Fungal biosensors

Project leader: Dr Hedda J. Weitz

Project start date: April, 1999

Objective: The development of bioluminescence-based, filamentous fungal biosensors for environmental diagnostics.

Introduction:
The development of filamentous fungal biosensors is required to provide a tool for interrogating pollutant bioavailability in the distinct and important range of environments (e.g. acid upland soils that represent the major soil type in Scotland and coniferous forest soils.) dominated by fungi. Fungal biosensors will also enable investigation of the important role fungi play in many environmental processes. In addition, the filamentous fungal biosensors will complement the existing biosensors that are based on naturally bioluminescent bacteria (e.g.Vibrio fischeri), lux-marked bacteria (e.g. Esc herichia coli HB101 pUCD607 and Pseudomonas putida F1 Tn 5 lux CDABE), luc -marked yeast ( Saccharomyces cerevisiae ) and luc -marked nematode ( Caenorhabditis elegans ). These bioluminescence-based biosensors have been shown to be suitable tools for ecotoxicity testing. Two approaches are being considered for the development of fungal biosensors: (i) naturally bioluminescent fungi and (ii) genetically modified bioluminescent fungi.

Background on Naturally bioluminescent fungi
Bacterial and firefly bioluminescence has been widely exploited as in marker systems for detection and tracking of cells in the environment and as biosensors for the detection of pollutants [1]. In contrast, there has been little research into fungal bioluminescence, although luminescent fungi are one of the most common forms of terrestrial bioluminescence causing the often reported 'glowing wood' [2]. It is thought that the biochemistry of fungal bioluminescence is different to that of other known systems [2]. There are currently thought to be naturally bioluminescent fungi in 42 species within 9 genera, all of which are basidiomycetes [2]. Examples of bioluminescent fungi include Armillaria mellea, Mycena citricolor (syn. Omphalia flavida), Omphalotus olearius (syn. Clitocybe illudens) and Panellus stipticus [2,3], although luminescence is exhibited only by the North American strains of P. stipticus and not by the Eurasian strains [2]. Luminescence may be present in mycelia, for example in a number of Mycena species, or in both mycelia and fruiting bodies, for example in P. stipticus and O. olearius  [3].

References
[1] Chatterjee J, Meighen EA (1995) Biotechnological applications of bacterial bioluminescence ( lux) genes. Photochem. Photobiol. 62, 641-650.
[2] Herring PJ (1994) Luminous fungi. Mycologist 8, 181-183.
[3] Wassink EC (1978) Luminescence in fungi. In: Bioluminescence in Action (Herring, P.J., Ed.), pp. 171-195. Academic Press, London.

Current Research:

• Development of a bioluminescence-based, filamentous fungal bioassay for ecotoxicity testing. Naturally bioluminescent fungi, in particularA. mellea and M. citricolor are being used as fungal biosensors.
• In order to use naturally bioluminescent fungi as reporters in environmental studies, it is necessary to determine if there is a relationship between luminescence and metabolic activity.
• The effect of culture conditions (temperature, light and pH) on the mycelial growth and bioluminescence of four naturally bioluminescent fungi, A. mellea, M. citricolor, O. olearius and P. stipticus.
• The effect of media composition on the mycelial growth and bioluminescence of four naturally bioluminescent fungi, A. mellea, M. citricolor, O. olearius and P. stipticus.

Publications:
Weitz HJ, Ballard AL, Campbell CD, Killham K (2001) The effect of culture conditions on the mycelial growth and luminescence of naturally bioluminescent fungi. FEMS Microbiology Letters 202, 165-170.

Presentations:
Weitz HJ (2000) Naturally bioluminescent fungi. 5th Environmental Microbiology Workshop, University of Aberdeen, 26 July 2000 ­ presented as a talk

Weitz HJ, Ballard AL, Campbell CD, Killham K (2001) Naturally bioluminescent fungi - potential fungal biosensors? Society for General Microbiology 148th Ordinary Meeting, University of Heriot-Watt, 26-30 March 2001 ­ presented as a poster

Weitz HJ, Campbell CD, Killham K (2001) Naturally bioluminescent fungi - potential fungal biosensors? 9th International Symposium on Microbial Ecology, Amsterdam, The Netherlands, 26-31 August, 2001 ­ presented as a poster.

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