Inoculum Size Effect in Dimorphic Fungi: Extracellular Control of Yeast-Mycelium Dimorphism in Ceratocystis ulmi

Jacob M. Hornby, Sarah M. Jacobitz-Kizzier, Donna J. McNeel, Ellen C. Jensen, David S. Treves, Kenneth W. Nickerson

Research output: Contribution to journalArticle

55 Citations (Scopus)

Abstract

We studied the inoculum size effect in Ceratocystis ulmi, the dimorphic fungus that causes Dutch elm disease. In a defined glucose-proline-salts medium, cells develop as budding yeasts when inoculated at ≥106 spores per ml and as mycelia when inoculated at ≥106 spores per ml. The inoculum size effect was not influenced by inoculum spore type, age of the spores, temperature, pH, oxygen availability, trace metals, sulfur source, phosphorous source, or the concentration of glucose or proline. Similarly, it was not influenced by added adenosine, reducing agents, methyl donors, amino sugars, fatty acids, or carbon dioxide. Instead, growing cells excreted an unknown quorum-sensing factor that caused a morphological shift from mycelia to budding yeasts. This yeast-promoting effect is abolished if it is extracted with an organic solvent such as ethyl acetate. The quorum-sensing activity acquired by the organic solvent could be added back to fresh medium in a dose-dependent fashion. The quorum-sensing activity in C. ulmi spent medium was specific for C. ulmi and had no effect on the dimorphic fungus Candida albicans or the photomorphogenic fungus Penicillium isariaeforme. In addition, farnesol, the quorum-sensing molecule produced by C. albicans, did not inhibit mycelial development of C. ulmi when present at concentrations of up to 100 μM. We conclude that the inoculum size effect is a manifestation of a quorum-sensing system that is mediated by an excreted extracellular molecule, and we suggest that quorum sensing is a general phenomenon in dimorphic fungi.

Original languageEnglish (US)
Pages (from-to)1356-1359
Number of pages4
JournalApplied and environmental microbiology
Volume70
Issue number3
DOIs
StatePublished - Mar 1 2004

Fingerprint

Ulmus
Ceratocystis ulmi
Quorum Sensing
quorum sensing
size effect
Mycelium
dimorphism
mycelium
yeast
spore
inoculum
Fungi
Yeasts
fungus
yeasts
Spores
fungi
spores
glucose
Saccharomycetales

ASJC Scopus subject areas

  • Biotechnology
  • Food Science
  • Applied Microbiology and Biotechnology
  • Ecology

Cite this

Inoculum Size Effect in Dimorphic Fungi : Extracellular Control of Yeast-Mycelium Dimorphism in Ceratocystis ulmi. / Hornby, Jacob M.; Jacobitz-Kizzier, Sarah M.; McNeel, Donna J.; Jensen, Ellen C.; Treves, David S.; Nickerson, Kenneth W.

In: Applied and environmental microbiology, Vol. 70, No. 3, 01.03.2004, p. 1356-1359.

Research output: Contribution to journalArticle

Hornby, Jacob M. ; Jacobitz-Kizzier, Sarah M. ; McNeel, Donna J. ; Jensen, Ellen C. ; Treves, David S. ; Nickerson, Kenneth W. / Inoculum Size Effect in Dimorphic Fungi : Extracellular Control of Yeast-Mycelium Dimorphism in Ceratocystis ulmi. In: Applied and environmental microbiology. 2004 ; Vol. 70, No. 3. pp. 1356-1359.
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