Bacterial and Fungal Endophytic Microbiomes of Salicornia europaea

We examined Salicornia europaea, a nonmycorrhizal halophyte associated with specific and unique endophytic bacteria and fungi. The microbial community structure was analyzed at two sites differing in salinization history (anthropogenic and naturally saline site), in contrasting seasons (spring and fall) and in two plant organs (shoots and roots) via 16S rRNA and internal transcribed spacer amplicon sequencing. We observed distinct communities at the two sites, and in shoots and roots, while the season was of no importance. The bacterial community was less diverse in shoot libraries than in roots, regardless of the site and season, whereas no significant differences were observed for the fungal community. Proteobacteria and Bacteroidetes dominated bacterial assemblages, and Ascomycetes were the most frequent fungi. A root core microbiome operational taxonomic unit belonging to the genus Marinimicrobium was identified. We detected a significant influence of the Salicornia bacterial community on the fungal one by means of cocorrespondence analysis. In addition, pathways and potential functions of the bacterial community in Salicornia europaea were inferred and discussed. We can conclude that bacterial and fungal microbiomes of S. europaea are determined by the origin of salinity at the sites. Bacterial communities seemed to influence fungal ones, but not the other way around, which takes us closer to understanding of interactions between the two microbial groups. In addition, the plant organs of the halophyte filter the microbial community composition

Mixed growth of Salix species can promote phosphate-solubilizing bacteria in the roots and rhizosphere

Phosphorus (P) is an essential plant nutrient that can limit plant growth due to low availability in the soil. P-solubilizing bacteria in the roots and rhizosphere increase the P use efficiency of plants. This study addressed the impact of plant species, the level of plant association with bacteria (rhizosphere or root endophyte) and environmental factors (e.g., seasons, soil properties) on the abundance and diversity of P-solubilizing bacteria in short-rotation coppices (SRC) of willows (Salix spp.) for biomass production. Two willow species (S. dasycladoscv. Loden and S. schwerinii × S. viminalis cv. Tora) grown in mono-and mixed culture plots were examined for the abundance and diversity of bacteria in the root endosphere and rhizosphere during two seasons (fall and spring) in central Sweden and northern Germany. Soil properties, such as pH and available P and N, had a significant effect on the structure of the bacterial community. Microbiome analysis and culture-based methods revealed a higher diversity of rhizospheric bacteria than endophytic bacteria. The P-solubilizing bacterial isolates belonged mainly to Proteobacteria (85%), Actinobacteria (6%) and Firmicutes (9%). Pseudomonas was the most frequently isolated cultivable bacterial genus from both the root endosphere and the rhizosphere. The remaining cultivable bacterial isolates belonged to the phyla Actinobacteria and Firmicutes. In conclusion, site-specific soil conditions and the level of plant association with bacteria were the main factors shaping the bacterial communities in the willow SRCs. In particular, the concentration of available P along with the total nitrogen in the soil controlled the total bacterial diversity in willow SRCs. A lower number of endophytic and rhizospheric bacteria was observed in Loden willow species compared to that of Tora and the mix of the two, indicating that mixed growth of Salix species promotes P-solubilizing bacterial diversity and abundance. Therefore, a mixed plant design was presented as a management option to increase the P availability for Salix in SRCs. This design should be tested for further species mixtures

The Effects of Host Plant Genotype and Environmental Conditions on Fungal Community Composition and Phosphorus Solubilization in Willow Short Rotation Coppice

Phosphorus (P) is an essential plant nutrient. Low availability of P in soil is mainly caused by high content of Fe2O3 in the clay fraction that binds to P making it unavailable. Beneficial microbes, such as P solubilizing microorganisms can increase the available P in soil and improve plant growth and productivity. In this study, we evaluated the effects of environmental conditions (climate, soil parameters), plant genotype, and level of plant association (rhizosphere or endophytic root organism) on the abundance and diversity of phosphorus solubilizing microorganisms in a Salix production system. We hypothesized that a lower number of endophytic fungi may possess the ability to solubilize P compared to the number of rhizosphere fungi with the same ability. We also expect that the plant genotype and the experimental site with its environmental conditions will influence fungal diversity. Two Salix genotypes grown in pure and mixed cultures were investigated for their fungal microbiome community and diversity in the rhizosphere and endosphere during two growing seasons. We found that the rhizosphere fungal community was more diverse. A general dominance of Ascomycota (Dothideomycetes) and Basidiomycota (Tremellomycetes) was observed. The classes Agaricomycetes and Pezizomycetes were more frequent in the endosphere, while Tremellomycetes and Mortierellomycetes were more abundant in the rhizosphere. Plot-specific soil properties (pH, total organic carbon, and nitrogen) significantly influenced the fungal community structure. Among the culturable fungal diversities, 10 strains of phosphate solubilizing fungi (PSFs) from roots and 12 strains from rhizosphere soil were identified using selective media supplemented with di-calcium and tri-calcium phosphates. The fungal density and the number of PSF were much higher in the rhizosphere than in the endosphere. Penicillium was the dominant genus of PSF isolated from both sites; other less frequent genera of PSFs were Alternaria, Cladosporium, and Clonostachys. Overall the main factors controlling the fungal communities (endophytic vs. rhizosphere fungi) were the soil properties and level of plant association, while no significant influence of growing season was observed. Differences between Salix genotypes were observed for culturable fungal diversity, while in metagenomic data analysis, only the class Dothideomycetes showed a significant effect from the plant genotype

A window into fungal endophytism in Salicornia europaea: deciphering fungal characteristics as plant growth promoting agents

Aim Plant-endophytic associations exist only when equilibrium is maintained between both partners. This study analyses the properties of endophytic fungi inhabiting a halophyte growing in high soil salinity and tests whether these fungi are beneficial or detrimental when non-host plants are inoculated. Method Fungi were isolated from Salicornia europaea collected from two sites differing in salinization history (anthropogenic and naturally saline) and analyzed for plant growth promoting abilities and non-host plant interactions. Results Most isolated fungi belonged to Ascomycota (96%) including dematiaceous fungi and commonly known plant pathogens and saprobes. The strains were metabolically active for siderophores, polyamines and indole-3-acetic acid (mainly Aureobasidium sp.) with very low activity for phosphatases. Many showed proteolytic, lipolytic, chitinolytic, cellulolytic and amylolytic activities but low pectolytic activity. Different activities between similar fungal species found in both sites were particularly seen for Epiccocum sp., Arthrinium sp. and Trichoderma sp. Inoculating the non-host Lolium perenne with selected fungi increased plant growth, mainly in the symbiont (Epichloë)-free variety. Arthrinium gamsii CR1-9 and Stereum gausapatum ISK3-11 were most effective for plant growth promotion. Conclusions This research suggests that host lifestyle and soil characteristics have a strong effect on endophytic fungi, and environmental stress could disturb the plant-fungi relations. In favourable conditions, these fungi may be effective in facilitating crop production in non-cultivable saline lands

Ectomycorrhizal Diversity and Exploration Types in <i>Salix caprea</i>

The tree species Salix caprea shows high adaptability to different habitat conditions and is economically valuable as a woody crop for biomass production. Moreover, S. caprea is dependent on mycorrhizal fungi, which are crucial for its growth and adaptability in different environments. Hence, this study explores the ectomycorrhizal diversity of S. caprea by utilizing the taxonomy (morphotyping and a molecular approach using the ITS and LSU regions) and trait diversity (exploration types) at two test sites in Germany and Poland. In total, 19 ectomycorrhizal (EM) morphotypes of S. caprea were characterized. Seven taxa were identified at the species level (Hebeloma populinum, Cortinarius atrocoerulaeus, Inocybe hirtella, Laccaria cf. ochropurpurea, Tuber maculatum, Cenococcum geophilum, and Phialophora finlandia) and twelve at the genus level (Tomentella spp. 1–8, Hebeloma sp. 1, Inocybe sp. 1, and Tuber spp. 1–2). The EM colonization ranged from 14 to 28% of the fine root tips. At both test sites, the largest portion of the total EM colonization consisted of Thelephoraceae. The exploration types were classified as medium-distance smooth (Tomentella sp. 1–8 and L. ochropurpurea) and medium-distance fringe (C. atrocoerulaeus), while the other taxa were short-distance exploration types, highlighting their potential functional role in the adaptation and growth of S. caprea

Large effect of phosphate-solubilizing bacteria on the growth and gene expression of Salix spp. at low phosphorus levels

Phosphorus is one of the most important nutrients required for plant growth and development. However, owing to its low availability in the soil, phosphorus is also one of the most difficult elements for plants to acquire. Phosphorus released into the soil from bedrock quickly becomes unavailable to plants, forming poorly soluble complexes. Phosphate-solubilizing bacteria (PSB) can solubilize unavailable phosphorus-containing compounds into forms in which phosphorus is readily available, thus promoting plant growth. In this study, two willow species, Salix dasyclados cv. Loden and Salix schwerinii × Salix viminalis cv. Tora, were inoculated with two selected bacterial strains, Pantoea agglomerans and Paenibacillus spp., to evaluate the plant growth parameters and changes in gene expression in the presence of different concentrations of tricalcium phosphate: 0 mM (NP), 1 mM (LP), and 2 mM (HP). Inoculation with PSB increased root, shoot and leaf biomass, and for the HP treatment, significant changes in growth patterns were observed. However, the growth responses to plant treatments tested depended on the willow species. Analysis of the leaf transcriptomes of the phosphate-solubilizing bacterium-inoculated plants showed a large variation in gene expression between the two willow species. For the Tora willow species, upregulation of genes was observed, particularly for those involved in pathways related to photosynthesis, and this effect was strongly influenced by bacterial phosphate solubilization. The Loden willow species was characterized by a general downregulation of genes involved in pathway activity that included ion transport, transcription regulation and chromosomes. The results obtained in this study provide an improved understanding of the dynamics of Salix growth and gene expression under the influence of PSB, contributing to an increase in yield and phosphorus-use efficiency

Functional Properties of Gelatin/Polyvinyl Alcohol Films Containing Black Cumin Cake Extract and Zinc Oxide Nanoparticles Produced via Casting Technique

This study aimed to develop and characterize gelatin/polyvinyl alcohol (G/PVA) films loaded with black cumin cake extract (BCCE) and zinc oxide nanoparticles (ZnONPs). The BCCE was also applied for the green synthesis of ZnONPs with an average size of less than 100 nm. The active films were produced by a solvent-casting technique, and their physicochemical and antibacterial properties were investigated. Supplementation of G/PVA film in ZnONPs decreased the tensile strength (TS) from 2.97 MPa to 1.69 MPa. The addition of BCCE and ZnONPs increased the elongation at the break (EAB) of the enriched film by about 3%. The G/PVA/BCCE/ZnONPs film revealed the lowest water vapor permeability (WVP = 1.14 &times; 10&minus;9 g&middot;mm&middot;Pa&minus;1&middot;h&minus;1&middot;mm&minus;2) and the highest opacity (3.41 mm&minus;1). The QUick, Easy, New, CHEap and Reproducible (QUENCHER) methodologies using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2&prime;-azino-bis(3-ethylbenzothiazoline-6- sulfonic acid) (ABTS) and cupric ion reducing antioxidant capacity (CUPRAC) were applied to measure antioxidant capacity (AC) of the prepared films. The incorporation of BCCE and ZnONPs into G/PVA films enhanced the AC by 8&ndash;144%. The films containing ZnONPs and a mixture of BCCE and ZnONPs inhibited the growth of three Gram-positive bacterial strains. These nanocomposite films with desired functional properties can be recommended to inhibit microbial spoilage and oxidative rancidity of packaged food

Development and Characterization of Active Gelatin Films Loaded with Rapeseed Meal Extracts

The use of industrial waste as a material for the development of natural innovative and active packaging is economically and environmentally appealing. The aim of this study was to develop and characterize active gelatin films incorporating rapeseed oil industry waste. Water (RM-WE) and methanolic (RM-MWE) extracts of rapeseed meal (RM) were used as active agents in film formulations. The active films were produced by a casting technique. The physicochemical, mechanical, optical, morphological, radical scavenging, and antibacterial properties of the films were analyzed. The addition of RM-WE and RM-MWE in the concentrations range between 4 and 12% promoted an increase of Young’s modulus (YM) and radical scavenging properties of films investigated by the direct QUick, Easy, New, CHEap and Reproducible procedure using 2,2-diphenyl-1-picrylhydrazyl (QUENCHERDPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (QUENCHERABTS) radicals. The antibacterial properties of films were examined against five bacterial strains: E. coli, S. enterica, M. luteus, L. monocytogenes, and S. aureus. Additionally, color and opacity of the control and fortified films differed significantly. The gelatin films with RM extracts are resistant to the microbial spoilage and could be used to produce active packaging for food that is vulnerable to rancidity effects