Number Of Yeast Species Research Articles

Efficient production of fatty acid methyl esters by a wastewater-isolated microalgae-yeast co-culture.

Improving the competitiveness of biodiesel production by microalgae cultures requires the application of several strategies to obtain a high content of lipids, rapid biomass growth and a capacity to adapt to different kinds of environment, with the aim of using non-renewable nutrient sources. Therefore, the use of an individual indigenous microalgae strain or a consortium from natural or anthropogenic sites is now considered an alternative for biofuel production. This study examined the temporal behaviour of secondary metabolites produced by a native microalgae and yeast consortium isolated from wastewater, which was characterized by a genetic identification method based on the MiSeq system. The predominant species in the consortium was Scenedesmus obliquus, representing 68% of the organisms. In addition, the consortium contained a number of yeast species, including Candida pimensis (43%), Arthroderma vanbreuseghemii (23%), Diaporthe aspalathi/Diaporthe meridionalis (25%) and Hericium americanum (3%). This indigenous co-culture of microalgae and yeast showed biomass productivity of 0.06gl-1day-1, with a content of 30% (w/w) carbohydrates, 4% (w/w) proteins and 55% (w/w) lipids. Transesterification of the extracted lipids produced fatty acid methyl esters (FAMEs), which were analysed by gas chromatography (GC). The FAMEs included methyl pentadecanoate (1.90%), cis-10-pentanedecanoic acid methyl ester (1.36%), methyl palmitate (2.64%), methyl palmitoleate (21.36%), methyl oleate (64.95%), methyl linolenate (3.83%) and methyl linolelaidate (3.95%). This composition was relevant for biodiesel production based on the co-culture of indigenous microalgae and yeast consortia.

Improvement of γ-decalactone production by stimulating the import of ricinoleic acid and suppressing the degradation of γ-decalactone in Saccharomyces cerevisiae

A number of yeast species can transform ricinoleic acid into γ-decalactone, a high-value compound with fruity aroma, through β-oxidation. This study investigated the effect of l-carnitine on γ-decalactone production by Saccharomyces cerevisiae MF013 to increase the β-oxidation rate. Results showed that l-carnitine shortened the biotransformation period by approximately 10 h and increased γ-decalactone production by 19.5%. γ-Caprolactone, γ-octalactone, and γ-dodecalactone were separately added to the medium to prevent γ-decalactone degradation by yeast cells at the end of biotransformation. γ-Octalactone competitively inhibited γ-decalactone from binding to lactonase, resulting in an 11% increase in γ-decalactone production. This research proposed an effective approach to improve the γ-decalactone production rate, shorten the biotransformation period, and suppress the γ-decalactone degradation in S. cerevisiae.

Type 1 diabetes in children is not a predisposing factor for oral yeast colonization.

Type 1 diabetes mellitus (T1D) is considered a risk factor associated with oral yeast infections. The aim of this study was to evaluate the yeast oral carriage (in saliva and mucosal surface) of children with T1D and potential relation with host factors, particularly the subset of CD4+ T cells. Yeasts were quantified and identified in stimulated saliva and in cheek mucosal swabs of 133 diabetic T1D and 72 healthy control subjects. Salivary lymphocytes were quantified using flow cytometry. The presence of yeasts in the oral cavity (60% of total patients) was not affected by diabetes, metabolic control, duration of the disease, salivary flow rate or saliva buffer capacity, by age, sex, place of residence, number of daily meals, consumption of sweets or frequency of tooth brushing. Candida albicans was the most prevalent yeast species, but a higher number of yeast species was isolated in nondiabetics. T1D children with HbA1c ≤ 7.5 (metabolically controlled) presented higher number of CD4+ T salivary subsets when compared with the other groups of children (non-diabetic and nonmetabolically controlled) and also presented the highest number of individuals without oral yeast colonization. In conclusion, T1D does not predisposes for increased oral yeast colonization and a higher number of salivary CD4+T cells seems to result in the absence of oral colonization by yeasts.

Editorial: DNA Replication Origins in Microbial Genomes.

In all three domains of life, DNA replication initiates on defined genome sites, termed replication origins. In bacteria, replication typically initiates from a single replication origin (oriC). In eukaryotic genomes, replication initiates from significantly more replication origins, ranging from hundreds in yeast to tens of thousands in human (Gao et al., 2012). Within the archaeal domain, multiple replication origins have been identified in Sulfolobus species, haloarchaea etc. (Lundgren et al., 2004; Robinson et al., 2004; Wu et al.; Yang et al., 2015). The research on replication origins is important not only in providing insights into the structure and function of the replication origins but also in understanding the regulatory mechanisms of the initiation step in DNA replication. Therefore, intensive studies, by in silico analyses as well as in vivo and in vitro experiments, have been carried out in the last two decades. Based on the sequence-derived features, various in silico approaches have been developed to identify microbial replication origins (Frank and Lobry, 2000; Breier et al., 2004; Mackiewicz et al., 2004; Zhang and Zhang, 2005; Worning et al., 2006; Gao and Zhang, 2007, 2008a; Gao et al., 2013; Gao, 2014). For example, the locations of replication origins sites have been predicted for thousands of bacterial genomes by Ori-Finder, a web-based system for finding oriCs in bacterial genomes (Gao and Zhang, 2007; Gao et al., 2013). A new version of Ori-Finder for archaea, Ori-Finder 2, has been developed to predict oriCs in archaeal genomes automatically (Luo et al.). To confirm the predicted replication origins, it is important to choose a most suitable experimental strategy. Song et al. summarize the main existing experimental methods to determine the replication origin regions and their practical applications (Song et al.). As a study from in silico to in vitro, the experimental supports are provided for the identified replication origins in Cyanothece ATCC 51142 (Gao and Zhang, 2008b), and their interactions with the initiator protein DnaA (Huang et al.). In spite of a great variety of origin sequences across species, all bacterial replication origins contain the information necessary to guide assembly of the DnaA protein complex at oriC, triggering the unwinding of DNA and the beginning of replication. Therefore, oriC-encoded instructions should be interpreted particularly in the context of replication initiation and its regulation (Wolanski et al.). Wolanski et al. show that oriC-encoded instructions allow not only for initiation but also for precise regulation of replication initiation and coordination of chromosomal replication with the cell cycle (also in response to environmental signals; Wolanski et al.). Frimodt-Moller et al. find control regions for chromosome replication are conserved with respect to sequence and location among Escherichia coli strains (Frimodt-Moller et al.). Based on the single origin usage strategy that distinguishes bacteria, Marczynski et al. redefine the bacterial origins as centralized information processors, and describe how negative-feedback, phospho-relay, and chromosome-partitioning systems act to regulate chromosome replication (Marczynski et al.). On the other hand, the in silico analyses show that some bacteria, although very few, may have multiple origins of replication per chromosome (Frank et al., 2015; Gao), and the recent work also suggests that there are multiple replication origins in Synechocystis that fire asynchronously, as in eukaryotic nuclear chromosomal replication (Ohbayashi et al., 2015). For eukaryotic organisms, replication origins are best characterized in the unicellular eukaryote budding yeast Saccharomyces cerevisiae and the fission yeast Schizosaccharomyces pombe. With the recent development of genome-wide approaches, the number of yeast species involved in ORIs research has increased dramatically, which has created opportunities for the sequence, protein, and comparative analysis of replication origins in yeast genomes (Li et al.; Zheng et al.; Peng et al.). The Frontiers in Microbiology Research Topic on DNA replication origins in microbial genomes is devoted to address the issues mentioned above, and aims to provide a comprehensive overview of the current research in this field.

Effect of pelleting agent on microbiological and mycotoxicological safety of feed mixtures

The study was conducted to determine effect of pelleting agents on physical and chemical characteristics as well as microbiological and mycotoxicological safety of pelleted feed mixtures for laying hens. Four feed mixtures were analyzed: Control (K) - without supplemented pelleting agent, and three experimental ones (A, B and C) with supplemented pelleting agent. Lignocellulose concentrate-based agent was added in feed mixture A -?Arbocel? (2%), and bentonite-based agent in feed mixture B ?Bentopel? (2%), while both agents were added in feed mixture C in the concentration of 1%. The pellets of highest hardness (6 Khal J/kg ) were found in feed mixture B. The pellets of rather good hardness (5.5 Khal J/kg ) were found in feed mixture A, while the pellets in feed mixture C (3.5 Khal J/kg) were of the lowest hardness. Total number of bacteria was the highest in diet K amounting to 39000/g sample, and significantly lower in the experimental feeds mixtures ranging from 2,100 (C) to 5,000 (B). Pathogenic bacteria were not detected in the analyzed feeds mixtures. The highest number of yeast species (8) was found in feed mixture K, and in experimental feeds mixtures this number was significantly lower. In feed mixture A one yeast species was found, in feed mixture B three and in feed mixture C 6, respectively. The predominant were the representatives of the Aspergillus species, a typical mycobiota developed in the animal feed warehouses. Presence of mycotoxins (aflatoxin B1, ochratoxin A, zearalenone, deoxynivalenol, diacetoxyscirpenol and T-2 toxin) was not detected in analyzed feeds mixture.

Detection of Candida albicans DNA from blood samples using a novel electrochemical assay

The genus Candida contains a number of yeast species which are opportunistic pathogens and are associated with life-threatening infections in immunocompromised individuals. Provision of appropriate therapy relies on the rapid identification of the infecting species, and existing methods of identifying Candida species in clinical samples are time and resource intensive and are not always specific enough to differentiate between drug-susceptible and drug-resistant species. We have previously developed a system for the rapid detection of yeast pathogens in clinical samples using PCR followed by hybridization with a suite of five species-specific, electrochemically labelled DNA probes. The limit of detection of the assay was shown to be 37 fg (∼1 genome) per reaction using extracted genomic DNA. We carried out a study to test the limit of detection of one of the probes, CA PR3, using blood samples from a healthy donor that were spiked with genomic DNA or with C. albicans cells. Our results demonstrated a limit of detection of 37 fg (ml blood)(-1) (∼1 genome ml(-1)) using extracted DNA or 10 c.f.u. (ml blood)(-1) using C. albicans cells, indicating that the assay is capable of detecting C. albicans nucleic acid at levels that are encountered in clinical samples.

A history of research on yeasts 9: regulation of sugar metabolism1

A history of research on yeasts 9: regulation of sugar metabolism1

AFLP fingerprinting for analysis of yeast genetic variation.

Amplified fragment length polymorphism (AFLP) was used to investigate genetic variation in commercial strains, type strains and winery isolates from a number of yeast species. AFLP was shown to be effective in discriminating closely related strains. Furthermore, sufficient similarity in the fingerprints produced by yeasts of a given species allowed classification of unknown isolates. The applicability of the method for determining genome similarities between yeasts was investigated by performing cluster analysis on the AFLP data. Results from two species, Saccharomyces cerevisiae and Dekkera bruxellensis, illustrate that AFLP is useful for the study of intraspecific genetic relatedness. The value of the technique in strain differentiation, species identification and the analysis of genetic similarity demonstrates the potential of AFLP in yeast ecology and evolutionary studies.

Genetic aspects of yeast flocculation: in particular, the role of FLO genes in the flocculation of Saccharomyces cerevisiae

Lectin-mediated flocculation has been shown in a number of yeast species and genera. The genetics of flocculation have lagged behind other areas of study and to date, have only been studied in the mannose-sensitive form of flocculation (Flol phenotype) in Saccharomyces cerevisiae. Some 40 years ago, flocculation was shown to be an inheritable characteristic of certain yeast strains. This demonstrated that flocculation was not a purely colloidal or chemical phenomenon. A number of dominant FLO genes were later discovered. Yeasts containing FLO genes after genetic crossing, were found to flocculate. FLO1, FLO2 and FLO4 were allelic and currently FLO1 (chromosome I), FLO5 (chromosome I) and FLO8 (chromosome VIII) are recognised. Flocculation may be suppressed by genes fsu1 and fsu2. Non-flocculent strains have been shown to flocculate following mutation at the TUPI (chromosome III) or CYC8 (chromosome II) loci. Other mutations, abs, wal, FH4C, sfl1, cka2, also cause flocculation, as does expression of human HA-ras p21 or viral HTLV-1 tax, or over-expression of yeast CHS2. In view of the similarity in flocculation caused by FLO genes and tup1 or cyc8, it has been suggested that most, possibly all S. cerevisiae strains contain lectin genes which are expressed following regulatory mutation. It is therefore possible that FLO genes are regulatory rather than structural lectin genes.

Yeast communities of the cactus Pilosocereus arrabidae as resources for larval and adult stages of Drosophila serido.

The feeding behavior of Drosophila serido on the yeast communities of necrotic stem tissue of Pilosocereus arrabidae were studied in a sand dune ecosystem of Rio de Janeiro, Brazil. The prevalence of cactophilic yeasts including Pichia barkeri, Candida sonorensis and Geotrichum sp. in the crops and external surfaces of D. serido reflected its association with the cactus habitat. The effective number of yeasts vectored on the surface of flies was higher than that in the crops. Also overlap between the yeasts from stems and from crops was partial suggesting selective feeding by the flies in the substrates visited. The females had a higher effective number of yeast species and a lower similarity than males with the yeast community of P. arrabidae. This was probably related to the search for oviposition sites by females. The presence of Pichia thermotolerans-like and Pichia amethionina var pachycereana in the flies, but not in P. arrabidae stems, indicated that D. serido was not limited to this cactus species. The larvae and adults lived in different patches with the adults feeding in patches with higher yeast species richness. The larvae had a narrower feeding niche and higher overlap with P. arrabidae, and preferred P. barkeri and Pichia cactophila as food. Adult flies fed on patches with the most frequent yeasts except for P. cactophila. Pichia caribaea was found in higher frequency in the adult crops than in the stems. Our data suggested that there was food selection and diet partitioning between adult and larval stages of D. serido.

Heterogeneity of the yeast flora in the breeding sites of cactophilic Drosophila

Yeasts were isolated from 278 rots in cladodes and basal stems of Opuntia stricta sampled over 15 months at one locality. The most common yeast species among 370 nonidentical isolates representing 20 species were Candida sonorensis (27% of isolates) and Pichia cactophila (24%). These species generally were present in all months and throughout the area sampled. Other relatively common species (3–9% of alt isolates) had much more restricted distributions in both time and space. The mean number of yeast species per rot was 1.27 ± 0.082, and no yeasts were isolated from 20% of the rots sampled. Significant differences among months or seasons in average number of yeast species per rot were due primarily to lower numbers in the summer and winter months, while differences among rot types resulted mainly from a higher number in the longer persisting basal stem rots. Both hierarchical diversity analysis and analysis of the distributions of the 10 most common yeast species showed temporal effects (month or season) to be the major component contributing to heterogeneity, while microgeographic effects and rot type also were significant. The seasonal and microgeographic heterogeneity are interpreted in terms of longer persisting rots in part of the locality providing a reservoir for yeast species through the winter and are discussed in relation to the maintenance of genetic variation in cactophilic Drosophila that utilize the rots as feeding and breeding sites.

Exo-beta-glucanases in yeast.

1. A number of yeast species were examined for the presence of beta-glucanases. Extracts obtained by cell disruption of Saccharomyces cerevisiae, Fabospora fragilis and Hansenula anomala hydrolysed laminarin and pustulan with the production of glucose. Enzymic activities were also detected in the culture fluids of F. fragilis and H. anomala grown aerobically in buffered mineral medium with glucose as the carbon source. 2. F. fragilis and H. anomala possessed approximately sevenfold higher beta-(1-->3)-glucanase activity than S. cerevisiae. 3. Intracellular exo-beta-glucanase from baker's yeast was purified 344-fold from the dialysed cell extract. 4. Exo-beta-glucanase from F. fragilis was purified 114-fold from the dialysed culture fluid and 423-fold from the dialysed intracellular extract. The purified extracellular and intracellular enzymes had similar properties and essentially the same specific activity, 79 enzyme units/mg. of protein. 5. Extracellular exo-beta-glucanase of H. anomala was purified 600-fold. 6. The optimum pH of the enzymes from F. fragilis, S. cerevisiae and H. anomala was 5.5 in each case. Chromatographic evidence indicated that the three enzymes remove glucosyl units sequentially from laminarin as well as pustulan. 7. The ratio of activities towards laminarin and pustulan remained constant during purification of the exo-beta-glucanase obtained from the three species, suggesting a single enzyme. Additional evidence for its unienzymic nature are: (i) the two activities were destroyed at exactly the same rate on heating of the purified enzyme from F. fragilis at three different temperatures; (ii) the competitive inhibitor glucono-delta-lactone gave the same value of K(i) when tested with either substrate; (iii) quantitative application of the ;mixed-substrate' method with the purified enzyme of S. cerevisiae gave data that were in excellent agreement with those calculated on the assumption of a single enzyme. 8. The purified exo-beta-glucanases of the different species of yeast had different kinetic constants. The ratios of maximal velocities and K(m) values with laminarin and pustulan differed markedly. Comparison of V(max.) and K(m) values suggests that the rapid release of spores from asci in F. fragilis might be explained in terms of an enzyme with higher maximal velocity and higher affinity to the ascus wall than that present in baker's yeast. 9. The estimated molecular weights for exo-beta-glucanases from F. fragilis, S. cerevisiae and H. anomala were 22000, 40000 and 30000 respectively.

Studies on polygalacturonase of certain yeasts

1. 1. Among a considerable number of yeast species, representing nearly all yeast genera, only six were found which were capable of causing certain changes in pectin, when grown in its presence. These six cultures could all be identified with Saccharomyces fragilis (and a variety of this species) and its imperfect form Candida pseudotropicalis, as well as certain varieties of the latter. (See Discussion section.) These organisms cannot use pectin as a source of carbon, but require an added sugar for development. 2. 2. S. fragilis var. No. 351 was used for most of the studies reported herein. When it was grown in the presence of pectin, clarification of the liquid culture media took place with the formation of an amorphous precipitate consisting of about 1% of the pectin added. The jellying power of the pectin is destroyed, but the amount of calcium pectate and alcohol precipitate, obtainable from a clarified solution, is practically unchanged as compared to control solutions. 3. 3. The action was found to be due to an exocellular, nonadaptive, polygalacturonase-like enzyme, free of pectinesterase. The action of this yeast polygalacturonase is characteristic in that pectic acid, when used as a substrate, is only partially hydrolyzed. In contrast to fungus polygalacturonase, the enzyme cannot hydrolyze pectic acid completely to monogalacturonic acid. The velocity constant of the (initially) first-order reaction was found to be 0.196 at 22 °C. and at a pH of 3.40. The optimum pH was approximately 3.5–4.0, and the maximum rate was in the region of 55–60 °C.