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Applied and Environmental Microbiology, February 2006, p. 1542-1550, Vol. 72, No. 2
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.2.1542-1550.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Induction by Klebsiella aerogenes of a Melanin-Like Pigment in Cryptococcus neoformans

Susana Frases,1 Stuart Chaskes,2 Ekaterina Dadachova,3 and Arturo Casadevall1,4*

Department of Microbiology and Immunology,1 Department of Medicine,4 Department of Nuclear Medicine, Albert Einstein College of Medicine, Bronx, New York 10461,3 Department of Biology, Farmingdale State University of New York, Farmingdale, New York 117352

Received 26 July 2005/ Accepted 8 November 2005

While studying the interaction of Cryptococcus neoformans with Dictyostelium discoideum, we noticed that yeast colonies in agar with a feeder lawn of Klebsiella aerogenes were brown. This finding was intriguing because C. neoformans colonies are not pigmented unless they are provided with precursors for melanization. Strains of all C. neoformans serotypes produced brown pigment in response to K. aerogenes at 22, 30, and 37°C. Pigment production required fungal laccase and was suppressed by high concentrations of glucose. Treatment of brown cells with guanidinium isothiocyanate and hot concentrated HCl yielded particulate material that had the physical and chemical characteristics of melanins. No pigment formation was observed when C. neoformans was exposed to live Escherichia coli or heat-killed K. aerogenes. Analysis of K. aerogenes supernatants revealed the presence of dopamine, which can be a substrate for melanin synthesis by C. neoformans. Our findings illustrate a remarkable interaction between a pathogenic fungus and a gram-negative bacterium, in which the bacterium produces a substrate that promotes fungal melanization. This observation provides a precedent that could explain the source of a substrate for C. neoformans melanization in the environment.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461. Phone: (718) 430-2215. Fax: (718) 430-8968. E-mail: casadeva{at}aecom.yu.edu.

Applied and Environmental Microbiology, February 2006, p. 1542-1550, Vol. 72, No. 2
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.2.1542-1550.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Chaskes, S., Frases, S., Cammer, M., Gerfen, G., Casadevall, A. (2008). Growth and Pigment Production on D-Tryptophan Medium by Cryptococcus gattii, Cryptococcus neoformans, and Candida albicans. J. Clin. Microbiol. 46: 255-264 [Abstract] [Full Text]  
  • Eisenman, H. C., Mues, M., Weber, S. E., Frases, S., Chaskes, S., Gerfen, G., Casadevall, A. (2007). Cryptococcus neoformans laccase catalyses melanin synthesis from both D- and L-DOPA. Microbiology 153: 3954-3962 [Abstract] [Full Text]  


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