Search

The new yeast Metschnikowia persimmonesis KCTC 12991BP (KIOM G15050 strain) exhibits strong antimicrobial activity against some pathogens. This activity may be related to the medicinal profile of secondary metabolites that could be found in the genome of this species. Therefore, to explore its future possibility of producing some beneficial activities, including medicinal ability, we report high-quality whole-genome assembly of M. persimmonesis produced by PacBio RS II sequencer. The final draft assembly consisted of 16 scaffolds with GC content of 45.90% and comprised a fairly complete set (82.8%) of BUSCO result using Saccharomycetales lineage data set. The total length of the genome was 16.473Mb, with a scaffold N50 of 1.982Mb. Annotation of the M. persimmonesis genome revealed presence of 7029 genes and 6939 functionally annotated proteins. Based on the analysis of phylogenetic relationship and the average nucleotide identities, M. persimmonesis was proved to a novel species within the Metschnikowia genus. This finding is expected to significantly contribute to the discovery of high-value natural products from M. persimmonesis as well as for genome biology and evolution comparative analysis within Metschnikowia species. [ABSTRACT FROM AUTHOR]

Abstract Background Pathogenic fungi often cause serious infections mainly in immunocompromised persons. The number of infections caused by the non-albicans Candida or other species has significantly increased over the last years. These infections present a major challenge in the health sector because these pathogenic fungi have strong virulence and often show resistance to the commonly used antifungal treatments. To solve the problems caused by the drug resistant pathogenic fungi, it is necessary to find new antifungal agents and their sources. The aim of this study was to give evidence that yeasts can effectively fight against strains which belong to pathogenic fungi and reveal those yeasts which are able to inhibit growth of Kodamaea ohmeri, Pichia kudriavzevii, Naganishia albida or Candida tropicalis. Furthermore, we wanted to determine the effects of certain culturing factors on the growth inhibition. Results Our screening revealed that although the strains belonging to pathogenic species were much more tolerant to the yeast-produced bioactive agents than the non-disease-associated yeasts, growth of Kodamaea ohmeri and Candida tropicalis could be inhibited by Metschnikowia andauensis, while Naganishia albida could be controlled by Pichia anomala or Candida tropicalis. Our data proved that the experimental circumstances could have a serious impact on the inhibitory capacity of the yeasts. Appearance of inhibition strongly depended on media, pH and temperature. Our data also shed some light on the fact that Pichia kudriavzevii must have high natural resistance to the yeast-produced agents, while other species, such as Saccharomycopsis crataegensis belonged to the easily inhibitable species. Conclusions Our study suggests that yeast-produced bioactive agents could be potential growth inhibitory agents against the disease-associated fungi and yeasts can also contribute to alternative approaches to combat against pathogenic fungi. Our data revealed an important role of the culturing factors in inhibition and pointed to the complex nature of antagonism.

The sweet potato is less known in Romania. The highly different storage conditions between sweet potatoes (lpomoea batatas, Convolvulaceae family) and potatoes (Solanum tuberosum, Solanaceae family) make it difficult to maintain the quality of the tubers during storage. Sweet potatoes are sensitive to relatively low temperatures (<12°C), which can produce chilling injuries. The wounds created by the cold can lead to over-infection with storage pathogenic fungi. In order to reduce the potential losses caused by storage fungal infections, we recommend the use of beneficial yeasts, with biocontrol activity. These yeasts were selected from the natural epiphytic microbiota and do not present toxicity risks to consumers. The selected isolates have shown inhibitory activity against the main storage pathogenic fungi of sweet potato: Botrytis cinerea, Fusarium oxysporum, Penicillium sp, Rhizopus stolonifer and Sclerotium bataticola. [ABSTRACT FROM AUTHOR]

Nine Metschnikowia spp. strains and six Yarrowia lipolytica strains were tested for lipid production on raw glycerol from a biodiesel plant. Metschnikowia sp. 271 and Y. lipolytica 347 were selected for biomass and lipid production, and optimized using central composite factorial design (CCD) and response surface methodology (RSM). The lipid production (2.60 g/L) of Y. lipolytica 347 was maximized at C/N 118, time 144 h and 90 g/L glycerol, while the maximum lipid production (0.49 g/L) of Metschnikowia sp. 271 was obtained under similar conditions but after a further incubation for 7 days at 16 °C. The fatty acids profile of Y. lipolytica exhibited a considerable amount of C18:1n7 (~36 %), C18:1n9 (~16 %), and C16:0 (~16 %), whereas Metschnikowia sp. produced mainly C18:1n9 (~33 %), C16:0 (~21 %), and C16:1n7 (~21 %). Both yeasts showed similar amounts of unsaturated fatty acids (~70 %). However, considerable amounts of polyunsaturated fatty acid (PUFAs) were exhibited only by Metschnikowia sp. (~12 %). [ABSTRACT FROM AUTHOR]

Background: Although inducible defences have been studied extensively, only little is known about how the presence of parasites might interfere with these anti-predator adaptations. Both parasites and predators are important factors shaping community structure and species composition of ecosystems. Here, we simultaneously exposed Daphnia magna to predator cues (released by the tadpole shrimp, Triops, or by a fish) and spores of the yeast parasite Metschnikowia sp. to determine how life history and morphological inducible defences against these two contrasting types of predators are affected by infection. Results: The parasite suppressed some Triops-induced defences: Daphnia lost the ability to produce a greater number of larger offspring, a life-history adaptation to Triops predation. In contrast, the parasite did not suppress inducible defences against fish: induction (resulting in smaller body length of the mothers as well as of their offspring) and infection acted additively on the measured traits. Thus, fish-induced defences may be less costly than inducible defences against small invertebrate predators like Triops; the latter defences could no longer be expressed when the host had already invested in fighting off the parasite. Conclusions: In summary, our study suggests that as specific inducible defences differ in their costs, some might be suppressed if a target prey is additionally infected. Therefore, adding parasite pressure to predator-prey systems can help to elucidate the costs of inducible defences. [ABSTRACT FROM AUTHOR]

Abstract: During the growing seasons 2007 and 2008, 210 isolates of yeasts or yeast-like fungi were obtained from the carposphere of temperate fruit collected from organic orchards in Northern Italy. Through six rounds of in vivo screening, three isolates showing the highest biocontrol efficacy against Monilinia laxa on peaches were selected. By using molecular and morphological tools, the strain AP6 was identified as Pseudozyma fusiformata, the strain AP47 as Metschnikowia sp., and the strain PL5 as Aureobasidium pullulans. This research represents the first evidence about the potential use of P. fusiformata to control postharvest diseases of fruit. By co-culturing in vitro M. laxa in the presence of the three antagonists, neither the inactivated cells nor the culture filtrate of the three isolates had any significant effect on spore germination or germ tube elongation, allowing exclusion of the production of secreted toxic metabolites. The antagonistic activity of A. pullulans PL5 and P. fusiformata AP6 was dependent on the cell concentration. Metschnikowia sp. AP47 significantly inhibited spore germination at the three concentrations tested (106 cells/mL, 107 cells/mL, and 108 cells/mL). The efficacy of the three strains was tested on peaches stored at three different temperatures, and their effectiveness was higher at 1°C than at 8°C or 20°C. In trials carried out in semi-commercial conditions with peaches inoculated by spraying 105 spores/mL of M. laxa and stored for 21d at 1°C and 96% RH, a cell concentration effect on the control of brown rot incidence was observed. AP6 and PL5 showed no significant differences in efficacy when applied at 1×108 cells/mL or at 1×107 cells/mL, indicating that they could be used at a lower concentration in potential biofungicide formulations. Finally, in an experiment in semi-commercial conditions on fruit not inoculated with the pathogen with 21d storage at 1°C and 96% RH, the evaluation of postharvest quality parameters, including firmness, total soluble solids, ascorbic acid content, and titratable acidity, showed that none of the three screened antagonists impaired peach quality, when applied before storage. The present study identified three antagonistic microorganisms with potential exploitation as active ingredients for the development of products for postharvest control of brown rot on peaches. [Copyright &y& Elsevier]

• Fruit-based Metschnikowia sp. was identified by molecular tools. • Pectinase-free Metschnikowia sp. inhibited Penicillium fungi on lemons. • Metschnikowia sp. significantly reduced incidence and lesion diameters. • Iron depletion, lytic enzymes, biofilm, and VOCs formation caused antagonism. • Metschnikowia aff. fructicola had the highest biocontrol efficacy on Penicillium. In this study, various fruit were employed as biocontrol yeast reservoirs, and eleven distinct yeast cultures of Metschnikowia sp. belonging to 6 different species were identified with sequence-based analysis of the D1/D2 domain of 26S rDNA. For initial screening, Metschnikowia isolates were tested on Fusarium oxysporum, Botrytis cinerea, Penicillium digitatum, Penicillium expansum, and Alternaria alternata. The highest antagonism was obtained on green and blue Penicillium (83.63–100 %). All tested yeasts showed chitinase activity, while some had protease, pectinase, cellulase, β-1−3 glucanase, and gelatinase activities. Since lemons have high pectin content, three pectinase-free cultures at tested conditions with high in vitro antagonism on Penicillium were selected and used on lemons. The activities of the in vitro antifungal studies were found to be compatible with those of the in vivo , and P. digitatum 's incidence was found to be higher than that of P. expansum on lemons. All tested pectinase-free Metschnikowia sp. lead to a significant reduction in the disease incidences and lesions at varying levels. The combined effect of lytic enzyme secretion, iron depletion, and volatile organic compounds (VOCs) production determined the antifungal mechanism of action. M. aff. fructicola demonstrated the highest biocontrol efficacy against Penicillium on lemons with an increasing shelf-life. The use of tentatively pectinase-negative Metschnikowia sp. as an antifungal biocontrol agent on lemons was considered for the first time. The findings will shed light on the effective use of Metschnikowia sp. as a potential biofungicide against the growth of postharvest fungal pathogens. [ABSTRACT FROM AUTHOR]

Anaerobic fermentation of organic compounds is used in many biotechnological processes and has been the subject of much research. A variety of process conditions and different growth media can be used to obtain microbial metabolites. The media must be free from contamination before fermentation. Sterilization is most often achieved by applying heat or other treatments, such as ozonation. Sterilization of liquid media using ozone can be very beneficial, but this method introduces high concentrations of residual oxygen, which inhibit anaerobic processes. Deoxidation is therefore necessary to remove the oxygen from ozonated broths. This study evaluates the effectiveness of three deoxidation agents for two kinds of fermentation media based on malt or molasses: ultrasound, iron(II) sulfate, and Metschnikowia sp. yeast. The time needed for deoxidation varied, depending on the kind of broth and the deoxidation agent. In general, the dynamics of oxygen removal were faster in malt broth. A comparative analysis showed that yeast biomass was the most effective agent, achieving deoxidation in the shortest time. Moreover, the fully deoxidated broth was supplemented with yeast biomass, which is rich in biogenic substrates, expressed as a protein content of 0.13–0.73 g/L. Application of Metschnikowia sp. may therefore be considered as an effective strategy for simultaneous deoxidation and nutrient supplementation of broths used in anaerobic biotechnological processes. [ABSTRACT FROM AUTHOR]