1,720,978 research outputs found
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
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)
Microbial Consortium of Streptomyces spp. from Mining Environments Enhances Phytoremediation Potential of Lemna minor L
Full text linkThe presence of substantial amounts of heavy metals in the environment can result in various significant ecological issues and human health risks. Currently, bioremediation employing microorganisms is garnering significant interest due to its effectiveness. The present investigation aimed to isolate actinobacterial strains from an Italian mine and to characterise them for heavy metals resistance and plant growth-promoting characteristics. The different samples were processed for DNA extraction and 16S rRNA gene metabarcoding to investigate the bacteria and archaea communities. Cultivable microbiota were isolated and evaluated for heavy metals tolerance and different PGP traits. The most pertinent strains were tested for compatibility, merged into a consortium, and tested on Lemna minor L. Metabarcoding analysis revealed that amplicon sequence variants (ASVs) at the phylum level were mostly assigned to proteobacteria and bacteroidota. Uncultured and unknown taxa were the most prevalent in the samples at the genus level. A total of ten strains were obtained from the culture-dependent approach exhibiting interesting heavy metals tolerance and plant growth-promoting traits. The best strains (MTW 1 and MTW 5) were selected and further characterised by 16S barcoding. These strains were identified as Streptomyces atratus (99.57% identity). An in planta experiment showed that the metal-tolerant consortium MTW 1-5 improved plant physiology by significantly optimising plant growth and tolerance to heavy metals. The experiment conducted provided evidence for the possibility of using actinobacteria as bioaugmentation agents to improve the phytoextraction abilities of L. minor
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
Isolation and characterization of cyanobacteria and microalgae from a sulfuric pond: Plant growth-promoting and soil bioconsolidation activities
Full text linkSustainable alternatives are essential to improving agriculture production to meet the growing world's critical demands. Cyanobacteria and microalgae are considered renewable resources with a wide range of potential uses in the agricultural sector. We aimed to isolate cyanobacteria and microalgae from the mud of a carbon dioxide-rich sulfur pond and to investigate their plant growth- promoting (PGP) and soil bio-consolidating ability. Mud samples were subjected to DNA extraction and 16S rRNA gene sequencing to characterize the prokaryotic community. Phototrophic culturable microbiota was isolated and evaluated for different PGP properties. The most relevant isolates were combined in a consortium and used for in vitro bioconsolidation activity. In a greenhouse experiment, the isolates were evaluated for their ability to promote salinity stress tolerance in sunflower plants. Metabarcoding results showed that most Amplicon Sequence Variants (ASV) were associated with Actinobacteriota (35%), Proteobacteria (19%), and Acidobacteriota (11%) at the phylum level and Unknown (32%) and uncultured (31%) lineages at the genus level. The culture-dependent method yielded eight isolates associated with cyanobacteria and microalgae genera. The isolates obtained showed interesting PGP activities. Isolates C1, C2, and M1 were selected based on phosphate solubilization (85.6 mu g PO 4 3- mL-1 on average), indoles (C1 and M1 0.54 mu g mL-1 IAA equivalents on average), and ACC deaminase activity (C2 and M1 6.00 mu mol alpha-KB mg proteins-1 h -1) . The consortium efficiently consolidated sand particles in the presence of calcium carbonate by forming biomineralized aggregates. In planta results showed positive effects of the consortium on Helianthus annuus L. , plant growth under normal conditions and salt stress. The positive effects on soil and plants indicated their effectiveness as bioconsolidants and biostimulant agents. Our findings highlight the interesting potential of cyanobacteria and microalgae applications in sustainable agriculture
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
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
Selection of a Bacterial Conditioner to Improve Wheat Production Under Salinity Stress
Full text linkThis study investigated the isolation and formulation of a bacterial conditioner as a biostimulant for Triticum durum (durum wheat) under salinity stress. An Algerian alkaline-saline soil was sampled, characterized for its physical and chemical characteristics and its culturable and total microbial community (16S rRNA gene metabarcoding). Three bacterial strains showing high 16S rRNA gene similarity to Pseudomonas putida, Bacillus proteolyticus, and Niallia nealsonii were selected for their plant growth-promoting (PGP) traits under different salinity levels, including phosphate solubilisation (194 mu g mL-1), hormone production (e.g., gibberellin up to 56 mu g mL-1), and good levels of hydrocyanic acid, ammonia, and siderophores. N. nealsonii maintained high indole production under saline conditions, while B. proteolyticus displayed enhanced indole synthesis at higher salt concentrations. Siderophore production remained stable for P. putida and N. nealsonii, whereas for B. proteolyticus a complete inhibition was registered in the presence of salt stress. The consortium density and application were tested under controlled conditions using Medicago sativa as a model plant. The effective biostimulant formulation was tested on Triticum durum under greenhouse experiments. Bacterial inoculation significantly improved plant growth in the presence of salt stress. Root length increased by 91% at 250 mM NaCl. Shoot length was enhanced by 112% at 500 mM NaCl. Total chlorophyll content increased by 208% at 250 mM NaCl. The chlorophyll a/b ratio increased by 117% at 500 mM. Also, reduced amounts of plant extracts were necessary to scavenge 50% of radicals (-22% at 250 mM compared to the 0 mM control). Proline content increased by 20% at both 250 mM and 500 mM NaCl. These results demonstrate the potential of beneficial bacteria as biostimulants to mitigate salt stress and enhance plant yield in saline soils
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