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Povzetek: Groundwater is the most important source of drinking water supply, irrigation, and industrial use, as well as a habitat for a diverse range of (micro)organisms. Some of the first studies of underground environments were carried out in the Dinaric Karst region of Slovenia, which harbors one of the highest subterranean biodiversities in the world. Despite their ecological importance, groundwater microbial communities remain underexplored. In this study, we conducted a comprehensive microbiome analysis of karst groundwater, investigating the abundance and diversity of viruses, archaea, bacteria, fungi, and protozoa. We detected a high diversity of both prokaryote- and eukaryote-infecting viruses, indicating the connection of subterranean environments with surface waters. In the archaeal community, seven different phyla were identified, dominated by members of "Candidatus Woesearchaeota" and Nitrososphaerota (syn. Thermoproteota). In the bacterial community of majority of the samples, the Pseudomonadota was the most abundant phylum, followed by Bacteroidota, Actinomycetota, and Verrucomicrobiota. Fungal abundance and diversity differed greatly between cave water samples, with the Ascomycota families Cladosporiaceae, Didymellaceae, Aspergillaceae and saprotrophic Basidiomycota detected in all samples. Besides fungi, microscopic eukaryotic diversity consisted of ciliates, copepods and golden-brown algae present in all samples. Differences in microbial communities between the sampling sites highlight the need for tailored site-specific groundwater conservation and monitoring strategies. Moreover, the identification of microbes associated with anthropogenic activities underscores their potential as source-specific indicators of groundwater pollution. As the first holistic overview of microbial diversity of subterranean water, the study establishes a valuable baseline for future research and conservation of these unique karst ecosystems.
Ključne besede: Karst cave water, high-throughput sequencing, viruses, archaea, bacteria, fungi, protozoa
Objavljeno v DiRROS: 02.03.2026; Ogledov: 326; Prenosov: 204
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Povzetek: The "yeast-like" fungus, Aureobasidium pullulans, isolated from fruit and leaves exhibits strong biocontrol activity against postharvest decays on various fruit. Some strains were even developed into commercial products. We obtained 20 of these strains and investigated their characteristics related to biocontrol. Phylogenetic analyses based on internal transcribed spacer (ITS) and the D1/D2 domains of rRNA 28S gene regions confirmed that all the strains are most closely related to A. pullulans species. All strains grew at 0°C, which is very important to control decay at low storage temperature, and none grew at 37°C, which eliminates concern for human safety. Eighteen strains survived 2 hrs exposures to 50°C and two strains even survived for 24 hrs. Salt-tolerance varied; however, all strains grew on medium with 14% NaCl and 14 even with 18% NaCl. Such tolerances to high temperature and elevated salinity enable compatibility with postharvest practices. Substantial differences were observed in enzymatic activity, especially with respect to production of chitinases, xylanase, or urease. Siderophore production was detected and the ability to form biofilm varied widely between the strains. Knowledge of common characteristics of these strains may be very useful in future selection of the best antagonists within this species.
Ključne besede: biological control, postharvest disease management, antagonism, physiological variability, stress tolerance
Objavljeno v DiRROS: 04.03.2025; Ogledov: 945; Prenosov: 543
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Povzetek: Soil salinity and drought are among the most serious agricultural and environmental problems of today. Therefore, investigations of plant resistance to abiotic stress have received a lot of attention in recent years. In this study, we identified the complete coding sequence of a 3′-phosphoadenosine-5′-phosphatase protein, ApHal2, from the halotolerant yeast Aureobasidium pullulans. Expression of the ApHAL2 gene in a Saccharomyces cerevisiae hal2 mutant complemented the mutant auxotrophy for methionine, and rescued the growth of the hal2 mutant in media with high NaCl concentrations. A 21-amino-acids-long region of the ApHal2 enzyme was inserted into the Arabidopsis thaliana homologue of Hal2, the SAL1 phosphatase. The inserted sequence included the META motif, which has previously been implicated in increased sodium tolerance of the Hal2 homologue from a related fungal species. Transgenic Arabidopsis plants overexpressing this modified SAL1 (mSAL1) showed improved halotolerance and drought tolerance. In a medium with an elevated salt concentration, mSAL1-expressing plants were twice as likely to have roots in a higher length category in comparison with the wild-type Arabidopsis and with plants overexpressing the native SAL1, and had 5% to 10% larger leaf surface area under moderate and severe salt stress, respectively. Similarly, after moderate drought exposure, the mSAL1-expressing plants showed 14% increased dry weight after revitalisation, with no increase in dry weight of the wild-type plants. With severe drought, plants overexpressing native SAL1 had the worst rehydration success, consistent with the recently proposed role of SAL1 in severe drought. This was not observed for plants expressing mSAL1. Therefore, the presence of this fungal META motif sequence is beneficial under conditions of increased salinity and moderate drought, and shows no drawbacks for plant survival under severe drought. This demonstrates that adaptations of extremotolerant fungi should be considered as a valuable resource for improving stress-tolerance in plant breeding in the future.
Ključne besede: soil salinity and drought, plant resistance, abiotic stress
Objavljeno v DiRROS: 02.08.2024; Ogledov: 1257; Prenosov: 1082
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Povzetek: The genetic platforms of Deinococcus species remain the only systems in which massive ionizing radiation (IR)-induced genome damage can be investigated in vivo at exposures commensurate with cellular survival. We report the whole genome sequence of the extremely IR-resistant rod-shaped bacterium Deinococcus ficus KS 0460 and its phenotypic characterization. Deinococcus ficus KS 0460 has been studied since 1987, first under the name Deinobacter grandis, then Deinococcus grandis. The D. ficus KS 0460 genome consists of a 4.019 Mbp sequence (69.7% GC content and 3894 predicted genes) divided into six genome partitions, five of which are confirmed to be circular. Circularity was determined manually by mate pair linkage. Approximately 76% of the predicted proteins contained identifiable Pfam domains and 72% were assigned to COGs. Of all D. ficus KS 0460 proteins, 79% and 70% had homologues in Deinococcus radiodurans ATCC BAA-816 and Deinococcus geothermalis DSM 11300, respectively. The most striking differences between D. ficus KS 0460 and D. radiodurans BAA-816 identified by the comparison of the KEGG pathways were as follows: (i) D. ficus lacks nine enzymes of purine degradation present in D. radiodurans, and (ii) D. ficus contains eight enzymes involved in nitrogen metabolism, including nitrate and nitrite reductases, that D. radiodurans lacks. Moreover, genes previously considered to be important to IR resistance are missing in D. ficus KS 0460, namely, for the Mn-transporter nramp, and proteins DdrF, DdrJ and DdrK, all of which are also missing in Deinococcus deserti. Otherwise, D. ficus KS 0460 exemplifies the Deinococcus lineage.
Ključne besede: Deinococcus-Thermus, Deinococcaceae, Deinococcus ficus, radiation-resistant, rod-shaped, phenotype characterization, genome analysis, phylogenetic analysis
Objavljeno v DiRROS: 25.07.2024; Ogledov: 1332; Prenosov: 800
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Povzetek: The black yeast Aureobasidium pullulans is a textbook example of a generalistic and ubiquitous fungus thriving in a wide variety of environments. To investigate whether A. pullulans is a true generalist, or alternatively, whether part of its versatility can be attributed to intraspecific specialization masked by cryptic diversification undetectable by traditional phylogenetic analyses, we sequenced and analysed the genomes of 50 strains of A. pullulans from different habitats and geographic locations. No population structure was observed in the sequenced strains. Decay of linkage disequilibrium over shorter physical distances (<100 bp) than in many sexually reproducing fungi indicates a high level of recombination in the species. A homothallic mating locus was found in all of the sequenced genomes. Aureobasidium pullulans appears to have a homogeneous population genetics structure, which is best explained by good dispersal and high levels of recombination. This means that A. pullulans is a true generalist that can inhabit different habitats without substantial specialization to any of these habitats at the genomic level. Furthermore, in the future, the high level of A. pullulans recombination can be exploited for the identification of genomic loci that are involved in the many biotechnologically useful traits of this black yeast.
Ključne besede: black yeast, genome
Objavljeno v DiRROS: 24.07.2024; Ogledov: 1044; Prenosov: 912
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