Yeasts Isolated from Neotropical Wood-Boring Beetles in SE Peru

Some temperate wood-boring cerambycid beetles harbor intracellular gut yeasts believed to augment host nutrition, but species belonging to the subfamily Lamiinae are thought to lack endosymbionts. Almost 49 percent of Neotropical cerambycid species are lamiines, therefore, comparatively few rain forest species would be expected to host symbiotic gut yeasts. This study reports the isolation of gut yeasts from closely related Neotropical lamiines. We investigated species that feed on trees in the Brazil nut family (Lecythidaceae), because host plant associations are relatively well known. Our objectives were to determine if gut yeasts were present and, if possible, infer their mode of transmission. We collected and dissected 18 beetle specimens from three tree species, including 17 cerambycids and one curculionid. Every insect specimen yielded a gut yeast. DNA sequence libraries were used for a rapid identification of the yeasts and their larval hosts. The cerambycids included five lamiine species and one cerambycine. Six ascomycete yeasts were isolated from their guts; we found no evidence of strict vertical transmission. Larval gut yeasts were genetically similar to yeasts previously isolated from insects associated with wood or fungi, implying potential habitat specificity. The yeasts have not yet been localized, and potential function is not known, but they may contribute to rapid nutrient cycling or serve as the first line of defense against plant toxins.     

The vectoring of cactophilic yeasts by Drosophila

Summary At two locations in the Sonoran Desert, yeasts were sampled from species of Drosophila, the flies' cactus hosts, and other neighboring sources of cactophilic yeasts to determine the relation between the yeasts vectored by the fly and the yeasts found in their breeding sites. D. mojavensis, D. nigrospiracula, and D. mettleri vectored yeast assemblages significantly more similar to the yeast species found on the rot from which the flies were collected than to the yeasts found on other rots from the flies host cactus or other rotting cactus at the same site. Rots with Drosophila had fewer yeast species than those without flies, suggesting that flies were associated with younger rots. Rots with flies and the Drosophila also had more yeast species with the capability to produce ethyl acetate than rots without flies. The results support the contention that cactophilic Drosophila feed on a subset of the yeasts available in an area, and may act to maintain differences among the yeast communities found on different species of cactus.     

Yeasts associated with fresh and frozen pulps of Brazilian tropical fruits

The occurrence of yeasts on ripe fruits and frozen pulps of pitanga (Eugenia uniflora L), mangaba (Hancornia speciosa Gom.), umbu (Spondias tuberosa Avr. Cam.), and acerola (Malpighia glaba L) was verified. The incidence of proteolytic, pectinolytic, and mycocinogenic yeasts on these communities was also determined. A total of 480 colonies was isolated and grouped in 405 different strains. These corresponded to 42 ascomycetous and 28 basidiomycetous species. Candida sorbosivorans, Pseudozyma antarctica, C. spandovensis-like, C. spandovensis, Kloeckera apis, C. parapsilosis, Rhodotorula graminis, Kluyveromyces marxianus, Cryptococcus laurentii, Metchnikowia sp (isolated only from pitanga ripe fruits), Issatchenkia occidentalis and C. krusei (isolated only from mangaba frozen pulps), were the most frequent species. The yeast communities from pitanga ripe fruits exhibited the highest frequency of species, followed by communities from acerola ripe fruits and mangaba frozen pulps. Yeast communities from frozen pulp and ripe fruits of umbu had the lowest number of species. Except the yeasts from pitanga, yeast communities from frozen pulp exhibited higher number of yeasts than ripe fruit communities. Mycocinogenic yeasts were found in all of the substrates studied except in communities from umbu ripe fruits and pitanga frozen pulps. Most of the yeasts found to produce mycocins were basidiomycetes and included P. antarctica, Cryptococcus albidus, C. bhutanensis-like, R. graminis and R. mucilaginosa-like from pitanga ripe fruits as well as black yeasts from pitanga and acerola ripe fruits. The umbu frozen pulps community had the highest frequency of proteolytic species. Yeasts able to hydrolyse casein at pH 5.0 represented 38.5% of the species isolated. Thirty-seven percent of yeast isolates were able to hydrolyse casein at pH 7.0. Pectinolytic yeasts were found in all of the communities studied, excepted for those of umbu frozen pulps. The highest frequency of pectinolytic activity was found in mangaba frozen pulp communities. Around 30% of all isolates produced pectinases. The ability to split arbutin was observed in all communities ranging from 8% in yeasts from pitanga frozen pulps to 40.6% in acerola ripe fruit communities. Among 432 species tested, 125 were active for beta-glucosidase production, and Kloeckera apis, P. antarctica, C. sorbosivorans, and C. spandovensis-like were the most active species.     

The gut of Guatemalan passalid beetles: a habitat colonized by cellobiose- and xylose-fermenting yeasts

The gut of insects is a productive environment for discovering undescribed species of yeasts, and the gut of wood-feeding insects of several families is especially rich in yeasts that carry out the fermentation of cellobiose and xylose. Passalid beetles (Passalidae, Coleoptera) live in dead wood that they ingest as their primary food source. We report the isolation, molecular identification and physiological characterization of 771 yeast cultures isolated from the gut of 16 species of passalids collected in nine localities in Guatemala. Ascomycete yeasts were present in the gut of every passalid studied, and the xylose-fermenting (X-F) yeasts Scheffersomyces shehatae and Scheffersomyces stipitis were the most abundant taxa isolated. The gut of the beetles also contained undescribed cellobiose-fermenting and X-F species in the Lodderomyces, Scheffersomyces and Spathaspora, and undescribed species in Sugiyamaella clades as well as rare yeast species in the Phaffomyces and Spencermartinsiella clades. Basidiomycete yeasts in the genera Cryptococcus and Trichosporon were also common. The yeast species richness was influenced by the host species and the substrate, and gut-inhabiting yeasts have the ability to survive the differing physiological conditions of several gut compartments.     

Polyphasic identification of yeasts isolated from bark of cork oak during the manufacturing process of cork stoppers

A two-step protocol was used for the identification of 52 yeasts isolated from bark of cork oak at initial stages of the manufacturing process of cork stoppers. The first step in the identification was the separation of the isolates into groups by their physiological properties and RFLPs of the ITS-5.8S rRNA gene. The second step was the sequencing of the D1/D2 domains of the 26S rRNA gene of selected isolates representing the different groups. The results revealed a predominance of basidiomycetous yeasts (11 species), while only two species represented the ascomycetous yeasts. Among the basidiomycetous yeasts, members representing the species Rhodosporidium kratochvilovae and Rhodotorula nothofagi, that have been previously isolated from plant material, were the most abundant. Yeasts pertaining to the species Debaryomyces hansenii var. fabryii, Rhodotorula mucilaginosa and Trichosporon mucoides were isolated in small numbers.     

Alcoholic glucose and xylose fermentations by the coculture process: compatibility and typing of associated strains.

As part of the simultaneous fermentation of both glucose and xylose to ethanol by a coculture process, compatibilities between xylose-fermenting yeasts and glucose-fermenting species were investigated. Among the Saccharomyces species tested, none inhibited growth of the xylose-fermenting yeasts. By contrast, many xylose-fermenting yeasts, among the 11 tested, exerted an inhibitory effect on growth of the selected Saccharomyces species. Killer character was demonstrated in three strains of Pichia stipitis. Such strains, despite their high fermentative performances, cannot be used to ferment D-xylose in association with the selected Saccharomyces species. From compatibility tests between xylose-fermenting yeasts and Saccharomyces species, pairs of microorganisms suitable for simultaneous xylose and glucose fermentations by coculture are proposed. Strains associated in the coculture process are distinguished by their resistance to mitochondrial inhibitors. The xylose-fermenting yeasts are able to grow on media containing erythromycin (1 g/L) or diuron (50 mg/L), whereas the Saccharomyces species are inhibited by these mitochondrial inhibitors.     

Seasonal dynamic of the numbers of epiphytic yeasts

The numbers of epiphytic yeasts on the leaves and flowers of 25 plant species throughout their vegetation period was determined. The numbers of yeasts on the leaves were found to change regularly throughout the year. The average dynamics for all of the plant species investigated included an increase in yeast numbers during spring and summer with the maximum in late autumn and early winter. The character of the yeasts’ dynamics depends on the ecological characteristics of the plants and the duration of the ontogenesis of their leaves and flowers. Three types of dynamics of epiphytic yeasts were revealed: year-round with an increase in autumn-winter, year-round without visible changes, and seasonal with a terminal increase for annual plants.     

Yeasts associated with Drosophila in tropical forests of Rio de Janeiro, Brazil.

The distribution and diversity of yeast species vectored by and from the crop of eight species groups of Drosophila is described for two rain forest sites and an urban wooded area in Rio de Janeiro, Brazil. The typical forest Drosophila groups guarani, tripunctata, and willistoni showed a higher diversity of yeasts than the cosmopolitan melanogaster species group, suggesting different strategies of utilization of substrates. Apiculate yeasts, including Kloeckera apis, Kloeckera javanica, and Kloeckera japonica, were the prevalent species. Geotrichum spp. and Candida citea were also frequent isolates in the forest sites. Similarities between the yeasts from the external surfaces and crops of Drosophila suggested that the feeding substrates were the main source of the yeasts vectored by these flies. Most of the yeasts were strong fermenters and assimilated few compounds, usually sucrose, cellobiose, and glycerol. This indicated a preference of the flies for food sources such as fruits. Some yeasts were primarily isolated from one group of Drosophila; for example, Kloeckera javanica from the melanogaster group, Debaryomyces vanrijiae var. yarrowii from the tripunctata group, and Kluyveromyces delphensis from the willistoni group. These associations and differences in the yeast communities among the fly groups suggested a differentiation of diets and specialization of the yeast-Drosophila association in the tropical forests.     

Seasonal dynamics of the structure of epiphytic yeast communities

The seasonal dynamics of the species structure of epiphytic yeasts on the leaves and in the flowers of 25 plant species was studied throughout the period of their vegetation. It was shown that, on average for the vegetation period, the composition of epiphytic yeast communities was nonspecific. The same species of epiphytic yeasts dominated on different plant species, irrespective of their taxonomic identity and ecological peculiarities. However, different species of yeasts exhibited different types of seasonal dynamics of relative abundance. Therefore, a combination of the dynamics of yeast species and the ontogenetic cycles of plants creates a pattern of the dynamics of the epiphytic yeast population, which is unique for each plant species. The species diversity of yeasts on the leaves of a plant is determined by the duration of its ontogenetic cycle: the longer the vegetation of a plant, the higher the diversity of the epiphytic yeasts population. The greatest diversity of epiphytic yeasts was revealed on the leaves of perennial hygrophytes and mesophytes; the minimal diversity, on ephemeroids and annuals with a short ontogenetic cycle.     

The utilization of naturally occurring yeasts by Drosophila species, using chemically defined substrates

The ability of three Drosophila species; Drosophila obscura, D. subobscura and D. phalerata, to utilize a range of naturally occurring yeasts as food sources was determined. The yeasts used were the dominant species of two commonly used breeding sites, Sorbus aucuparia fruits and the fruiting bodies of the fungus Phallus impudicus. The range of yeast species used was found to reflect the degree ot substrate specialization exhibited by these three species, with D. subobscura being broader niched than the other two species. There was an indication that D. phalerata was adapted to those yeasts normally found on its natural breeding site, Phallus impudicus. Many factors were found to affect the nutritional adequacy of the yeasts, including their growth period, the larval density, the presence of competitors and particularly the chemical composition of the basal growth medium.     

Production of alditols fromd-xylose by yeasts

Production of glycerol, tetritols, pentitols, hexitols and heptitols was tested with 193 strains of yeasts and yeast-like microorganisms belonging to 13 genera. According to the production of alditols, the yeast species were divided into four groups. The largest group consisted of pentitol-producing yeasts. Only few species produced glycerol, tetritol and hexitol. Production of heptitols was found mainly in sporulating yeasts. Translated by Č. Novotny     

The incidence of killer activity of non-Saccharomyces yeasts towards indigenous yeast species of grape must: potential application in wine fermentation

Fourteen killer yeasts were assayed for their ability to kill species of yeast that are commonly associated with fermenting grape must and wine. A total of 147 of a possible 364 killer-sensitive interactions were observed at pH 4.5. Of the killer yeasts studied, Pichia anomala NCYC 434 displayed the broadest killing range. At a pH value comparable with those of wine ferments, pH 3.5, the incidence of killer-sensitive interactions was reduced by 700% across all the yeasts. Williopsis saturnus var. mrakii CBS 1707 exhibited the broadest killing range at the lower pH, killing more than half of the tester strains. Intraspecific variation in sensitivity to killer yeasts was observed in all species where more than one strain was tested. Also, in strains of Pichia anomala, Kluyveromyces lactis and Pichia membranifaciens, the three species in which more than one killer yeast was analysed, intraspecific variation in killer activity was observed.     

Occurrence of molds and yeasts in dairy products

Summary In the search for additional techniques for determining fungal populations of dairy products, 23 species of filamentous fungi and 25 species of yeasts were recovered from a variety of raw, pasteurized, and processed dairy products. The usefulness of media containing rose bengal and antibiotics is indicated. The occurrence of a number of the species found is discussed together with some of the results of physiological studies of yeasts used in species characterization.     

Content and chemical compositions of cerebrosides in lactose-assimilating yeasts

Cerebrosides were found in ten lactose-assimilating yeasts. Representative component ceramide moieties of cerebrosides from nine of these yeasts contained 9-methyl-4-trans, 8-trans-sphingadienine, and 2-hydroxy fatty acid with carbon chain lengths of 16 or 18. The major ceramide moieties in Brettanomyces anomalus, however, differed from those in other yeasts, and were predominately moieties containing 2-hydroxymyristic acid. Thus we found that various cerebroside molecular species are present in yeasts.     

Three new species of anamorphic yeasts phenotypically and phylogenetically related toCandida mesenterica: The description ofCandida fungicola sp. nov.,Candida sagamina sp. nov., andCandida fukazawae sp. nov. isolated from fruit bodies of mushrooms

Four strains of anamorphic yeasts isolated from fruit bodies of mushrooms collected in Japan were found to represent three new species of the genusCandida. These species resembleCandida mesenterica in characteristics commonly employed in the classification of yeasts. On the basis of DNA-DNA reassociation, however, they were clearly distinguished fromC. mesenterica and from one another. Three new species,Candida fungicola, Candida sagamina, andCandida fukazawae, are proposed for these yeasts. The analysis of SSU rDNA sequences suggested that these three species were closely related to each other and toC. mesenterica andC. suecica.     

Identification and characterization of yeasts in sugarcane silages

Aims: To enumerate the micro‐organisms and to identify the yeast species present during the ensilage of different sugarcane (Saccharum spp.) cultivars. Method: Samples of sugarcane silage were collected at 10, 20, 30 and 40 days from the start of fermentation. Population levels of lactic acid bacteria (LAB), mesophilic facultative anaerobic (MFA) bacteria, filamentous fungi and yeasts were determined. Nine species of yeasts were classified according to traditional methods and confirmed using molecular techniques. Conclusions: LAB dominated the ensiling process of sugarcane, although yeasts were present at relatively high population levels throughout the whole fermentation period. The detected species of yeasts varied according to sugarcane cultivar and time of fermentation. Torulaspora delbrueckii was the predominant yeast, followed by Pichia anomala and Saccharomyces cerevisiae. Significance and Impact of the Study: Knowledge of the population of micro‐organisms in general, and of yeasts in particular, present during the fermentation of sugarcane is of fundamental importance in the development of more effective ensiling processes.     

Nutrition and phylogeny of predacious yeasts

Yeast predation was studied with respect to the range of its distribution among ascomycetous yeasts, the range of yeast species that can be affected, and nutritional aspects of the phenomenon. The yeasts identified as predators belong to the Saccharomycopsis clade as defined on the basis of rDNA sequence relatedness. The 11 recognized species in the clade, plus three undescribed but related Candida species, were shown to be incapable of utilizing sulfate as sole source of sulfur, and all but two (Saccharomycopsis capsularis and Saccharomycopsis vini) were observed to penetrate and kill other yeasts under some conditions. Other unrelated sulfate transport-deficient yeasts (strains in the genera Pichia and Candida and the two known species of Starmera) are not predacious. The predacious species vary considerably as to the optimal environmental conditions that favour predation. Some are inhibited by the presence of rich nitrogenous nutrients, organic sulfur compounds, or higher concentrations of ammonium nitrogen, whereas other species may be stimulated under the same conditions. An attempt was made to correlate prey susceptibility to the excretion of substances that stimulate the growth of predators, but no correlation was detected between the two phenomena. The range of susceptible prey covers both ascomycetes and basidiomycetes, and includes Schizosaccharomyces pombe, which was previously thought to be immune. The achlorophyllous alga Prototheca zopfii is not killed by predacious yeasts, but the initial steps of penetration have been observed in some cases. Predacious species attack other predacious species, and in some cases, young cultures may penetrate older cultures of the same strain.     

浙江雁荡山山脉叶栖酵母菌资源与物种多样性

对北雁荡山、中雁荡山、南雁荡山、西雁荡山和东雁荡山等广阔区域内的叶栖酵母菌资源进行考察,旨在弄清雁荡山山脉叶栖酵母菌资源和多样性。采用PDA平板对雁荡山地区的叶栖酵母菌资源进行分离和纯化,根据酵母菌培养物26S rDNA D1/D2序列和系统发育关系明确酵母菌的分类地位,分析该地区叶栖酵母菌群落的多样性、组成和分布情况。结果发现,分离自雁荡山山脉的1118株叶栖酵母菌可以被鉴定为56个已知类群和19个疑似新种,其中38种酵母菌在该地区比较常见。常见的酵母菌类群中,包括Derxomyces属5种,Sporobolomyces属3种,Bannoa、Bulleribasidium、Rhodosporidiobolus、Symmetrospora、Taphrina、Tilletiopsi和Udeniomyces属各2种,Bullera、Coniochaeta、Coniosporium、Cryptococcus、Elsinoe、Erythrobasidium、Fellozyma、Golubevia、Kockovaella、Kondoa、Leucosporidium、Moesziomyces、Oberwinklerozyma、Phyllozyma、Ruinenia和Saitozyma属各1种。根据常见酵母菌类群的相对频率,在该地区分离到的叶栖酵母菌中Derxomyces mrakii具有明显分布优势,并探讨了Derxomyces mrakii株间26S rDNA D1/D2序列的稳定性和变异幅度。根据雁荡山地区常见叶栖酵母菌组成和相似程度,可以推测地理上相近地区的酵母菌物种分布具有更大相似性。基于雁荡山山脉常见叶栖酵母菌种类和数量而绘制出的物种累积曲线,证明雁荡山地区绝大多数的叶栖酵母菌种类已经被分离到,研究结果可以真实反映该地区叶栖酵母菌资源和物种多样性的存在状况。     

云南高原湖泊杞麓湖冬季可培养酵母菌多样性分析

【目的】探究云南杞麓湖酵母菌群落结构及其与环境因子的相互关系。【方法】采用原位培养方法对杞麓湖14个水样进行酵母菌分离,应用26S r DNA D1/D2区域序列分析,并结合形态及生理生化指标将对分离获得的酵母菌进行鉴定,运用软件bio-dap和Canoco分析酵母菌类群的丰富度及其与环境因子间的相互关系。【结果】从杞麓湖中分离得到321株酵母菌,鉴定为14个属27个种和1个潜在的新类群。Rhodosporidium kratochvilovae和出芽短梗霉(Aureobasidium pullulans)是优势种,分别为总菌株数的29.6%和16.8%。水体总磷含量是影响产色素红冬孢酵母属(Rhodosporidium)分布的重要环境因子,而p H为隐球酵母属(Cryptococcus)分布的一个重要选择条件。【结论】杞麓湖酵母菌具有较为丰富的群落多样性。     

Lethality of the petite mutation in petite negative yeasts

Yeast species from which respiratory deficient, or petite, mutants cannot easily be obtained (petite negative species) give rise to micro-colony-producing mutants when subjected to an acriflavine treatment that induces the production of petite mutants in several other yeasts (petite positive species). As a rule, the micro-colonies die before becoming visible to the naked eye. Sometimes they can be subcultured and the respiratory deficiency of the mutants can then be demonstrated. The results of growth experiments under anaerobic conditions suggest that the functioning of a respiratory system is more important to the petite negative yeasts than it is to the petite positive yeasts. An incidental lethal side-effect of acriflavine, specifically on petite negative yeasts, is improbable since mutagenic treatment with supraoptimum temperatures induced viable petite mutants in petite positive yeasts only, and again a lethal mutation in petite negative yeasts.