Adaptive traits for chitin utilization in the saprotrophic aquatic chytrid fungus Rhizoclosmatium globosum

Chrismas, N, Bird, K, Laundon, D, Lieng, C, Hesketh-Best, P and Cunliffe, M 2025 Adaptive traits for chitin utilization in the saprotrophic aquatic chytrid fungus Rhizoclosmatium globosum. Proceedings of the Royal Society Series B-Biological Sciences, 292 (2047). 10.1098/rspb.2025.0337

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Abstract/Summary

The Chytridiomycota (chytrids) are early diverging fungi, many of which function in ecosystems as saprotrophs; however, associated adaptive traits are poorly understood. We focused on chitin degradation, a common ecosystem function of aquatic chytrids, using the model chitinophilic Rhizoclosmatium globosum and comparison of other chytrid genomes. Zoospores are chemotactic to the chitin monomer N-acetylglucosamine and accelerate development when grown with chitin. The R. globosum secretome is dominated by different glycoside hydrolase (GH) family GH18 chitinases, with abundance matching reciprocal transcriptome mRNA sequences. Models of the secreted chitinases indicate a range of sizes and domain configurations. Along with R. globosum, the genomes of other chitinophilic chytrids also have expanded inventories of GH-encoding genes responsible for chitin processing. Several R. globosum GH18 chitinases have bacteria-like chitin-binding module domains, also present in the genomes of other chitinophilic chytrids yet absent in non-chitinophilic chytrids. Chemotaxis, increased abundance and diversity of secreted chitinases, complemented with the acquisition of novel chitin-binding capability, are probably adaptive traits that facilitate chitin saprotrophy. Our study reveals the underpinning mechanisms that have supported the niche expansion of some chytrids to utilize lucrative chitin-rich particles in aquatic ecosystems and is a demonstration of the adaptive ability of this successful fungal group

Item Type:	Publication - Article
Additional Keywords:	chytrids, Chytridiomycota, aquatic, horizontal gene transfer, gene expansion
Subjects:	Marine Sciences
Divisions:	Marine Biological Association of the UK > Marine Microbiome
Depositing User:	Ms Kristina Hixon
Date made live:	12 Jun 2025 11:21
Last Modified:	12 Jun 2025 11:21
URI:	https://plymsea.ac.uk/id/eprint/10424

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