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PubMed1989

Expression of functional chicken oviduct progesterone receptors in yeast (Saccharomyces cerevisiae).

The cDNAs encoding full-length chicken oviduct progesterone receptor B (PRB) and a truncated receptor (C1C2) lacking the amino-terminal domain were expressed in yeast (Saccharomyces cerevisiae) using a ubiquitin fusion system. The expression of the fusion protein is under the control of a copper-responsive yeast metallothionein promoter, and the fusion protein is subsequently cleaved by the yeast host enzyme to produce receptor protein. Western immunoblot analyses of yeast extracts containing full-length PRB revealed a polypeptide co-migrating with authentic chicken oviduct PRB. Using a polyclonal antibody (907) directed against the "hinge" region of the authentic chicken progesterone receptor, a 42-kDa polypeptide was detected by Western analysis in yeast extracts containing C1C2 receptors. Standard hormone binding assays indicated that these receptors produced in yeast cells exhibited steroid binding affinity and specificity characteristic of the authentic chicken progesterone receptor. To test for progesterone receptor-mediated activation of transcription in yeast, reporter plasmids were constructed to transform yeast cells expressing PRB or C1C2 receptors. The reporter gene contained two copies of a progesterone response element upstream of the yeast proximal CYC1 promoter fused to the beta-galactosidase gene of Escherichia coli. The induction of beta-galactosidase activity by PRB and C1C2 was strictly dependent on specific ligand and the presence of a progesterone response element. However, overproduced C1C2 receptors had an adverse effect on the transcription of the lacZ gene. It was found that when overproduced C1C2 was activated by progesterone, an inhibitory effect on normal yeast cell growth was evident. These observations suggest that C1C2 is a potent trans-acting factor in yeast and that the amino-terminal domain of the chicken progesterone receptor may play a role in selective modulation of target gene activation.

Animals↗

PubMed1994

Yeast communities of the cactus Pilosocereus arrabidae and associated insects in the Sandy coastal plains of southeastern Brazil.

The yeast communities from necrotic tissues, decaying flowers and fruits, and from larval feeding sites of the moth Sigelgaita sp. in the cactus Pilosocereus arrabidae were surveyed in three restinga ecosystems in Southeastern Brazil. Insects associated with these substrates were sampled to verify the vectoring of yeasts. The cactus Pilosocereus arrabidae was shown to have four different yeast communities associated with it. Necrotic stems had a diverse yeast community with the prevalent species Pichia barkeri, Candida sonorensis, Pichia cactophila, Geotrichum sp., Myxozyma mucilagina and Sporopachydermia sp. A, representing about 80% of the total isolates. Pichia sp. A and a Candida domercqii-like species represented more than 90% of the yeast isolates from decaying flowers. Fruits had a heterogeneous yeast community with typical fruit yeasts of the genus Kloeckera, basidiomicetous anamorphs of the genus Cryptococcus, the black yeast Aureobasidium pullulans, Pichia sp. A, a Candida domercqii-like species, and some cactophilic yeasts, especially Clavispora opuntiae. The feeding site of Sigelgaita sp. larvae had Clavispora opuntiae as the prevalent species. Insect vectors are suggested as one the most important factors influencing the composition of these yeast communities.

Animals↗

PubMed2006

Yeast diversity in the extreme acidic environments of the Iberian Pyrite Belt.

In the Iberian Pyrite Belt (IPB), acid rock drainage gives rise to aquatic habitats with low pH and high concentrations of heavy metals, a situation that causes important environmental problems. We investigated the occurrence and diversity of yeasts in two localities of the IPB: São Domingos (Portugal) and Rio Tinto (Spain). Yeast isolation was performed on conventional culture media (MYP), acidified (pH 3) media (MYP3), and on media prepared with water from the study sites (MYPw). The main goal of the study was to determine the structure of the yeast community; a combination of molecular methods was used for accurate species identifications. Our results showed that the largest fraction of the yeast community was recovered on MYPw rather than on MYP and MYP3. Twenty-seven yeast species were detected, 48% of which might represent undescribed taxa. Among these, an undescribed species of the genus Cryptococcus required low pH for growth, a property that has not been observed before in yeasts. The communities of S. Domingos and R. Tinto showed a considerable resemblance, and eight yeast species were simultaneously found in both localities. Taking into consideration the physicochemical parameters studied, we propose a hierarchic organization of the yeast community in terms of high-, intermediate-, or low-stress conditions of the environment. According to this ranking, the acidophile yeast Cryptococcus sp. 5 is considered the most tolerant species, followed by Cryptococcus sp. 3 and Lecytophora sp. Species occurring in situations of intermediate environmental stress were Candida fluviatilis, Rhodosporidium toruloides, Williopsis californica, and three unidentified yeasts belonging to Rhodotorula and Cryptococcus.

Biodiversity↗

PubMed1996

The occurrence of killer, sensitive, and neutral yeasts in Brazilian Riesling Italico grape must and the effect of neutral strains on killing behaviour.

The occurrence of killer toxins amongst yeast in Brazilian Riesling Italico grape must was investigated by using the sensitive strain EMBRAPA-26B as a reference strain at 18 degrees C and 28 degrees C. From a total of 85 previously isolated yeasts, 21 strains showed ability to kill the sensitive strain on unbuffered grape must/agar (MA-MB) and 0.1 M citrate/phosphate-buffered yeast extract/peptone/dextrose/agar (YEPD-MB) media both supplemented with 30 mg/l methylene blue. The killer activity of only four yeasts depended on the incubation temperature rather than the medium used. At 28 degrees C, the strains 11B and 53B were not able to show killer action. On the other hand, strains 49B and 84B did not kill the sensitive yeast at 18 degrees C. The killer strain EMBRAPA-91B and a commercial wine killer yeast K-1 were employed to examine the sensitivity of the isolated yeasts on YEPD-MB and MA-MB at 18 degrees C. The sensitivity and neutral characteristics of yeasts were shown to be dependent on the medium and the killer strain. Interactions, including K-R-, K-R+ and K+R+ strains, simultaneously, have revealed that some K-R+ strains appear to protect the K-R- strain against the killer toxin. Sensitive dead cells, although to a less extent, also exhibited similar protection. Kinetic studies have shown that the maximum specific growth rates were higher for the 20B YEPD-MB-sensitive strains (mu(max) = 0.517 h-1) than for both the 91B (mu(max) = 0.428 h-1) and K-1 (mu(max) = 0.466 h-1) killer strains. The protective capacity of neutral or sensitive cells that contaminate a fermentation, as well as the higher maximum specific growth rate of sensitive yeasts, besides other factors, may preclude the dominance of a killer strain. This protective capacity may also reduce the risk of a sensitive inoculum being killed by wild-type killer yeasts in open non-sterile fermentation.

Fruit↗

PubMed2003

The Phaff school of yeast ecology.

Herman Jan Phaff's legacy includes pioneering work on the yeast cell envelope and the application of molecular approaches to yeast systematics. Clearly, his interest and knowledge spanned the whole gamut of yeast biology. Yet, his most original and most heartfelt contribution was to our understanding of the position occupied by yeasts in nature. This view developed through the juxtaposition of his childhood exposure to industrial fermentations and his training in the tradition of Beijerinck's Delft School of Microbiology. Through some of Phaff's recent writings, I have attempted to formulate the themes or principles that were implicit to his ecological thinking. Six focal points emerge. (1) Yeasts in themselves are a sufficient object of study. (2) A clear idea of a yeast community cannot be obtained unless the yeast species are correctly identified. (3) Ecologically meaningful conclusions require an adequate sample size. (4) The bacteriological dictum "everything is everywhere" is a poor account of yeast distributions. (5) The habitat is the cornerstone of yeast ecology. (6) Ecology is the most exciting aspect of yeast biology.

Ecosystem↗

PubMed2004

The presence of Enterococcus, coliforms and E. coli in a commercial yeast manufacturing process.

This study evaluated a typical commercial yeast manufacturing process for bacterial contamination. Product line samples of a commercial yeast manufacturing process and the corresponding seed yeast manufacturing process were obtained upstream from the final compressed and dry yeast products. All samples were analysed before (non-PI) and after preliminary incubation (PI) at 37 degrees C for 24 h. The PI procedure was incorporated for amplification of bacterial counts below the lower detection limit. Enterococcus, coliform and Escherichia coli counts were quantified by standard pour-plate techniques using selective media. Presence at all stages and progressive increases in counts of Enterococcus, coliforms and E. coli during processing in the commercial manufacturing operation suggested that the primary source of contamination of both compressed and dry yeast with these bacteria was the seed yeast manufacturing process and that contamination was amplified throughout the commercial yeast manufacturing process. This was confirmed by surveys of the seed yeast manufacturing process which indicated that contamination of the seed yeast with Enterococcus, coliforms and E. coli occurred during scale up of seed yeast biomass destined as inoculum for the commercial fermentation.

Colony Count, Microbial↗

PubMed1991

A fraction derived from brewer's yeast inhibits cholesterol synthesis by rat liver preparations in vitro.

Brewer's yeast was grown on a defined medium containing tracer 51Cr with or without added chromium. The two batches of yeast contained 10 microgram/g (high-Cr) or 80 ng/g (low-Cr). Extracts were prepared and fractionated. A third batch of yeast (third batch) was grown with added Cr, and fractionated. Rats were reared on either rat cubes (normal diet) or on a low-Cr diet (low-Cr), or on rat cubes with added cholestyramine (cholestyramine diet). Preparations of rat liver, both cell-free and intact hepatocytes, incorporated acetate-carbon into fatty acids and cholesterol. These processes were inhibited by a yeast fraction containing small, neutral, water-soluble compounds. The degree of inhibition was the same whether the liver came from normal rats or rats fed on the low-Cr diet. Similarly the inhibitory effect was found with identical amounts of extracts from low- or high-Cr yeasts. Therefore, Cr compounds do not appear to account for the inhibitory effects of brewer's yeast. Use of other substrates indicated that the site of inhibition of sterol synthesis was apparently between acetyl-CoA and mevalonate. One inhibitory substance was isolated from yeast and was found to be nicotinamide riboside. This may have been produced from NAD(P) during the preparation of yeast extracts, and it may be produced from dietary yeast supplements during digestion in vivo. Nicotinamide riboside may be partly responsible for the reported effects of yeast supplements on plasma lipids in humans.

Animals↗

PubMed2005

Yeast mediates lactic acidosis suppression after antibiotic cocktail treatment in short small bowel?

During acidotic periods in a girl with a short small bowel, very high D-lactic acid concentrations were measured in blood and urine; the patient's characteristic faecal flora contained mainly lactobacilli, and during antibiotic cocktail treatment also many yeasts. In this case report we sought to understand the beneficial effect of the antibiotic cocktail. Microbiological analysis was performed in faecal samples. Total lactic acid in serum and urine was studied using capillary gas chromatography-mass spectrometry, and D- and L-lactic acid in serum and urine by enzymatic assay. The results were coupled to patient's condition. Antibiotic cocktail therapy reduced the acidosis-associated symptoms, faecal lactobacilli and D-lactic acid production, but simultaneously the antibiotic therapy strongly increased the percentage of yeast in the faecal flora. Four to six weeks after each course of treatment the percentage of yeast decreased, whereas the percentage of intestinal lactobacilli increased; D-lactic acid also simultaneously increased in blood and urine. The patient felt well and showed a high percentage of intestinal yeast, but she often suffered from acidosis owing to a high percentage of lactobacilli. The yeast was identified as the pathogenic Candida glabrata. From the mentioned data together with data from the literature it was concluded that during several weeks the selected pathogenic yeast, C. glabrata, acted as a microbiological and metabolic buffer. Shortly after the course of antibiotic treatment this intestinal yeast strongly competed with the intestinal lactobacilli and thus prevented renewed rapid growth, massive D-lactic acid production from glucose and consequently also D-lactic acid-associated acidosis. The emergence of this yeast led us to consider probiotic lactobacilli or yeast for therapeutic use. The lack of knowledge regarding bile acid-deconjugating activity in both lactobacilli and probiotic yeast means that a final recommendation is not yet possible.

Acidosis, Lactic↗

PubMed2005

Evaluation of relative yeast cell surface hydrophobicity measured by flow cytometry.

OBJECTIVE: To develop an efficient method for evaluating cell surface hydrophobicity and to apply the method to demonstrate the effects of fungal growth conditions on cell surface properties. METHODS: Yeast isolates were suspended in phosphate-buffered saline and mixed with deep blue-dyed polystyrene microspheres. Flow cytometry was used to detect the degree of microsphere binding to yeast cells. Different strains of yeast were compared for intrinsic microsphere binding activity and changes in growth conditions were invoked to modify the relative surface hydrophobicity. RESULTS: Commercially available blue-dyed polystyrene microspheres showed strong fluorescence in the FL3 channel, whereas yeast cells did not show appreciable FL3 fluorescence. Microspheres and yeast were generally distinguishable on the basis of size revealed by forward light scatter. This method showed a wide variation in intrinsic cell surface hydrophobicity among Candida albicans strains. Likewise, variation in hydrophobicity of non-albicans yeast species was observed. Growth on solid media, incubation at 25 degrees C, or 250 mg/dl glucose concentration increased hydrophobicity compared with growth in liquid media, incubation at 37 degrees C, or 50 mg/dl glucose, respectively. Growth in 1 x 10(-9) M estradiol had no appreciable effect on hydrophobicity. CONCLUSIONS: Stained latex microspheres fluoresced in the FL3 channel of the flow cytometer and bound to yeast cells to an extent related to the surface hydrophobicity of the yeast. Binding detected by flow cytometry showed that clinical yeast isolates varied in intrinsic binding capacity and this binding ability was altered by different growth conditions. The implications for virulence regulation among yeast isolates are discussed.

Cell Adhesion↗

PubMed2001

Transformation systems of non-Saccharomyces yeasts.

This review describes the transformation systems including vectors, replicons, genetic markers, transformation methods, vector stability, and copy numbers of 13 genera and 31 species of non-Saccharomyces yeasts. Schizosaccharomyces pombe was the first non-Saccharomyces yeast studied for transformation and genetics. The replicons of non-Saccharomyces yeast vectors are from native plasmids, chromosomal DNA, and mitochondrial DNA of Saccharomyces cerevisiae, non-Saccharomyces yeasts, protozoan, plant, and animal. Vectors such as YAC, YCp, YEp, YIp, and YRp were developed for non-Saccharomyces yeasts. Forty-two types of genes from bacteria, yeasts, fungi, and plant were used as genetic markers that could be classified into biosynthetic, dominant, and colored groups to construct non-Saccharomyces yeasts vectors. The LEU2 gene and G418 resistance gene are the two most popular markers used in the yeast transformation. All known transformation methods such as spheroplast-mediating method, alkaline ion treatment method, electroporation, trans-kingdom conjugation, and biolistics have been developed successfully for non-Saccharomyces yeasts, among which the first three are most widely used. The highest copy number detected from non-Saccharomyces yeasts is 60 copies in Kluyveromyces lactis. No general rule is known to illustrate the transformation efficiency, vector stability, and copy number, although factors such as vector composition, host strain, transformation method, and selective pressure might influence them.

Genetic Markers↗

PubMed2001

Yeast identification in the clinical microbiology laboratory: phenotypical methods.

Emerging yeast pathogens are favoured by increasing numbers of immunocompromised patients and by certain current medical practices. These yeasts differ in their antifungal drug susceptibilities, and rapid species identification is imperative. A large variety of methods have been developed with the aim of facilitating rapid, accurate yeast identification. Significant recent commercial introductions have included species-specific direct enzymatic colour tests, differential chromogenic isolation plates, direct immunological tests, and enhanced manual and automated biochemical and enzymatic panels. Chromogenic isolation media demonstrate better detection rates of yeasts in mixed cultures than traditional media, and allow the direct identification of Candida albicans by means of colony colour. Comparative evaluation of rapid methods for C. albicans identification, including the germ tube test, shows that chromogenic media may be economically advantageous. Accurate tests for single species include the Bichrolatex Albicans and Krusei Color tests, both immunologically based, as well as the Remel Rapid Trehalose Assimilation Broth for C. glabrata. Among broad-spectrum tests, the RapID Yeast Plus system gives same-day identification of clinical yeasts, but performance depends on inoculum density and geographic isolate source. The API 20 C AUX system is considered a reference method, but newer systems such as Auxacolor and Fungichrom are as accurate and are more convenient. Among automated systems, the ID 32 C strip, the Vitek Yeast Biochemical Card and the Vitek 2 ID-YST system correctly identify >93% of common yeasts, but the ID-YST is the most accurate with uncommon yeasts, including C. dubliniensis. Spectroscopic methods such as Fourier transformed-infrared spectroscopy offer potential advantages for the future. Overall, the advantages of rapid yeast identification methods include relative simplicity and low cost. For all rapid methods, meticulous, standardized multicenter comparisons are needed before tests are fully accepted.

Candida↗

PubMed2006

Effect of antifungal treatment on the prevalence of yeasts in HIV-infected subjects.

Oral candidiasis, the most common opportunistic infection in patients with HIV infection, is usually associated with Candida albicans. Several factors may influence the carriage of Candida, including immunocompromised conditions and HIV infection, colonization by yeasts from different geographical areas and antimycotic treatment. This study investigated the Candida carrier rate, level and types of yeast in HIV-positive and -negative subjects, and the effect of previous exposure to antifungal drugs on the level of yeasts in HIV-positive patients in Gauteng, South Africa. Unstimulated saliva was collected from 332 HIV-positive patients and 100 HIV-negative subjects and cultured for yeasts. The number and species of yeast were determined. HIV-positive patients who carried yeasts were divided into two groups depending upon their previous antifungal drug exposure, and the level of Candida carriage in each group was compared. The Candida carrier rate in the HIV-positive patients (81.3%) was slightly higher than previously reported and significantly higher (P<0.001) than in the HIV-negative group (63%). The carrier rate in the HIV-negative group was also higher than in earlier studies. Fourteen per cent of the HIV-positive patients carried more than 10,000 c.f.u. ml-1 whereas none of the HIV-negative subjects carried this large a number of yeasts (P<0.001). Seventy per cent of the yeasts were identified as C. albicans and approximately 30% as non-albicans species. In conclusion, the Candida carrier rate is higher in the South African population than elsewhere. HIV-positive patients carry more and a greater variety of yeasts than HIV-negative subjects. Exposure to antifungal drugs has no effect on the level of yeast carriage in HIV-positive patients.

Adolescent↗

PubMed2005

Yeasts associated to Malbec grape berries from Mendoza, Argentina.

AIMS: The aims of this work were to evaluate different pre-isolation treatments applied to complete yeast extraction from grapes and to identify the yeast microflora associated to Malbec grapes from two vineyards located in Mendoza, Argentina. METHODS AND RESULTS: The pre-isolation treatments evaluated were shaking, jet streaming with pressurized water and grape blending. The overall results clearly indicated that when a more vigorous and disruptive pre-isolation treatment was applied; larger numbers of yeast species were recovered. The yeast population on healthy and ripe Malbec grapes was in the order of 10(5)-10(6) CFU g(-1). Eight different yeast species were isolated from berries, including Kloeckera apiculata, Metschnikowia pulcherrima, Pichia membranifaciens, Saccharomycodes ludwigii, Candida species (Candida stellata and Candida raghi), Issatchenkia orientalis and Rhodotorula spp. CONCLUSIONS: Grape blending gave the highest yeast counts. Rainfall near grape harvest time quantitatively and qualitatively modifies the yeast microflora. The yeast species identified on ripe grapes from the Mendoza region, partially match those previously documented in different parts of the world related. S. ludwigii has not been previously reported in grapes. SIGNIFICANCE AND IMPACT OF THE STUDY: The report is on yeast microbiota in grapes from Mendoza, Argentina. Saccharomycodes ludwigii was found in high percentage (17%), this species has not been described before on grapes surface. The importance of pre-isolation steps to the recovery of high number of yeasts was shown. Influence of climatic conditions near harvest time on microflora was confirmed.

Argentina↗

PubMedDate not supplied

Yeast (different sources and levels) as protein source in diets of reared piglets: effects on protein digestibility and N-metabolism.

The aim of this study was to examine the feeding value of different yeasts as a substitute for soya bean meal, the main protein source in diets of weaned piglets. Tested two yeasts were already available on the market, Saccharomyces cerevisiae and Kluyveromyces lactis (beer and milk yeast), which replaced 40% of the soya bean meal in the diets. Furthermore, a yeast (Kluyveromyces fragilis) grown on whey, a side-product of cheese production, was used in increasing concentrations in the diets, so that increasing amounts of the soya bean meal (20%, 40% and 60%) could be replaced. As proved in these experiments, a replacement of 60% of the soya protein with whey yeast protein had positive effects on the performances (daily weight gain) and on the N-metabolism and did not have negative effects on the health or the faeces consistency. The whey yeast stands out because of its high protein quality (N-digestibility and N-retention). Furthermore, the replacement of soya bean meal with highly digestible yeasts is welcomed under the aspect of animal health, because of the reduction of anti-nutritive soya components (stachyose, glycinin) in diets of weaned piglets. The controlled production conditions of the yeasts result in a high feed safety; in addition, the yeast as an end-of-pipe-product is a resource conserving and valuable feed. A main stimulus for the use of yeasts, however, in a food production controlled by economic standpoints, is their price and the costs of other competing feeds.

Animal Feed↗

PubMed1969

Microbial interference between indigenous yeast and lactobacilli in the rodent stomach.

Indigenous yeasts grow in layers in the mucus on the secreting epithelium of the stomachs of some strains of rats and mice raised under conventional conditions. Likewise, indigenous lactobacilli appear in layers on the nonsecreting epithelium of the stomachs of rats and mice. The two microbial layers can coexist in the same animals. When I gave such rodents penicillin solution in the place of drinking water, the lactobacilli disappeared, and the yeast from the secreting epithelium colonized the nonsecreting epithelium within 24 hr. The yeast remained in layers on the nonsecreting, as well as the secreting epithelium, as long as penicillin was administered. There is no inflammatory reaction or any sign that the yeast invaded below the keratin layer. When the penicillin treatment was discontinued, within 5 to 8 days the indigenous lactobacilli again colonized the nonsecreting epithelium. Concomitantly the yeast was displaced from the keratinized tissue and once more could be found only on the secreting epithelium. Only 2 days were required, however, for the bacteria to recolonize the keratin layer and displace the yeast when the mice were given indigenous lactobacilli in pure culture immediately after the penicillin treatment was discontinued. The lactobacilli must displace the yeast from the nonsecreting epithelium by interfering either with multiplication of the yeast on the tissue or with attachment of the yeast cells to the keratin layer. This interference must proceed continuously during normal life since the yeast never populates the nonsecreting epithelium as long as the lactobacilli are present.

Animals↗

PubMed1999

Importance of selective media for recovery of yeasts from clinical specimens.

We compared the recovery of yeasts from clinical specimens cultured on routine bacteriological media to the recovery of yeast from specimens cultured on a selective fungal medium (Sabouraud agar). The use of Sabouraud agar was especially important in cases of mixed cultures, since in such cases yeast was recovered on bacteriological media from only 50% of 44 yeast-positive pus specimens and from 22. 5% of 22 yeast-positive throat specimens. The use of a selective fungal medium is therefore necessary to ensure the detection of yeast in specimens containing a mixture of bacteria and yeasts. As a result, clinicians must request yeast isolation when clinically indicated, and the microbiological laboratory must add a selective fungal medium when clinically significant yeasts are likely to be encountered. It is also important that selective fungal media be used in clinical studies of yeast infections.

Bacteria↗

PubMed1999

Comparison of three commercial systems for identification of yeasts commonly isolated in the clinical microbiology laboratory.

We evaluated three commercial systems (RapID Yeast Plus System; Innovative Diagnostic Systems, Norcross, Ga.; API 20C Aux; bioMerieux-Vitek, Hazelwood, Mo.; and Vitek Yeast Biochemical Card, bioMerieux-Vitek) against an auxinographic and microscopic morphologic reference method for the ability to identify yeasts commonly isolated in our clinical microbiology laboratory. Two-hundred one yeast isolates were compared in the study. The RapID Yeast Plus System was significantly better than either API 20C Aux (193 versus 167 correct identifications; P < 0.0001) or the Vitek Yeast Biochemical Card (193 versus 173 correct identifications; P = 0.003) for obtaining correct identifications to the species level without additional testing. There was no significant difference between results obtained with API 20C Aux and the Vitek Yeast Biochemical Card system (P = 0.39). The API 20C Aux system did not correctly identify any of the Candida krusei isolates (n = 23) without supplemental testing and accounted for the major differences between the API 20C Aux and RapID Yeast Plus systems. Overall, the RapID Yeast Plus System was easy to use and is a good system for the routine identification of clinically relevant yeasts.

Candida↗

PubMed2004

Effect of foliar disease on the epiphytic yeast communities of creeping bentgrass and tall fescue.

The effect of mechanical wounding or foliar diseases caused by Sclerotinia homoeocarpa or Rhizoctonia solani on the epiphytic yeast communities on creeping bentgrass and tall fescue were determined by leaf washing and dilution plating. Total yeast communities on healthy bentgrass and tall fescue leaves ranged from 7.9 x 103 to 1.4 x 105 CFU.cm-2 and from 2.4 x 103 to 1.6 x 104 CFU.cm-2, respectively. Mechanically wounded leaves (1 of 2 trials) and leaves with disease lesions (11 of 12 trials) supported significantly larger communities of phylloplane yeasts. Total yeast communities on S. homoeocarpa infected or R. solani infected bentgrass leaves were 3.6-10.2 times and 6.2-6.4 times larger, respectively, than the communities on healthy leaves. In general, healthy and diseased bentgrass leaves supported larger yeast communities than healthy or diseased tall fescue leaves. We categorized the majority of yeasts as white-pigmented species, including Cryptococcus laurentii, Cryptococcus flavus, Pseudozyma antarctica, Pseudozyma aphidis, and Pseudozyma parantarctica. The percentage of pink yeasts in the total yeast community ranged from 2.6% to 9.9% on healthy leaves and increased to 32.0%-44.7% on S. homoeocarpa infected leaves. Pink-pigmented yeasts included Rhodotorula glutinis, Rhodotorula mucilaginosa, Sakaguchia dacryoidea, and Sporidiobolus pararoseus. Foliar disease significantly affected community size and composition of epiphytic yeasts on bentgrass and tall fescue.

Agrostis↗