Search Results (243)

This study is Part II of a five-year (2018–2022) field trial in western Portugal evaluating the effects of three microbial biofertilizers—Mycoshell^® (Glomus spp. + humic/fulvic acids), Kiplant iNmass^® (Azospirillum brasilense, Bacillus megaterium, Saccharomyces cerevisiae), and Kiplant All-Grip^® (Bacillus megaterium, Pseudomonas spp.)—applied at different dosages alongside two mineral fertilizer regimes, T100 (full dose) and T70 (70% of T100, alone or combined with biofertilizers), on the physiological performance of ‘Gala Redlum’ apple trees. Part I had shown that Myc4 (Mycoshell^®, 4 tablets/tree), iNM6, and iNM12 (Kiplant iNmass^®, 6 and L ha⁻¹, respectively) consistently enhanced fruit growth, yield, and selected quality traits. While Part I showed clear agronomic gains, Part II demonstrates that these improvements occurred without significant alterations in seasonal photosynthetic performance, canopy reflectance, or chlorophyll fluorescence parameters over five years, highlighting the contrast between observed yield improvements and physiological stability. Seasonal monitoring of physiological traits—including specific leaf area (SLA), chlorophyll content index (CCI), gas exchange (A_n, g_s, E, C_i), spectral indices (NDVI, OSAVI, SIPI, GM2), and chlorophyll fluorescence (OJIP). It is clear that physiological values remained largely stable across biofertilizer treatments and years. Importantly, this stability was maintained even under a 30% reduction in mineral fertilizer (T70), indicating that specific microbial biofertilizers can sustain physiological resilience under reduced nutrient inputs, thereby providing a physiological basis for the yield-enhancing effects observed and supporting their integration into fertilizer reduction strategies in Mediterranean orchards. Full article

Background: Plant growth promoting bacteria (PGPB) are non-pathogenic bacteria that enhance plant growth through several mechanisms such as nutrient mobilization, phytohormones production, defense against phytopathogens, and alleviation of plant stress. Hence, these bacteria are used as ecologic biofertilizers to diminish the use of agrochemicals. Nevertheless, some PGPR strains can harbor antibiotic resistance determinants and the possibility of spreading them upon releasing these bacteria is an environmental concern. Objectives: The objectives of this work are as follows: (1) evaluating the antibiotic resistance in a collection of PGPB, and (2) prospecting antibiotic resistance genes in the genomes of PGPB in order to predict the risk for antibiotic resistance dissemination. Methods: The resistance towards 12 antibiotics in a collection of 20 PGPB (10 Gram-positive and 10 Gram-negative strains) has been evaluated using disk diffusion in agar, broth microdilution, and agar dilution tests. In addition, the whole genomes of six strains have been sequenced in order to find the correlation between the resistance levels and AMR genes by using bioinformatic tools. Results: The results indicated a wide range of halo diameters, but in general Gram-negatives showed higher resistance compared to Gram-positives. The four most resistant strains and the two more susceptible strains were selected for further analysis and sequencing the whole genomes. The resistant strains were identified as Achromobacter spanius N6, Leclercia adecarboxylata H17, Priestia aryabhattai strain MHA1, and Bacillus cereus N25. The susceptible strains were identified as Pantoea sp. S3 and Priestia megaterium MS4. Mining antibiotic resistance genes in the genomes confirmed the existence of resistance determinants responsible for the phenotypic behavior, indicating the potential of genomics for predicting antibiotic resistance in PGPB. However, there was not an exact correspondence between the presence of the genes and the level of resistance, suggesting the existence of additional regulatory mechanisms. Conclusions: The information obtained by genomics must be complemented experimentally by tests for antibiotic resistance determination. In this regard, it is necessary to develop a global antibiotic resistance database for PGPB, due to the difficulty of interpretation of the antibiotic susceptibility tests after comparing the experimental results with those tabulated for clinical species. Full article

In this study, eight treatment groups were set up with three replicates in each group to investigate the effects of Bacillus, Lactobacillus, and molasses on the chemical composition and fermentation quality of fermented rice straw. Furthermore, an animal experiment was conducted to determine the nutrition apparent digestibility, ruminal fermentation characteristics, and methane emission in Hu sheep. The results showed that the dry matter (DM) and crude protein (CP) content in the group treated with Bacillus megaterium and Lactobacillus acidophilus (BMLB) was significantly higher than that in the group with no additive (CK) (p < 0.05). Compared with the CK group, all treatments with single or composite addition of Bacillus significantly reduced the content of neutral detergent fiber (NDF) and acid detergent fiber (ADF) (p < 0.05). The content of acetate, propionate, and NH₃-N in the BMLB group were significantly lower than those in the CK group (p < 0.05). In addition, the Hu sheep in the BMLB group showed a significant reduction in daily methane emission per unit of metabolic body weight. In conclusion, the BMLB treatment significantly improved the nutritional value, fermentation quality, ruminal fermentation, and methane emission of rice straw haylage in Hu sheep. Full article

The use of electronic cigarettes has increased in the U.S. with menthol and mint flavors showing notably higher sales. While research on the bacterial microbiome of traditional tobacco products is growing, particularly regarding menthol and nicotine effects, data regarding potential microbial contaminants within electronic liquids (e-liquids) remain limited. Additionally, the potential antibacterial properties of e-liquids remain sparse. To address these gaps, we evaluated the prevalence of viable bacteria in e-liquids; characterized their antimicrobial susceptibility patterns; and tested the antibacterial activity of the e-liquids. Two e-liquid flavors (menthol and non-menthol) across three different nicotine concentrations (0, 6 and 12 mg/mL) were tested using culture-based methods and Sanger sequencing. Antimicrobial susceptibility testing and e-liquid antibacterial activity assays were performed using the Kirby Bauer disc diffusion method. The majority of the isolates (63.15%) were identified as Pseudomonas aeruginosa and Bacillus spp. (B. pumilus, B. megaterium and B. cereus). Notably, P. aeruginosa and P. fluorescens isolates exhibited multidrug resistance against penicillin, tetracyclines, and phenicols. The e-liquids also demonstrated antimicrobial activity, inhibiting the growth of B. cereus, P. aeruginosa, and Staphylococcus aureus, with greater inhibition of P. aeruginosa growth at higher (12 mg/mL) compared to lower (0 mg/mL) nicotine concentrations across the menthol-flavored samples. These findings offer preliminary evidence of viable, multidrug-resistant bacteria and antibacterial properties in e-liquids, underscoring potential public health concerns regarding user exposure risks and microbial interactions, and emphasizing the need for continued surveillance of microbial safety in electronic cigarette products. Full article

The stability of spore-forming soil bacteria is crucial for their effective use in agricultural biopreparations. This study evaluated the long-term survivability of selected strains (Paenibacillus amylolyticus, Priestia megaterium, Bacillus velezensis, Bacillus subtilis, and Bacillus licheniformis) with potential applications in biopreparations for crop residue decomposition. The effects of different storage and preservation conditions on vegetative cells and bacterial spores were studied over 12 months. Bacteria were stored at different temperatures (15 °C, 21 °C, 30 °C), pH levels (5, 9, and post-cultivation liquid pH), and osmotic pressures (2%, 5%, and 10% of carbamide, calcium chloride, and multicomponent fertilizer). Additionally, freeze-drying, spray-drying and freezing were performed using cryoprotectants (skimmed milk, trehalose, and glycerol). The results showed that bacterial stability depended on both the strain and storage conditions. Vegetative cells of P. amylolyticus and B. velezensis were most sensitive to temperatures of 30 °C, whereas the spores of most strains demonstrated high temperature resistance. The tested strains exhibited better survivability at pH 5 than pH 9. The addition of calcium chloride, carbamide, or multicomponent fertilizer proved beneficial for maintaining viability, especially increasing spore numbers. Trehalose and skimmed milk were the most effective cryoprotectants overall, though efficacy varied by strain and cell form. These findings provide insight into the optimal conditions for preserving the bacterial viability of spore-producing bacteria in bioformulations, which is crucial for maintaining their effectiveness in agricultural applications. Full article

The unique cytochrome P450 BM3 from Priestia megaterium (syn. Bacillus megaterium) is renowned for its versatile high catalytic activity. The cyp102A1-LG23 gene encoding its CYP102A1-LG23 mutant variant was expressed in Escherichia coli and Mycolicibacterium smegmatis. The in vivo activity of the heterologous enzyme was assessed with respect to androstenedione (AD), androstadienedione (ADD), testosterone (TS) and dehydroepiandrosterone (DHEA). Alongside 7β-hydroxylation, the heterologous enzyme catalyzed the mono- and dihydroxylation of C19 steroids. For the first time, the formation of 7β-, 6β- and 11α-hydroxylated derivatives of ADD using a bacterial enzyme, as well as the hydroxylation of DHEA at the C7α and C7β positions, and its dihydroxylation with the formation of the 7α,15α-dihydroxylated derivative using the mutant cytochrome P450 BM3 were demonstrated. The steroid structures were confirmed using mass spectrometry and ¹H NMR spectroscopy. The advantages of using mycolicibacteria as a bacterial chassis for gene expression were also shown. The results demonstrate the unusual properties of the mutant cytochrome P450 BM3-LG23 and open up prospects for its application in the biotechnological production of valuable hydroxysteroids. Full article

Biofertilizers are sustainable alternatives to mineral fertilizers in perennial crops, reducing the need for mineral inputs. This five-year field study evaluated three biofertilizers—Mycoshell^® (Glomus spp. + humic/fulvic acids), Kiplant iNmass^® (Azospirillum brasilense, Bacillus megaterium, and Saccharomyces cerevisiae), and Kiplant All-Grip^® (Bacillus megaterium and Pseudomonas spp.)—at different dosages alongside two mineral fertilizer regimes, T100 (full recommended dose) and T70 (70% of T100, alone or combined with biofertilizers), in an apple orchard under Mediterranean conditions. Biofertilizers maintained or increased soil nutrient availability by 5–15% and leaf N, P, K, Mg, and Zn concentrations by 5–12% compared with T100. Trees under biofertilizers, particularly Myc2 and Myc4, exhibited greater shoot growth (up to 30.4 m/year), trunk cross-sectional area (TCSA: 11.9 cm² in 2022), and canopy volume (2.21 m³), representing 10–20% increases. Selected biofertilizer treatments produced 6–7.5 kg/tree, 130–145 g average fruit weight, 66–74 mm diameter, 13.9–18.7 °Brix, and 13–18% dry matter, maintaining >90% of yield and fruit size relative to T100, with more balanced medium- and large-sized fruit distribution. Principal Component Analysis explained 66–72% of soil and leaf nutrient variance, confirming their multivariate impact. Overall, biofertilizers applied at recommended doses and timings can partially replace mineral fertilizers, sustaining productivity and quality, enhancing nutrient availability, and supporting long-term orchard sustainability. While climate remains the main driver of annual production, these findings provide evidence for integrating biofertilizers into environmentally friendly fertilization strategies. Full article

Facility agriculture is essential for modernizing the production of horticultural plants, while long-standing over-fertilization and improper tillage in some vegetable facilities in northern China have resulted in reduced soil quality, increased greenhouse gas (GHG) emissions, and diminished vegetable yields and quality. This study systematically analyzed the deteriorating health of typical cucumber facility soils in Hebei Province, China, induced by long-term over-fertilization. Based on field surveys, we explored dynamic changes in soil physicochemical properties across different durations of over-fertilization. Subsequently, a series of field trials were conducted to assess whether reducing nitrogen application, either alone or when combined with microbial agents, could ameliorate soil properties, reduce greenhouse gas emissions, and enhance cucumber productivity. The initial field assessment revealed severe topsoil salt and nutrient accumulation, with water-soluble salt content in 5-year-old greenhouses from Yongqing soaring to 3.82 g·kg⁻¹, nearly eight times the level found in 1-year-old plots. Field experiments demonstrated that a 20% reduction in nitrogen application from the conventional rate of 900 kg·hm⁻² effectively mitigated salt accumulation, improved the structure of the microbial community, and maintained cucumber yield at 66,914 kg·hm⁻², an output comparable to conventional practices. More notably, integrating this 20% nitrogen reduction with an inoculation of Bacillus megaterium reduced the overall global warming potential by 26.7% and simultaneously increased cucumber yield to 72,747 kg·hm⁻². The most comprehensive strategy combined deep tillage, soybean straw incorporation, and B. megaterium application under reduced nitrogen, which boosted nitrogen use efficiency by 13.7% and achieved the highest yield among all treatments. In conclusion, our findings demonstrate that a combined approach of nitrogen reduction, microbial amendment, and straw application offers an effective strategy to restore soil health, enhance crop productivity, and mitigate environmental impacts in protective vegetable production systems. Full article

The use of bioinoculants aligns with ecological intensification in agriculture, but their effects on crop performance and soil microbiota under different fertilization regimes remain unclear. This study evaluated the impact of a bioinoculant containing two phosphate-solubilizing bacterial strains (Priestia megaterium and Bacillus subtilis) on maize yield, root architecture, and rhizosphere microbial communities via seed inoculation in a clayey soil. Maize was cultivated for two consecutive seasons under treatments combining inoculation, phosphorus sources (triple superphosphate or reactive rock phosphate), and P doses (0 or 120 kg ha⁻¹ of P₂O₅). Root traits, phosphatase activities, and microbial diversity were assessed at flowering, while agronomic parameters and nutrient content were measured at harvest. In the first season, microbial alpha diversity was higher, accompanied by a 31.5% increase in root surface area and a 46.2% increase in P-resin availability. In contrast, the second season showed greater phosphatase activity and higher grain P and K concentrations, by 42.3% and 38.2%, respectively. Grain yield did not differ significantly between inoculated and non-inoculated treatments; however, root, plant, and microbial traits varied markedly across seasons. Principal component analysis revealed that productivity was primarily driven by seasonal variation rather than by fertilization or inoculation. These findings emphasize that the effectiveness of bioinoculants and P fertilization, as well as their influence on the microbiota, are highly context-dependent, being shaped by environmental conditions, soil nutrient availability, and crop genotype. Full article

Biostimulants based on Bradyrhizobium japonicum are commonly used in soybean production. However, the effect of nitrogen-fixing bacteria in consortia with other plant growth-promoting rhizobacteria (PGPR) and their integration with mineral nutrients on soybean seed quality has not been explored. The study aimed to examine the effects of five treatments on seed germination and initial seedling growth of two soybean cultivars (‘NS Apolo’, ‘NS Rubin’): control (untreated seeds); Br. japonicum (BJ), BJ and nutrient complex (NC), BJ, Azotobacter chroococcum (AC), Bacillus subtilis (BS), and NC; BJ, AC, Bacillus megaterium (BM), and NC. Seed treatments significantly enhanced germination energy, seedling vigor index, root length, fresh shoot weight, fresh root weight, dry shoot weight, and dry root weight of both cultivars, as well as final germination, shoot length, and shoot elongation rate of ‘NS Rubin’, as compared to the control. The highest effect on the investigated parameters was achieved by integrated use of PGPR and nutrients (BJ + BM + AC + NC), indicating that integration of PGPR with a targeted NC represents an innovative approach with practical implications for improving early soybean establishment and field performance. Full article

Potato (Solanum tuberosum) is an important food crop. However, intensive cultivation has led to increased reliance on chemical fertilizers, raising environmental and economic concerns. One of the concerns in potato plantations is phosphorus, which often exhibits low availability due to leaching and poor use efficiency, coupled with rising fertilizer production costs. This study investigates the agronomic and economic impacts of using natural rock amendments combined with plant growth-promoting rhizobacteria (PGPR) as sustainable alternatives to chemical fertilizers on the yield and tuber quality of potato. A field experiment assessed three treatments: conventional chemical fertilizers (T1), reduced chemical fertilizers combined with PGPR (Bacillus megaterium, Bacillus mucilaginosus, and Azotobacter) (T2), and natural rock amendments of potassium feldspar and rock phosphate combined with PGPR (T3). Results showed that T2 and T3 demonstrated improved tuber quality compared to T1, with T3 achieving the highest starch content (314.05 mg/g FW) and reduced sugar content (102.03 mg/g FW). Furthermore, T3 improved soil quality after the growing season, showing higher phosphorus and potassium availability compared to T1. Economically, T3 reduced operating costs by 11% and achieved the highest yield (42 tons/ha). The return on investment for T3 reached approximately 79.48% (USD 3988/ha), with a 40.9% profit increase compared to T1 (USD 2460/ha) These findings confirm that integrating PGPR with natural rock fertilizers offers a cost-effective and durable alternative to conventional fertilization practices, enhancing productivity and profitability while providing significant opportunities for achieving the Sustainable Development Goals and promoting long-term soil sustainability. Full article

Polyurethane (PU) is a widely used plastic material whose persistence in the environment entails a serious ecological challenge. This study aimed to isolate and characterize environmental bacteria capable of degrading PU, using Impranil DLN as a model substrate, and to investigate their enzymatic mechanisms and phylogenetic relationships. A total of 31 bacterial isolates were obtained from four waste accumulation sites and taxonomically identified across 12 different genera using MALDI-TOF MS and 16S rRNA gene sequencing. This analysis revealed genera not previously reported as PU biodegraders, including Priesta, Dermacoccus, Gordonia, Micrococcus, Pseudarthrobacter, and Agromyces. The Bacillus cereus clade was the most prevalent group, followed by the Priestia megaterium clade and Achromobacter sp. Biodegradation assays revealed high variability among strains, with the most efficient degrading over 90% of Impranil DLN. Protease activity was the most frequently detected enzymatic function, followed by urease and esterase activities. However, no clear correlation was observed between enzymatic profiles and degradation efficiency. Selected strains were tested on polyether PU foam, revealing biodegradative activity, an uncommon observation for bacteria on such recalcitrant material. These findings contribute to our understanding of bacterial diversity and enzymatic mechanisms involved in PU biodegradation, as well as their potential applications in plastic waste bioremediation. Full article

Lucky bamboo is an economically crucial ornamental plant worldwide due to its durability, rapid growth capacity, and versatile uses. However, diseases caused by various fungal pathogens negatively affect bamboo production, resulting in yield losses. In the present study, fungal agents causing disease in Dracaena sanderiana were isolated and evaluated for their pathogenicity. The MF-1 and MF-2 isolates that showed pathogenicity were characterized morphologically and molecularly. Chitinase enzymes were partially purified from four different bacteria and biochemically characterized, and the antifungal activities of these bacteria and chitinases were evaluated. As a result of the diagnosis, both isolates were identified as Fusarium oxysporum with ~99% similarity. It was determined that the partially purified chitinases from Pseudomonas chlororaphis C-37A and Agrobacterium radiobacter A-16 had the highest activity with values of 9.44 and 1.02 EU/mL, respectively. Additionally, the pH and temperature values at which C-37A’s chitinase exhibited optimal activity were determined to be 8 and 30 °C, while those for A-16’s chitinase were found to be pH 4 and 40 °C. After 120 min, C-37A’s chitinase retained 50% of its activity at 90 °C, while A-16’s chitinase retained 80% of its activity at 40 °C. C-37A inhibited the growth of MF-1 and MF-2 by 83% and 75%, respectively. Additionally, the inhibition rates of A-16, Bacillus megaterium M-3, and KBA-10 ranged from 68% to 29%. In chitinase applications, the highest inhibition rates of 28% (MF-1) and 23% (MF-2) were obtained from C-37A chitinase. In conclusion, it was observed that bioagent bacteria provide sustainable biological effects against F. oxysporium in D. Sanderiana, and that the chitinase enzyme purified from these isolates can be used as a biocontrol agent in agriculture, as well as potentially evaluated in various industrial applications. Full article

Concrete cracks and sulfate degradation severely compromise structural durability, highlighting the need for sustainable solutions to enhance longevity and minimize environmental impact. This study assesses the efficacy of bacterial self-healing technology utilizing Bacillus megaterium (BM) and Bacillus sphaericus (BS) in enhancing the resistance of concrete to sulfate attacks and improving its mechanical properties. Bacterial suspensions (1% and 2.5% of cement weight) were mixed with concrete containing silica fume or fly ash (10% of cement weight) and cured in freshwater or sulfate solutions (2%, 5%, and 10% concentrations). Specimens were tested for compressive strength, flexural strength, and microstructure using a Scanning Electron Microscope (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), and X-ray diffraction (XRD) at various ages. The results indicate that a 2.5% bacterial content yielded the best performance, with BM surpassing BS, enhancing compressive strength by up to 41.3% and flexural strength by 52.3% in freshwater-cured samples. Although sulfate exposure initially improved early-age strength by 1.97% at 7 days, it led to an 8.5% loss at 120 days. Bacterial inclusion mitigated sulfate damage through microbially induced calcium carbonate precipitation (MICP), sealing cracks, and bolstering durability. Cracked specimens treated with BM recovered up to 93.1% of their original compressive strength, promoting sustainable, sulfate-resistant, self-healing concrete for more resilient infrastructure. Full article

The cultivation of cowpea (Vigna unguiculata), a vital vegetable crop, faces significant threats from Fusarium spp.-induced root rot. In this study, three fungal pathogens (Fusarium falciforme HKFf, Fusarium incarnatum HKFi, and Fusarium oxysporum HKFo) were isolated from symptomatic cowpea plants, and we screened 90 rhizobacteria from healthy rhizospheres using six culture media. Among these pathogens, Priestia megaterium TSA-10E showed a notable suppression of F. oxysporum HKFo (63.21%), F. incarnatum HKFi (55.16%), and F. falciforme HKFf (50.93%). In addition, Bacillus cereus KB-6 inhibited the mycelial growth of F. incarnatum HKFi and F. oxysporum HKFo by 42.39% and 47.93%, respectively. Critically, cell-free filtrates from P. megaterium TSA-10E and B. cereus KB-6 cultures reduced conidial germination in F. oxysporum HKFo and F. incarnatum HKFi, highlighting their role in disrupting the early infection stages. In greenhouse trials, TSA-10E and KB-6 reduced disease severity by 48.7% and 40.4%, respectively, with treated plants maintaining healthy growth while untreated controls succumbed to wilting. Broad-spectrum assays revealed that B. subtilis TSA-6E and P. megaterium TSA-10E were potent antagonists against both economic and grain crop pathogens. These findings underscore the potential of rhizobacteria as sustainable biocontrol agents for managing root rot disease caused by Fusarium spp. in cowpea cultivation. Full article