Deacetylation of Fungal Exopolysaccharide Mediates Adhesion and Biofilm Formation

ABSTRACT The mold Aspergillus fumigatus causes invasive infection in immunocompromised patients. Recently, galactosaminogalactan (GAG), an exopolysaccharide composed of galactose and N-acetylgalactosamine (GalNAc), was identified as a virulence factor required for biofilm formation. The molecular me...

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Autores principales:	Mark J. Lee, Alexander M. Geller, Natalie C. Bamford, Hong Liu, Fabrice N. Gravelat, Brendan D. Snarr, François Le Mauff, Joseé Chabot, Benjamin Ralph, Hanna Ostapska, Mélanie Lehoux, Robert P. Cerone, Stephanie D. Baptista, Evgeny Vinogradov, Jason E. Stajich, Scott G. Filler, P. Lynne Howell, Donald C. Sheppard
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2016
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/ca26861971b54fcea0b6f4b5258f1164
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spelling	oai:doaj.org-article:ca26861971b54fcea0b6f4b5258f11642021-11-15T15:41:41ZDeacetylation of Fungal Exopolysaccharide Mediates Adhesion and Biofilm Formation10.1128/mBio.00252-162150-7511https://doaj.org/article/ca26861971b54fcea0b6f4b5258f11642016-05-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00252-16https://doaj.org/toc/2150-7511ABSTRACT The mold Aspergillus fumigatus causes invasive infection in immunocompromised patients. Recently, galactosaminogalactan (GAG), an exopolysaccharide composed of galactose and N-acetylgalactosamine (GalNAc), was identified as a virulence factor required for biofilm formation. The molecular mechanisms underlying GAG biosynthesis and GAG-mediated biofilm formation were unknown. We identified a cluster of five coregulated genes that were dysregulated in GAG-deficient mutants and whose gene products share functional similarity with proteins that mediate the synthesis of the bacterial biofilm exopolysaccharide poly-(β1-6)-N-acetyl-d-glucosamine (PNAG). Bioinformatic analyses suggested that the GAG cluster gene agd3 encodes a protein containing a deacetylase domain. Because deacetylation of N-acetylglucosamine residues is critical for the function of PNAG, we investigated the role of GAG deacetylation in fungal biofilm formation. Agd3 was found to mediate deacetylation of GalNAc residues within GAG and render the polysaccharide polycationic. As with PNAG, deacetylation is required for the adherence of GAG to hyphae and for biofilm formation. Growth of the Δagd3 mutant in the presence of culture supernatants of the GAG-deficient Δuge3 mutant rescued the biofilm defect of the Δagd3 mutant and restored the adhesive properties of GAG, suggesting that deacetylation is an extracellular process. The GAG biosynthetic gene cluster is present in the genomes of members of the Pezizomycotina subphylum of the Ascomycota including a number of plant-pathogenic fungi and a single basidiomycete species, Trichosporon asahii, likely a result of recent horizontal gene transfer. The current study demonstrates that the production of cationic, deacetylated exopolysaccharides is a strategy used by both fungi and bacteria for biofilm formation. IMPORTANCE This study sheds light on the biosynthetic pathways governing the synthesis of galactosaminogalactan (GAG), which plays a key role in A. fumigatus virulence and biofilm formation. We find that bacteria and fungi use similar strategies to synthesize adhesive biofilm exopolysaccharides. The presence of orthologs of the GAG biosynthetic gene clusters in multiple fungi suggests that this exopolysaccharide may also be important in the virulence of other fungal pathogens. Further, these studies establish a molecular mechanism of adhesion in which GAG interacts via charge-charge interactions to bind to both fungal hyphae and other substrates. Finally, the importance of deacetylation in the synthesis of functional GAG and the extracellular localization of this process suggest that inhibition of deacetylation may be an attractive target for the development of novel antifungal therapies.Mark J. LeeAlexander M. GellerNatalie C. BamfordHong LiuFabrice N. GravelatBrendan D. SnarrFrançois Le MauffJoseé ChabotBenjamin RalphHanna OstapskaMélanie LehouxRobert P. CeroneStephanie D. BaptistaEvgeny VinogradovJason E. StajichScott G. FillerP. Lynne HowellDonald C. SheppardAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 7, Iss 2 (2016)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Mark J. Lee Alexander M. Geller Natalie C. Bamford Hong Liu Fabrice N. Gravelat Brendan D. Snarr François Le Mauff Joseé Chabot Benjamin Ralph Hanna Ostapska Mélanie Lehoux Robert P. Cerone Stephanie D. Baptista Evgeny Vinogradov Jason E. Stajich Scott G. Filler P. Lynne Howell Donald C. Sheppard Deacetylation of Fungal Exopolysaccharide Mediates Adhesion and Biofilm Formation
description	ABSTRACT The mold Aspergillus fumigatus causes invasive infection in immunocompromised patients. Recently, galactosaminogalactan (GAG), an exopolysaccharide composed of galactose and N-acetylgalactosamine (GalNAc), was identified as a virulence factor required for biofilm formation. The molecular mechanisms underlying GAG biosynthesis and GAG-mediated biofilm formation were unknown. We identified a cluster of five coregulated genes that were dysregulated in GAG-deficient mutants and whose gene products share functional similarity with proteins that mediate the synthesis of the bacterial biofilm exopolysaccharide poly-(β1-6)-N-acetyl-d-glucosamine (PNAG). Bioinformatic analyses suggested that the GAG cluster gene agd3 encodes a protein containing a deacetylase domain. Because deacetylation of N-acetylglucosamine residues is critical for the function of PNAG, we investigated the role of GAG deacetylation in fungal biofilm formation. Agd3 was found to mediate deacetylation of GalNAc residues within GAG and render the polysaccharide polycationic. As with PNAG, deacetylation is required for the adherence of GAG to hyphae and for biofilm formation. Growth of the Δagd3 mutant in the presence of culture supernatants of the GAG-deficient Δuge3 mutant rescued the biofilm defect of the Δagd3 mutant and restored the adhesive properties of GAG, suggesting that deacetylation is an extracellular process. The GAG biosynthetic gene cluster is present in the genomes of members of the Pezizomycotina subphylum of the Ascomycota including a number of plant-pathogenic fungi and a single basidiomycete species, Trichosporon asahii, likely a result of recent horizontal gene transfer. The current study demonstrates that the production of cationic, deacetylated exopolysaccharides is a strategy used by both fungi and bacteria for biofilm formation. IMPORTANCE This study sheds light on the biosynthetic pathways governing the synthesis of galactosaminogalactan (GAG), which plays a key role in A. fumigatus virulence and biofilm formation. We find that bacteria and fungi use similar strategies to synthesize adhesive biofilm exopolysaccharides. The presence of orthologs of the GAG biosynthetic gene clusters in multiple fungi suggests that this exopolysaccharide may also be important in the virulence of other fungal pathogens. Further, these studies establish a molecular mechanism of adhesion in which GAG interacts via charge-charge interactions to bind to both fungal hyphae and other substrates. Finally, the importance of deacetylation in the synthesis of functional GAG and the extracellular localization of this process suggest that inhibition of deacetylation may be an attractive target for the development of novel antifungal therapies.
format	article
author	Mark J. Lee Alexander M. Geller Natalie C. Bamford Hong Liu Fabrice N. Gravelat Brendan D. Snarr François Le Mauff Joseé Chabot Benjamin Ralph Hanna Ostapska Mélanie Lehoux Robert P. Cerone Stephanie D. Baptista Evgeny Vinogradov Jason E. Stajich Scott G. Filler P. Lynne Howell Donald C. Sheppard
author_facet	Mark J. Lee Alexander M. Geller Natalie C. Bamford Hong Liu Fabrice N. Gravelat Brendan D. Snarr François Le Mauff Joseé Chabot Benjamin Ralph Hanna Ostapska Mélanie Lehoux Robert P. Cerone Stephanie D. Baptista Evgeny Vinogradov Jason E. Stajich Scott G. Filler P. Lynne Howell Donald C. Sheppard
author_sort	Mark J. Lee
title	Deacetylation of Fungal Exopolysaccharide Mediates Adhesion and Biofilm Formation
title_short	Deacetylation of Fungal Exopolysaccharide Mediates Adhesion and Biofilm Formation
title_full	Deacetylation of Fungal Exopolysaccharide Mediates Adhesion and Biofilm Formation
title_fullStr	Deacetylation of Fungal Exopolysaccharide Mediates Adhesion and Biofilm Formation
title_full_unstemmed	Deacetylation of Fungal Exopolysaccharide Mediates Adhesion and Biofilm Formation
title_sort	deacetylation of fungal exopolysaccharide mediates adhesion and biofilm formation
publisher	American Society for Microbiology
publishDate	2016
url	https://doaj.org/article/ca26861971b54fcea0b6f4b5258f1164
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Deacetylation of Fungal Exopolysaccharide Mediates Adhesion and Biofilm Formation

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