Kazachstania bromeliacearum sp. nov., a yeast species from water tanks of bromeliads.

Cultures of a novel nutritionally specialized, fermentative yeast species were isolated from 34 water tanks of five bromeliad species, two mangrove sediment samples and one swamp water sample in Rio de Janeiro, Brazil. Sequence analysis of the D1/D2 domains of the large subunit of the rRNA gene showed that the novel species belongs to the genus Kazachstania. The novel species differs from Kazachstania martiniae by 11 substitutions and 2 gaps in the sequence of the domains D1/D2 of the LSU rRNA gene. The name Kazachstania bromeliacearum sp. nov. is proposed for the novel species. The type strain is IMUFRJ 51496T (=CBS 7996T=DBVPG 6864T=UFMG BR-174T).

In vitro antimycotic activity of a Williopsis saturnus killer protein against food spoilage yeasts.

The in vitro antimycotic activity of a purified killer protein (KT4561) secreted by a strain of Williopsis saturnus was tested against 310 yeast strains belonging to 21 food spoilage species of 14 genera (Candida, Debaryomyces, Dekkera, Hanseniaspora, Issatchenkia, Kazachstania, Kluyveromyces, Pichia, Rhodotorula, Saccharomyces, Schizosaccharomyces, Torulaspora, Yarrowia and Zygosaccharomyces). Minimum inhibitory concentration (MIC) determinations showed that over 65% of the target strains were susceptible to concentrations < or = 32 microg/ml of KT4561. Three conventional food-grade antimicrobial agents were used as controls: 41, 33 and 40% of the target strains were sensitive to < or = 512 mg/ml of ethyl 3-hydroxybenzoate (E214), potassium sorbate (E202) or potassium metabisulphite (E224), respectively. The susceptibility of food spoilage yeasts towards KT4561, E214, E202 and E224 was species- and strain-dependent. In most cases KT4561 exhibited MIC values several orders of magnitude lower (100 to 100,000 times) than those observed for E214, E202 and E224. With only a few exceptions, the activity of KT4561 was pH-, ethanol-, glucose- and NaCl-independent. The present study demonstrates the potential of this yeast killer protein as a novel and natural control agent against food spoilage yeasts.

Psychrophilic yeasts in glacial environments of Alpine glaciers.

The presence of psychrophilic yeasts in supra- and subglacial sediments, ice and meltwater collected from two glaciers of the Italian Alps (Forni and Sforzellina-Ortles-Cevedale group) was investigated. After incubation at 4 degrees C, subglacial sediments contained from 1.3 x 10(3) to 9.6 x 10(3) CFU of yeasts g(-1). The number of yeast cells in supraglacial sediments was c. 10-100-fold lower. A significant proportion of isolated yeasts exhibited one or more extracellular enzymatic activities (starch-degrading, lipolytic, esterolytic, proteolytic and pectinolytic activity) at 4 degrees C. Selected isolates were able to grow at 2 degrees C under laboratory-simulated in situ conditions. In all, 106 isolated yeasts were identified by MSP-PCR fingerprinting and 26S rRNA gene sequencing of the D1/D2 region as belonging to 10 species: Aureobasidium pullulans, Cryptococcus gilvescens (over 50% of the total), Cryptococcus terricolus, Mrakia gelida, Naganishia globosa, Rhodotorula glacialis, Rhodotorula psychrophenolica, Rhodotorula bacarum, Rhodotorula creatinivora and Rhodotorula laryngis. Four strains, all belonging to a new yeast species, yet to be described, were also isolated.

The use of killer sensitivity patterns for biotyping yeast strains: the state of the art, potentialities and limitations.

In recent years molecular techniques have been the most useful tools for the unequivocal identification of undetermined strains at the species level. In many instances, however, a further discrimination at the strain level (biotyping) is required, such as during epidemiological investigations, in which the distribution of pathogenic microorganisms is studied, and for patent protection purposes. Although molecular methods are routinely used also for yeast biotyping, several nonmolecular techniques have been proposed. One of these, the determination of the killer sensitivity pattern (KSP) towards a panel of selected killer toxins has proven to be a good auxiliary method. Despite the plethora of studies published, the potential and limitations of the determination of KSPs have never been critically evaluated. In this review the use of this nonmolecular technique as a biotyping tool is discussed and compared with some currently used DNA-based procedures. In addition, methodological, mechanistic and ecological implications are evaluated.

Production of volatile organic compounds (VOCs) by yeasts isolated from the ascocarps of black (Tuber melanosporum Vitt.) and white (Tuber magnatum Pico) truffles.

Twenty-nine yeast strains were isolated from the ascocarps of black and white truffles (Tuber melanosporum Vitt. and Tuber magnatum Pico, respectively), and identified using a polyphasic approach. According to the conventional taxonomic methods, MSP-PCR fingerprinting and sequencing of the D1/D2 domain of 26S rDNA, the strains were identified as Candida saitoana, Debaryomyces hansenii, Cryptococcus sp., Rhodotorula mucilaginosa, and Trichosporon moniliiforme. All isolates assimilated L: -methionine as a sole nitrogen source and produced the volatile organic compounds (VOCs), 2-methyl butanol, 3-methyl butanol, methanethiol, S-methyl thioacetate, dimethyl sulfide, dimethyl disulfide, dimethyl trisulfide, dihydro-2-methyl-3(2H)-thiophenone and 3-(methylthio)-1-propanol (MTP). ANOVA analysis of data showed significant (P<0.01) differences in VOCs produced by different yeasts, with MTP as the major component (produced at concentrations ranging from 19.8 to 225.6 mg/l). In addition, since some molecules produced by the isolates of this study are also characteristic of truffle complex aroma, it is possible to hypothesize a complementary role of yeasts associated with this ecosystem in contributing to final Tuber spp. aroma through the independent synthesis of yeast-specific volatile constituents.

Two new species in the Pichia guilliermondii clade: Pichia caribbica sp. nov., the ascosporic state of Candida fermentati, and Candida carpophila comb. nov.

Pichia caribbica sp. nov. (type strain DBVPG 4519, NRRL Y-27274, CBS 9966) is described as the ascosporic state of Candida fermentati, and Candida guilliermondii var. carpophila (type strain DBVPG 7739, NRRL Y-17905, CBS 5256) is elevated to species status as Candida carpophila comb. nov. These new taxa, which are indistinguishable on the basis of conventional taxonomic criteria, differ from one another and from Pichia guilliermondii by low DNA base sequence relatedness, different electrophoretic karyotypes, and nucleotide divergence in domains D1/D2 of 26S rDNA. Pichia caribbica produces one, rarely two, saturn-shaped ascospores in persistent asci. On the basis of molecular criteria, C. carpophila comb. nov., C. fukuyamaensis, and C. xestobii are conspecific, with the name C. carpophila having taxonomic priority.

Reflections on the classification of yeasts for different end-users in biotechnology, ecology, and medicine.

The approach to yeast identification has significantly changed in just a few decades due to the rapid increase in basic biological knowledge, increased interest in the practical applications and biodiversity of this important microbial group, and enormous technological advances. While some conventional methods can still be validly applied, many molecular techniques have been developed that allow for strain classification on all taxonomic levels. A critical evaluation of the actual scope of each identification procedure will in the end determine the most appropriate use of the many protocols now available. Nonetheless, the oldest tool of microbiology, the microscope, is still a fundamental accessory for studies involving yeast biology, biodiversity and taxonomy.