regions termed polysaccharide utilization loci (PULs). While some studies have shown involvement of PULs in the degradation of algal polysaccharides, the specific substrates are for the most part still unknown. We investigated four marine Bacteroidetes isolated from the southern North Sea that harbour putative mannan‐specific PULs. These PULs are similarly organized as PULs in human gut Bacteroides that digest α‐ and β‐mannans from yeasts and plants respectively. Using proteomics and defined growth experiments with polysaccharides as sole carbon sources we could show that the investigated marine Bacteroidetes express the predicted functional proteins required for α‐ and β‐mannan degradation. Our data suggest that algal mannans play an as yet unknown important role in the marine carbon cycle, and that biochemical principles established for gut or terrestrial microbes also apply to marine bacteria, even though their PULs are evolutionarily distant.

Significance of single β-mannanase supplementation on performance and energy utilization in broiler chickens, laying hens, turkeys, sows, and nursery-finish pigs: a meta-analysis and systematic review

“…β-mannans from plants are polysaccharides of d -mannose units linked together by β-(1-4) glycosidic bonds and are distinct from yeast cell wall backbone of d -mannose units that are linked by α-(1-6) glycosidic bonds substituted by mannan units linked by α-(1-2) and α-(1-3) glycosidic bonds ( Chen et al, 2018 ). Structurally, β-mannans are linear polymers of β-1,4-linked mannose residues backbone without (linear mannan) or with combination of glucose and mannose residues (glucomannan) and occasional side chains of α-1,6-linked galactose residues (galactomannan or galactoglucomannan).…”

“…Typical analytical approach for determining the concentration of β-mannans in feedstuffs is through estimation of total free mannose sugar ( Englyst and Cummings, 1984 ; Hsiao et al, 2006 ). Such approach will not obviously distinguish between β-mannans characteristic to plant feedstuffs and yeast cell walls ( Chen et al, 2018 ). This might explain observed variability of β-mannans concentration in corn and wheat DDGS.…”

Carbohydrate Hydrolytic Potential and Redundancy of an Anaerobic Digestion Microbiome Exposed to Acidosis, as Uncovered by Metagenomics

“…5B) (55, 56). Previously biochemically validated PULs included a galactomannan-targeting PUL from a marine Bacteroidetes (57) and a cellulose-degrading one from a rumen-isolated bacterium (58). Here, we propose a model of PUL-assisted acetylated glucomannan degradation for a Bacteroidetes species (Fig.…”

Microbial iron and carbon metabolism as revealed by taxonomy-specific functional diversity in the Southern Ocean

“…Algal mannans are widely distributed in marine ecosystems, and α-mannans were identified in red seaweed [88,89] and the diatom Phaeodactylum tricornutum [90]. Recent studies demonstrated that marine bacteria, especially Bacteroidota, can degrade mannans [91][92][93]. Although whether the GH92 PUL facilitates the growth of MAG_73 across all sampling sites requires further study due to the incompleteness of MAGs.…”