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Cited by 253Antifungal resistance and susceptibilityFungal and yeast genetics researchFungal Infections and Studies

Melanin is an essential component for the integrity of the cell wall of Aspergillus fumigatus conidia

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Pihet, Marc, Vandeputte, Patrick, Tronchin, Guy, Renier, Gilles, Saulnier, Patrick, Georgeault, Sonia, Mallet, Romain, Chabasse, Dominique +2 more·2009·BMC Microbiology
DOI 10.1186/1471-2180-9-177PMC PMC2740851
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Abstract

BACKGROUND: Aspergillus fumigatus is the most common agent of invasive aspergillosis, a feared complication in severely immunocompromised patients. Despite the recent commercialisation of new antifungal drugs, the prognosis for this infection remains uncertain. Thus, there is a real need to discover new targets for therapy. Particular attention has been paid to the biochemical composition and organisation of the fungal cell wall, because it mediates the host-fungus interplay. Conidia, which are responsible for infections, have melanin as one of the cell wall components. Melanin has been established as an important virulence factor, protecting the fungus against the host's immune defences. We suggested that it might also have an indirect role in virulence, because it is required for correct assembly of the cell wall layers of the conidia. RESULTS: We used three A. fumigatus isolates which grew as white or brown powdery colonies, to demonstrate the role of melanin. Firstly, sequencing the genes responsible for biosynthesis of melanin (ALB1, AYG1, ARP1, ARP2, ABR1 and ABR2) showed point mutations (missense mutation, deletion or insertion) in the ALB1 gene for pigmentless isolates or in ARP2 for the brownish isolate. The isolates were then shown by scanning electron microscopy to produce numerous, typical conidial heads, except that the conidia were smooth-walled, as previously observed for laboratory mutants with mutations in the PKSP/ALB1 gene. Flow cytometry showed an increase in the fibronectin binding capacity of conidia from mutant isolates, together with a marked decrease in the binding of laminin to the conidial surface. A marked decrease in the electronegative charge of the conidia and cell surface hydrophobicity was also seen by microelectrophoresis and two-phase partitioning, respectively. Ultrastructural studies of mutant isolates detected considerable changes in the organisation of the conidial wall, with the loss of the outermost electron dense layer responsible for the ornamentations seen on the conidial surface in wild-type strains. Finally, analysis of the conidial surface of mutant isolates by atomic force microscopy demonstrated the absence of the outer cell wall rodlet layer which is composed of hydrophobins. CONCLUSION: These results suggest that, in addition to a protective role against the host's immune defences, melanin is also a structural component of the conidial wall that is required for correct assembly of the cell wall layers and the expression at the conidial surface of adhesins and other virulence factors.

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Crossref · 10.1186/1471-2180-9-177

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  • In Aspergillus fumigatus, melanin in conidial walls is essential for the proper expression of adhesins and other virulence factors, while inducing only minimal inflammatory cytokine responses to circumvent host antifungal defenses.

    “In A. fumigatus, melanin in conidial walls is essential for the proper expression of adhesins and other virulence factors, while inducing only minimal inflammatory cytokine responses to circumvent host antifungal defenses [40,41].”

    From Fungal Melanin in Plant Pathogens: Complex Biosynthesis Pathways and Diverse Biological Functions (2025) · cites this paper as [40]

    The Conclusion states that melanin is required for correct assembly of A. fumigatus conidial-wall layers and for surface expression of adhesins and other virulence factors. The Background and Discussion describe protection against host immune defenses, but our copy does not say melanin induces only minimal inflammatory cytokine responses; a search for cytokines found no supporting passage. (LLM, conf=0.88)

    Experimental — accuracy not yet measured

  • Under high-temperature conditions, melanin helps maintain cell wall integrity, preventing cell death due to wall rupture.

    “Under high-temperature conditions, the cell wall is susceptible to damage, and melanin helps maintain its integrity, thereby preventing cell death due to wall rupture [40].”

    From Fungal Melanin in Plant Pathogens: Complex Biosynthesis Pathways and Diverse Biological Functions (2025) · cites this paper as [40]

    The Conclusion says melanin is a structural component required for correct assembly of Aspergillus fumigatus conidial wall layers, and the Results report thinner walls lacking the outermost layer when melanin production is impaired. The paper does not establish that melanin prevents heat-induced wall rupture or cell death; its incubation at 37°C is not a test of high-temperature damage. No page numbers are available in our copy. (LLM, conf=0.88)

    Experimental — accuracy not yet measured

  • Melanin plays a vital role in fungal survival under extreme temperatures by acting as a thermal buffer through heat absorption and scattering.

    “Melanin plays a vital role in fungal survival under extreme temperatures by acting as a thermal buffer through heat absorption and scattering.”

    From Fungal Melanin in Plant Pathogens: Complex Biosynthesis Pathways and Diverse Biological Functions (2025) · cites this paper as [40]

    The Discussion and Conclusion describe melanin’s roles in protecting against host immune defenses and maintaining the conidial cell wall. A search of the indexed paper for extreme temperatures, heat absorption, scattering, and thermal buffering found no passage addressing the claimed mechanism or survival under extreme temperatures. (LLM, conf=0.75)

    Experimental — accuracy not yet measured

  • As an integral component of the fungal cell wall, melanin interacts with other wall constituents to enhance structural stability.

    “As an integral component of the fungal cell wall, melanin interacts with other wall constituents to enhance structural stability.”

    From Fungal Melanin in Plant Pathogens: Complex Biosynthesis Pathways and Diverse Biological Functions (2025) · cites this paper as [40]

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Authors
Pihet, M., Vandeputte, P., Tronchin, G., Renier, G., Saulnier, P., Georgeault, S., Mallet, R., Chabasse, D., Symoens, F., & Bouchara, J.-P.
Affiliations
  • Centre Hospitalier Universitaire d'Angers (FR)
  • Université d'Angers (FR)
  • Inserm (FR)
  • Institut Scientifique de Santé Publique (BE)
Corresponding author
  • Pihet, Marc
  • Bouchara, Jean-Philippe
ORCID
Venue
BMC Microbiology
Publisher
Springer Science and Business Media LLC
Published
2009
Volume
9
Issue
1
Pages
177
ISSN
1471-2180 (ISSN-L)
DOI
10.1186/1471-2180-9-177
PMC
PMC2740851
OpenAlex
W2094245023
Cited by
253
References
1
Citations by year
2026: 11 · 2025: 14 · 2024: 14 · 2023: 15 · 2022: 21 · 2021: 20 · 2020: 23 · 2019: 11 · 2018: 17 · 2017: 21 · 2016: 9 · 2015: 16 · 2014: 16 · 2013: 13 · 2012: 10
FWCI
6.84
Type
journal article
Language
en
Open access
Licence
cc-by
Locations
  • BMC Microbiology (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • HAL (submittedVersion, other-oa)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion)
Topics
  • Health Sciences › Medicine › Infectious Diseases › Antifungal resistance and susceptibility
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Fungal and yeast genetics research
  • Health Sciences › Medicine › Epidemiology › Fungal Infections and Studies
Keywords
Aspergillus fumigatus, melanin, conidia, fungal cell wall, invasive aspergillosis, virulence factors, Arp2, fibronectin binding, laminin binding, cell surface hydrophobicity, cell surface charge, hydrophobins
MeSH terms
Aspergillosis, Aspergillus fumigatus, Cell Wall, DNA, Fungal, Flow Cytometry, Fungal Proteins, Melanins, Microscopy, Electron, Scanning, Spores, Fungal, Virulence, Sequence Analysis, DNA

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