Zeiner Carolyn A, Purvine Samuel O, Zink Erika, Wu Si, Paša-Tolić Ljiljana, Chaput Dominique L, Santelli Cara M, Hansel Colleen M
Department of Biology, University of St. Thomas, Saint Paul, MN, United States.
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, United States.
Front Microbiol. 2021 Feb 10;12:610497. doi: 10.3389/fmicb.2021.610497. eCollection 2021.
Manganese (Mn) oxides are among the strongest oxidants and sorbents in the environment, and Mn(II) oxidation to Mn(III/IV) (hydr)oxides includes both abiotic and microbially-mediated processes. While white-rot Basidiomycete fungi oxidize Mn(II) using laccases and manganese peroxidases in association with lignocellulose degradation, the mechanisms by which filamentous Ascomycete fungi oxidize Mn(II) and a physiological role for Mn(II) oxidation in these organisms remain poorly understood. Here we use a combination of chemical and in-gel assays and bulk mass spectrometry to demonstrate secretome-based Mn(II) oxidation in three phylogenetically diverse Ascomycetes that is mechanistically distinct from hyphal-associated Mn(II) oxidation on solid substrates. We show that Mn(II) oxidative capacity of these fungi is dictated by species-specific secreted enzymes and varies with secretome age, and we reveal the presence of both Cu-based and FAD-based Mn(II) oxidation mechanisms in all 3 species, demonstrating mechanistic redundancy. Specifically, we identify candidate Mn(II)-oxidizing enzymes as tyrosinase and glyoxal oxidase in sp. SRC1lsM3a, bilirubin oxidase in sp. and AP3s5-JAC2a, and GMC oxidoreductase in all 3 species, including sp. DS3sAY3a. The diversity of the candidate Mn(II)-oxidizing enzymes identified in this study suggests that the ability of fungal secretomes to oxidize Mn(II) may be more widespread than previously thought.
锰（Mn）氧化物是环境中最强的氧化剂和吸附剂之一，将Mn（II）氧化为Mn（III/IV）（氢）氧化物包括非生物过程和微生物介导的过程。虽然白腐担子菌真菌在木质纤维素降解过程中利用漆酶和锰过氧化物酶氧化Mn（II），但丝状子囊菌真菌氧化Mn（II）的机制以及这些生物体中Mn（II）氧化的生理作用仍知之甚少。在这里，我们结合化学和凝胶内分析以及质谱分析法，证明了三种系统发育不同的子囊菌中基于分泌组的Mn（II）氧化，其机制与固体基质上与菌丝相关的Mn（II）氧化不同。我们表明，这些真菌的Mn（II）氧化能力由物种特异性分泌酶决定，并随分泌组年龄而变化，并且我们揭示了所有3个物种中都存在基于铜和基于黄素腺嘌呤二核苷酸（FAD）的Mn（II）氧化机制，证明了机制冗余。具体而言，我们确定候选Mn（II）氧化酶为SRC1lsM3a种中的酪氨酸酶和乙二醛氧化酶、AP3s5-JAC2a种中的胆红素氧化酶以及所有3个物种（包括DS3sAY3a种）中的葡萄糖甲醇胆碱（GMC）氧化还原酶。本研究中鉴定出的候选Mn（II）氧化酶的多样性表明，真菌分泌组氧化Mn（II）的能力可能比以前认为的更为广泛。
