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In order to determine the occurrence, distribution, and significance of mold species in groundwater-and surface water-derived drinking water in Norway, molds isolated from 273 water samples were identified. Samples of raw water, treated water, and water from private homes and hospital installations were analyzed by incubation of 100-ml membrane-filtered samples on dichloran-18% glycerol agar. The total count (number of CFU per 100 ml) of fungal species and the species diversity within each sample were determined. The identification of mold species was based on morphological and molecular methods. In total, 94 mold species belonging to 30 genera were identified. The mycobiota was dominated by species of Penicillium, Trichoderma, and Aspergillus, with some of them occurring throughout the drinking water system. Several of the same species as isolated from water may have the potential to cause allergic reactions or disease in humans. Other species are common contaminants of food and beverages, and some may cause unwanted changes in the taste or smell of water. The present results indicate that the mycobiota of water should be considered when the microbiological safety and quality of drinking water are assessed. In fact, molds in drinking water should possibly be included in the Norwegian water supply and drinking water regulations.

The type strain of Yarrowia lipolytica and 38 strains identified as Yarrowia lipolytica, four strains of Candida deformans, including the type and two subcultures of the type, two strains of Candida galli and six unidentified strains that resembled Y. lipolytica were examined by PCR fingerprints using primers M13 and (GAC)5. The same strains, together with four strains of the recently introduced Candida yakushimensis nom. inval., were sequenced for the D1/D2 domain of the 26S rRNA gene and parts of the ITS domain and also studied for their physiological properties. Of the strains identified previously as Y. lipolytica, CBS 2076 had the same fingerprint as the type of C. deformans and strain CBS 4855 was distinct from all other strains. The six strains that resembled Y. lipolytica were separated into two groups distinct from any of the other clades. A total of six groups obtained by fingerprint and sequence data were evaluated by performing DNA reassociation reactions. Mating experiments among the 35 strains of Y. lipolytica sensu stricto showed that 15 strains represented one mating type and 16 strains represented the opposite mating type, while four strains were self-sporulating. Teleomorph states were not produced by C. deformans, C. galli or any of the unidentified isolates. However, positive mating reactions were rarely observed in crosses among C. galli and some strains of Y. lipolytica and C. deformans. Consequently, sharing the same mating type system, C. deformans and C. galli could be considered anamorphs of unnamed Yarrowia species. Results from PCR fingerprints, sequencing and mating studies support the grouping of the studied strains into Y. lipolytica, C. galli, C. deformans, C. yakushimensis nom. inval. and three novel species in the Yarrowia clade: Candida oslonensis sp. nov. (type strain CBS 10146T =NRRL Y-48252T; Mycobank number MB 510769), Candida alimentaria sp. nov. (type strain CBS 10151T =NRRL Y-48253T; Mycobank number MB 510770) and Candida hollandica sp. nov. (type strain CBS 4855T =NRRL Y-48254T; Mycobank number MB 510771).

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