Oxidative cleavage of cellulose in the horse gut

Abstract

Background Lytic polysaccharide monooxygenases (LPMOs) belonging to the auxiliary activity 9 family (AA9) are widely found in aerobic fungi. These enzymes are O2-dependent copper oxidoreductases that catalyze the oxidative cleavage of cellulose. However, studies that have investigated AA9 LPMOs of aerobic fungi in the herbivore gut are scare. To date, whether oxidative cleavage of cellulose occurs in the herbivore gut is unknown. Results We report for the first time experimental evidence that AA9 LPMOs from aerobic thermophilic fungi catalyze the oxidative cleavage of cellulose present in the horse gut to C1-oxidized cellulose and C1- and C4-oxidized cello-oligosaccharides. We isolated and identified three thermophilic fungi and measured their growth and AA9 LPMO expression at 37 °C in vitro. We also assessed the expression and the presence of AA9 LPMOs from thermophilic fungi in situ. Finally, we used two recombinant AA9 LPMOs and a native AA9 LPMO from thermophilic fungi to cleave cellulose to yield C1-oxidized products at 37 °C in vitro. Conclusions The oxidative cleavage of cellulose occurs in the horse gut. This finding will broaden the known the biological functions of the ubiquitous LPMOs and aid in determining biological significance of aerobic thermophilic fungi.

Changes of endophytic microbial community in Rhododendron simsii roots under heat stress and its correlation with leaf physiological indicators

“…Moreover, the rapid action of soil microorganisms may bring changes to available N contents, which accelerated the oxidation of soil organic N (Ashraf et al, 2019;Wen et al, 2019;Chen et al, 2020). Similarly, our previous study found that heat stress significantly increased the abundance of soil bacteria such as Burkholderia-Caballeronia-Paraburkholderia, Occallatibacte and soil fungi such as Candida, Mortierella and Boothiomyces, which may have changed NH 4 + -N content (Liu, N. et al, 2022).…”

“…Another species of this genus, Pezicula neosporulosa, is involved in the metabolism of carbohydrates and the synthesis of enzymes that affect the secondary metabolites of plant and can provide nutrients to plant ( Yuan et al, 2022 ). In addition, fungi within genus Acidothermus have been shown to hydrolyze insoluble digestible cellulose and produce soluble products, that can use trifluoroacetic acid to hydrolyze their products into monosaccharides ( Liu, N. et al, 2022 ). Moreover, Paracoccus, a heterotrophic nitrification-aerobic denitrification bacterium, which has been studied in recent years that plays an important role in N cycling ( Chen et al, 2020 ).…”