Comparative Analysis of Secretome Profiles of Manganese(II)-Oxidizing Ascomycete Fungi

Abstract

Fungal secretomes contain a wide range of hydrolytic and oxidative enzymes, including cellulases, hemicellulases, pectinases, and lignin-degrading accessory enzymes, that synergistically drive litter decomposition in the environment. While secretome studies of model organisms such as Phanerochaete chrysosporium and Aspergillus species have greatly expanded our knowledge of these enzymes, few have extended secretome characterization to environmental isolates or conducted side-by-side comparisons of diverse species. Thus, the mechanisms of carbon degradation by many ubiquitous soil fungi remain poorly understood. Here we use a combination of LC-MS/MS, genomic, and bioinformatic analyses to characterize and compare the protein composition of the secretomes of four recently isolated, cosmopolitan, Mn(II)-oxidizing Ascomycetes (Alternaria alternata SRC1lrK2f, Stagonospora sp. SRC1lsM3a, Pyrenochaeta sp. DS3sAY3a, and Paraconiothyrium sporulosum AP3s5-JAC2a). We demonstrate that the organisms produce a rich yet functionally similar suite of extracellular enzymes, with species-specific differences in secretome composition arising from unique amino acid sequences rather than overall protein function. Furthermore, we identify not only a wide range of carbohydrate-active enzymes that can directly oxidize recalcitrant carbon, but also an impressive suite of redox-active accessory enzymes that suggests a role for Fenton-based hydroxyl radical formation in indirect, non-specific lignocellulose attack. Our findings highlight the diverse oxidative capacity of these environmental isolates and enhance our understanding of the role of filamentous Ascomycetes in carbon turnover in the environment.

Optimization of Dothideomycetes sp. css035 chitosanase productivity and activity using response surface methodology

“…In the current research the molecular identification of the chitosanase producer fungal isolate showed 99% similarity with Dothideomycetes sp. Kirk et al, [25] reported that Dothideomycetes was the largest and the most diverse class of Ascomycetes and it was reported to produce chitosanase by Ramos-Garza et al, [26] and Zeiner et al, [27].…”

Terrestrial and marine Antarctic fungi extracts active against Xanthomonas citri subsp. citri

“…also has a cosmopolitan distribution in soil, having been found in several environments around the world. This species also has shown potential as agents for biological control and as producers of antimicrobial metabolites, showing success in the control of plant pathogens (Zeiner et al 2016). However, there are no reports on the antimicrobial activity of members from the Paraconiothyrium, Cadophora, Toxicocladosporium, Penicillium and Pseudogymnoascus against X. citri.…”

Oxygen isotope analysis of bacterial and fungal manganese oxidation

“…The four organisms ( Bacillus, Pyrenochaeta, Paraconiothyrium sporulosum, and Stagonospora ) that oxidize Mn(II) through direct enzymatic activity exhibit a fairly narrow range (−20.9‰ to −23.1‰) for values of . The putative enzymes involved in fungal Mn(II) oxidation are bifunctional solanapyrone synthase and/or an unspecified FAD‐binding protein for Pyrenochaeta , bilirubin oxidase for Stagonospora , and GMC oxidoreductase and/or bilirubin oxidase for Paraconiothyrium sporulosum (Zeiner, ; Zeiner et al., ). Mn(II) oxidation by Bacillus occurs via direct oxidation by a multicopper oxidase, MnxG, present in the exosporium of dormant Bacillus spores.…”