Mitigation of salt stress in Sorghum bicolor L. by the halotolerant endophyte Pseudomonas stutzeri ISE12.

Increasing soil salinity, exacerbated by climate change, threatens seed germination and crop growth, causing significant agricultural losses. Using bioinoculants based on halotolerant plant growth-promoting endophytes (PGPEs) in modern agriculture is the most promising and sustainable method for supporting plant growth under salt-stress conditions. Our study evaluated the efficacy of Pseudomonas stutzeri ISE12, an endophyte derived from the extreme halophyte Salicornia europaea, in enhancing the salinity tolerance of sorghum (Sorghum bicolor L.). We hypothesized that P. stutzeri ISE12 would improve sorghum salt tolerance to salinity, with the extent of the increase in tolerance depending on the genotype's sensitivity to salt stress. Experiments were conducted for two sorghum genotypes differing in salinity tolerance (Pegah - salt tolerant, and Payam - salt sensitive), which were inoculated with a selected bacterium at different salinity concentrations (0, 100, 150, and 200 mM NaCl). For germination, we measured germination percentage and index, mean germination time, vigor, shoot and root length of seedlings, and fresh and dry weight. In pot experiments, we assessed the number of leaves, leaf area, specific leaf area, leaf weight ratio, relative root weight, plantlet shoot and root length, fresh and dry weight, proline and hydrogen peroxide concentrations, and peroxidase enzyme activity. Our study demonstrated that inoculation significantly enhanced germination and growth for both sorghum genotypes. The salinity-sensitive genotype (Payam) responded better to bacterial inoculation during germination and early seedling growth stages, showing approximately 1.4 to 1.8 times greater improvement than the salinity-tolerant genotype (Pegah). Payam also displayed better performance at the plantlet growth stage, between 1.1 and 2.6 times higher than Pegah. Furthermore, inoculation significantly reduced hydrogen peroxide, peroxidase activity, and proline levels in both sorghum genotypes. These reductions were notably more pronounced in Payam, with up to 1.5, 1.3, and 1.5 times greater reductions than in Pegah. These results highlight the efficacy of P. stutzeri ISE12 in alleviating oxidative stress and reducing energy expenditure on defense mechanisms in sorghum, particularly benefiting salt-sensitive genotypes. Our findings highlight the potential of the bacterial endophyte P. stutzeri ISE12 as a valuable bioinoculant to promote sorghum growth under saline conditions.

The effects of Pinus sylvestris L. geographical origin on the community and co-occurrence of fungal and bacterial endophytes in a common garden experiment.

Below-ground microorganisms, particularly endophytes, are pivotal for plant establishment and functioning through nutrient acquisition and enhancing resistance to abiotic and biotic stresses. The impact of host plant origin within a species on the composition and interaction networks of root endophytic fungi and bacteria has been less explored compared with plant phylogeny and biological distance. This study investigates the effect of geographic origin on the fungal and bacterial microbiomes of Pinus sylvestris L. root endophytes. Roots from plants grown in a common garden, originating from six locations, were harvested in two distinct seasons. Fungal and bacterial microbiomes were analyzed using Illumina MiSeq sequencing. The operational taxonomic unit (OTU) richness of endophytic fungi and bacteria showed no significant variation due to tree origin or season. However, the Shannon diversity index for endophytic fungi was seasonally influenced. The composition of endophytic fungal and bacterial communities was affected by both tree origin and season, correlating with host root biochemical parameters, such as starch, total non-structural carbohydrates, carbon, nitrogen, and climatic factors, such as mean annual precipitation and temperature. Moreover, the abundance of specific endophytic fungi and bacteria varied across different P. sylvestris origins, depending on the season. The complexity of the co-occurrence networks of fungal and bacterial endophytes within P. sylvestris also differed by geographical origin and season. This study highlights the significant role of biochemical and climatic factors associated with tree origin in shaping interactions with endophytic communities, potentially affecting plant health and adaptability across diverse environments. IMPORTANCE: This study advances our understanding of how plant ecotype and seasonal changes influence root endophytic communities in Scots pine (Pinus sylvestris). By examining trees from various origins grown in a common garden, it highlights the role of tree origin and season in shaping fungal and bacterial community and co-occurrence networks. Importantly, this research demonstrates that tree origin impacts the composition and interaction networks of root endophytes and depends on the season. The study's findings suggest that root biochemical traits and climatic conditions (e.g., temperature, precipitation) associated with tree origin are crucial in determining the assembly of endophytic communities. This understanding could lead to innovative strategies for enhancing plant health and adaptability across different environments, contributing to forestry and conservation efforts. The research underscores the complexity of plant-microbe interactions and the need for a comprehensive approach to studying them, highlighting the interplay between tree origin and microbial ecology in forest ecosystems.

Microbial Allies in Plastic Degradation: Specific bacterial genera as universal plastic-degraders in various environments.

Microbiological degradation of polymers offers a promising approach for mitigating environmental plastic pollution. This study (i) elucidated the diversity and structure of bacterial microbiomes from distinct environments (landfill soil, sewage sludge, and river water) characterized by specific physicochemical parameters, and (ii) utilized environment-derived microbial cultures enriched with microplastics (MPs) to investigate the degradation of polymers and identify culturable bacterial strains contributing to the plastisphere. We found that alpha diversity was notably higher in river water (∼20%) compared to landfill soil and sewage sludge. Dominant phyla included Pseudomonadota in sewage sludge (39.1%) and water (23.7%), while Actinomycetota prevailed in soil (38.5%). A multistage experiment, involving successive subcultures of environmental microbiomes exposed to polypropylene (PP), polyvinyl chloride (PVC), polycarbonate (PC), and polylactic acid (PLA), facilitated the assessment of MPs degradation processes. Analysis of carbonyl indices CIs and FTIR spectra revealed substantial structural changes in the treatment PVC-landfill soil, as well as in PLA- and PC-sludge enriched cultures. Further, using enriched cultures as a source of microorganisms, the study obtained 17 strains of plastic degraders from landfill soil, 14 from sewage sludge, and 6 from river water. Remarkably, similar bacterial genera were isolated across environmental microbiomes regardless of the MPs substrate used in enriched cultures. Among the 37 identified strains, Pseudomonadota predominated (64.86%) and were accompanied by Bacteroidota (16.22%), Actinomycetota (13.51%), and Bacillota (5.41%). This study highlights the complex relationship between microbiome diversity and the biodegradation efficiency of plastics, showing the potential for using microbial communities in the plastic pollution management.

Metabolic niches in the rhizosphere microbiome: dependence on soil horizons, root traits and climate variables in forest ecosystems.

Understanding belowground plant-microbial interactions is important for biodiversity maintenance, community assembly and ecosystem functioning of forest ecosystems. Consequently, a large number of studies were conducted on root and microbial interactions, especially in the context of precipitation and temperature gradients under global climate change scenarios. Forests ecosystems have high biodiversity of plants and associated microbes, and contribute to major primary productivity of terrestrial ecosystems. However, the impact of root metabolites/exudates and root traits on soil microbial functional groups along these climate gradients is poorly described in these forest ecosystems. The plant root system exhibits differentiated exudation profiles and considerable trait plasticity in terms of root morphological/phenotypic traits, which can cause shifts in microbial abundance and diversity. The root metabolites composed of primary and secondary metabolites and volatile organic compounds that have diverse roles in appealing to and preventing distinct microbial strains, thus benefit plant fitness and growth, and tolerance to abiotic stresses such as drought. Climatic factors significantly alter the quantity and quality of metabolites that forest trees secrete into the soil. Thus, the heterogeneities in the rhizosphere due to different climate drivers generate ecological niches for various microbial assemblages to foster beneficial rhizospheric interactions in the forest ecosystems. However, the root exudations and microbial diversity in forest trees vary across different soil layers due to alterations in root system architecture, soil moisture, temperature, and nutrient stoichiometry. Changes in root system architecture or traits, e.g. root tissue density (RTD), specific root length (SRL), and specific root area (SRA), impact the root exudation profile and amount released into the soil and thus influence the abundance and diversity of different functional guilds of microbes. Here, we review the current knowledge about root morphological and functional (root exudation) trait changes that affect microbial interactions along drought and temperature gradients. This review aims to clarify how forest trees adapt to challenging environments by leveraging their root traits to interact beneficially with microbes. Understanding these strategies is vital for comprehending plant adaptation under global climate change, with significant implications for future research in plant biodiversity conservation, particularly within forest ecosystems.

Colonization of Raphanus sativus by human pathogenic microorganisms.

Contamination of vegetables with human pathogenic microorganisms (HPMOs) is considered one of the most important problems in the food industry, as current nutritional guidelines include increased consumption of raw or minimally processed organic vegetables due to healthy lifestyle promotion. Vegetables are known to be potential vehicles for HPMOs and sources of disease outbreaks. In this study, we tested the susceptibility of radish (Raphanus sativus) to colonization by different HPMOs, including Escherichia coli PCM 2561, Salmonella enterica subsp. enterica PCM 2565, Listeria monocytogenes PCM 2191 and Bacillus cereus PCM 1948. We hypothesized that host plant roots containing bactericidal compounds are less prone to HPMO colonization than shoots and leaves. We also determined the effect of selected pathogens on radish growth to check host plant-microbe interactions. We found that one-week-old radish is susceptible to colonization by selected HPMOs, as the presence of the tested HPMOs was demonstrated in all organs of R. sativus. The differences were noticed 2 weeks after inoculation because B. cereus was most abundant in roots (log10 CFU - 2.54), S. enterica was observed exclusively in stems (log10 CFU - 3.15), and L. monocytogenes and E. coli were most abundant in leaves (log10 CFU - 4.80 and 3.23, respectively). The results suggest that E. coli and L. monocytogenes show a higher ability to colonize and move across the plant than B. cereus and S. enterica. Based on fluorescence in situ hybridization (FISH) and confocal laser scanning microscopy (CLSM) approach HPMOs were detected in extracellular matrix and in some individual cells of all analyzed organs. The presence of pathogens adversely affected the growth parameters of one-week-old R. sativus, especially leaf and stem fresh weight (decreased by 47-66 and 17-57%, respectively). In two-week-old plants, no reduction in plant biomass development was noted. This observation may result from plant adaptation to biotic stress caused by the presence of HPMOs, but confirmation of this assumption is needed. Among the investigated HPMOs, L. monocytogenes turned out to be the pathogen that most intensively colonized the aboveground part of R. sativus and at the same time negatively affected the largest number of radish growth parameters.

Endophytic microbiota and ectomycorrhizal structure of Alnus glutinosa Gaertn. at saline and nonsaline forest sites.

The tolerance of European alder (Alnus glutinosa Gaertn.) to soil salinity can be attributed to symbiosis with microorganisms at the absorptive root level. However, it is uncertain how soil salinity impacts microbial recruitment in the following growing season. We describe the bacterial and fungal communities in the rhizosphere and endosphere of A. glutinosa absorptive roots at three tested sites with different salinity level. We determined the morphological diversity of ectomycorrhizal (ECM) fungi, the endophytic microbiota in the rhizosphere, and the colonization of new absorptive roots in the following growing season. While bacterial diversity in the rhizosphere was higher than that in the absorptive root endosphere, the opposite was true for fungi. Actinomycetota, Frankiales, Acidothermus sp. and Streptomyces sp. were more abundant in the endosphere than in the rhizosphere, while Actinomycetota and Acidothermus sp. dominated at saline sites compared to nonsaline sites. Basidiomycota, Thelephorales, Russulales, Helotiales, Cortinarius spp. and Lactarius spp. dominated the endosphere, while Ascomycota, Hypocreales and Giberella spp. dominated the rhizosphere. The ECM symbioses formed by Thelephorales (Thelephora, Tomentella spp.) constituted the core community with absorptive roots in the spring and further colonized new root tips during the growing season. With an increase in soil salinity, the overall fungal abundance decreased, and Russula spp. and Cortinarius spp. were not present at all. Similarly, salinity also negatively affected the average length of the absorptive root. In conclusion, the endophytic microbiota in the rhizosphere of A. glutinosa was driven by salinity and season, while the ECM morphotype community was determined by the soil fungal community present during the growing season and renewed in the spring.

Evaluation of probiotic growth stimulation using prebiotic ingredients to optimize compounds for in ovo delivery.

The use of probiotics, prebiotics and synbiotics in poultry diets beneficially stimulates the gut microbiome thus promoting the health and welfare of the animals. In this study, we analyzed 7 poultry probiotics (Lactobacillus plantarum - B1 and B4, Lactobacillus rhamnosus - B3, Bifidobacterium lactis - B2, Carnobacterium divergens - B5, Propionibacterium thoenii - B6, Clostridium butyricum - B7) and 12 prebiotics, differing in chemical composition and source of origin (fungi, algae, animal, etc.). The main goal of our research was to select the most promising candidates to develop synbiotic combinations. We determined the growth kinetics of all probiotics in the presence of prebiotics in a series of in vitro studies to select optimal combinations. Five out of seven investigated probiotics were significantly stimulated by astragalus polysaccharide, and this prebiotic was characterized in our work as the most effective. Moreover, in the case of three probiotics, B2, B3 and B4, significant growth stimulation has been found when beta-glucan, vegetable protein hydrolysate and liquid seaweed extract were supplied. Strain B1 (L. plantarum) was stimulated by 6 out of 12 prebiotics. The growth of B4 (L. plantarum) and B2 (B. lactis) was enhanced by prebiotics after 2 h of incubation. A high growth rate of 3.13% was observed in the case of L. plantarum (B4) and a 3.37% higher rate for B. lactis (B3), compared to the growth of probiotics in the control medium with glucose but no prebiotics. The best candidates for synbiotic combinations based on this in vitro work are the strains belonging to L. plantarum (B4), L. rhamnosus (B3) and B. lactis (B2), consistent with prebiotics such as astragalus polysaccharides and vegetable protein hydrolysate. These combinations will be subject to future in vivo poultry trials involving the in ovo microbiome modulation.

Trichoderma viride Colonizes the Roots of Brassica napus L., Alters the Expression of Stress-Responsive Genes, and Increases the Yield of Canola under Field Conditions during Drought.

In this work, we present the results of the inoculation of canola seeds (Brassica napus L.) with Trichoderma viride strains that promote the growth of plants. Seven morphologically different strains of T. viride (TvI-VII) were shown to be capable of synthesizing auxins and exhibited cellulolytic and pectinolytic activities. To gain a deeper insight into the molecular mechanisms underlying canola-T. viride interactions, we analyzed the canola stress genes metallothioneins (BnMT1-3) and stringent response genes (BnRSH1-3 and BnCRSH). We demonstrated the presence of cis-regulatory elements responsive to fungal elicitors in the promoter regions of B. napus MT and RSH genes and observed changes in the levels of the transcripts of the above-mentioned genes in response to root colonization by the tested fungal strains. Of the seven tested strains, under laboratory conditions, T. viride VII stimulated the formation of roots and the growth of canola seedlings to the greatest extent. An experiment conducted under field conditions during drought showed that the inoculation of canola seeds with a suspension of T. viride VII spores increased yield by 16.7%. There was also a positive effect of the fungus on the height and branching of the plants, the number of siliques, and the mass of a thousand seeds. We suggest that the T. viride strain TvVII can be used in modern sustainable agriculture as a bioinoculant and seed coating to protect B. napus from drought.

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.

AMF species do matter: Rhizophagus irregularis and Funneliformis mosseae affect healthy and PVY-infected Solanum tuberosum L. in a different way.

Arbuscular mycorrhizal fungi (AMF) were documented to positively influence plant growth and yield, which is extremely important for the production of many crops including potato. However, the nature of the interaction between arbuscular mycorrhiza and plant virus that share the same host is not well characterized. In this study, we examined the effect of different AMF, Rhizophagus irregularis and Funneliformis mosseae, on healthy and potato virus Y (PVY)-infected Solanum tuberosum L. The analyses conducted included the measurement of potato growth parameters, oxidative stress indicators, and photosynthetic capacity. Additionally, we evaluated both the development of AMF in plant roots and the virus level in mycorrhizal plants. We found that two AMF species colonized plant roots to varying degrees (ca. 38% for R. irregularis vs. 20% for F. mosseae). Rhizophagus irregularis had a more positive effect on potato growth parameters, causing a significant increase in the total fresh and dry weight of tubers, along with virus-challenged plants. Furthermore, this species lowered hydrogen peroxide levels in PVY-infected leaves and positively modulated the levels of nonenzymatic antioxidants, i.e., ascorbate and glutathione in leaves and roots. Finally, both fungal species contributed to reduced lipid peroxidation and alleviation of virus-induced oxidative damage in plant organs. We also confirmed an indirect interaction between AMF and PVY inhabiting the same host. The two AMF species seemed to have different abilities to colonize the roots of virus-infected hosts, as R. irregularis showed a stronger drop in mycorrhizal development in the presence of PVY. At the same time, arbuscular mycorrhiza exerted an effect on virus multiplication, causing increased PVY accumulation in plant leaves and a decreased concentration of virus in roots. In conclusion, the effect of AMF-plant interactions may differ depending on the genotypes of both symbiotic partners. Additionally, indirect AMF-PVY interactions occur in host plants, diminishing the establishment of arbuscular mycorrhiza while changing the distribution of viral particles in plants.

Selection of microorganisms capable of polyethylene (PE) and polypropylene (PP) degradation.

Microorganisms degrade microplastics, but their potential is still not fully exploited, e.g., due to inadequate selection of microorganisms. We developed an effective selection method of microorganisms capable of polyethylene (PE) and polypropylene (PP) degradation and assessed the scale of polymer degradation by microbial populations. We isolated seven bacterial strains (three Priestia megaterium strains, Klebsiella pneumoniae, Pseudomonas fluorescens, Enterobacter ludwigii, Chryseobacterium sp.) and seven fungal strains (four Fusarium spp., two Lecanicillium spp. and Trichoderma sp.) with PE degradation potential, as well as seven bacterial strains (five Serratia marcescens and two Enterobacter spp.) and six fungal strains (four Aspergillus spp., Fusarium oxysporum and Penicillium granulatum) with PP degradation ability. Scanning electron microscopy (SEM) analysis confirmed the presence of a biofilm and revealed surface changes in both PE and PP pellets, but the greatest changes (microcracks and corrugations) were observed for PP incubated with bacteria. Fourier transform infrared (FTIR) spectroscopy confirmed the structural changes on the studied polymer surfaces. In conclusion, the isolation of plastic-degrading bacteria and fungi from waste landfills represents an effective strategy for the collection of microorganisms with high potential for PE and PP degradation. The bacteria and fungi revealed better potential for PP degradation and PE degradation, respectively.

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. dasyclados cv. 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.

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 × 10-9 g·mm·Pa-1·h-1·mm-2) and the highest opacity (3.41 mm-1). The QUick, Easy, New, CHEap and Reproducible (QUENCHER) methodologies using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-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 8-144%. 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.

Pseudomonas stutzeri and Kushneria marisflavi Alleviate Salinity Stress-Associated Damages in Barley, Lettuce, and Sunflower.

Soil salinity is one of the most important abiotic factors limiting plant productivity. The aim of this study was to determine the effect of selected halotolerant plant growth-promoting endophytes (PGPEs, Pseudomonas stutzeri ISE12 and Kushneria marisflavi CSE9) on the growth parameters of barley (Hordeum vulgare), lettuce (Lactuca sativa), and sunflower (Helianthus annuus) cultivated under salt stress conditions. A negative effect of two higher tested salinities (150 and 300 mM NaCl) was observed on the growth parameters of all investigated plants, including germination percentage and index (decreasing compared to the non-saline control variant in the ranges 5.3-91.7 and 13.6-90.9%, respectively), number of leaves (2.2-39.2%), fresh weight (24.2-81.6%); however, differences in salt stress tolerance among the investigated crops were observed (H. annuus > H. vulgare > L. sativa). Our data showed that the most crucial traits affected by endophyte inoculation under salt stress were chlorophyll concentration, leaf development, water storage, root development, and biomass accumulation. Thus, the influence of endophytes was species specific. K. marisflavi CSE9 promoted the growth of all tested plant species and could be considered a universal PGPEs for many plant genotypes cultivated under saline conditions (e.g., increasing of fresh weight compared to the non-inoculated control variant of barley, lettuce, and sunflower in the ranges 11.4-246.8, 118.9-201.2, and 16.4-77.7%, respectively). P. stutzeri ISE12 stimulated growth and mitigated salinity stress only in the case of barley. Bioaugmentation of crops with halotolerant bacterial strains can alleviate salt stress and promote plant growth; however, the selection of compatible strains and the verification of universal plant stress indicators are the key factors.

Potential of Serratia plymuthica IV-11-34 strain for biodegradation of polylactide and poly(ethylene terephthalate).

Serratia plymuthica strain IV-11-34 belongs to the plant growth promoting bacteria (PGPR). In the sequenced genome of S. plymuthica IV-11-34, we have identified the genes involved in biodegradation and metabolisms of xenobiotics. The potential of S. plymuthica IV-11-34 for the degradation of biodegradable aliphatic polyester polylactide (PLA) and resistant to biodegradation - poly(ethylene terephthalate) (PET) was assessed by biochemical oxygen consumption (BOD) and carbon dioxide methods. After seven days of growth, the bacteria strain showed more than 80% and 60% increase in respiratory activity in the presence of PLA and PET, respectively. We assume that during biodegradation, S. plymuthica IV-11-34 colonise the surface of PLA and PET, since the formation of a biofilm on the surface of polymers was shown by the LIVE/DEAD method. We have demonstrated for the relA gene, which is an alarmone synthetase, a 1.2-fold increase in expression in the presence of PLA, and a 4-fold decrease in expression in the presence of PET for the spoT gene, which is a hydrolase of alarmones. Research has shown that the bacterium has the ability to biodegrade PLA and PET, and the first stage of this process involves bacterial stringent response genes responsible for survival under extreme conditions.

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.

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.

Choosing source of microorganisms and processing technology for next generation beet bioinoculant.

The increase of human population and associated increasing demand for agricultural products lead to soil over-exploitation. Biofertilizers based on lyophilized plant material containing living plant growth-promoting microorganisms (PGPM) could be an alternative to conventional fertilizers that fits into sustainable agricultural technologies ideas. We aimed to: (1) assess the diversity of endophytic bacteria in sugar and sea beet roots and (2) determine the influence of osmoprotectants (trehalose and ectoine) addition during lyophilization on bacterial density, viability and salt tolerance. Microbiome diversity was assessed based on 16S rRNA amplicons sequencing, bacterial density and salt tolerance was evaluated in cultures, while bacterial viability was calculated by using fluorescence microscopy and flow cytometry. Here we show that plant genotype shapes its endophytic microbiome diversity and determines rhizosphere soil properties. Sea beet endophytic microbiome, consisting of genera characteristic for extreme environments, is more diverse and salt resistant than its crop relative. Supplementing osmoprotectants during root tissue lyophilization exerts a positive effect on bacterial community salt stress tolerance, viability and density. Trehalose improves the above-mentioned parameters more effectively than ectoine, moreover its use is economically advantageous, thus it may be used to formulate improved biofertilizers.

Transcriptome profiling and environmental linkage to salinity across Salicornia europaea vegetation.

BACKGROUND: Salicornia europaea, a succulent obligatory halophyte is the most salt-tolerant plant species in the world. It survives salt concentrations of more than 1 M. Therefore, it is a suitable model plant to identify genes involved in salt tolerance mechanisms that can be used for the improvement of crops. The changes in a plant's gene expression in response to abiotic stresses may depend on factors like soil conditions at the site, seasonality, etc. To date, experiments were performed to study the gene expression of S. europaea only under controlled conditions. Conversely, the present study investigates the transcriptome and physicochemical parameters of S. europaea shoots and roots from two different types of saline ecosystems growing under natural conditions. RESULTS: The level of soil salinity was higher at the naturally saline site than at the anthropogenic saline site. The parameters such as ECe, Na+, Cl-, Ca+, SO42- and HCO3- of the soils and plant organs significantly varied according to sites and seasons. We found that Na+ mainly accumulated in shoots, whereas K+ and Ca2+ levels were higher in roots throughout the growing period. Moreover, changes in S. europaea gene expression were more prominent in seasons, than sites and plant organs. The 30 differentially expressed genes included enzymes for synthesis of S-adenosyl methionine, CP47 of light-harvesting complex II, photosystem I proteins, Hsp70 gene, ATP-dependent Clp proteases, ribulose bisphosphate carboxylase/oxygenase (Rubisco), phenylalanine ammonia-lyase (PAL), cytochrome c oxidase (COX) and ATP synthase. CONCLUSION: The comparisons made based on two seasons, plant organs and two different sites suggest the importance of seasonal variations in gene expression of S. europaea. We identify the genes that may play an important role in acclimation to season-dependent changes of salinity. The genes were involved in processes such as osmotic adjustment, energy metabolism and photosynthesis.

Salicornia europaea L. as an underutilized saline-tolerant plant inhabited by endophytic diazotrophs.

Despite the great interest in using halophyte Salicornia europaea L. as a crop in extreme saline habitats, little is known about the role played by associated endophytic bacteria in increasing tolerance of the host-plant to nutrient deficiency. Main objectives of this study were to investigate the community composition of diazotrophic endophytes of S. europaea grown under natural conditions, and determine the proportion of plant-growth promoting bacterial strains able to fix N2. To quantify the abundance of diazotrophic bacterial endophytes in stems and roots of S. europaea, nifH gene and 16S rDNA copy numbers were assessed by quantitative real-time PCR, and characterized the taxonomic structure of cultivable bacteria based on selective medium for diazotrophs. The highest copy numbers of nifH and 16S rDNA were observed in the stems of plants growing at the test site characterized by lower salinity, and correlated with high N concentrations in plant tissues. The abundance of bacterial diazotrophs isolated from plant tissues ranged from 3.6 to 6.3 (log10 of cfu per gram dry plant tissue) and varied in a site- and plant-organ manner. Proteobacteria dominated in plants growing in lower salinity while Actinobacteria prevailed in plants originating from higher salinity, what suggest better adaptation of this group of bacteria to extreme salinity. The results provide insights into new species of diazotrophs associated with halophytes that can be used to optimize strategies for selecting biostimulants useful in saline soils.