Search Results (241)

This study aims to identify and evaluate the phosphate-solubilizing ability of endophytic bacteria isolated from roots of Chinese Cymbidium and to assess their impact on phosphorus uptake and plant growth. Thirty strains of endophytic bacteria were isolated from six orchid varieties. Molecular identification based on 16S rRNA gene sequencing revealed that the most frequently isolated strains belonged to the genera Pseudomonas and Burkholderia. Among them, 10 bacterial strains exhibited the capacity to solubilize inorganic and organic phosphorus. Two strains, designated X1 (Paraburkholderia sp. Beta-32) and X13 (Rhizobium freirei PRF81 (X13), were identified as the most effective phosphate-solubilizing bacteria (PSB). Gluconic acid was the dominant organic acid secreted, driving inorganic phosphorus solubilization, while alkaline phosphatase activities facilitated organic phosphorus mineralization. Inoculation with phosphate-solubilizing bacteria (PSB) resulted in increased plant growth and phosphorus content in both leaves and roots as compared to the control plants. PSB treatments also increased available phosphorus content in soil, reduced total phosphorus content, and increased exopolysaccharide and alkaline phosphatase activities. Real-time q-PCR analysis showed that PSB inoculation significantly upregulated the expression of phosphorus transport-related genes, including PDR2, PHF1, PHR1, PHT1;9, and PHT4;4, thereby enhancing phosphorus absorption. Moreover, strains X1 and X13 not only exhibited strong phosphate-solubilizing capacity but also demonstrated stable colonization in both roots and root rhizosphere soil of orchids over extended periods. In conclusion, the endophytic PSB identified with phosphate-solubilizing abilities increased phosphorus availability and its uptake in Chinese Cymbidium, thereby promoting plant growth and development. This is the first attempt to characterize endophytic PSB from roots of Chinese Cymbidium orchids. These findings provide a basis for selection of PSB that are efficient in P uptake for application in microbial fertilizers for orchid cultivation. Full article

Halophilic isolates were screened to mitigate postharvest losses caused by citrus canker disease in lemon fruits. Among all isolates, SWIS03, isolated from the Sambhar Salt Lake in Rajasthan, India, exhibited the highest exopolysaccharide production, with good stability and antibacterial activity against Xanthomonas citri. Isolate SWIS03 was identified as halophilic Bacillus licheniformis DET601. It produced a very high EPS content in optimized sterilized seawater-based minimal media fortified with 2.5% sucrose and 0.3% beef extract, which was purified through repeated deproteinization and Sephadex G-75 chromatography. HPTLC analysis of composition check indicated the presence of glucose, mannose, and galactose. FTIR analysis also confirmed the presence of sugar and bound water, as well as the presence of hydroxyl, amine, amide, and methyl groups. Rheological characterization revealed a pseudoplastic nature, making it suitable for uniform coating. EPS was reported to have bioactive properties, including antioxidant activity (84.7 ± 1.75% DPPH scavenging potential), antimicrobial activity against human pathogens, and a noncytotoxic nature, which are essential for use in edible coatings. The effect of EPS coating formulation on healthy lemon fruits resulted in shelf-life extension of up to 26.6 ± 1.14 days and 18.0 ± 1.41 days at 4 °C and 30 °C in coated lemons, respectively, as demonstrated by physiological parameters such as % weight loss, firmness, titratable acidity, and shelf life of lemons. Also, EPS coating preserved the quality of fruits in terms of phenolic compounds and Vitamin C content, and reduced lipid peroxidation during storage. Biocontrol potential of halophilic EPS coating on lemon fruits revealed an 86.50% and 68.64% reduction in % disease incidence compared to uncoated fruits at 4 °C and 30 °C, respectively. Similarly, a significantly lower disease incidence (46.80% at 4 °C and 67.03% at 30 °C) was also reported compared to paraffin-coated (positive control) lemons. Consequently, halophilic Bacillus licheniformis DET601 EPS is an effective coating material for citrus fruits to prevent canker disease in post-harvest settings for agricultural and food industry applications. Full article

The use of plant growth-promoting bacteria (PGPB) tolerant to abiotic stress factors can enhance plant performance when applied under both optimal and stress conditions in crops. In this study, bacterial strains associated with the rhizosphere of the halophyte Distichlis spicata were isolated and characterized for their ability to produce siderophores, solubilize phosphate, synthesize indole-3-acetic acid (IAA) and exopolysaccharides (EPS), and tolerate salinity. IAA production and antioxidant capacity were further assessed under saline stress. As expected, salinity negatively impacted bacterial growth, IAA biosynthesis, and antioxidant activity—even in strains from a salt-tolerant plant. Nevertheless, all strains except RD2 maintained growth and IAA production in LB broth supplemented with up to 1 M NaCl. Five halotolerant strains (RD2, RD4, RD17, RD26, and RD27) were selected for greenhouse inoculation assays in tomato (Solanum lycopersicum) seedlings. Inoculation with RD26 significantly enhanced seedling performance, promoting tomato growth, increasing leaf area by 22%, stem diameter by 17%, shoot dry biomass by 30%, and root biomass by 27% as compared to the uninoculated control. RD27 and RD4 also improved shoot biomass by 25 and 23%, respectively. Based on 16S rRNA gene sequencing, RD26 was identified as Pseudomonas sp. and RD27 as Zhihengliuella halotolerans. These findings demonstrate that salt stress impairs plant growth-promoting traits in rhizospheric bacteria, yet selected strains such as RD26 and RD27 can significantly promote plant growth. Their use as bioinoculants represents a promising strategy for improving crop performance in saline environments. Full article

The bacterial phylum Verrucomicrobiota accommodates free-living and symbiotic microorganisms, which inhabit a wide range of environments and specialize in polysaccharide degradation. Due to difficulties in cultivation, much of the currently available knowledge about these bacteria originated from cultivation-independent studies. A phylogenetic clade defined by the free-living bacterium from oilsands tailings pond, Oleiharenicola alkalitolerans, and the symbiont of the tunicate Lissoclinum sp., Candidatus Didemniditutus mandelae, is a poorly studied verrucomicrobial group. This clade includes two dozen methagenome-assembled genomes (MAGs) retrieved from aquatic and soil habitats all over the world. A new member of this clade, strain Vm1, was isolated from a methane-fed laboratory bioreactor with a Methylococcus-dominated methane-oxidizing consortium and characterized in this study. Strain Vm1 was represented by ultra-small, motile cocci with a mean diameter of 0.4 µm that grew in oxic and micro-oxic conditions at temperatures between 20 and 42 °C. Stable development of strain Vm1 in a co-culture with Methylococcus was due to the ability to utilize organic acids excreted by the methanotroph and its exopolysaccharides. The finished genome of strain Vm1 was 4.8 Mb in size and contained about 4200 predicted protein-coding sequences, including a wide repertoire of CAZyme-encoding genes. Among these CAZymes, two proteins presumably responsible for xylan and arabinan degradation, were encoded in several MAGs of Vm1-related free-living verrucomicrobia, thus offering an insight into the reasons behind wide distribution of these bacteria in the environment. Apparently, many representatives of the Oleiharenicola–Candidatus Didemniditutus clade may occur in nature in trophic associations with methanotrophic bacteria, thus participating in the cycling of methane-derived carbon. Full article

This review explores the biofilm architecture and drug resistance of Enterococcus faecalis in clinical and environmental settings. The biofilm in E. faecalis is a heterogeneous, three-dimensional, mushroom-like or multilayered structure, characteristically forming diplococci or short chains interspersed with water channels for nutrient exchange and waste removal. Exopolysaccharides, proteins, lipids, and extracellular DNA create a protective matrix. Persister cells within the biofilm contribute to antibiotic resistance and survival. The heterogeneous architecture of the E. faecalis biofilm contains both dense clusters and loosely packed regions that vary in thickness, ranging from 10 to 100 µm, depending on the environmental conditions. The pathogenicity of the E. faecalis biofilm is mediated through complex interactions between genes and virulence factors such as DNA release, cytolysin, pili, secreted antigen A, and microbial surface components that recognize adhesive matrix molecules, often involving a key protein called enterococcal surface protein (Esp). Clinically, it is implicated in a range of nosocomial infections, including urinary tract infections, endocarditis, and surgical wound infections. The biofilm serves as a nidus for bacterial dissemination and as a reservoir for antimicrobial resistance. The effectiveness of first-line antibiotics (ampicillin, vancomycin, and aminoglycosides) is diminished due to reduced penetration, altered metabolism, increased tolerance, and intrinsic and acquired resistance. Alternative strategies for biofilm disruption, such as combination therapy (ampicillin with aminoglycosides), as well as newer approaches, including antimicrobial peptides, quorum-sensing inhibitors, and biofilm-disrupting agents (DNase or dispersin B), are also being explored to improve treatment outcomes. Environmentally, E. faecalis biofilms contribute to contamination in water systems, food production facilities, and healthcare environments. They persist in harsh conditions, facilitating the spread of multidrug-resistant strains and increasing the risk of transmission to humans and animals. Therefore, understanding the biofilm architecture and drug resistance is essential for developing effective strategies to mitigate their clinical and environmental impact. Full article

Plant growth-promoting rhizobacteria (PGPR) are eco-friendly and sustainable options for agrochemicals, particularly for enhancing crop productivity under stress conditions. The present research aims to isolate and characterize native PGPR from tomato rhizospheric soil and to evaluate their effectiveness as a dose-dependent response to enhance the growth of tomato seedlings. Out of 112 isolates, 10 bacterial strains were selected based on key PGPR traits, including indole-3-acetic acid (IAA), ammonia production, hydrogen cyanide (HCN), exopolysaccharide (EPS) synthesis, hydrolytic enzyme activity, potassium solubilization, antifungal activity against Fusarium oxysporum, and tolerance to pH and heat stress. Molecular identification via 16S rRNA gene sequencing confirmed that these isolates belong to the genera Serratia and Enterobacter. S. marcescens So-1 and Enterobacter sp. So-12 produced the highest levels of IAA (2.6–24.1 µg/mL). In vitro tomato seed germination tests using bacterial suspensions at three concentrations (10⁶, 10⁷, and 10⁸ CFU/mL) showed dose-dependent improvements, with T1 increasing germination up to 108.3% compared to the control. In polyhouse trials using cocopeat formulations, seedling growth improved noticeably. T2 increased the root length (28.3 ± 2.98 cm) by over 1560%, and the shoot length (35.7 ± 0.57 cm) increased by 55% against the control, whose root length is 1.7 ± 0.47. The chlorophyll amount of the treated leaves further showed significant results over the control. Collectively, these findings suggest that using native PGPR in a dose-dependent way can help tomato seedlings grow better and promote more sustainable crop production. Full article

The genus Xanthomonas (family Xanthomonadaceae) comprises 39 validly published species and is associated with a broad host range, infecting hundreds of monocot and dicot plants worldwide. While many Xanthomonas species are notorious for causing leaf spot and blight diseases in major agricultural crops, less attention has been given to their impact on ornamental plants. In Hawaii and other key production regions, xanthomonads have posed persistent threats to popular ornamentals in the Araceae and Araliaceae families. This review synthesizes the evolving phylogenetic and taxonomic framework of Xanthomonas strains isolated from Araceae and Araliaceae, highlighting recent advances enabled by multilocus sequence analysis and whole genome sequencing. We discuss the reclassification of key pathovars, unresolved phylogenetic placements, and the challenges of pathovar delineation within these plant families. Additionally, we examine current knowledge of molecular determinants of pathogenicity, including gene clusters involved in exopolysaccharide and lipopolysaccharide biosynthesis, flagellar assembly, cell-wall-degrading enzymes, and secretion systems (types II, III, and VI). Comparative genomics and functional studies reveal that significant gaps remain in our understanding of the genetic basis of host adaptation and virulence in these xanthomonads. Addressing these knowledge gaps will be crucial for developing effective diagnostics and management strategies for bacterial diseases in ornamental crops. Full article

Heparin, a widely used polysaccharidic anticoagulant of animal origin, is associated with risks of contamination and adverse effects, notably bleeding and thrombocytopenia. These limitations have prompted interest in alternative sulfated polysaccharides with anticoagulant properties and improved safety profiles. This study explored the anticoagulant potential of two marine bacterial exopolysaccharides (EPS), infernan and diabolican. It assessed whether chemical modifications (depolymerization, oversulfation) could enhance their anticoagulant properties compared to unfractionated and low molecular weight heparins. Native EPS were depolymerized to generate different molecular weights and then chemically oversulfated to increase negative charge density. Anticoagulant activities were evaluated using clotting and thrombin generation assays (TGA). Molecular docking was performed to model interactions with antithrombin and heparin cofactor II. Only highly sulfated derivatives significantly prolonged activated partial thromboplastin time while showing negligible effect on thrombin time and anti-factor Xa activity. They present different structures, and their binding to antithrombin is not achieved via the classic pentasaccharide motif. In TGA, these derivatives inhibited thrombin formation at higher doses than heparin but induced a marked delay in clot generation. Docking analyses supported their ability to bind serpins, albeit with lower specificity than heparin. Their limited anti-Xa activity and non-animal origin position them as promising anticoagulant candidates. Full article

Aims: Soil compaction is one of the main challenges in agriculture, negatively affecting cotton growth (Gossypium hirsutum L.), nutrition, and productivity. This study evaluated the efficacy of plant growth-promoting bacteria (PGPB), Exiguobacterium sibiricum, and Pantoea vagans in mitigating the effects of different soil compaction levels (65%, 75%, 85%, and 95%) on cotton performance. Methods: Parameters such as plant height, stem diameter, number of leaves, shoot dry matter (SDM), and nutrient content in leaves, stems, and roots were assessed. The methodology included variance analysis and mean clustering to identify significant differences among treatments using R software. Results: The results indicated that PGPB inoculation improved plant growth and nutrition even under high compaction levels. Cotton height increased by up to 45% in compacted soils (95%), while stem diameter and SDM also showed significant gains. Foliar nutrient levels of N (37.2 g kg⁻¹), Ca, and Mg remained within the adequate range for cotton cultivation, reflecting the efficiency of PGPB in enhancing nutrient absorption. Under severe compaction, Ca accumulation dropped to 18.2 g kg⁻¹, highlighting the physical constraints imposed on the roots; however, the bacterial action mitigated this impact. Additionally, bacterial strains increased the availability of N and P in the soil due to their ability to fix nitrogen, solubilize phosphates, and produce exopolysaccharides that improve soil structure. Conclusions: In conclusion, inoculation with Exiguobacterium sibiricum and Pantoea vagans is an effective strategy to mitigate the impacts of soil compaction on cotton. These bacteria promote plant growth and nutrition and enhance the soil’s physical and biological properties. Full article

Egypt’s rapid population increase has resulted in higher water demand. It may significantly reduce the amount of water available for agriculture, increasing the chance of using saline water in agriculture. Using saline water certainly poses a major threat to maize growth and may severely affect the growth and productivity of this important crop. Therefore, the aim of this study was to isolate newly native salt-tolerant bacteria from Egyptian saline soils and assess their ability to produce growth-promoting substances under salinity stress, as well as test the mitigating impact of these isolated salt-tolerant bacteria along with arbuscular mycorrhizal fungi (AMF) in maize plants under salinity stress. We isolated ninety-seven salt-tolerant bacterial isolates, and these isolates show a high ability to grow under different concentrations of NaCl. The nine most efficient isolates show a high ability to produce indole acetic acid (IAA), gibberellic acid (GA), P-solubilized exopolysaccharides (EPS), proline, and antioxidants under different NaCl concentrations. Using the 16S rRNA gene, the most effective isolate STB 89 was identified, and its impact, along with AMF, on the growth of salinity-stressed maize was tested in a pot experiment. Our results showed that the growth parameters (shoot length, root length, dry weight, and leaf area), photosynthetic-related pigments (Chlorophyll a, b, and carotenoids), NPK content, and antioxidant enzymes (PPO, POX, and CAT) were improved significantly at p ≤ 0.05 due to the bioinoculant applications, while reduced proline accumulation, Na uptake, and the Na⁺/K⁺ ratio in maize plant tissues were observed compared to the control plants. Moreover, the indices of AMF colonization in maize roots and the count of bacteria in the rhizosphere were enhanced due to the bioinoculant applications under salinity stress. In addition, we found that the combined application was more pronounced than the individual application impact. Hence, our results recommended that salt-tolerant bacteria (STB 89) could support salinity, mitigating the impact of AMF in maize plants, as well as allowing better practical techniques for maize cultivation and soil sustainability under salinity stress. Full article

Vibrio harveyi, a pathogenic vibrio, is ubiquitous and the most prevalent disease infecting tropical and subtropical mariculture animals in marine and estuarine environments. It presents a major risk to mariculture companies worldwide and can cause serious disease problems in aquaculture. Recent studies have shown that various pathogens employ post-translational modifications (PTMs) to regulate cellular processes. One of the major PTMs is lysine succinylation, which is widespread in eukaryotic and prokaryotic cells. Many basic biological functions of bacteria are associated with the regulation of lysine (K) succinylation (Ksuc). However, little is known about the role of lysine succinylation in V. harveyi pathogenesis. Here, we performed LC-MS/MS analysis of 1271 proteins from V. harveyi to identify 4252 Ksuc modification sites. The modification of S-ribosylhomocysteine lyase (LuxS) and transcription elongation factor GreA proteins by Ksuc was confirmed through immunoprecipitation combined with Western blot, further validating our proteomics results. Bioinformatics study revealed that the identified Ksuc proteins play roles in multiple cellular processes and vital metabolic pathways, including LuxS, biofilm exopolysaccharide biosynthesis protein EpsG, and the general secretory system (Sec systems), and are proteins that regulate bacterial virulence. Generally, this scientific study serves as the basis for additional research on the pathogenic nature of Ksuc in V. harveyi and reveals potential targets that would accelerate the manufacturing of attenuated vaccines. Full article

Climate-change-induced drought threatens forest restoration by limiting seedling establishment. To address this, we developed synthetic bacterial communities (SynComs) tailored to support drought tolerance in two Mediterranean tree species, Quercus pubescens and Sorbus domestica. Bacteria were isolated from forest soil exposed to long-term drought, sampling across soil depths and root-associated compartments. We selected strains with key plant-beneficial traits, including exopolysaccharide (EPS) production, hormone synthesis (auxin, ABA), siderophore release, and osmotic tolerance. SynComs were assembled based on functional complementarity and ecological origin. Biofilm assays showed that even weak individual producers could enhance community-level performance. After initial screening on Arabidopsis thaliana, the most and least effective SynComs were tested on Q. pubescens and S. domestica seedlings. Compared to controls, the best-performing SynComs reduced the proportion of drought-symptomatic seedlings by 47% in Q. pubescens and 71% in S. domestica, outperforming single-strain inoculants. Notably, EPS-rich SynCom B aligned with the conservative root traits of Q. pubescens, while hormone-rich SynCom F matched the acquisitive strategy of S. domestica. Predictive modeling identified bacterial identity and symptom timing as key predictors of drought resilience. Our results highlight the value of matching microbial traits with plant strategies and drought context for climate-smart forest restoration. Full article

Phycosphere niches host rich, unique microbial consortia that harbor complex algae–bacteria interactions with fundamental significance in underpinning most functions of aquatic ecological processes. Therefore, harvesting the uncultured phycobacteria is crucial for understanding the intricate mechanisms governing these dynamic interactions. Here, we characterized and compared microbial community composition of the phycosphere microbiota from six harmful algal bloom-forming marine dinoflagellates, Alexandrium spp., and their bacterial associations. Furthermore, based on a combinational enhanced cultivation strategy (CECS) procedure for the selected isolation for cultivable phycobacteria, a new yellow-pigmented bioactive bacterium designated ABI-6-9 was successfully recovered from cultivable phycobacteria of the highly toxic A. minutum strain amtk4. An additional phylogenomic analysis fully identified this new isolate as a potential novel species of the genus Mameliella within the family Roseobacteraceae. The bioactivity evaluation observed that strain ABI-6-9 can significantly promote the cell growth of its algal host and altered the gonyautoxin accumulation profiles in the co-culture circumstance. Additionally, the bacterial production of active bioflocculanting exopolysaccharides (EPSs) by strain ABI-6-9 was also measured after culture optimization. Thus, these findings revealed the potential environmental and biotechnological implications of this new microalgae growth- promoting phycobacterium. Full article

Photothermal therapy combines the effects of near-infrared laser (NIR laser) and strong light-absorbing materials to combat pathogens and unwanted biofilms. Graphene derivatives have a negative effect on microorganisms, and the combination of NIR laser irradiation and carbon nanomaterials (CNMs) can enhance their antibacterial effect. This investigation is devoted to the determination of the expression level of bacterial stress response genes (soxS and rpoS) under graphene oxide (GO), reduced graphene oxide (rGO), and NIR laser irradiation (1270 nm). GO, rGO and NIR laser irradiation separately and irradiation in the presence of graphene derivatives cause an increase in the expression level of rpoS associated with the general stress response of bacteria. GO and rGO do not change the expression level of soxS associated with the cell response to oxidative stress, and decrease it in the presence of a strong oxidizing agent paraquat (PQ). The expression of soxS increases under laser irradiation, but decreases under NIR laser irradiation in combination with graphene derivatives. The effect of GO, rGO, and NIR laser irradiation on the formation and eradication of E. coli biofilms was studied. NIR laser with GO and rGO suppresses the metabolic rate and decreases the intracellular ATP content by 94 and 99.6%, respectively. CNMs are shown to reduce biofilm biomass and the content of extracellular polymeric substances (EPSs), both exopolysaccharides and protein in the biofilm matrix. Graphene derivatives in combination with NIR laser irradiation may be an effective means of combating emerging and mature biofilms of Gram-negative bacteria. Full article

Bacillus halotolerans, a halophilic bacterial species of the genus Bacillus, is emerging as a biological control agent with immense potential for sustainable agriculture, particularly in extreme conditions and environmental rehabilitation. This review summarizes the current state of research on B. halotolerans, emphasizing its diverse applications in the biocontrol of plant pathogens, plant growth promotion under salinity stress, nematode management, and bioremediation. B. halotolerans utilizes several mechanisms such as the production of siderophores and phytohormones, secretion of exopolysaccharides, and the release of antifungal and nematicidal compounds, which allows it to mitigate both abiotic and biotic stresses in various crops, including wheat, rice, date palm, tomato, and others. In addition, genomic and metabolomic analyses have revealed its potential for secondary metabolite production that improves its antagonistic and growth-promoting traits. Despite significant progress, challenges remain in translating laboratory results into field applications. Future research should focus on formulating effective bioinoculants and field trials to maximize the practical utility of B. halotolerans for sustainable agriculture and environmental resilience. Full article