Bacterial Inoculation Research Articles

Gallium and silver-doped titanium surfaces provide enhanced osteogenesis, reduce bone resorption and prevent bacterial infection in co-culture

Bacterial infection remains a significant problem associated with orthopaedic surgeries leading to surgical site infection (SSI). This unmet medical need can become an even greater complication when surgery is due to malignant bone tumor. In the present study, we evaluated in vitro titanium (Ti) implants subjected to gallium (Ga) and silver (Ag)-doped thermochemical treatment as strategy to prevent SSI and improve osteointegration in bone defects caused by diseases such as osteoporosis, bone tumor, or bone metastasis. Firstly, as Ga has been reported to be an osteoinductive and anti-resorptive agent, its performance in the mixture was proved by studying human mesenchymal stem cells (hMSC) and pre-osteoclasts (RAW264.7) behaviour. Then, the antibacterial potential provided by Ag was assessed by resembling “The Race for the Surface” between hMSC and Pseudomonas aeruginosa in two co-culture methods. Moreover, the presence of quorum sensing molecules in the co-culture was evaluated. The results highlighted the suitability of the mixture to induce osteodifferentiation and reduce osteoclastogenesis in vitro. Furthermore, the GaAg surface promoted strong survival rate and retained osteoinduction potential of hMSCs even after bacterial inoculation. Therefore, GaAg-modified titanium may be an ideal candidate to repair bone defects caused by excessive bone resorption, in addition to preventing SSI. Statement of significanceThis article provides important insights into titanium for fractures caused by osteoporosis or bone metastases with high incidence in surgical site infection (SSI) because in this situation bacterial infection can become a major disaster. In order to solve this unmet medical need, we propose a titanium implant modified with gallium and silver to improve osteointegration, reduce bone resorption and avoid bacterial infection. For that aim, we study osteoblast and osteoclast behavior with the main novelty focused on the antibacterial evaluation. In this work, we recreate “the race for the surface” in long-term experiments and study bacterial virulence factors (quorum sensing). Therefore, we believe that our article could be of great interest, providing a great impact on future orthopedic applications.

Energy and Environmental Assessment of Bacteria-Inoculated Mineral Fertilizer Used in Spring Barley Cultivation Technologies

In the scientific literature there is a lack of information on the integrated effect of bioenriched complex mineral fertilizers in the energy and environmental aspects of spring barley production technology. The aim of this study was to validate the type of phosphorus-releasing bacteria and to carry out an energy and environmental assessment of the use of mineral fertilizers enriched with them for barley fertilization. The experimental field studies (2020–2022) were carried out in open ground on sandy loam soil in southern Lithuania. Four barley cultivation technologies (SC) were applied. Control (SC–1) did not use complex mineral fertilizers; in SC–2, 300 kg ha−1 of N5P20.5K36 fertilizer was applied. In SC–3, the same fertilizer was enriched with a bacterial inoculant (Paenibacillus azotofixans, Bacillus megaterium, Bacillus mucilaginosus, and Bacillus mycoides) at a rate of 150 kg ha−1, and in SC–4, 300 kg ha−1 of N5P20.5K36 fertilizer were applied and the same enrichment with the bacterial inoculant was carried out. The results confirmed the hypothesis that spring barley cultivation technologies using bacterial inoculants (SC–3 and SC–4) have higher mineral fertilizer efficiency than SC–2. In all three years, the bacterial inoculant had a positive effect on phosphorus fertilizer efficiency. In SC–4 (2020) it was 8%, in 2021—7%, and in 2022—even 17% higher compared to SC–2. In terms of energy balance, a significant influence of the bacterial inoculant was found. In 2020 and 2021, the energy balance of SC–4 was 10%, and in 2022, 22.8% higher compared to SC–2. The increase in fertilizer use efficiency resulted in a positive environmental impact, with greenhouse gas (GHG) emissions decreasing by 10% in 2020, 15% in 2021, and 19% in 2022 when comparing SC–4 and SC–2. The use of the tested bacterial formulations, without changing the mineral fertilizer rate, can lead to an average reduction in GHG emissions of about 15%. This study demonstrates that enriching mineral fertilizers with specific bacterial inoculants for spring barley cultivation significantly enhances phosphorus efficiency, improves energy balance, and reduces greenhouse gas emissions, underscoring the potential for bioaugmented fertilizers to optimize agricultural sustainability.

Two microbes assisting Miscanthus floridulus in remediating multi-metal(loid)s-contaminated soil.

Miscanthus has good tolerance to multi-metal(loid)s and has received increasing attention in remediated studies of metal(loid)s-contaminated soil. In this study, we conducted phytoextraction techniques to investigate the synergic effects of remediation of multi-metal(loid)s-contaminated soil by Miscanthus floridulus (Lab.) and two plant growth-promoting bacteria (PGPB), TS8 and MR2, affiliated to Enterobacteriaceae. The results exhibited a decrease of arsenic (15.27-21.50%), cadmium (8.64-15.52%), plumbum (5.92-12.76%), and zinc (12.84-24.20%) except for copper contents in the soil in bacterial inoculation groups, indicating that MR2 and TS8 could enhance the remediation of metal(loid)s. Moreover, increased fresh/dry weight and height indicated that inoculated bacteria could promote Miscanthus growth. Although the activities of antioxidant enzymes and the content of chlorophyll in the overground tissues showed no significant increase or even decrease, the activities of antioxidant enzymes in the underground tissues and soil were elevated by 48.95-354.17%, available P by 19.07-23.02%, and available K by 15.34-17.79% (p < 0.05). Bacterial inoculants could also decrease the soil pH. High-throughput sequencing analysis showed that the bacterial inoculant affected the rhizosphere bacterial community and reduced community diversity, but the relative abundance of some PGPB was found to increase. Phylogenetic molecular ecological networks indicated that bacterial inoculants reduced interactions between rhizosphere bacteria and thereby led to a simpler network structure but increased the proportion of positive-correlation links and enhanced the metabiosis and symbiosis of those bacteria. Spearman's test showed that OTUs affiliated with Enterobacteriaceae and soil nutrients were critical for metal(loid) remediation and Miscanthus growth. The results of this study provide a basis for the synergic remediation of multi-metal(loid)s-contaminated soils by Miscanthus and PGPB and provide a reference for the subsequent regulation of Miscanthus remediation efficiency by the other PGPB or critical bacteria.

Effect of Spraying with Salicylic Acid and Bacterial Inoculation on Yield and Yield Components of some Soybean Cultivars under El-Minia Governorate Conditions

Effect of Spraying with Salicylic Acid and Bacterial Inoculation on Yield and Yield Components of some Soybean Cultivars under El-Minia Governorate Conditions

Effectiveness of &lt;i&gt;Pseudomonas Aeruginosa&lt;/i&gt; in Destruction of Harmful Lipids in Lipidemia Patients

Pseudomonas aeruginosa is a type of harmful microorganism that belongs to a large group of Gram-negative bacteria, these bacteria can secrete many extracellular enzymes such as microbial lipase and oxidase that act on certain lipids. This study aims to activate certain enzymes of P. aeruginosa like lipase and oxidase in order to decrease high plasma triglycerides and cholesterol in lipidemia patients. Serum can also be used due to the fact that lipids are found in both serum and plasma. Five ml. of blood were collected from 100 lipidemia patients at Baghdad Teaching Hospital laboratories in Medical city, P. aeruginosa was isolated from medical wastes; cultured on bacterial media, gram stained and biochemically tested in vitro. Methods depend on inoculation of bacterial broth containing colonies of P. aeruginosa adjusted to McFarland standard turbidity with 50% of blood plasma were added, then cultures were incubated at 37°C for 6 days, activation of bacterial lipase and oxidase were done during the incubation period by addition of certain activators to the broth like glycogen liquid. The results showed that 100% of patients had cholesterol &lt;200 mg/dl and 99% of patients had normal triglyceride level (&lt;200mg/dl) after bacterial inoculation and activation of microbial lipase and oxidase. As conclusion, the high plasma lipids level of patients was decreased four times by P. aeruginosa may be due to the activation of microbial lipase and oxidase which could needs to future research to extract them and used them as treatment for these cases.

The interplay between the inoculation of plant growth-promoting rhizobacteria and the rhizosphere microbiome and their impact on plant phenotype

Microbial inoculation stands as a pivotal strategy, fostering symbiotic relationships between beneficial microorganisms and plants, thereby enhancing nutrient uptake, bolstering resilience against environmental stressors, and ultimately promoting healthier and more productive plant growth. However, while the advantageous roles of inoculants are widely acknowledged, the precise and nuanced impacts of inoculation on the intricate interactions of the rhizosphere microbiome remain significantly underexplored. This study explores the impact of bacterial inoculation on soil properties, plant growth, and the rhizosphere microbiome. By employing various bacterial strains and a synthetic community (SynCom) as inoculants in common bean plants, the bacterial and fungal communities in the rhizosphere were assessed through 16 S rRNA and ITS gene sequencing. Concurrently, soil chemical parameters, plant traits, and gene expression were evaluated. The findings revealed that bacterial inoculation generally decreased pH and V%, while increasing H+Al and m% in the rhizosphere. It also decreased gene expression in plants related to detoxification, photosynthesis, and defense mechanisms, while enhancing bacterial diversity in the rhizosphere, potentially benefiting plant health. Specific bacterial strains showed varied impacts on rhizosphere microbiome assembly, predominantly affecting rhizospheric bacteria more than fungi, indirectly influencing soil conditions and plants. Notably, Paenibacillus polymyxa inoculation improved plant nitrogen (by 5.2%) and iron levels (by 28.1%), whereas Bacillus cereus boosted mycorrhization rates (by 70%). Additionally, inoculation led to increased complexity in network interactions within the rhizosphere (∼15%), potentially impacting plant health. Overall, the findings highlight the significant impact of introducing bacteria to the rhizosphere, enhancing nutrient availability, microbial diversity, and fostering beneficial plant-microbe interactions.

Growth and Phytochemistry of Cymbopogon citratus Stapf Inoculated with Plant Growth-Promoting Bacteria under Different Lead Levels.

This study aimed to investigate the phytochemistry of lemongrass (Cymbopogon citratus) inoculated with Azospirillum brasilense and grown in lead (Pb)-contaminated soil to assess its responses to inoculation under different Pb levels. The experimental design was completely randomized in a 2 × 5 factorial scheme: two levels of A. brasilense (absence or presence) and five Pb levels. After four months of treatment, the following were analyzed: total and reducing sugars, total phenolic content, flavonoids, antioxidant activity, antioxidant enzymes, proline, and essential oil (EO) content and composition. Soil Pb levels and A. brasilense inoculation affected phytochemicals in lemongrass plants. Azospirillum inoculation reduced total sugars in the roots at all soil Pb levels, while increasing Pb levels favored a rise in sugar contents. There was an increase in flavonoid content in treatments associated with Pb and inoculated with A. brasilense. Antioxidant capacity was lower at lower Pb levels, regardless of bacterial inoculation. Enzymatic response was mainly affected by Pb concentrations between 50 and 100 mg kg-1 soil. EO content was influenced by soil Pb levels, with higher EO production at 500 mg Pb kg-1 soil and without A. brasilense inoculation. Overall, lemongrass cultivation in Pb-contaminated areas can be an alternative to phytoremediation and EO production for the industry.

PGPR-based biofertilizer modulates strawberry photosynthetic apparatus tolerance responses by severe drought, soil salinization and short extreme heat event

Drought, soil salinization and the extreme heat events increments associate to climate change will notably impact sensitive crop species, such as strawberry. A greenhouse experiment was arranged to evaluate the potential of a PGPR-based biofertilizer, with multiple PGP properties, including ACC deaminase production highly related to the limitation of ethylene levels under abiotic stress, in modulation of photosynthetic apparatus tolerance responses by severe drought (complete water withholding), salinity in irrigation water (340 mM NaCl) and short extreme heat event (37/28 °C maximum and minimum temperature range). Our results show that all stress factors triggered acute injury effects on strawberry carboxylation capacity and photosystem II energy assimilation efficiency ability; whose intensity varied depending on factor nature. However, bacterial inoculation diminished ∼67 %, 20 % and 18 % the deleterious impact imposed by drought, heat and salinity stress on the net photosynthetic rate (AN). This effect was primarily mediated by counterbalancing the diffusion of CO2 in the stomata and biochemical limitations in response to heat and salinity stress, while the reduction of biochemical damage was more notable in response to drought. Complementarily, inoculation was able to highly buffer the photochemical limitations imposed by all abiotic stress factors tested. Despite these positive effects, the application of PGPR-based biofertilizer was unable to completely reverse the impact of stress factors on strawberry photosynthesis metabolism. However, the signal of these ameliorative effects was significant enough to consider the implementation of PGPR-based biofertilizer application as a complementary tool in the management of strawberry cultivation in increasingly stressful agronomic contexts.

Phosphate bio-solubilization and cadmium tolerance interplay in the root-microbe interface and consequences on root P absorption in wheat

Functional soil microbial communities, including phosphate solubilizing bacteria (PSB), are known for their ability to enhance P availability along with additional properties such as the immobilization of trace elements like cadmium (Cd). Bacterial P solubilization and tolerance to Cd are important biological processes that might occur simultaneously with positive influence on plant growth, thus physiological mechanisms controlling both processes need to be deciphered. This interplay was investigated in three PSB isolates (Bacillus siamensis "B. Siam", Rahnella aceris "R. Acer" and Bacillus cereus "B. Cer") and their consortium (PSBCs) with contrasting P solubilizing capacities (high-medium-low), through bacterial culture-based and plant inoculation experiments under increasing Cd concentrations and low P availability conditions (Tri-calcium P "TCP" and Rock P "RP"). Results show that PSB, particularly R. Acer and PSBCs, significantly increased P bioavailability (from TCP) under increasing Cd2+ concentrations (33 ppm “Cd33”, 67 ppm “Cd67”, 134 ppm “Cd134” and 201 ppm “Cd201”). The enhanced bioavailable P strongly correlated (B. Siam and PSBCs) with Cd bioaccumulation capacity, phosphatase enzyme activity, and organic acids (OA) production. Co-application of RP and PSB inoculation under Cd2+ stress (Cd8 and Cd16) improved wheat seedling root growth, P acquisition, and root hairs density in the piliferous zone and root cap. Moreover, inoculation with B. Cer significantly improved root inorganic P (Pi) (384 and 752%) and root acid phosphatases (176 and 131%) under Cd8 and Cd16 compared to uninoculated Cd-stressed seedlings. Such a beneficial root adaptation mechanism could be explained by the significant correlations (mainly under Cd16) between Pi content and morphological traits of wheat roots. Findings from this study demonstrate that P solubilization and Cd tolerance are likely interconnected rhizosphere processes triggered by inoculation that presumably induced the elongation of root hairs and likely the rigidity of the root cell wall to reduce Cd entrance while increasing P acquisition.

Performance of microbial inoculation and tricalcium phosphate on nitrogen retention and conversion: Core microorganisms and enzyme activity during kitchen waste composting

The substantial release of NH3 during composting leads to nitrogen (N) losses and poses environmental hazards. Additives can mitigate nitrogen loss by adsorbing NH3/NH4, adjusting pH, and enhancing nitrification, thereby improving compost quality. Herein, we assessed the effects of combining bacterial inoculants (BI) (1.5%) with tricalcium phosphate (CA) (2.5%) on N retention, organic N conversion, bacterial biomass, functional genes, network patterns, and enzyme activity during kitchen waste (KW) composting. Results revealed that adding of 1.5%/2.5% (BI + CA) significantly (p < 0.05) improved ecological parameters, including pH (7.82), electrical conductivity (3.49 mS/cm), and N retention during composting. The bacterial network properties of CA (265 node) and BI + CA (341 node) exhibited a substantial niche overlap compared to CK (210 node). Additionally, treatments increased organic N and total N (TN) content while reducing NH4+-N by 65.42% (CA) and 77.56% (BI + CA) compared to the control (33%). The treatments, particularly BI + CA, significantly (p < 0.05) increased amino acid N, hydrolyzable unknown N (HUN), and amide N, while amino sugar N decreased due to bacterial consumption. Network analysis revealed that the combination expanded the core bacterial nodes and edges involved in organic N transformation. Key genes facilitating nitrogen mediation included nitrate reductase (nasC and nirA), nitrogenase (nifK and nifD), and hydroxylamine oxidase (hao). The structural equation model suggested that combined application (CA) and microbial inoculants enhance enzyme activity and bacterial interactions during composting, thereby improving nitrogen conversion and increasing the nutrient content of compost products.

Niche availability and competitive loss by facilitation control proliferation of bacterial strains intended for soil microbiome interventions

Microbiome engineering – the targeted manipulation of microbial communities – is considered a promising strategy to restore ecosystems, but experimental support and mechanistic understanding are required. Here, we show that bacterial inoculants for soil microbiome engineering may fail to establish because they inadvertently facilitate growth of native resident microbiomes. By generating soil microcosms in presence or absence of standardized soil resident communities, we show how different nutrient availabilities limit outgrowth of focal bacterial inoculants (three Pseudomonads), and how this might be improved by adding an artificial, inoculant-selective nutrient niche. Through random paired interaction assays in agarose micro-beads, we demonstrate that, in addition to direct competition, inoculants lose competitiveness by facilitating growth of resident soil bacteria. Metatranscriptomics experiments with toluene as selective nutrient niche for the inoculant Pseudomonas veronii indicate that this facilitation is due to loss and uptake of excreted metabolites by resident taxa. Generation of selective nutrient niches for inoculants may help to favor their proliferation for the duration of their intended action while limiting their competitive loss.

Enhancing sunflower resilience: Zinc-solubilizing bacteria mitigate cadmium uptake and translocation

&lt;p&gt;Cadmium (Cd) is a highly hazardous metal known for its easy absorption and accumulation in plants, particularly in edible vegetable oils. Sunflower (Helianthus annuus L.) holds global significance as an oil crop. This study aims to assess the potential of zinc-solubilizing bacterial strains in reducing cadmium uptake by enhancing zinc availability in sunflower plants. For this investigation, we selected twelve pre-isolated zinc-solubilizing bacterial (ZSB) strains for screening against cadmium tolerance and were evaluated for their exopolysaccharides (EPS) and siderophore production capabilities. Four strains exhibiting excellent tolerance to cadmium, EPS production, and siderophore production were subsequently inoculated into sunflower plants to determine the cadmium concentration to determine EC50 at various cadmium levels (ranging from 0 to 200 mg kg-1). Following the compatibility assessment of these strains as single and consortium inoculation, sunflower seeds were cultivated in jars containing soil with two cadmium levels (0 and 125 mg kg-1), totaling 600 g of soil. Our findings demonstrated that the application of ZSB significantly enhanced sunflower growth while simultaneously reducing cadmium uptake. Particularly noteworthy was the performance of the bacterial consortium, composed of strains ZM27 and AN31, which resulted in a remarkable 96% reduction in cadmium translocation, an 86% decrease in cadmium bioaccumulation, and a 97% reduction in overall cadmium uptake compared to the control group. Moreover, the same treatment has caused increase in root length (21.6%), shoot length (18.8%), chlorophyll contents (23.5%), Zn in shoot (30.8%), root Zn contents (13.5%), seedling vigor (49.6%) and leaf area (23.1%) of sunflower under Cd stress as compared to control. The present study concludes that zinc-solubilizing bacterial strains, in consortium ZM27+AN31 were found effective in mitigating the adverse effects of cadmium uptake in sunflower plants. These results suggest that bacterial inoculation strategies hold significant promise for reducing cadmium content in sunflower crops, thereby enhancing the safety and suitability of sunflower-derived edible oils for human consumption and safeguarding human health.&lt;/p&gt;

Plant growth-promoting bacteria improve the Cd phytoremediation efficiency of soils contaminated with PE–Cd complex pollution by influencing the rhizosphere microbiome of sorghum

Composite pollution by microplastics and heavy metals poses a potential threat to the soilplant system and has received increasing attention. Plant growth-promoting bacteria (PGPB) have good application potential for the remediation of combined microplastic and heavy metal pollution, but few related studies exist. The present study employed a pot experiment to investigate the effects of inoculation with the PGPB Bacillus sp. SL-413 and Enterobacter sp. VY-1 on sorghum growth and Cd accumulation under conditions of combined cadmium (Cd) and polyethylene (PE) pollution. Cd+PE composite contamination led to a significant reduction in sorghum length and biomass due to increased toxicity. Inoculation with Bacillus sp. SL-413 and Enterobacter sp. VY-1 alleviated the stress caused by Cd+PE complex pollution, and the dry weight of sorghum increased by 25.7% to 46.1% aboveground and by 12.3% to 45.3% belowground. Bacillus sp. SL-413 and Enterobacter sp. VY-1 inoculation increased the Cd content and accumulation in sorghum and improved the phytoremediation efficiency of Cd. The inoculation treatment effectively alleviated the nutrient stress caused by the reduction in soil mineral nutrients due to Cd+PE composite pollution. The composition of the soil bacterial communities was also affected by the Cd, Cd+PE and bacterial inoculation treatments, which affected the diversity of the soil bacterial communities. Network analyses indicated that bacterial inoculation regulated the interaction of rhizospheric microorganisms and increased the stability of soil bacterial communities. The Mantel test showed that the changes in the soil bacterial community and function due to inoculation with Bacillus sp. SL-413 and Enterobacter sp. VY-1 were important factors influencing sorghum growth and Cd remediation efficiency. The results of this study will provide new evidence for the research on joint plantmicrobe remediation of heavy metal and microplastic composite pollution.

Chromium-stress alleviation study using plant growth promoting rhizobacteria for maize ( Zea mays L.)

Heavy metal contamination is one of the major environmental threats due to industrialization and urbanization. Among various heavy metals, chromium is of recent concern because it is considered the most hazardous metal pollutant in the environment. Its toxicity alters the process of germination and various other growth parameters ultimately affecting its yield. While maize (Zea mays L.) is one of the most widely cultivated cereal crop being used for fodder, feed and food purposes. It is multipurpose cereal crop and is also used as raw material for different industries. Hence, it is mandatory to come up with effective eco-friendly technique to remediate chromium (Cr) to protect the environment from its toxic impacts. During current research, plant microbe interaction was carried out with Cr resistant strains of Bacillus cereus (3a), Pseudomonas aeruginosa (DS4), Bacillus nitratireducens (TP8), Enterobacter cloacae (A9G) and Pseudomonas sp. (B3) that were selected to observe their beneficial impact on corn (Zea mays L.) growth in presence of Cr stress (150 &amp; 300 µg/mL). Results have indicated that growth and biochemical parameters were enhanced due to bacterial inoculation. In comparison to control, maximum increment in shoot length, number of leaves, root length and fresh weight of inoculated plants was noted up to 46, 115, 76, and 42% respectively. Maximum increment in protein and chlorophyll content of inoculated plants was noted up to 304 and 71% respectively as compared to control. The present study suggests the use of above-mentioned highly chromium resistant bacterial strains to remediate chromium contaminated sites and to improve agricultural production.

Impact of Inoculation Practices on Microbiota Assembly and Community Stability in a Fabricated Ecosystem

Studying plant–microbe–soil interactions is challenging due to their high complexity and variability in natural ecosystems. While fabricated ecosystems provide opportunities to recapitulate aspects of these systems in reduced complexity and controlled environments, inoculation can be a significant source of variation. To tackle this, we evaluated how different bacterial inoculation practices and plant harvesting time points affect the reproducibility of a synthetic microbial community (SynCom) in association with the model grass Brachypodium distachyon. We tested three microbial inoculation practices, seed inoculation, transplant inoculation, and seedling inoculation, and two harvesting points, early (14-day-old plants) and late (21 days postinoculation). We grew our plants and bacterial strains in sterile devices (EcoFABs) and characterized the microbial community from root, rhizosphere, and sand using 16S ribosomal RNA gene sequencing. The results showed that inoculation practices significantly affected the rhizosphere microbial community when harvesting at an early time point but not at the late time point. As the SynCom showed a persistent association with B. distachyon at 21 days postinoculation regardless of inoculation practices, we assessed the reproducibility of each inoculation method and found that transplant inoculation showed the highest reproducibility. Moreover, plant biomass was not adversely affected by transplant inoculation treatment. We concluded that bacterial inoculation while transplanting coupled with a later harvesting time point gives the most reproducible microbial community in the EcoFAB− B. distachyon−SynCom fabricated ecosystem. We recommend this method as a standardized protocol for use with fabricated ecosystem experimental systems. [Formula: see text] This manuscript has been authored by an author at Lawrence Berkeley National Laboratory under Contract number DE-AC02-05CH11231 with the U.S. Department of Energy. The U.S. Government retains, and the publisher, by accepting the article for publication, acknowledges, that the U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. Government purposes. This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Enhancing Native Plant Establishment in Mine Tailings under Drought Stress Conditions through the Application of Organo-Mineral Amendments and Microbial Inoculants

The implementation of phytoremediation strategies under arid and semiarid climates requires the use of appropriate plant species capable of withstanding multiple abiotic stresses. In this study, we assessed the combined effects of organo-mineral amendments and microbial inoculants on the chemical and biological properties of mine tailings, as well as on the growth of native plant species under drought stress conditions. Plants were cultivated in pots containing 1 kg of a mixture of mine tailings and topsoil (i.e., pre-mined superficial soil) in a 60:40 ratio, 6% marble sludge, and 10% sheep manure. Moreover, a consortium of four drought-resistant plant growth-promoting rhizobacteria (PGPR) was inoculated. Three irrigation levels were applied: well-watered, moderate water deficit, and severe water deficit, corresponding to 80%, 45%, and 30% of field capacity, respectively. The addition of topsoil and organo-mineral amendments to mine tailings significantly improved their chemical and biological properties, which were further enhanced by bacterial inoculation and plants’ establishment. Water stress negatively impacted enzymatic activities in amended tailings, resulting in a significant decrease in acid and alkaline phosphatases, urease, and dehydrogenase activities. Similar results were obtained for bacteria, fungi, and actinomycete abundance. PGPR inoculation positively influenced the availability of phosphorus, total nitrogen, and organic carbon, while it increased alkaline phosphatase, urease (by about 10%), and dehydrogenase activity (by 50%). The rhizosphere of Peganum harmala showed the highest enzymatic activity and number of culturable microorganisms, especially in inoculated treatments. Severe water deficit negatively affected plant growth, leading to a 40% reduction in the shoot biomass of both Atriplex halimus and Pennisetum setaceum compared to well-watered plants. P. harmala showed greater tolerance to water stress, evidenced by lower decreases observed in root and shoot length and dry weight compared to well-watered plants. The use of bioinoculants mitigated the negative effects of drought on P. harmala shoot biomass, resulting in an increase of up to 75% in the aerial biomass in plants exposed to severe water deficit. In conclusion, the results suggest that the combination of organo-mineral amendments, PGPR inoculation, and P. harmala represents a promising approach to enhance the phytoremediation of metal-polluted soils under semiarid conditions.

Analysis Of Microbial Culture Learning: Understanding The Relationship Between Technical Competence And Students' Perspectives At Dharmawangsa University, Medan

This study examines the relationship between test scores and students' perceptions of learning microbial cultures. The objectives of the research were to determine how students' technical skills correspond with their subjective perceptions of difficulty in various aspects of learning, and to identify the most difficult aspects of learning microbial cultures. Data were collected through tests and questionnaires administered to microbiology practicum students. Analysis revealed a significant correlation between test scores and student perceptions in most aspects of learning, but with variation between aspects. Aspects of basic microbial culture concepts showed a positive correlation, suggesting that students with a strong understanding of the concepts perceived less difficulty. In contrast, bacterial inoculation techniques showed a negative correlation, indicating a mismatch between technical ability and perceived difficulty. The analysis provides a comprehensive view of the factors influencing the learning of microbial culture. The results show that students perceive bacterial inoculation techniques as the most challenging aspect, despite moderately skilled students demonstrating adequate technical ability. Potential sources of technical complexity in the inoculation process, such as steps requiring precision and access to hands-on equipment, contribute to students' perceived difficulty. Although the relationship between test scores and student perceptions of microbial culture learning has been explored in this study, additional research is needed to delve deeper into the complex factors that contribute to this relationship

A novel, reverse-phase-shifting, thermoreversible foaming hydrogel containing antibiotics for the treatment of thermal burns in a swine model – A pilot study

BackgroundThis study compared a novel topical hydrogel burn dressing (CI-PRJ012) to standard of care (silver sulfadiazine) and to untreated control in a swine thermal burn model, to assess for wound healing properties both in the presence and absence of concomitant bacterial inoculation. MethodsEight equal burn wounds were created on six Yorkshire swine. Half the wounds were randomized to post-burn bacterial inoculation. Wounds were subsequently randomized to three treatments groups: no intervention, CI-PRJ012, or silver sulfadiazine cream. At study end, a blinded pathologist evaluated wounds for necrosis and bacterial colonization. ResultsWhen comparing CI-PRJ012 and silver sulfadiazine cream to no treatment, both agents significantly reduced the amount of necrosis and bacteria at 7 days after wound creation (p < 0.01, independently for both). Further, CI-PRJ012 was found to be significantly better than silver sulfadiazine (p < 0.02) in reducing bacterial colonization. For wound necrosis, no significant difference was found between silver sulfadiazine cream and CI-PRJ012 (p = 0.33). ConclusionsCI-PRJ012 decreases necrosis and bacterial colonization compared to no treatment in a swine model. CI-PRJ012 appeared to perform comparably to silver sulfadiazine. CI-PRJ012, which is easily removed with the application of room-temperature water, may provide clinical advantages over silver sulfadiazine.

Optimizing tomato seedling growth with indigenous mangrove bacterial inoculants and reduced NPK fertilization.

The search for ecofriendly products to reduce crop dependence on synthetic chemical fertilizers presents a new challenge. The present study aims to isolate and select efficient native PGPB that can reduce reliance on synthetic NPK fertilizers. A total of 41 bacteria were isolated from the sediment and roots of mangrove trees (Avicennia marina) and assessed for their PGP traits under in vitro conditions. Of them, only two compatible strains of Bacillus species were selected to be used individually and in a mix to promote tomato seedling growth. The efficiency of three inoculants applied to the soil was assessed in a pot experiment at varying rates of synthetic NPK fertilization (0, 50, and 100% NPK). The experiment was set up in a completely randomized design with three replications. Results showed that the different inoculants significantly increased almost all the studied parameters. However, their effectiveness is strongly linked to the applied rate of synthetic fertilization. Applying bacterial inoculant with only 50% NPK significantly increased the plant height (44-51%), digital biomass (60-86%), leaf area (77-87%), greenness average (29-36%), normalized difference vegetation index (29%), shoot dry weight (82-92%) and root dry weight (160-205%) compared to control plants. Concerning the photosynthetic activity, this treatment showed a positive impact on the concentrations of chlorophyll a (25-31%), chlorophyll b (34-39%), and carotenoid (45-49%). Interestingly, these increases ensured the highest values significantly similar to or higher than those of control plants given 100% NPK. Furthermore, the highest accumulation of N, P, K, Cu, Fe, Zn, and Ca in tomato shoots was recorded in plants inoculated with the bacterial mix at 50% NPK. It was proven for the first time that the native PGP bacteria derived from mangrove plant species A. marina positively affects the quality of tomato seedlings while reducing 50% NPK.

Seedling microbiota engineering using bacterial synthetic community inoculation on seeds.

Synthetic Communities (SynComs) are being developed and tested to manipulate plant microbiota and improve plant health. To date, only few studies proposed the use of SynCom on seed despite its potential for plant microbiota engineering. We developed and presented a simple and effective seedling microbiota engineering method using SynCom inoculation on seeds. The method was successful using a wide diversity of SynCom compositions and bacterial strains that are representative of the common bean seed microbiota. First, this method enables the modulation of seed microbiota composition and community size. Then, SynComs strongly outcompeted native seed and potting soil microbiota and contributed on average to 80% of the seedling microbiota. We showed that strain abundance on seed was a main driver of an effective seedling microbiota colonization. Also, selection was partly involved in seed and seedling colonization capacities since strains affiliated to Enterobacteriaceae and Erwiniaceae were good colonizers while Bacillaceae and Microbacteriaceae were poor colonizers. Additionally, the engineered seed microbiota modified the recruitment and assembly of seedling and rhizosphere microbiota through priority effects. This study shows that SynCom inoculation on seeds represents a promising approach to study plant microbiota assembly and its consequence on plant fitness.