1. Effects of desiccation and freezing on microbial ionizing radiation survivability : considerations for Mars sample returnWilliam H. Horne, Tine Grebenc, Rok Tkavc, Cene Gostinčar, Nina Gunde-Cimerman, 2022, izvirni znanstveni članek Povzetek: Increasingly, national space agencies are expanding their goals to include Mars exploration with sample return. To better protect Earth and its biosphere from potential extraterrestrial sources of contamination, as set forth in the Outer Space Treaty of 1967, international efforts to develop planetary protection measures strive to understand the danger of cross-contamination processes in Mars sample return missions. We aim to better understand the impact of the martian surface on microbial dormancy and survivability. Radiation resistance of microbes is a key parameter in considering survivability of microbes over geologic times on the frigid, arid surface of Mars that is bombarded by solar and galactic cosmic radiation. We tested the influence of desiccation and freezing on the ionizing radiation survival of six model microorganisms: vegetative cells of two bacteria (Deinococcus radiodurans, Escherichia coli) and a strain of budding yeast (Saccharomyces cerevisiae); and vegetative cells and endospores of three Bacillus bacteria (B. subtilis, B. megaterium, B. thuringiensis). Desiccation and freezing greatly increased radiation survival of vegetative polyploid microorganisms when applied separately, and when combined, desiccation and freezing increased radiation survival even more so. Thus, the radiation survival threshold of polyploid D. radiodurans cells can be extended from the already high value of 25 kGy in liquid culture to an astonishing 140 kGy when the cells are both desiccated and frozen. However, such synergistic radioprotective effects of desiccation and freezing were not observed in monogenomic or digenomic Bacillus cells and endospores, which are generally sterilized by 12 kGy. This difference is associated with a critical requirement for survivability under radiation, that is, repair of genome damage caused by radiation. Deinococcus radiodurans and S. cerevisiae accumulate similarly high levels of the Mn antioxidants that are required for extreme radiation resistance, as do endospores, though they greatly exceed spores in radioresistance because they contain multiple identical genome copies, which in D. radiodurans are joined by persistent Holliday junctions. We estimate ionizing radiation survival limits of polyploid DNA-based life-forms to be hundreds of millions of years of background radiation while buried in the martian subsurface. Our findings imply that forward contamination of Mars will essentially be permanent, and backward contamination is a possibility if life ever existed on Mars.
Ključne besede: ionizing radiation, life on Mars, astrobiology, radiation, fungi, bacteria, radiotolerance
Objavljeno v DiRROS: 03.11.2022; Ogledov: 144; Prenosov: 43
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4. Distribution and phylogeography of the genus Mattirolomyces with a focus on the Asian M. terfezioides haplotypesJ. Wei, Tine Grebenc, Xuan Zhang, SiMin Xiang, Yongjun Fan, 2022, izvirni znanstveni članek Povzetek: Mattirolomyces is an edible commercial sequestrate genus that is globally distributed. From the five described taxa of this genus, Mattirolomyces terfezioides is the most common species in Asia. Our recent attempts to locate M. terfezioides outside its current distribution area in China documented its first records in areas of poplar trees with the lowest known temperature and precipitation averages ever recorded for this species. This peculiar ecology was not reflected on the species-morphological features nor on its phylogenetic position in the genus. The first attempt to apply the phylogenetic network approach to Mattirolomyces revealed its geographic origin in the Asian-Pacific areas prior to frequent long-distance migration events. Based on data from recent study areas, we found that the collections from Inner Mongolia and the Shanxi province were similar to European collections. Asian haplotypes were less distant from the outgroup comparing to collections from Europe, supporting the hypothesis that M. terfezioides was originated from this Chinese area and was subsequently transported to Europe. Exploring M. terfezioides ecology and its mycorrhiza potential to grow in association with poplars would be of great importance for planning cultivation projects of this valuable desert truffle species in Central and Eastern China, a currently underexploited economic sector that deserves further ecological and M. terfezioides mycorrhizal synthesis investigations.
Ključne besede: biodiversity, biogeography, mycology, Mattirolomyces terfezioides, Desert truffle, Inner Mongolia, phylogeography
Objavljeno v DiRROS: 05.08.2022; Ogledov: 181; Prenosov: 104
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5. Buckwheat milling waste effects on root morphology and mycorrhization of Silver fir seedlings inoculated with Black Summer Truffle (Tuber aestivum Vittad.)Tina Unuk, Tine Grebenc, Daniel Žlindra, Tanja Mrak, Matevž Likar, Hojka Kraigher, Zlata Luthar, 2022, izvirni znanstveni članek Povzetek: Large amounts of buckwheat waste are generated annually by the industry and are used in several different ways. To date, there has been little research regarding its suitability as a medium for growing seedlings in nurseries. The aim of this study was therefore to analyze the suitability of common and Tartary buckwheat wastes (brans and husks) as media used for raising seedlings. A pot experiment with five different treatments was carried out, in which silver fir root parameters were analyzed and compared 6 and 12 months after summer truffle-spore inoculation. A significantly higher concentration of the antioxidant rutin was confirmed in Tartary buckwheat bran compared to other buckwheat waste used. We also confirmed a significantly positive effect of added Tartary buckwheat husks on specific root length, root tip density, and specific root tip density compared to added common buckwheat husks or Tartary buckwheat bran, for which a significantly negative effect on branching density was confirmed. A significantly negative effect of added buckwheat husks and Tartary buckwheat bran was confirmed for summer truffle mycorrhization level.
Ključne besede: buckwheat waste, root growth, summer truffle, forest nursery, silver fir, inoculation with ectomycorrhizal fungi
Objavljeno v DiRROS: 09.02.2022; Ogledov: 378; Prenosov: 287
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7. Potential link between ectomycorrhizal community composition and host tree phenologyTina Unuk, Rok Damjanić, Hojka Kraigher, Tine Grebenc, 2021, izvirni znanstveni članek Povzetek: The timing of leaf phenology tends to be crucial in controlling ecosystem processes such as the acquisition of carbon and water loss as well as in controlling tree nutrient cycling. To date, tree phenology has mostly been associated with environmental control (e.g., temperature and photoperiod) in a relationship with inheritance, while it has rarely been linked with ectomycorrhizal community compositional changes through the host tree’s phenological stages. Seasonal variations of fungal communities have been widely studied, but little is known about mycorrhiza community composition changes along phenological stages. Therefore, we analyzed ectomycorrhizal communities associated with silver fir and their compositional changes during the transition between phenological stages. The phenological stages of each individual tree and time of bud break were monitored weekly for two years and, at the same time, ectomycorrhiza was harvested from selected silver fir trees. In total, 60 soil cores were analyzed for differences in the ectomycorrhizal community between phenological stages using Sanger sequencing of individual ectomycorrhizal morphotypes. A significant difference in beta diversity for an overall ectomycorrhizal community was confirmed between analyzed time periods for both sampled years. Species-specific reactions to transitions between phenological stages were confirmed for 18 different ectomycorrhizal taxa, where a positive correlation of Russula ochroleuca, Russula illota, Tomentella sublilacina, and Tylospora fibrillosa was observed with the phenological stage of bud burst.
Ključne besede: Abies alba (Mill.), ectomycorrhizal community, phenological stages
Objavljeno v DiRROS: 20.12.2021; Ogledov: 424; Prenosov: 262
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8. Ectomycorrhizal fungal community in mature white poplar plantationMarina Milović, Saša Orlović, Tine Grebenc, Marko Bajc, Branislav Kovačević, Hojka Kraigher, 2021, izvirni znanstveni članek Povzetek: Ectomycorrhizal communities are rarely studied on seasonal basis, especially in poplar plantations. In this study we analysed the ectomycorrhizal community in a mature twenty-year-old white poplar (Populus alba L.) plantation during four consecutive seasons. Using morpho-anatomical and molecular identification 30 taxa of ectomycorrhizal fungi were recorded of which 15 were identified to the species level, 12 to the genus level, 2 to the family, and one morphotype of ectomycorrhizae remained unidentified. The most abundant among identified ectomycorrhizal fungi were: Inocybe griseovelata, Inocybe splendens, Tuber rufum, and Tomentella sp. 2, which together represented up to 50% of all ectomycorrhizal root tips. The number of ectomycorrhizal fungal taxa and the percentage of vital ectomycorrhizal root tips were highest in winter and spring, respectively. The diversity indices of ectomycorrhizae, number of vital ectomycorrhizal root tips, and total fine roots in the studied poplar plantation did not differ between seasons. Ectomycorrhizal fungi belonging to Inocybaceae family and the short-distance exploration strategy were dominant in all four seasons. On the other hand, the abundance of ectomycorrhizal root tips belonging to the medium-distance exploration strategy type was significantly higher in spring in comparison with autumn and winter.
Ključne besede: Populus alba L., Ectomycorrhizal diversity, morpho-anatomical characterization, molecular identification, seasons
Objavljeno v DiRROS: 03.12.2021; Ogledov: 418; Prenosov: 170
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9. Ectomycorrhiza between Scleroderma Areolatum Ehrenb. and Fagus sylvatica L.Tanja Mrak, Katja Kühdorf, Tine Grebenc, Ines Štraus, Marko Bajc, Nada Žnidaršič, Bebette Münzenberger, Hojka Kraigher, 2015, objavljeni povzetek znanstvenega prispevka na konferenci Objavljeno v DiRROS: 03.11.2021; Ogledov: 410; Prenosov: 140
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