Biology subjects

Leivers, S.

Publications and source records attributed to Leivers, S..

3 recordsLinked to original sources

bioRxiv2025

Deacetylation of β-Mannans by Two Complementary Carbohydrate Esterases from the Human Gut Microbe Bacteroides cellulosilyticus

{beta}-Mannans are widespread in the human diet as components of plant-derived foods and as food additives. Several classes of {beta}-mannans are decorated with acetylations, which are key for their physicochemical properties and protection against enzymatic degradation. While the process for depolymerization of acetylated {beta}-mannans has been described in depth for members of the phylum Bacillota, there is limited mechanistic knowledge on how Bacteroidota utilize these glycans. Here, we combined proteomics and biochemical analyses to functionally characterize a pair of carbohydrate esterases (CEs) from Bacteroides cellulosilyticus that, together, deacetylate complex {beta}-mannans. We demonstrate that the newly identified BcCExxx enzyme, representing a novel carbohydrate esterase (CE) family, exhibits high specificity by selectively removing axially oriented 2-O-acetyl groups from mannose residues. In contrast, BcCE7 functions as a broad-spectrum esterase, capable of deacetylating oligosaccharides derived from structurally diverse substrates, including {beta}-mannans, xylans, and acetylated cellulose. In transesterification reactions, BcCExxx showed activity on both mannooligosaccharides and polymeric glucomannan. Overall, our findings provide new insight into the strategies that beneficial Bacteroides have evolved to deacetylate complex {beta}-mannans in the human gut. Significance Statement{beta}-Mannans, commonly found in various plant-based foods and used as food additives, can be metabolized by gut microbes, potentially impacting host health. Acetylation of {beta}-mannans enhances their resistance to enzymatic breakdown, making carbohydrate esterases crucial for gut bacteria to utilize these carbohydrates. This study explores the roles of two carbohydrate esterases (CEs) from a human commensal Bacteroides species in deacetylating complex {beta}-mannans. The two esterases together remove acetylations at different positions on mannose units. BcCE7 is a versatile esterase that deacetylates a variety of oligosaccharides, while the newly discovered BcCExxx is highly active towards 2-O-acetylations on mannose units in both oligosaccharides and polymeric {beta}-mannan. This research enhances our understanding of how Bacteroidota species deacetylate {beta}-mannans.

biochemistry↗

bioRxiv2020

Secondhand homes: Woodpecker cavity location and structure influences secondary nester's success.

O_LIUnderstanding how ecosystem engineers influence other organisms has long been a goal of ecologists. Woodpeckers select nesting sites with high food availability and will excavate and then abandon multiple cavities through their lifetime. These cavities are crucial to secondary cavity nesting birds (SCB) that are otherwise limited by the availability of naturally occurring cavities. C_LIO_LIOur study examined the role food resources have on the nest site location and home range size of woodpeckers, and the respective influence woodpeckers and the construction of cavities have on the nesting success of SCB. C_LIO_LIUsing five years of avian point count data to locate golden-fronted woodpeckers (GFWO: Melanerpes aurifrons), we correlated insect availability with GFWO home range size and determined differences in insect availability between GFWO occupied and unoccupied sites, while recording nesting success (success: [≥] 1 fledgling) for the GFWO and common SCB in south Texas: Black-crested Titmouse (Baeolophus atricristatus), Ash-throated Flycatcher (Myiarchus cinerascens), Brown-crested Flycatcher (Myiarchus tyrannulus), and Bewicks Wren (Thryomanes bewickii). We used model averaging to fit species-specific logistic regression models to predict nest success based on cavity metrics across all species. C_LIO_LISites occupied by GFWO had a higher biomass of insects in orders Coleoptera, Hymenoptera, and Orthoptera than unoccupied sites, and there was a negative correlation between the availability of these insect orders and home-range size. GFWO had increased nest success in trees with increased vegetation cover and lower levels of decay, while SCB had higher levels of nesting success in abandoned GFWO cavities opposed to naturally occurring ones, and in trees with low decay. C_LIO_LIOur results suggest that SCB may be drawn to nest in abandoned woodpecker cavities where they have higher rates of nest success compared to natural cavities. Additionally, the prevalence for GFWO to excavate cavities in trees with lower levels of decay contradicts previous literature and may indicate a novel temperature trade-off, with live trees requiring more energy to excavate, but providing more protection from high breeding season temperatures in arid and semi-arid areas. C_LI

ecology↗

bioRxiv2020

Synthesis of Glycoconjugates Utilizing the Regioselectivity of a Lytic Polysaccharide Monooxygenase

Polysaccharides from plant biomass are the most abundant renewable chemicals on Earth and can potentially be converted to a wide variety of useful glycoconjugates. While anomeric hydroxyl groups of carbohydrates are amenable to a variety of useful chemical modifications, selective cross-coupling to non-reducing ends has remained challenging. Several lytic polysaccharide monooxygenases (LPMOs), powerful enzymes known for their application in cellulose degradation, specifically oxidize non-reducing ends, introducing carbonyl groups that can be utilized for chemical coupling. This study provides a simple and highly specific approach to produce oxime-based glycoconjugates from LPMO-functionalized oligosaccharides. The products are evaluated by HPLC, mass spectrometry and NMR. Furthermore, we demonstrate potential biodegradability of these glycoconjugates using selective enzymes.

biochemistry↗