1,720,981 research outputs found
Role of Actinomycetes in Mitigating the Impact of Climate Change: Mechanisms of Action and Perspectives
No full textCharacterization of plant growth-promoting traits and inoculation effects on triticum durum of actinomycetes isolates under salt stress conditions
Full text linkThis study aimed to characterize the halotolerant capability, in vitro, of selected actino-mycetes strains and to evaluate their competence in promoting halo stress tolerance in durum wheat in a greenhouse experiment. Fourteen isolates were tested for phosphate solubilization, indole acetic acid, hydrocyanic acid, and ammonia production under different salt concentrations (i.e., 0, 0.25, 0.5, 0.75, 1, 1.25, and 1.5 M NaCl). The presence of 1-aminocyclopropane-1-carboxylate deaminase activity was also investigated. Salinity tolerance was evaluated in durum wheat through plant growth and development parameters: shoot and root length, dry and ash-free dry weight, and the total chlorophyll content, as well as proline accumulation. In vitro assays have shown that the strains can solubilize inorganic phosphate and produce indole acetic acid, hydrocyanic acid, and ammonia under different salt concentrations. Most of the strains (86%) had 1-aminocyclopropane-1-carboxylate deaminase activity, with significant amounts of α-ketobutyric acid. In the greenhouse experiment, inoculation with actinomycetes strains improved the morpho-biochemical parameters of durum wheat plants, which also recorded significantly higher content of chlorophylls and proline than those uninoculated, both under normal and stressed conditions. Our results suggest that inoculation of halotolerant actinomycetes can mitigate the negative effects of salt stress and allow normal growth and development of durum wheat plants
Microbial Community Investigation of Wild Brambles with Root Nodulation from a Calcareous Nitrogen-Deficient Soil
Full text linkThis study examines culturable diazotrophs and non-culturable bacteria found in the rhizospheres and root pseudonodules of wild blackberry plants (Rubus ulmifolius) that dwell on an unmanaged calcareous nitrogen-deficient soil. The DNA was extracted from the nodules and rhizospheres, and 16S rRNA gene metabarcoding was carried out. The metagenome functions were predicted with bioinformatic approaches. The soil samples were analyzed for the physico-chemical properties. The culturable diazotrophs were isolated and evaluated for the biochemical and plant growth-promoting properties. The soil was classified as nutrient-depleted calcareous soil. The microbial communities of the nodules and rhizospheres showed marked differences. The Pseudomonadota was the nodules’ dominant phyla (90%), while the Actinobacteriota was the most abundant (63%) in the rhizospheres. Stenotrophomonas was the dominant genus (55%) in the nodules, while the Streptomyces genus was widely present (39%) in the rhizospheres. The differences among the nodule and rhizosphere microbial communities were also highlighted by the metagenome function predictions. The gene copies (KOs) revealed the most interesting findings. Similar KOs involved in the nitrogen fixation were found to be similar in terms of the nodules and rhizospheres. However, the nitrate reduction was higher in the rhizosphere, while the denitrification was more prominent in the nodules. Nine diazotrophs were isolated from the nodules and rhizospheres. The plant growth promoting traits’ characterization has shown the interesting potential of the isolates in improving the acquisition of nutrients in plants, promoting their growth, and tolerating stress. Based on interesting biochemical and plant growth-promoting traits, the isolate N2A was further characterized and identified as Pantoea agglomerans
Actinomycetes from Caves: An Overview of Their Diversity, Biotechnological Properties, and Insights for Their Use in Soil Environments
Full text linkThe environmental conditions of caves shape microbiota. Within caves’ microbial com-munities, actinomycetes are among the most abundant bacteria. Cave actinomycetes have gained increasing attention during the last decades due to novel bioactive compounds with antibacterial, antioxidant and anticancer activities. However, their potential role in soil environments is still un-known. This review summarises the literature dealing with actinomycetes from caves, underlining for the first time their potential roles in soil environments. We provide an overview of their diversity and biotechnological properties, underling their potential role in soil environments applications. The contribution of caves’ actinomycetes in soil fertility and bioremediation and crops biostimulation and biocontrol are discussed. The survey on the literature show that several actinomycetes genera are present in cave ecosystems, mainly Streptomyces, Micromonospora, and Nocardiopsis. Among caves’ actinomycetes, Streptomyces is the most studied genus due to its ubiquity, survival capabilities, and metabolic versatility. Despite actinomycetes’ outstanding capabilities and versatility, we still have inadequate information regarding cave actinomycetes distribution, population dynamics, biogeo-chemical processes, and metabolisms. Research on cave actinomycetes needs to be encouraged, especially concerning environmental soil applications to improve soil fertility and health and to antagonise phytopathogens
Preliminary indication of the role of AHL-dependent quorum sensing systems in calcium carbonate precipitation in Gram-negative bacteria
Full text linkNumerous microbial species participate in precipitation of carbonates in various natural environments, including soils, geological formations, freshwater biofilms and oceans. Despite the geochemical interest of such a biomineralization process, its molecular mechanisms and adaptive aspects remain poorly known. Many Gram-negative bacteria use cell-to-cell communication systems relying on N-acylhomoserine lactone (AHLs) signal molecules to express certain phenotypic traits in a density-dependent manner, a phenomenon referred as to quorum-sensing (QS). In this work, bacterial isolates collected from cave and rhizosphere soil were analyzed to study the occurrence of the AHL-mediated QS in bacterial calcium carbonate (CaCO3) precipitation. To test the production of AHLs signal molecules, we cross-streaked Gram-negative calcifying strains, selected among the environmental strains studied, with the AHL-negative mutant Chromobacterium subtsugae strain CV026. Only Burkholderia ambifaria LMG 11351 was able to restore violacein production in CV026 among the tested strains. The constructed AHL-negative mutant of B. ambifaria LMG 11351 could not precipitate CaCO3 on B-4 agar. Scanning Electron Microscopy (SEM) analysis on CaCO3 crystals obtained in vitro shows crystals of different morphologies, calcified biofilms and bacteria in close contact with the precipitated crystals. In the inner layers of the bioliths deposited by B. ambifaria LMG 11351, a stream-like organization of the Burkholderia imprints was not detected by SEM. Our data provide preliminary evidence that the activation of AHL-regulated genes may be a prerequisite for in vitro bacterial carbonatogenesis, in some cases, confirming the specific role of bacteria as CaCO3 precipitating agents. We enhance the understanding of bacterial CaCO3 biomineralization and has potential biotechnology implications for QS-based strategies to enhance or decrease CaCO3 precipitation through specific bacterial processes. The AHL-negative mutant of B. ambifaria LMG 11351 (a well-known plant growth-promoting bacterium) could also be used to study plant-bacteria interactions. The adaptive role of bacterial CaCO3 biomineralization was also discussed
Actinomycete strains isolated from saline soils: Plant-growth-promoting traits and inoculation effects on solanum lycopersicum
Full text linkExcessive use of chemical products in agriculture is causing significant environmental pollution and the loss of lands and fertility of agricultural soils. Plant-growth-promoting bacteria are a valid alternative strategy for sustainable agriculture. The aim of this study was to select actinomycete strains based on their plant-growth-promoting traits and to investigate their root association abilities and biostimulant effects on Solanum lycopersicum. The strains were investigated for their phosphate solubilization ability, production of indole-3-acetic acid, hydrocyanic acid, and ammonia, and several enzymatic activities. Bacteria-plant-root associations were studied by scanning electron microscopy. A greenhouse experiment was carried out to assess inoculation effects. Of sixty isolates, fourteen strains showed significant plant-growth-promoting traits. All fourteen strains solubilized phosphate, produced ammonia, and showed several enzymatic activities at different rates. The production of indole-3-acetic acid was shown by nine strains, while hydrocyanic acid production was observed in eleven of them. Scanning electron microscopy revealed that strains have good in vitro plant root association and colonization abilities. In planta inoculation by actinomycete strains positively influenced plant growth parameters. The best results were shown by seven actinomycete strains, suggesting their possible utilization as biofertilizer agents for sustainable agriculture
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Characterization of plant growth-promoting traits and inoculation effects on Triticum durum of Actinomycetes isolates under salt stress conditions
Full text linkThis study aimed to characterize the halotolerant capability, in vitro, of selected actinomycetes strains and to evaluate their competence in promoting halo stress tolerance in durum wheat
in a greenhouse experiment. Fourteen isolates were tested for phosphate solubilization, indole acetic
acid, hydrocyanic acid, and ammonia production under different salt concentrations (i.e., 0, 0.25,
0.5, 0.75, 1, 1.25, and 1.5 M NaCl). The presence of 1-aminocyclopropane-1-carboxylate deaminase
activity was also investigated. Salinity tolerance was evaluated in durum wheat through plant
growth and development parameters: shoot and root length, dry and ash-free dry weight, and the
total chlorophyll content, as well as proline accumulation. In vitro assays have shown that the strains
can solubilize inorganic phosphate and produce indole acetic acid, hydrocyanic acid, and ammonia
under different salt concentrations. Most of the strains (86%) had 1-aminocyclopropane-1-carboxylate
deaminase activity, with significant amounts of α-ketobutyric acid. In the greenhouse experiment,
inoculation with actinomycetes strains improved the morpho-biochemical parameters of durum
wheat plants, which also recorded significantly higher content of chlorophylls and proline than those
uninoculated, both under normal and stressed conditions. Our results suggest that inoculation of
halotolerant actinomycetes can mitigate the negative effects of salt stress and allow normal growth
and development of durum wheat plants
Erratic calcareous deposits: Biotic formation insights and biomineralising bacterial strain isolation
Full text linkThe present study investigated the contribution of microbial communities in producing "living stones" and the suitability of these clasts as sources of microorganisms with biomineralisation abilities. The calcareous samples were analysed for their microbial community (16S rRNA gene metabarcoding and culturable approach) and in vitro regeneration tests. Scanning electron microscopy and Energy Dispersive Spectroscopy (SEM-EDX) were applied to investigate microbial aggregation structures and footprints in natural and in vitro samples. The metabarcoding unveiled amplicon sequence variants (ASVs) assigned to lineages with biomineralisation abilities (e.g., Proteobacteria and Actinobacteriota). The culturable approach resulted in nineteen calcifying isolates with diverse morphological, metabolic, and mineral precipitation properties. Based on mineralising properties, Stenotrophomonas maltophilia, Lysinbacillus fusiformis, and Microbacterium ginsengiterrae were identified at the molecular level. In vitro regeneration tests and SEM-EDX analyses confirmed the active role of the endogenous microorganisms in forming these “living stones”. These findings allow us to hypothesise an essential role of microbial precipitation in forming these “living stones”, previously described as of abiotic origin. The current study findings provide a solid scientific foundation for future investigations. The obtained bacterial isolates and their potential applications in bioremediation, construction, and cultural heritage restoration demonstrate the direct applicability of our study in sectors involving biomaterials application. Statement of significance: We studied some "living stones" that can be found worldwide and whose origin is still not completely understood. Geologists have not yet fully explained the origin of these inorganic structures that grow in size over time. The results obtained from our microbiological investigations allowed us to discover that microorganisms play a crucial role in forming these masses. In the investigations of the structures and microbial communities within the stones, we identified specific bacteria that actively contribute to forming minerals and isolated bacteria that can form biominerals. These findings deepen our understanding of natural processes involved in the formation of these structures and show their potential for several applications (e.g., building materials or cultural heritage preservation)
- …
