Analysis of Black Fungal Biofilms Occurring at Domestic Water Taps (I): Compositional Analysis Using Tag-Encoded FLX Amplicon Pyrosequencing
- 606 Downloads
Mass growth of dark fungal biofilms on water taps and associated habitats was observed in various German drinking water distribution systems recently. Customers of affected drinking water systems are anxious about potential and unknown health risks. These environments are known to harbour a fungal flora also comprising a variety of fungal opportunists that are well known to cause superficial mycoses in humans (Exophiala equina, Exophiala lecanii-corni) but are not known to establish dark biofilms so far. To gain profound insight on composition of respective biofilms, a metagenomic approach using Tag-Encoded FLX Amplicon Pyrosequencing (TEFAP) of the ribosomal internal transcribed spacer 2 region in comparison with a classical cultivation approach using Sabouraud agar with chloramphenicol and erythritol-chloramphenicol-agar was performed. E. lecanii-corni was found to be the major component in 10 of 13 biofilms analysed independently of the method used. Alternaria sp., E. equina, Fusarium spp. and Ochroconis spp. were also relatively abundant. As expected, TEFAP usually revealed a higher diversity than the cultivation approaches. For example, opportunistic species like Candida albicans or Exophiala dermatitidis were detected in very low amounts. In conclusion, TEFAP turned out to be a promising and powerful tool for the semi-quantitative analysis of fungal biofilms. Referring to relevant literature, potential biological hazards caused by fungi of the dark biofilms can be regarded as low.
KeywordsFungal metagenome Black biofilms Tag-Encoded FLX Amplicon Pyrosequencing Water taps Exophiala lecanii-corni
One of the authors (G. Heinrichs) was supported by a research grant from RheinEnergie AG. We also want to thank Manfred Bovi, Institute of Pathology, RWTH Aachen University Hospital for performing the scanning electron microscopy and Kittipan Samerpitak, CBS for kindly checking DNA sequences in case Ochroconis spp.
- 37.Kangawa T. Bias and artifacts in multitemplate polymerase chain reactions (PCR). J Biosci Bioeng. 2003;96:317–23.Google Scholar
- 43.Nyaoke A, Weber ES, Innis C, Stremme D, Dowd C, Hinckley L, et al. Disseminated phaeohyphomycosis in weedy seadragons (Phyllopteryx taeniolatus) and leafy seadragons (Phycodurus eques) caused by species of Exophiala, including a novel species. J Vet Diagn Invest. 2009;21:69–79.PubMedCrossRefGoogle Scholar
- 46.Otis EJ, Wolke RE, Blazer VS. Infection of Exophiala salmonis in Atlantic salmon (Salmo salar L.). J Wildl Dis. 1985;21:61–4.Google Scholar
- 48.Porteous NB, Redding SW, Thompson EH, Grooters AM, de Hoog GS, Sutton DA. Isolation of an unusual fungus in treated dental unit waterlines. J Am Dent Assoc. 2003;134:853–8.Google Scholar
- 49.de Hoog GS, Guarro J, Gené J, Figueras MJ. Atlas of clinical fungi. 3rd ed. Utrecht: Centraalbureau voor Schimmelcultures; 2011.Google Scholar
- 54.Heinrichs G, Hübner I, Schmidt CK, de Hoog GS, Haase G. Analysis of black fungal biofilms occurring at domestic water taps (II): potential routes of entry. Mycopathologia. 2013. doi: 10.1007/s11046-013-9619-2.