Yeasts and Yeast-Like Fungi Associated with Tree Bark: Diversity and Identification of Yeasts Producing Extracellular Endoxylanases

A total of 239 yeast strains was isolated from 52 tree bark samples of the Medaram and Srisailam forest areas of Andhra Pradesh, India. Based on analysis of D1/D2 domain sequence of 26S rRNA gene, 114 strains were identified as ascomycetous; 107 strains were identified as basidiomycetous yeasts; and 18 strains were identified as yeast-like fungi. Among the ascomycetous yeasts, 51% were identified as members of the genus Pichia, and the remaining 49% included species belonging to the genera Clavispora, Debaryomyces, Kluyveromyces, Hanseniaspora, Issatchenkia, Lodderomyces, Kodamaea, Metschnikowia, and Torulaspora. The predominant genera in the basidiomycetous yeasts were Cryptococcus (48.6%), Rhodotorula (29%), and Rhodosporidium (12.1%). The yeast-like fungi were represented by Aureobasidium pullulans (6.7%) and Lecythophora hoffmanii (0.8%). Of the 239 yeast strains tested for Xylanase, only five strains of Aureobasidium sp. produced xylanase on xylan-agar medium. Matrix-assisted laser desorption ionization-time of flight analysis and N-terminal amino-acid sequence of the xylanase of isolate YS67 showed high similarity with endo-1-4-β-xylanase (EC 3.2.1.8) of Aureobasidium pullulans var. melanigenum. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

小蓬竹根际土壤微生物及内生真菌多样性分析

为了解喀斯特典型物种-小蓬竹根际土壤微生物及不同部位内生真菌多样性,采用沿等高线等距离取样法采集小蓬竹根际土壤及健康植株,通过可培养对根际土微生物及内生菌进行分离,利用分子技术对其进行鉴定,根据鉴定结果构建系统发育树,并计算小蓬竹根际土壤微生物和根茎叶内生真菌多样性。结果如下：（1）共从根际土壤、根、茎、叶分离得到139个真菌菌株,隶属于27属,其中根际土壤分离得到34个真菌菌株隶属于12属,根部分离得到的63个内生真菌菌株隶属于17个属,茎部分离得到的14个内生真菌菌株隶属于8个属,叶部分离得到28个内生真菌菌株隶属于9个属;（2）根际土壤共分离得到41株细菌菌株,隶属于7个属26个种,20株放线菌菌株,隶属于1属15种;从Shannon-Wiener多样性指数、均匀度指数、Simpson指数排序来看,真菌主要表现为根 > 根际土壤 > 茎 > 叶,细菌和放线菌多样性均较低。（3）按层次聚类分析可分别将真菌、细菌、放线菌聚为3支。小蓬竹根际土壤、根、茎和叶具有丰富的微生物多样性,不同部位菌群组成存在差异性（P<0.05）,且存在以假单胞菌属、芽孢杆菌属等为优势属的抗盐耐旱菌群,这有助于揭示小蓬竹对喀斯特生境的适应性,以及为微生物-植物群落之间相互关系提供一定基础数据,为后期寻找小蓬竹相关耐性功能菌奠定基础。     

Influence of Linoleate Hydroperoxide Minor Isomers on GLC Analysis of Oleate Hydroperoxides

The distribution of the methylcitric acid cycle and the modified ^-oxidation pathway for propionate catabolism was surveyed in yeasts and filamentous fungi, mainly by comparing the activities of the key enzymes. All the six tested species of filamentous fungi belonging to five genera and 21 species of yeasts belonging to eleven genera were found to catabolize propionate through the methylcitric acid cycle, with the exception of Candida rugosa and one group of strains of C. catenulata, which catabolize propionate through the ß-oxidation pathway. From the observed diversity of propionate catabolism among closely related strains or species, it was assumed that different minor pathways evolved from universal metabolic pathways, such as the citric acid cycle and the ^-oxidation pathway for fatty acids, in later stages of an evolutionary history.     

The Phylogenetic Relationship of the Conidium-forming Anamorphic Yeast Genera Sterigmatomyces,Kurtzmanomyces, Tsuchiyaea and Fellomyces,and the Teleomorphic Yeast Genus Sterigmatosporidium on the Basis of the Partial Sequences of 18S and 26S Ribosomal Ribonucleic Acids

The eleven strains of conidium-forming yeasts classified in the basidiomycetous anamorphic genera Sterigmatomyces, Kurtzmanomyces, Tsuchiyaea and Fellomyces, and the teleomorphic genus Sterigmatosporidium were examined as to the partial sequences of 18S rRNA and 26S rRNA. The positions determined (in Saccharomyces cerevisiae) were 1451 through 1618 of 18S rRNA, and 1618 through 1835 and 470 through 626 of 26S rRNA. The partial sequence determination of positions 470 through 626 of 26S rRNA indicated that T. wingfieldii should be included in the group comprised of Fellomyces and Sterigmatosporidium species. However, the genera Sterigmatomyces, Kurtzmanomyces, Tsuchiyaea and Fellomyces constituted their own separate clusters as to the partial sequences of positions 1451 through 1618 of 18S rRNA and 1618 through 1835 of 26S rRNA. The classification of the conidium-forming yeasts in the four basidiomycetous anamorphic genera mentioned above was proved to be reasonable from the phylogenetic point of view.     

Microbiology of pozol,a Mexican fermented maize dough

Mexican fermented maize dough, pozol, including traditional banana leaf-wrapped samples and material in plastic bags, was purchased. All samples were pH 4.7 to 5.7 approx. 12 h after preparation, pH declining to 3.6 to 3.9 after 6 to 9 days storage at ambient temperature. These latter samples had dry matter contents of 31% to 48% (w/w), 0.35% to 0.75% titratable acidity as lactic acid and lactic acid bacteria as predominant microbial flora at about 10⁸ c.f.u./ml. The lactic acid bacteria included strains of Leuconostoc mesenteroides, Lactobacillus plantarum, Lactobacillus confusus, Lactococcus lactis and Lactococcus raffinolactis. Fungi were not found in the samples stored in plastic bags. The samples wrapped in banana leaf, however, developed a large surface mycoflora within 2 days. This included Geotrichum candidum, yeasts and moulds. The majority of the lactic acid bacteria and approx. 50% of yeasts hydrolysed starch to some extent. No Geotrichum isolate hydrolysed starch. Lactate was assimilated by all the Geotrichum isolates and by 17 of 39 yeast strains.     

Strain differentiation of pathogenic yeasts by the killer system

High sensitivity rates to the activity of killer toxins produced by 25 species of yeasts belonging to the genera Candida, Hansenula, Pichia, Rhodotorula, Saccharomyces and Trichosporon have been observed among 112 yeast isolates (25 Cryptococcus neoformans, 29 C. glabrata, 16 C. parapsilosis, 20 C. pseudotropicalis and 22 C. tropicalis). The highest sensitivity has been observed among the C. parapsilosis isolates, the lowest in C. glabrata strains. Genera Pichia and Hansenula proved to have the greatest killer activity. A killer system, formerly used for differentiating C. albicans isolates within the species, proved to be valid as epidemiological marker when applied to 112 strains of pathogenic yeasts.     

Distribution and identification of red yeasts in deep-sea environments around the northwest Pacific Ocean

We isolated 99 yeast strains, including 40 red yeasts, from benthic animals and sediments collected from the deep-sea floor in various areas in the northwest Pacific Ocean. Comparing the yeast isolates from animals and sediments collected from shallow locations, the proportion of red yeasts differed considerably, comprising 81.5% and 10.6% of the isolates from animals and sediments, respectively. All of the red yeast isolates belonged to the genera Rhodotorula and Sporobolomyces. On the basis of morphological and physiological characteristics, the isolates were identified as R. aurantiaca, R. glutinis, R. minuta and R. mucilaginosa of the genus Rhodotorula, and S. salmonicolor and S. shibatanus of the genus Sporobolomyces. Only R. glutinis and R. mucilaginosa were isolated from sediments. All of the others were isolated from animal sources. Phylogenetic analyses based on internal transcribed spacer (ITS) regions and 5.8S rRNA gene sequences allowed us to establish the precise taxonomic placement of each of the isolates and thereby investigate the intraspecific relationships among the isolates. Twenty-two strains identified as members of R. glutinis, which showed a wide distribution in the deep-sea, and five isolates identified as R. minuta, which were isolated only from benthic animals, showed substantial heterogeneity within the species. The isolates phenotypically identified as Sporobolomyces species and R. mucilaginosa phylogenetically occupied the placements corresponding to these species. Some strains assigned to known species on the basis of phenotypic features should be regarded as new species as suggested by the results of molecular analysis.     

Killer yeasts of Kluyveromyces and Hansenula genera with potential application in fermentation and therapy

The killing/immunity interactions among killer strains of the genera Kluyveromyces, Hansenula and Saccharomyces from the Czechoslovak Collection of Yeasts were studied with the aim to find the strains with broad specificity and killer activity targeted against a range of undesirable wild yeasts causing stuck fermentations. Among 49 tested Kluyveromyces strains, five strains were found, and among 55 Hansenula strains, ten yeast strains were found with activity against a sensitive strain of Saccharomyces. Hansenula mrakii CCY 38-7-1 and Hansenula saturnus var. subsufficiens CCY 38-4-2 showed exceptional activity against the wine contaminants, Zygosaccharomyces bailii, as well as against pathogenic Candida species within a broad range of pH 2.9–5.1. Their potential biotechnological application is discussed.     

Yeasts from Tierra Del Fuego Province (Argentina): Biodiversity,Characterization and Bioprospection of Hydrolytic Enzymes

Abstract

Antarctic and sub-Antarctic regions are – with Polar Regions, mountains and the deep sea – the most extreme environments on Earth because of its low temperatures, dryness, high incidence of solar radiation and low nutrient availability. Nevertheless, microorganisms have successfully colonized these regions. In this study, culturable yeasts from soil samples collected from two different locations, a human-impacted area (Encerrada Bay) and a largely pristine and naturally vegetated area near Lago Escondido city (54°39′0″S, 67°46′48″W) from Tierra del Fuego province, Argentina were identified and characterized at different levels. They were characterized and classified as psychrotolerant and were considered as moderately halotolerant because of their ability to grow in the presence of 1.5?M of NaCl. Yeasts from phylum Ascomycota were affiliated to five genera: Candida, Yarrowia, Debaryomyces, Nadsonia, and Wickerhamiella, whereas from phylum Basidiomycota yeasts were affiliated to six genera: Naganishia, Rhodotorula, Leucosporidum, Tausonia, Cystofilobasidium, and Apiotrichum. Most of the yeasts demonstrated at least one extracellular enzymatic activity (mainly β-glucosidase, esterase, and protease activities). One isolate identified as Tausonia pullulans showed significant activity across the eight enzyme types tested. In light of these findings, Tierra del Fuego province could be considered as a cold environment with a potential source of cold-adapted yeasts producing industrially relevant cold-active enzymes.     

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。     

Production,characterization and gene cloning of the extracellular enzymes from the marine-derived yeasts and their potential applications

In this review article, the extracellular enzymes production, their properties and cloning of the genes encoding the enzymes from marine yeasts are overviewed. Several yeast strains which could produce different kinds of extracellular enzymes were selected from the culture collection of marine yeasts available in this laboratory. The strains selected belong to different genera such as Yarrowia, Aureobasidium, Pichia, Metschnikowia and Cryptococcus. The extracellular enzymes include cellulase, alkaline protease, aspartic protease, amylase, inulinase, lipase and phytase, as well as killer toxin. The conditions and media for the enzyme production by the marine yeasts have been optimized and the enzymes have been purified and characterized. Some genes encoding the extracellular enzymes from the marine yeast strains have been cloned, sequenced and expressed. It was found that some properties of the enzymes from the marine yeasts are unique compared to those of the homologous enzymes from terrestrial yeasts and the genes encoding the enzymes in marine yeasts are different from those in terrestrial yeasts. Therefore, it is of very importance to further study the enzymes and their genes from the marine yeasts. This is the first review on the extracellular enzymes and their genes from the marine yeasts.     

Screening microalgae for some potentially useful agricultural and pharmaceutical secondary metabolites

Nearly two hundred microalgal strains (174 Chlorophyta and 23 Cyanobacteria) were screened against some bacteria, filamentous fungi and yeasts using a disc-diffusion type bioassay. From this initial screening, 10 Chlorophyta strains from three genera (Desmococcus, Chlorella and Scenedesmus) were selected because of their high antimicrobial activity. These 10 strains were partially purified and tested using MIC antimicrobial and microtiter IC₅₀ anticancer assays. These preselected algal strains showed a high incidence of antibacterial activity against both Gram-positive (9 out of 10 species) and Gram-negative (7 out of 10 species) bacteria. The extracts were also effective against some tumour cell lines.     

Molecular characterization of carotenogenic yeasts from aquatic environments in Patagonia, Argentina

Fifteen aquatic environments (lakes, lagoons and rivers) of glacial origin in the northern Andean Patagonia (Argentina) were surveyed for the occurrence of red yeasts. Subsurface water samples were filtered and used for colony counting and yeast isolation. A preliminary quantitative analysis indicated that total yeast counts ranged between 0 and 250 cells l⁻¹. A polyphasic approach including physiological and molecular methods was used for the identification of 64 carotenogenic yeast strains. The molecular characterisation of the isolates was based on the mini/microsatellite-primed PCR technique (MSP-PCR) employing the (GTG)₅ and the M13 primers. Comparison of representative fingerprints of each group with those of the type strains of pigmented yeasts allowed the expeditious identification of 87.5% isolates. The sequence analysis of the D1/D2 domains of the 26S rDNA was employed to confirm identifications and in the characterization of the unidentified MSP-PCR groups. Teleomorphic yeast species were detected by performing sexual compatibility assays. The isolates corresponded to 6 genera and 15 yeast species, including four new yeast species of the genera Cryptococcus (1), Rhodotorula (1) and Sporobolomyces (2). Rhodotorula mucilaginosa was found in the majority of the samples and represented ca. 50% of the total number of isolates. However, this yeast was not detected in aquatic environments with very low anthropic influence. Other frequent yeast isolates were teleomorphic yeast species of Rhodosporidium babjevae, R. kratochvilovae and Sporidiobolus salmonicolor. This study represents the first report on red yeast occurrence and biodiversity in northwestern Patagonia. This revised version was published online in June 2006 with corrections to the Cover Date.     

Chemotaxonomic discrimination among the fungal genera Tolypocladium, beauveria and Paecilomyces

Fungi of the genera Beauveria and Paecilomyces were found to produce cyclotetradepsipeptides, beauverolides. Production of beauverolides was not detected at the genus Tolypocladium. Analysis of beauverolides therefore provides a very simple chemotaxonomic test which seems to be suitable for fast discrimination between the genera Beauveria vs Tolypocladium and complementing morphological examination. A GC-MS study of β-hydroxy acid distribution in the beauverolide hydrolyzates revealed that all strains prdouce γ-methyl-β-hydroxy acids only. Their occurrence thus cannot be used as a taxonomic marker of different species within the genera Beauveria and Paecilomyces.     

Biotransformation of electron-poor alkenes by yeasts: Asymmetric reduction of (4S)-(+)-carvone by yeast enoate reductases

Within the framework of a large-scale screening carried out on 146 yeasts of environmental origin, 16 strains (11% of the total) exhibited the ability to biotransform (4S)-(+)-carvone. Such positive yeasts, belonging to 14 species of 6 genera (Candida, Cryptococcus, Hanseniaspora, Kluyveromyces, Pichia and Saccharomyces), were thus used under different physiological state (growing, resting and lyophilised cells). Yields (expressed as% of biotransformation) varied from 0.14 to 30.04%, in dependence of both the strain and the physiological state of the cells. Products obtained from reduction of (4S)-(+)-carvone were 1S,4S- and 1R,4S-dihydrocarvone, (1S,2S,4S)-, (1S,2R,4S)- and (1R,2S,4S)-dihydrocarveol. Only traces of (1R,2R,4S)-dihydrocarveol were observed in a few strains. As far as the stereoselectivity of the biocatalysis, with the sole exception of a few strains, the use of yeasts determined the prevalent accumulation of 1S,4S-isomers [(1S,4S)-dihydrocarvone + (1S,2S,4S)-dihydrocarveol + (1S,2R,4S)-dihydrocarveol].The addition of glucose (acting as auxiliary substrate for cofactor-recycling system) to lyophilised yeast cells determined a considerable increase of biocatalytic activity: in particular, two strains showed a surprising increase of the% of biotransformation of (4S)-(+)-carvone (to values >98%).     

Selenium Tolerance of Yeasts

Selenium tolerance of yeasts widely varies: the growth of some yeasts can be inhibited by a selenium concentration as low as 10^–4 M, whereas others can grow in the presence of 10^–1 M selenium. Homogeneous yeast taxa are characterized by a certain level of selenium tolerance, and heterogeneous taxa show a variable level of tolerance to selenium. In general, ascomycetous yeasts are more tolerant to selenium than basidiomycetous yeasts. Among the ascomycetous yeasts, the genera Dekkera and Schizosaccharomyces exhibited the lowest and the species Candida maltosa, Hanseniaspora valbyensis, Kluyveromyces marxianus, and Yarrowia lipolytica the highest tolerance to selenium. Among the basidiomycetous yeasts, the genera Bullera, Cryptococcusand Holtermannia showed the lowest and the species Cryptococcus curvatus, Cr. humicola, and Trichosporon spp. the highest tolerance to selenium. The selenium tolerance of yeasts depends on the composition of the growth medium, in particular, on the presence of sulfate, sulfur-containing amino acids, and glutamine in the medium.     

Basidiomycetous Yeasts from Boletales Fruiting Bodies and Their Interactions with the Mycoparasite <Emphasis Type="Italic">Sepedonium chrysospermum</Emphasis> and the Host Fungus <Emphasis Type="Italic">Paxillus</Emphasis>

Interactions between mushrooms, yeasts, and parasitic fungi are probably common in nature, but are rarely described. Bolete fruiting bodies are associated with a broad spectrum of microorganisms including yeasts, and they are commonly infected with filamentous mycoparasites of the genus Sepedonium (teleomorph Hypomyces). We report the isolation of 17 yeast strains from Paxillus and Xerocomus, 16 of which were obtained from the surface tissue, the primary site of Sepedonium infection. Phylogenetic analyses with the D1/D2 region of the 28S ribosomal gene and the internal transcribed spacers placed the yeasts as Rhodotorula, Rhodosporidium, and Mastigobasidium from the Pucciniomycotina, Cryptococcus, Cystofilobasidium, Holtermanniella, and Trichosporon from the Agaricomycotina, and Kluyveromyces from the Saccharomycotina including the first isolation of Rhodotorula graminis from Europe. To investigate the influence of the yeast strains on the mycoparasite and the host fungus, in vitro assays were conducted with Sepedonium chrysospermum and Paxillus involutus. Both S. chrysospermum growth inhibitory and stimulating yeast strains were detected among the isolates. The number of S. chrysospermum inhibitory yeast strains increased and the number of S. chrysospermum stimulatory yeast strains decreased in the presence of P. involutus in co-cultures. Low nutrient levels in the culture medium also led to an increased number of S. chrysospermum inhibitory yeast strains and ten yeasts inhibited the mycoparasite in spatial separation by a crosswall. Six yeast strains inhibited P. involutus in dual culture, and the inhibitory P. involutus yeast interactions increased to nine in the presence of S. chrysospermum. Our results suggest that the bolete-associated yeasts influence the growth of the mycoparasitic fungus, which may affect the health of the fruiting bodies.     

Production of arabitol by yeasts: current status and future prospects

Arabitol belongs to the pentitol family and is used in the food industry as a sweetener and in the production of human therapeutics as an anticariogenic agent and an adipose tissue reducer. It can also be utilized as a substrate for chemical products such as arabinoic and xylonic acids, propylene, ethylene glycol, xylitol and others. It is included on the list of 12 building block C3‐C6 compounds, designated for further biotechnological research. This polyol can be produced by yeasts in the processes of bioconversion or biotransformation of waste materials from agriculture, the forest industry (l ‐arabinose, glucose) and the biodiesel industry (glycerol). The present review discusses research on native yeasts from the genera Candida, Pichia, Debaryomyces and Zygosaccharomyces as well as genetically modified strains of Saccharomyces cerevisiae which are able to utilize biomass hydrolysates to effectively produce l ‐ or d ‐arabitol. The metabolic pathways of these yeasts leading from sugars and glycerol to arabitol are presented. Although the number of reports concerning microbial production of arabitol is rather limited, the research on this topic has been growing for the last several years, with researchers looking for new micro‐organisms, substrates and technologies.     

The growth of various filamentous fungi and yeasts on n-alkanes and ketones

Summary Ninety-five fungi, hydrocarbon isolates as well as those obtained from various type culture collections, were tested for their ability to grow on liquid mineral media containing n-alkanes as sole source of carbon and energy. Of the 29 filamentous fungi tested, 18 were capable of growing on n-alkanes, which represented 11 of the 14 genera tested. Of the 66 yeasts (16 genera) examined only 11 exhibited this ability, predominantly members of the genera Candida, Rhodotorula (2 strains) and Debaryomyces (1 species). Of the hydrocarbon utilizing filamentous fungi and yeasts examined, almost all were capable of growing on n-alkanes having a chain length of 10 carbon atoms or more. However, only a few of the filamentous fungi and none of the yeasts tested possessed the ability to grow on the short chain n-alkanes. Of the 8 hydrocarbon utilizing yeasts examined, only 5 were capable of growing on a few of the wide variety of ketones tested, particularly on 2-hexanone or 2-heptanone.Deceased, April 9, 1966.     

Experimental approach for target selection of wild wine yeasts from spontaneous fermentation of “Inzolia” grapes

The aim of this research was the study of indigenous yeasts isolated from spontaneous fermentation of Inzolia grapes, one of the most widespread native white grapes in Sicily (Italy). The use of selective medium for the isolation and the screening for sulphur dioxide tolerance were useful for the first selection among 640 isolates. The yeasts characterized by high SO₂ tolerance were identified at species level by restriction analysis of ITS region; although the majority of isolates were identified as S. cerevisiae, some non-Saccharomyces yeasts were found. Forty-seven selected yeasts, both S. cerevisiae and non-Saccharomyces yeasts, were characterized for genetic and technological diversity. The genetic polymorphism was evaluated by RAPD-PCR analysis, whereas the technological diversity was analyzed by determining the main secondary compounds in the experimental wines obtained by inoculating these yeasts. Both the molecular and metabolic profiles of selected yeasts were able to clearly discriminate S. cerevisiae from non-Saccharomyces yeasts. This research was useful for the constitution of a collection of selected indigenous yeast strains, including S. cerevisiae and non-Saccharomyces species possessing interesting enological traits. This collection represents a source of wild yeasts, among of which it is possible to select indigenous starters able to maintain the specific organoleptic characteristics of Inzolia wine.