Deacetylation of Aspergillus fumigatus galactosamino – galactan is required for adherence and virulence

Ref ID: 19526

Author:

MJ Lee1*, AM Geller1, FN Gravelat1, H Liu2, BD Snarr1, SD Baptista1, D Nguyen3, M Nitz4,
JP Latgé7, T Fontaine7, PL Howell5, SG Filler2,6, DC Sheppard1,3

Author address:

1Microbiology and Immunology, McGill University, Montreal, Canada
2Division of Infectious Diseases, LA Biomed-UCLA, Torrance, USA
3Medicine, McGill University Hospital Center, Montreal, Canada
4Chemistry, University of Toronto, Toronto, Canada
5B

Full conference title:

6th Advances Against Aspergillosis 2014

Abstract:

Purpose:
To determine if deacetylation of A. fumigatus galactosaminogalactan is a required for its pathogenic
function.
Methods:
Galactosaminogalactan production and adherence to polystyrene were assayed using standard
protocols. Primary amine content was quantified using trinitrobenzene sulfonic acid (TNBSA). For
916;uge3 and 916;agd3 mutants cross-culture, conidia of one mutant were inoculated into the culture
supernatant of the other mutant, and adherence to polystyrene was assayed. To determine virulence
in an invertebrate model, 106 conidia of fungal strains were inoculated into wandering Galleria
mellonella larvae, and survival was monitored over the course of 10 days. For in silico analysis and
structural modeling, amino acid sequence was obtained from NCBI and various bioinformatics and
modeling tools were used.
Results:
Although the 916;age3 mutant produced wild-type amounts of galactosaminogalactan, it was not
deacetylated. Non-deacetylated galactosaminogalactan was unable to adhere to the surface of
hyphae, and could not support biofilm formation. In silico analysis of Agd3 predicted a signal peptide
suggestive of extracellular secretion of this enzyme. Consistent with this observation, co-culture of
the 916;agd3 mutant with culture supernatants from the galactosaminogalactan deficient 916;uge3 mutant
restored biofilm production. The converse of this experiment, where 916;uge3 mutant biofilm production
is restored by co-culturing with 916;agd3 mutant culture supernatants was also true, suggesting that
Agd3 mediated deacetylation occurs in the extracellular space. The 916;agd3 mutant had attenuated
virulence in Galleria mellanolla. Structural modeling revealed that the putative polysaccharide
deacetylase domain of Agd3 is structurally similar to bacterial polysaccharide deacetylases involved
in the production of bacterial exopolysaccharide.
Conclusion:
These data support the hypothesis that deacetylation of galactosaminogalactan is required for its
pathogenic function, likely because deacetylation generates a cationic polysaccharide that can
adhere to negatively charged surfaces such as the fungal cell wall, host cell membranes, and plastic.

Abstract Number: 53

Conference Year: 2014

Link to conference website: http://www.AAA2014.org

New link: NULL

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