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Carlos M Herrera - One of the best experts on this subject based on the ideXlab platform.
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Nectar-living Yeasts of a tropical host plant community: diversity and effects on community-wide floral nectar traits.
PeerJ, 2017Co-Authors: Azucena Canto, Carlos M Herrera, Rosalina RodríguezAbstract:We characterize the diversity of nectar-living Yeasts of a tropical host plant community at different hierarchical sampling levels, measure the associations between Yeasts and nectariferous plants, and measure the effect of Yeasts on nectar traits. Using a series of hierarchically nested sampling units, we extracted nectar from an assemblage of host plants that were representative of the diversity of life forms, flower shapes, and pollinator types in the tropical area of Yucatan, Mexico. Yeasts were isolated from single nectar samples; their DNA was identified, the yeast cell density was estimated, and the sugar composition and concentration of nectar were quantified using HPLC. In contrast to previous studies from temperate regions, the diversity of nectar-living Yeasts in the plant community was characterized by a relatively high number of equally common species with low dominance. Analyses predict highly diverse nectar yeast communities in a relatively narrow range of tropical vegetation, suggesting that the diversity of Yeasts will increase as the number of sampling units increases at the level of the species, genera, and botanical families of the hosts. Significant associations between specific yeast species and host plants were also detected; the interaction between Yeasts and host plants impacted the effect of yeast cell density on nectar sugars. This study provides an overall picture of the diversity of nectar-living Yeasts in tropical host plants and suggests that the key factor that affects the community-wide patterns of nectar traits is not nectar chemistry, but rather the type of Yeasts interacting with host plants.
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The impact of nectar chemical features on phenotypic variation in two related nectar Yeasts.
FEMS microbiology ecology, 2015Co-Authors: Maria I Pozo, Carlos M Herrera, Wim Van Den Ende, Kevin J. Verstrepen, Bart Lievens, Hans JacquemynAbstract:Floral nectars become easily colonized by microbes, most often species of the ascomycetous yeast genus Metschnikowia. Although it is known that nectar composition can vary tremendously among plant species, most probably corresponding to the nutritional requirements of their main pollinators, far less is known about how variation in nectar chemistry affects intraspecific variation in nectarivorous Yeasts. Because variation in nectar traits probably affects growth and abundance of nectar Yeasts, nectar Yeasts can be expected to display large phenotypic variation in order to cope with varying nectar conditions. To test this hypothesis, we related variation in the phenotypic landscape of a vast collection of nectar-living yeast isolates from two Metschnikowia species (M. reukaufii and M. gruessii) to nectar chemical traits using non-linear redundancy analyses. Nectar Yeasts were collected from 19 plant species from different plant families to include as much variation in nectar chemical traits as possible. As expected, nectar Yeasts displayed large variation in phenotypic traits, particularly in traits related to growth performance in carbon sources and inhibitors, which was significantly related to the host plant from which they were isolated. Total sugar concentration and relative fructose content significantly explained the observed variation in the phenotypic profile of the investigated yeast species, indicating that sugar concentration and composition are the key traits that affect phenotypic variation in nectarivorous Yeasts.
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Yeasts in nectar of an early blooming herb sought by bumble bees detrimental to plant fecundity
Ecology, 2013Co-Authors: Carlos M Herrera, Maria I Pozo, Monica MedranoAbstract:Through their effects on physicochemical features of floral nectar, nectar-dwelling Yeasts can alter pollinator behavior, but the effect of such changes on pollination success and plant reproduction is unknown. We present results of experiments testing the effects of nectar Yeasts on foraging patterns of captive and free-ranging bumble bees, and also on pollination success and fecundity of the early-blooming, bumble bee-pollinated Helleborus foetidus (Ranunculaceae). Under controlled experimental conditions, inexperienced Bombus terrestris workers responded positively to the presence of Yeasts in artificial sugar solutions mimicking floral nectar by visiting proportionally more yeast-containing artificial flowers. Free-ranging bumble bees also preferred yeast-containing nectar in the field. Experiments conducted in two different years consistently showed that natural and artificial nectars containing Yeasts were more thoroughly removed than nectars without Yeasts. Experimental yeast inoculation of the nectar of H. foetidus flowers was significantly associated with reductions in number of pollen tubes in the style, fruit set, seed set, and mass of individual seeds produced. These results provide the first direct evidence to date that nectar Yeasts can modify pollinator foraging patterns, pollination success, and the quantity and quality of seeds produced by insect-pollinated plants.
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Relationships among nectar-dwelling Yeasts, flowers and ants: patterns and incidence on nectar traits
Oikos, 2012Co-Authors: Clara De Vega, Carlos M HerreraAbstract:Nectar-dwelling Yeasts are emerging as widely distributed organisms playing a potentially signifi cant and barely unexplored ecological role in plant–pollinator mutualisms. Previous eff orts at understanding nectar – pollinator – yeast interactions have focused on bee-pollinated plants, while the importance of nectarivorous ants as vectors for yeast dispersal remains unexplored so far. Here we assess the abundance and composition of the nectar fungal microbiota of the ant-pollinated plant Cytinus hypocistis , study whether yeast transmission is coupled with ant visitation, and discern whether anttransported Yeasts promote changes in nectar characteristics. Our results show that a high percentage of fl owers (77%) and plants (94%) contained Yeasts, with yeast cell density in nectar reaching up to 6.2 10 4 cells mm 3 , being the highest densities associated with the presence of the nectar-specialist yeast Metschnikowia reukaufi i . Th e establishment of fungal microbiota in nectar required fl ower visitation by ants, with 70% of yeast species transported by them being also detected in nectar. Ant-vectored Yeasts diminished the nutritional quality of nectar, with fl owers exposed to pollinators and Yeasts containing signifi cantly lower nectar sugar concentration than virgin fl owers (13.4% and 22.8%, respectively). Nectar of fl owers that harbored M. reukaufi i showed the lowest quality, with nectar concentration declining signifi cantly with increasing yeast density. Additionally, Yeasts modifi ed patterns of interpopulation variation in nectar traits, homogenizing diff erences between populations in some nectar attributes. We show for the fi rst time that the outcome of the tripartite pollinator – fl ower – yeast interaction is highly dependent on the identity and inherent properties of the participants, even to the extent of infl uencing the species composition of this ternary system, and can be mediated by ecological characteristics of plant populations. Th rough their infl uence on plant functional traits, Yeasts have the potential to alter nectar consumption, pollinator foraging behavior and ultimately plant reproduction.
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nectar Yeasts warm the flowers of a winter blooming plant
Proceedings of The Royal Society B: Biological Sciences, 2010Co-Authors: Carlos M Herrera, Maria I PozoAbstract:Yeasts are ubiquitous in terrestrial and aquatic microbiota, yet their ecological functionality remains relatively unexplored in comparison with other micro-organisms. This paper formulates and tests the novel hypothesis that heat produced by the sugar catabolism of yeast populations inhabiting floral nectar can increase the temperature of floral nectar and, more generally, modify the within-flower thermal microenvironment. Two field experiments were designed to test this hypothesis for the winter-blooming herb Helleborus foetidus (Ranunculaceae). In experiment 1, the effect of Yeasts on the within-flower thermal environment was tested by excluding them from flowers, while in experiment 2 the test involved artificial inoculation of virgin flowers with Yeasts. Nectary temperature (Tnect), within-flower air temperature (Tflow) and external air temperature (Tair) were measured on experimental and control flowers in both experiments. Experimental exclusion of Yeasts from the nectaries significantly reduced, and experimental addition of Yeasts significantly increased, the temperature excess of nectaries (ΔTnect = Tnect − Tair) and the air space inside flowers in relation to the air just outside the flowers. In non-experimental flowers exposed to natural pollinator visitation, ΔTnect was linearly related to log yeast cell density in nectar, and reached +6°C in nectaries with the densest yeast populations. The warming effect of nectar-dwelling Yeasts documented in this study suggests novel ecological mechanisms potentially linking nectarivorous microbes with winter-blooming plants and their insect pollinators.
Maria I Pozo - One of the best experts on this subject based on the ideXlab platform.
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The impact of nectar chemical features on phenotypic variation in two related nectar Yeasts.
FEMS microbiology ecology, 2015Co-Authors: Maria I Pozo, Carlos M Herrera, Wim Van Den Ende, Kevin J. Verstrepen, Bart Lievens, Hans JacquemynAbstract:Floral nectars become easily colonized by microbes, most often species of the ascomycetous yeast genus Metschnikowia. Although it is known that nectar composition can vary tremendously among plant species, most probably corresponding to the nutritional requirements of their main pollinators, far less is known about how variation in nectar chemistry affects intraspecific variation in nectarivorous Yeasts. Because variation in nectar traits probably affects growth and abundance of nectar Yeasts, nectar Yeasts can be expected to display large phenotypic variation in order to cope with varying nectar conditions. To test this hypothesis, we related variation in the phenotypic landscape of a vast collection of nectar-living yeast isolates from two Metschnikowia species (M. reukaufii and M. gruessii) to nectar chemical traits using non-linear redundancy analyses. Nectar Yeasts were collected from 19 plant species from different plant families to include as much variation in nectar chemical traits as possible. As expected, nectar Yeasts displayed large variation in phenotypic traits, particularly in traits related to growth performance in carbon sources and inhibitors, which was significantly related to the host plant from which they were isolated. Total sugar concentration and relative fructose content significantly explained the observed variation in the phenotypic profile of the investigated yeast species, indicating that sugar concentration and composition are the key traits that affect phenotypic variation in nectarivorous Yeasts.
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Yeasts in nectar of an early blooming herb sought by bumble bees detrimental to plant fecundity
Ecology, 2013Co-Authors: Carlos M Herrera, Maria I Pozo, Monica MedranoAbstract:Through their effects on physicochemical features of floral nectar, nectar-dwelling Yeasts can alter pollinator behavior, but the effect of such changes on pollination success and plant reproduction is unknown. We present results of experiments testing the effects of nectar Yeasts on foraging patterns of captive and free-ranging bumble bees, and also on pollination success and fecundity of the early-blooming, bumble bee-pollinated Helleborus foetidus (Ranunculaceae). Under controlled experimental conditions, inexperienced Bombus terrestris workers responded positively to the presence of Yeasts in artificial sugar solutions mimicking floral nectar by visiting proportionally more yeast-containing artificial flowers. Free-ranging bumble bees also preferred yeast-containing nectar in the field. Experiments conducted in two different years consistently showed that natural and artificial nectars containing Yeasts were more thoroughly removed than nectars without Yeasts. Experimental yeast inoculation of the nectar of H. foetidus flowers was significantly associated with reductions in number of pollen tubes in the style, fruit set, seed set, and mass of individual seeds produced. These results provide the first direct evidence to date that nectar Yeasts can modify pollinator foraging patterns, pollination success, and the quantity and quality of seeds produced by insect-pollinated plants.
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nectar Yeasts warm the flowers of a winter blooming plant
Proceedings of The Royal Society B: Biological Sciences, 2010Co-Authors: Carlos M Herrera, Maria I PozoAbstract:Yeasts are ubiquitous in terrestrial and aquatic microbiota, yet their ecological functionality remains relatively unexplored in comparison with other micro-organisms. This paper formulates and tests the novel hypothesis that heat produced by the sugar catabolism of yeast populations inhabiting floral nectar can increase the temperature of floral nectar and, more generally, modify the within-flower thermal microenvironment. Two field experiments were designed to test this hypothesis for the winter-blooming herb Helleborus foetidus (Ranunculaceae). In experiment 1, the effect of Yeasts on the within-flower thermal environment was tested by excluding them from flowers, while in experiment 2 the test involved artificial inoculation of virgin flowers with Yeasts. Nectary temperature (Tnect), within-flower air temperature (Tflow) and external air temperature (Tair) were measured on experimental and control flowers in both experiments. Experimental exclusion of Yeasts from the nectaries significantly reduced, and experimental addition of Yeasts significantly increased, the temperature excess of nectaries (ΔTnect = Tnect − Tair) and the air space inside flowers in relation to the air just outside the flowers. In non-experimental flowers exposed to natural pollinator visitation, ΔTnect was linearly related to log yeast cell density in nectar, and reached +6°C in nectaries with the densest yeast populations. The warming effect of nectar-dwelling Yeasts documented in this study suggests novel ecological mechanisms potentially linking nectarivorous microbes with winter-blooming plants and their insect pollinators.
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Yeasts in floral nectar a quantitative survey
Annals of Botany, 2009Co-Authors: Carlos M Herrera, Clara De Vega, Azucena Canto, Maria I PozoAbstract:† Background and Aims One peculiarity of floral nectar that remains relatively unexplored from an ecological perspective is its role as a natural habitat for micro-organisms. This study assesses the frequency of occurrence and abundance of yeast cells in floral nectar of insect-pollinated plants from three contrasting plant communities on two continents. Possible correlations between interspecific differences in yeast incidence and pollinator com- position are also explored. † Methods The study was conducted at three widely separated areas, two in the Iberian Peninsula (Spain) and one in the Yucatan Peninsula (Mexico). Floral nectar samples from 130 species (37-63 species per region) in 44 families were examined microscopically for the presence of yeast cells. For one of the Spanish sites, the relation- ship across species between incidence of Yeasts in nectar and the proportion of flowers visited by each of five major pollinator categories was also investigated. † Key Results Yeasts occurred regularly in the floral nectar of many species, where they sometimes reached extra- ordinary densities (up to 4 � 10 5 cells mm 23 ). Depending on the region, between 32 and 44 % of all nectar samples contained Yeasts. Yeast cell densities in the order of 10 4 cells mm 23 were commonplace, and densities .10 5 cells mm 23 were not rare. About one-fifth of species at each site had mean yeast cell densities .10 4 cells mm 23 . Across species, yeast frequency and abundance were directly correlated with the proportion of floral visits by bumble-bees, and inversely with the proportion of visits by solitary bees. † Conclusions Incorporating nectar Yeasts into the scenario of plant -pollinator interactions opens up a number of intriguing avenues for research. In addition, with Yeasts being as ubiquitous and abundant in floral nectars as revealed by this study, and given their astounding metabolic versatility, studies focusing on nectar chemical fea- tures should carefully control for the presence of Yeasts in nectar samples.
Francis Duchiron - One of the best experts on this subject based on the ideXlab platform.
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Yeasts an attractive source of pectinases from gene expression to potential applications a review
Process Biochemistry, 2011Co-Authors: Parissa Alimardanitheuil, Angelique Gainvorsclaisse, Francis DuchironAbstract:Abstract Pectins are a major component of plant cell walls. A wide range of enzymes are known to catalyze pectin degradation by hydrolysis or trans-elimination. These enzymes are produced by plants and various microorganisms such as filamentous fungi, bacteria and Yeasts. In the last ten years, yeast pectinases have attracted a great deal of attention from various research groups worldwide as an alternative to fungal pectinases. This review first describes the classification of pectinases and the methods of detecting pectolytic activity. It then describes pectolytic Yeasts, focusing primarily on widely studied Yeasts such as Saccharomyces and Kluyveromyces but also touching on Yeasts living in extreme environments. An additional effort is made to describe the most recent molecular knowledge of yeast pectinase-encoding genes and their regulation. Finally, various studies of potential new industrial applications of yeast pectinases are reported.
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Yeasts: An attractive source of pectinases—From gene expression to potential applications: A review
Process Biochemistry, 2011Co-Authors: Parissa Alimardani-theuil, Angélique Gainvors-claisse, Francis DuchironAbstract:Pectins are a major component of plant cell walls. A wide range of enzymes are known to catalyze pectin degradation by hydrolysis or trans-elimination. These enzymes are produced by plants and various microorganisms such as filamentous fungi, bacteria and Yeasts. In the last ten years, yeast pectinases have attracted a great deal of attention from various research groups worldwide as an alternative to fungal pectinases. This review first describes the classification of pectinases and the methods of detecting pectolytic activity. It then describes pectolytic Yeasts, focusing primarily on widely studied Yeasts such as Saccharomyces and Kluyveromyces but also touching on Yeasts living in extreme environments. An additional effort is made to describe the most recent molecular knowledge of yeast pectinase-encoding genes and their regulation. Finally, various studies of potential new industrial applications of yeast pectinases are reported.
Dominik Begerow - One of the best experts on this subject based on the ideXlab platform.
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Parasitism in Yeasts
Yeasts in Natural Ecosystems: Ecology, 2017Co-Authors: Dominik Begerow, Martin Kemler, Anja Feige, Andrey YurkovAbstract:Yeasts are common in all habitats and interact with dead and living substrates such as plants, animals, and fungi. Besides their saprobic capabilities, parasitic interactions of Yeasts and yeast-like organisms were brought into focus through enhanced/new species discovery that expanded our knowledge about phylogenetic relationships of Yeasts and parasitic fungal lineages. Especially common dimorphism of many Basidiomycota goes along with an alternating saprobic yeast stage and parasitic filamentous stage. Interestingly, this seems to be a common feature not only for plant parasites but also for animal and fungal parasites. Even some Ascomycota share this character.
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Nectar sugars and bird visitation define a floral niche for basidiomycetous yeast on the Canary Islands
BMC Ecology, 2015Co-Authors: Moritz Mittelbach, Daniele Nocentini, Massimo Nepi, Andrey M Yurkov, Maximilian Weigend, Dominik BegerowAbstract:Background Studies on the diversity of Yeasts in floral nectar were first carried out in the late 19^th century. A narrow group of fermenting, osmophilous ascomycetes were regarded as exclusive specialists able to populate this unique and species poor environment. More recently, it became apparent that microorganisms might play an important role in the process of plant pollination. Despite the importance of these nectar dwelling Yeasts, knowledge of the factors that drive their diversity and species composition is scarce. Results In this study, we linked the frequencies of yeast species in floral nectars from various host plants on the Canary Islands to nectar traits and flower visitors. We estimated the structuring impact of pollination syndromes (nectar volume, sugar concentration and sugar composition) on yeast diversity. The observed total yeast diversity was consistent with former studies, however, the present survey yielded additional basidiomycetous Yeasts in unexpectedly high numbers. Our results show these basidiomycetes are significantly associated with ornithophilous flowers. Specialized ascomycetes inhabit sucrose-dominant nectars, but are surprisingly rare in nectar dominated by monosaccharides. Conclusions There are two conclusions from this study: (i) a shift of floral visitors towards ornithophily alters the likelihood of yeast inoculation in flowers, and (ii) low concentrated hexose-dominant nectar promotes colonization of flowers by basidiomycetes. In the studied floral system, basidiomycete Yeasts are acknowledged as regular members of nectar. This challenges the current understanding that nectar is an ecological niche solely occupied by ascomycetous Yeasts.
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Basidiomycetous Yeasts from Boletales Fruiting Bodies and Their Interactions with the Mycoparasite Sepedonium chrysospermum and the Host Fungus Paxillus
Microbial Ecology, 2012Co-Authors: Andrey Yurkov, Dirk Krüger, Norbert Arnold, Dominik Begerow, Marja-terttu TarkkaAbstract: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.
M. J. Gasson - One of the best experts on this subject based on the ideXlab platform.
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Prevention of yeast spoilage in feed and food by the yeast mycocin HMK.
Applied and environmental microbiology, 2000Co-Authors: K. Lowes, Claire Shearman, John Payne, Donald A. Mackenzie, David B. Archer, Roger J. Merry, M. J. GassonAbstract:The yeast Williopsis mrakii produces a mycocin or yeast killer toxin designated HMK; this toxin exhibits high thermal stability, high pH stability, and a broad spectrum of activity against other Yeasts. We describe construction of a synthetic gene for mycocin HMK and heterologous expression of this toxin in Aspergillus niger. Mycocin HMK was fused to a glucoamylase protein carrier, which resulted in secretion of biologically active mycocin into the culture media. A partial purification protocol was developed, and a comparison with native W. mrakii mycocin showed that the heterologously expressed mycocin had similar physiological properties and an almost identical spectrum of biological activity against a number of Yeasts isolated from silage and yoghurt. Two food and feed production systems prone to yeast spoilage were used as models to assess the ability of mycocin HMK to act as a biocontrol agent. The onset of aerobic spoilage in mature maize silage was delayed by application of A. niger mycocin HMK on opening because the toxin inhibited growth of the indigenous spoilage Yeasts. This helped maintain both higher lactic acid levels and a lower pH. In yoghurt spiked with dairy spoilage Yeasts, A. niger mycocin HMK was active at all of the storage temperatures tested at which yeast growth occurred, and there was no resurgence of resistant Yeasts. The higher the yeast growth rate, the more effective the killing action of the mycocin. Thus, mycocin HMK has potential applications in controlling both silage spoilage and yoghurt spoilage caused by Yeasts.
