Conditions For Microbial Growth Research Articles

Tracing residual patterns and microbial communities of pharmaceuticals and personal care products from 17 urban landfills leachate in China

Landfill leachate contributes significantly to the presence of pharmaceuticals and personal care products (PPCPs) in the environment, and is a crucial source of contamination. To examine the occurrence of PPCPs and microbial communities, this study comprehensively investigated the concentrations of PPCPs and the abundance of microorganisms in the leachate from 17 municipal landfills across China. Generally, Lidocaine, Linear alkylbenzene sulfonate-C11, and Triclocarban, which are closely associated with human activities, exhibited a detection frequency of 100 % in the leachate. Driven by consumer demand, analgesic and antipyretic drugs have emerged as the most prominent PPCPs in leachate (accounting for 39.9 %). Notably, the Ibuprofen peaked at 56.3 μg/L. Regarding spatial distribution, the contamination of PPCPs in leachates from the eastern regions of China was significantly higher than that in other regions, owing to the level of economic development and demographic factors. Furthermore, the 16S rRNA results revealed significant differences in microbial communities among the leachates from different areas. Although the impact of PPCPs on microbial communities may not be as significant as that of environmental factors, most positive correlations between PPCPs and microorganisms indicate their potential role in providing nutrients and creating favorable conditions for microbial growth. Overall, this research offers new perspectives on the residual features of PPCPs and the microbial community structure in leachates from various regions in China.

Mixed planting of subtropical Chinese fir in South China improves microbial carbon source metabolism and functional diversity through the accumulation of nutrients from soil aggregates.

Soil microbial functional traits are key indicators of soil microbial ecological traits; however, how mixing patterns of Chinese fir and broadleaved trees drive soil microbial functional trait variation at the aggregate scale and how soil microbial functional traits are linked to soil fertility factors have largely not been determined. In this study, soil from the 0-20 cm depths in three Chinese fir plantations was collected, and the soil samples were separated into >2 mm (large macro-aggregate), 0.25-2 mm (macro-aggregate) and <0.25 mm (micro-aggregate) by complying with an optimal moisture sieving procedure. The metabolic activities, functional diversity and different carbon sources utilization characteristics of the soil microorganisms were determined by the Biolog Eco microplate method. In all Chinese fir plantations, micro-aggregates (<0.25 mm) consistently exhibited the highest levels of microbial metabolic activity, a more uniform carbon source utilisation capacity, and the highest microbial diversity. Micro-aggregates also showed elevated levels of soil organic carbon (OC), total nitrogen (TN), total phosphorus (TP), and higher ratios of C/N and C/P compared to large macro-aggregates and macro-aggregates, indicating that micro-aggregates contain more resources available to soil microorganisms. Soil OC, TN, and TP content were enhanced by integration with Michelia macclurei, suggesting that this combination promotes relatively favourable soil conditions for microbial growth and multiplication. This, in turn, promotes microbial metabolic activity. Furthermore, redundancy and correlation analyses showed that soil OC, TN, and TP were identified as principal determinants of soil microbial functional properties in Chinese fir plantations. In summary, mixed cultivation and aggregate size influenced microbial functional properties via soil nutrient alterations. Consequently, adopting a mixed cultivation approach of Chinese fir and broadleaved trees is advocated in the subtropical regions of Guangxi. Employing a diversity of tree species, including M. macclurei, is recommended for optimal soil quality preservation.

Enhancing soil petrochemical contaminant remediation through nutrient addition and exogenous bacterial introduction

Biostimulation (providing favorable environmental conditions for microbial growth) and bioaugmentation (introducing exogenous microorganisms) are effective approaches in the bioremediation of petroleum-contaminated soil. However, uncertainty remains in the effectiveness of these two approaches in practical application. In this study, we constructed mesocosms using petroleum hydrocarbon-contaminated soil. We compared the effects of adding nutrients, introducing exogenous bacterial degraders, and their combination on remediating petroleum contamination in the soil. Adding nutrients more effectively accelerated total petroleum hydrocarbon (TPH) degradation than other treatments in the initial 60 days’ incubation. Despite both approaches stimulating bacterial richness, the community turnover caused by nutrient addition was gentler than bacterial degrader introduction. As TPH concentrations decreased, we observed a succession in microbial communities characterized by a decline in copiotrophic, fast-growing bacterial r-strategists with high rRNA operon (rrn) copy numbers. Ecological network analysis indicated that both nutrient addition and bacterial degrader introduction enhanced the complexity and stability of bacterial networks. Compared to the other treatment, the bacterial network with nutrient addition had more keystone species and a higher proportion of negative associations, factors that may enhance microbial community stability. Our study demonstrated that nutrient addition effectively regulates community succession and ecological interaction to accelerate the soil TPH degradation.

Effect of Nigella sativa L. essential oil on oxidative stability and microbial growth of local white Feta cheese

Controlling the development of pathogenic and spoilage microorganisms is critical for food manufacturers to preserve their products. Cheese provides favourable conditions for microbial growth and oxidative degradation due to the presence of water, fat, protein, and minerals. The present work thus aimed to determine the influence of Nigella sativa L. essential oil on microbial growth and oxidative stability of cheese made from fresh milk. The analysis of the chemical composition of N. sativa essential oil was performed by gas chromatography-mass spectrometry. The main compounds detected were 9,12-octadecadienoic acid (27.96%), cis-vaccenic acid (20.69%), 6-epi-shyobunol (7.08%), benzene, 1-methyl-3-(1-methylethyl)- (6.33%), n-hexadecanoic acid (3.86%), o-cymene (2.77%), and cis-4-methoxy thujane (2.71%). The antioxidant activity of N. sativa essential oil was calculated by the 2,2-diphenyl-1-picrylhydrazyl method with IC50 = 8.08 μg/mL. The microdilution test showed that the minimum inhibitory concentration (MIC) of N. sativa essential oil for all pathogens was 500 μg/mL, while the minimum bactericidal concentration (MBC) was 1,000 μg/mL for Staphylococcus aureus and Bacillus cereus, and 2,000 μg/mL for Escherichia coli and Pseudomonas aeruginosa. The physicochemical properties of the cheese showed that the addition of essential oil did not affect the dry matter, but increased the pH, decreased the % acidity, and decreased the peroxide value compared to the control sample (sample without essential oil). In addition, the essential oil reduced the bacterial and fungal counts of the cheese compared to the control sample, and affected the sensory characteristics of the cheese during the 90-day storage period. Results also showed that the addition of 0.5% essential oil of N. sativa not only prevented microbial growth and oxidative degradation, but also improved the taste and overall acceptability of cheese.

Characteristics, Sources, and Mechanisms of Soil Respiration under Simulated Rainfall in a Native Karst Forest in Southwestern China

Rainfall significantly affects soil respiration rates by altering microbial activity and organic matter decomposition. In karst regions, it also impacts carbonate dissolution and precipitation, further influencing soil CO2 flux. Investigating the mechanism of rainfall’s impact on soil respiration is essential for accurately evaluating and predicting changes in terrestrial ecosystems. However, our understanding of the interaction between rainfall and soil respiration in the extensive karst ecosystems of southwestern China remains limited. This study conducted field-based simulated rainfall experiments to examine variations in soil respiration rates and elucidate the associated control mechanisms through stable carbon isotope composition analysis. Simulated rainfall significantly increased the CO2 release via soil respiration. We observed significant differences in the δ13C value of soil-respired CO2 before and after simulated rainfall. Following the rain, the δ13C of soil-respired CO2 was enriched compared to that before the rain. Through isotope data analysis, we found that the increased soil CO2 emissions were primarily driven by heterotrophic respiration, likely stimulated via changes in soil moisture, affecting microbial growth conditions. Furthermore, the variation in soil moisture affected carbonate dissolution and precipitation, potentially increasing the soil CO2 release after rainfall. In conclusion, these findings expand our understanding of rainfall’s effects on soil respiration in the native karst forests of southwestern China, contributing to the prediction of carbon cycling processes in such ecosystems. The data from this study have significant implications for addressing the release of greenhouse gases in efforts to combat climate change.

Effects of Past Sulfur Deposition on the Soil Microbial Biomass at Spruce Forest Sites

During the last decades, forest soils in Central Europe recovered from former sulfur and acid deposition. As external S input into forests has strongly decreased and legacy S pools in the soils are diminishing, internal S cycling through mineralization will increasingly become important for ecosystem nutrition. However, it is not known how microbial biomass is affected by the S pool change in the formerly S surplus soils. Here, we present data on the status quo of C, N, and S in microbial biomass in relation to contents in mineral soil and organic layer. The results of forest soil in Eastern Germany (low and high liming), which is slowly recovering from former pollution, are compared to those of a site remote from air pollution in the Swiss Alps. The contents of C, N, and S in soil as well as in microbial biomass were clearly higher in the organic layer than in mineral topsoil at all sites. Despite the generally low content in the mineral A-horizon, the clean-air site showed indications of a more active S-turnover as compared to the high-pollution site. Liming at the high-pollution site improved the conditions for microbial growth (pH increase) in the organic layer resulting in more mobile S.

Biological Ammonia Production via Anaerobic Fermentation of Soy Meal Protein.

Conventional ammonia production methods, notably the energy-intensive Haber-Bosch process, are costly and contribute substantially to about 2% of the world's CO2 emissions. This study focuses on the biological approach to convert protein to ammonia via hyper-ammonia-producing bacteria (HAB) fermentation. A consortium of ruminal microbes was employed in this work to ferment soybean meal protein under varying processing conditions. The parameters investigated included pH (7-11), inoculum concentrations (1-10%), substrate concentrations (5-20%), and fermentation time (0-168 h). Optimal conditions for microbial growth and biological ammonia production were observed at pH 7, fermentation duration of 72 h, inoculum concentration of 10%, and substrate concentration of 10%. ~8000 mg/L biological ammonia was produced following HAB fermentation. By leveraging the capabilities of rumen HAB, this study contributes to the ongoing efforts to develop environmentally friendly processes for ammonia production that will mitigate both economic and environmental concerns associated with traditional methods.

Viscosity influence on kinetics parameters in dry anaerobic digestion

The viscosity that governs mass exchanges is a determining parameter of dry digestion kinetics. This observation leads to the measurement of viscosity influence on key kinetic parameters of digestion such as microbial growth, degradation of COD, biogas production and its CH4 quality. Thus, for limit viscosities at the beginning of digestion in batch mode at 37 °C and 55 °C of potato residues of 18–35 % TS content, the evolution of kinetic parameters is observed. The results show strong microbial growth for 4.39 × 10−2 Pa s and 7.5 × 10−2 Pa s in digestion at 37 °C and 4.12 × 10−2 Pa s in digestion at 55 °C. The reduction of COD is optimal for 7.50 × 10−2 Pa s at 37 °C and 6.57 × 10−2 Pa s at 55 °C. Biogas production is higher for 7.5 × 10−2 Pa s at 37 °C and 4.12 × 10−2 Pa s at 55 °C. Finally, the CH4 content of biogas is higher for 4.39 × 10−2 Pa s and 4.12 × 10−2 Pa s at 37 °C and 55 °C, respectively. These results show that optimal conditions for microbial growth and CH4 production are obtained with the 22 % TS scenario giving a viscosity of 4.39 × 10−2 Pa s at 37 °C and 4.12 × 10−2 Pa s at 55 °C. These results confirm the importance of the viscosity in biochemical kinetics in dry digestion.

Antiseptic Chitosan-Poly(hexamethylene) Biguanide Hydrogel for the Treatment of Infectious Wounds.

Topical wound infections create the ideal conditions for microbial colonization and growth in terms of moisture, temperature, and nutrients. When they are not protected, numerous types of bacteria from the internal microbiota and the external environment may colonize them, creating a polymicrobial population. Treatment of these wounds often necessitates the use of antibiotics that may have systemic harmful effects. Unlike antibiotics, topical antiseptics exhibit a wider range of activity and reduced systemic toxicity and resistance. In order to address this issue, we developed an antiseptic Chitosan-Poly (hexamethylene) Biguanide (CS-PHMB) hydrogel. The prepared hydrogel was characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). SEM images showed the smooth morphology and characteristic FTIR peaks of PHMB and confirmed the incorporation of the antiseptic into the chitosan (CS) hydrogel. A Water Vapor Permeation Rate study confirms the moisture retention ability of the CS-PHMB hydrogel. Rheological studies proved the gel strength and temperature stability. The prepared hydrogel inhibited the growth of S. aureus, P. aeruginosa, E. coli, methicillin-resistant Staphylococcus aureus (MRSA), and K. pneumoniae, which confirms its antibacterial properties. It also inhibited biofilm formation for S. aureus and E. coli. CS-PHMB hydrogel is also found to be hemo- and cytocompatible in nature. Thus, the developed CS-PHMB hydrogel is a very potent candidate to be used for treating infectious topical wounds with low systemic toxicity.

Biochar Benefits Green Infrastructure: Global Meta-Analysis and Synthesis.

Urbanization has degraded ecosystem services on a global scale, and cities are vulnerable to long-term stresses and risks exacerbated by climate change. Green infrastructure (GI) has been increasingly implemented in cities to improve ecosystem functions and enhance city resilience, yet GI degradation or failure is common. Biochar has been recently suggested as an ideal substrate additive for a range of GI types due to its favorable properties; however, the generality of biochar benefits the GI ecosystem function, and the underlying mechanisms remain unclear. Here, we present a global meta-analysis and synthesis and demonstrate that biochar additions pervasively benefit a wide range of ecosystem functions on GI. Biochar applications were found to improve substrate water retention capacity by 23% and enhance substrate nutrients by 12-31%, contributing to a 33% increase in plant total biomass. Improved substrate physicochemical properties and plant growth together reduce discharge water volume and improve discharge water quality from GI. In addition, biochar increases microbial biomass on GI by ∼150% due to the presence of biochar pores and enhanced microbial growth conditions, while also reducing CO2 and N2O emissions. Overall results suggest that biochar has great potential to enhance GI ecosystem functions as well as urban sustainability and resilience.

The potency of spores and biosurfactant of Bacillus clausii as a new biobased sol-gel coatings for corrosion protection of carbon steel ST 37 in water cooling systems

The structures of water cooling systems are prone to microbially-influenced corrosion (MIC) due to the favorable conditions for microbial growth. Biofilm formation accelerates corrosion, leading to reduced system efficiency, structural damage, and significant financial losses. Encapsulating viable bacterial spores and biosurfactant within a silica-based sol-gel coating offers an eco-friendly approach to prevent this type of corrosion. Bacillus clausii, known for its antimicrobial biosurfactant production capability, was utilized in this study to investigate the impact of spores and biosurfactant addition to silica-based sol-gel coatings in inhibiting biofilm formation and preventing corrosion in water cooling systems. Microbiological analysis of the biofilm was conducted using the total plate count method, while the corrosion process was analyzed through electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The viability of B. clausii spores within the sol-gel matrix was determined to be 20.8 %. The presence of bacterial spores and biosurfactant significantly increased the hydrophobicity of the sol-gel coating. Incorporating spores within the sol-gel matrix delayed biofilm formation for up to 12 days, while biosurfactant addition showed the smallest biofilm abundance (2.23×105 CFU/mL) at its maturation phase compare to others. After 180 days of incubation, analysis of Bode and Tafel plots demonstrated that the sol-gel coating containing biosurfactant maintained excellent anti-corrosion performance, exhibiting an impedance of 104 Ω cm2, Ecorr of -0.398 V vs SCE, and icorr of 0.51 µA/cm2. SEM-EDS analysis of the surface sample revealed a comparably smooth and uniform surface with a minimal abundance of exposed Fe atoms at 0.12 %. In conclusion, this study demonstrated the high potency of the sol-gel coating supplemented with biosurfactant in inhibiting biofilm formation and corrosion on metals in water cooling systems.

An approach to improve the existing ribbon retting of jute fibre using concrete tank and natural catalyst

The ribbon retting method has been developed as a remedy for the issues associated with the conventional water retting method. But this method has not yet gained popularity among jute growers due to the unavailability of catalyst, inadequate training and lack of interest of farmers. The study deals with the improvement of the existing ribbon retting process by using a concrete tank with or without fermented soybean as a natural catalyst in different proportions. For this purpose, 25 fibre samples were developed using different conditions such as concrete tank without natural catalyst, concrete tank with 2.5%, 5% and 7.5% natural catalyst and a micro pond without natural catalyst for various observational time periods. After that, samples collected under mentioned conditions which were measured to assess the fibre properties. The samples produced in a concrete tank with 7.5% natural catalyst demonstrated better fibre characteristics than the other conditions, including fibre fineness, fibre strength, improved fibre color, open surface structure and smooth surface etc. The best conditions for microbial growth were achieved using a concrete tank with more natural catalysts, which improved bacterial growth, fibre quality and reduced the retting time. The use of more natural catalysts increased microbial activity, which in turn affected total dissolved solids (TDS), Biochemical oxygen demand (BOD), Chemical oxygen demand (COD), and pH value of the retted water. In comparison to the existing ribbon retting method, this improved method is significantly faster and produces fibers with better properties. Farmers will gain more from the successful implementation of an improved ribbon retting method because it shortens retting time, conserves water, and uses a concrete tank during retting that can be used for multiple purposes.

Performance of tubular microbial fuel cells using different industrial wastewater

Microbial fuel cells (MFCs) can potentially ameliorate the extensive use of energy in the biological treatment step of wastewater treatment, among other benefits. This paper investigated the use of MFCs for different types of industrial wastewater using carbon fuel cell electrodes. The MFCs were inoculated with activated sludge and operated with industrial wastewater collected from Kuwait's most common industries (dairy, detergents, petrochemicals, and soft drinks). The results showed that MFCs have successively generated electricity from all industrial wastewater, except for that from the petrochemical industry. The MFCs achieved a maximum power density of 86 mW/m3 (dairy wastewater), 41 mW/m3 (detergents wastewater), 20 mW/m3 (soft drink wastewater), and 1 mW/m3 (petrochemical wastewater). Furthermore, the MFCs achieved an average Chemical Oxygen Demand (COD) removal efficiency of 75 % (dairy wastewater), 44 % (detergent wastewater), 7 % (petrochemical wastewater), and 79 % (soft drink wastewater). Conceivably, these removal rates correspond to bioelectrochemical utilization of the organic matter present in the different types of industrial wastewater to produce energy. Increasing batch duration from 7 to 14 days did not influence nutrients and heavy metals removal. In addition, it was found that the application of MFCs for petrochemical wastewater treatment was influenced by (high COD level = 15,114 mg/L), the content of inhibitive chemicals (such as surfactant, dimethylpolysiloxane, ferric sulfate, and benzalkonium chloride), and the hydrophobicity of the organics leading to deterioration in fuel cell electrode performance, catalyst deactivation, and generally unfavourable microbial growth conditions.

Diversity of virulence and antibiotic resistance genes expressed in Class A biosolids and biosolids-amended soil as revealed by metatranscriptomic analysis.

Class A biosolids is a treated sewage sludge, commonly applied to agricultural fields, home lawns/gardens, golf courses, forests, and remediation sites around the world. This practice is of public and agricultural concern due to the possibility that biosolids contain antibiotic-resistant bacteria and fungal pathogens that could persist for extended periods in soil. This possibility was determined by metatranscriptomic analysis of virulence, antibiotic resistance, and plasmid conjugation genes, a Class A biosolids, organically managed soil, and biosolids-amended soil under realistic conditions. Biosolids harbored numerous transcriptionally active pathogens, antibiotic resistance genes, and conjugative genes that annotated mostly to Gram-positive pathogens of animal hosts. Biosolids amendment to soil significantly increased the expression of virulence genes by numerous pathogens and antibiotic-resistant genes that were strongly associated with biosolids. Biosolids amendment also significantly increased the expression of virulence genes by native soil fungal pathogens of plant hosts, which suggests higher risks of crop damage by soil fungal pathogens in biosolids-amended soil. Although results are likely to be different in other soils, biosolids, and microbial growth conditions, they provide a more holistic, accurate view of potential health risks associated with biosolids and biosolids-amended soils than has been achievable with more selective cultivation and PCR-based techniques.

Beyond Cultivation: Combining Culture-Dependent and Culture-Independent Techniques to Identify Bacteria Involved in Paint Spoilage

Due to globally increasing problems concerning biodeterioration of paints, it is worthwhile to enhance the determination of colony forming units (CFU) as a gold standard method via more rapid and culture-independent techniques. Here, we combined traditional culture-dependent techniques with subsequent sequencing, quantitative qPCR, and a serial quantification method (most probable number; MPN) to detect paint degrading bacteria in general and sulfate-reducing bacteria (SRB) in particular. During our investigation of three water-based paints that showed visible contamination, we found high bacterial counts of up to 107 CFU mL−1. Subsequent sequencing allowed the identification of common paint degraders including Bacillus sp. and Pseudomonas sp., but less frequently detected bacteria such as Rhodococcus sp. and Delftia spp. were also found to be present. MPN, as well as dsrA-targeted qPCR to detect SRB, only showed positive results for two out of three samples. These results coincided with the inherent physicochemical properties of the paints offering suitable conditions for microbial growth or not. The MPN method can be used for a diversity of aerobic and anaerobic bacteria and is rapid and reproducible. A combination of culture-independent techniques such as qPCR or NGS can help to fully elucidate the bacterial diversity in spoiled paint by also recovering anaerobic and unculturable ones.

Responses of soil microbial activities to soil overburden thickness in restoring a coal gangue mound in an alpine mining area

This study analyzes the changes in soil microbial community diversity after five years of restoration in an alpine mining area using different soil overburden thicknesses, in which MiSeq high-throughput sequencing technology was applied to analyze soil microbial community diversity and its influential environmental factors. The results showed that vegetation restoration obviously changed the species composition of soil microorganisms at the OTUs (Operational Taxonomic Units) level under different soil overburden thicknesses, and the OTUs species of soil fungi and bacteria changed significantly in the 15 cm soil overburden thickness. The bacterial diversity index was higher than that of fungal microorganisms in all three soil overburden thicknesses, and the microbial diversity index without soil overburden thickness was significantly higher than that in the soil overburden thickness (P < 0.05). The dominant phyla and genera of soil bacteria and fungi were almost the same. The bacteria were Proteobacteria, Pseudoarthrobacter and Sphinomonas, and the fungi were Ascomycota and Tricharina. The relative abundance of soil bacteria and fungi varied with the soil overburden thickness. Vegetation height, coverage, moss coverage, soil temperature, moisture, organic matter, nitrogen content, pH and soil overburden thickness were the key factors affecting the soil microbial community structure. A soil overburden thickness of 10 cm was recommended as an ideal soil reconstruction measure in apline mining areas. During the restoration period of the coal gangue mound in the alpine region, significant improvement was observed in the sensitivity of soil microorganisms to thickness over the course of five years. However, in order to facilitate continuous restoration of microorganisms, it is recommended to implement measures such as covering the area with non-woven fabrics and adjusting the pH of the soil to create more favorable conditions for microbial growth.

An Antimicrobial Fabric Using Nano-Herbal Encapsulation of Essential Oils.

Lab coats are widely used in biohazard laboratories and healthcare facilities as protective garments to prevent direct exposure to pathogens, spills, and burns. These cotton-based protective coats provide ideal conditions for microbial growth and attachment sites due to their porous nature, moisture-holding capacity, and retention of warmth from the user's body. Several studies have demonstrated the survival of pathogenic bacteria on hospital garments and lab coats, acting as vectors of microbial transmission. A common approach to fix these problems is the application of antimicrobial agents in textile finishing, but concerns have been raised due to the toxicity and environmental effects of many synthetic chemicals. The ongoing pandemic has also opened a window for the investigation of effective antimicrobials and eco-friendly and toxic-free formulations. This study uses two natural bioactive compounds, carvacrol and thymol, encapsulated in chitosan nanoparticles, which guarantee effective protection against four human pathogens with up to a 4-log reduction (99.99%). These pathogens are frequently detected in lab coats used in biohazard laboratories. The treated fabrics also resisted up to 10 wash cycles with 90% microbial reduction, which is sufficient for the intended use. We made modifications to the existing standard fabric tests to better represent the typical scenarios of lab coat usage. These refinements allow for a more accurate evaluation of the effectiveness of antimicrobial lab coats and for the simulation of the fate of any accidental microbial spills that must be neutralized within a short time. Further studies are recommended to investigate the accumulation of pathogens over time on antimicrobial lab coats compared to regular protective coats.

The power of the smallest: The inhibitory activity of microbial volatile organic compounds against phytopathogens.

Plant diseases caused by phytopathogens result in huge economic losses in agriculture. In addition, the use of chemical products to control such diseases causes many problems to the environment and to human health. However, some bacteria and fungi have a mutualistic relationship with plants in nature, mainly exchanging nutrients and protection. Thus, exploring those beneficial microorganisms has been an interesting and promising alternative for mitigating the use of agrochemicals and, consequently, achieving a more sustainable agriculture. Microorganisms are able to produce and excrete several metabolites, but volatile organic compounds (VOCs) have huge biotechnology potential. Microbial VOCs are small molecules from different chemical classes, such as alkenes, alcohols, ketones, organic acids, terpenes, benzenoids and pyrazines. Interestingly, volatilomes are species-specific and also change according to microbial growth conditions. The interaction of VOCs with other organisms, such as plants, insects, and other bacteria and fungi, can cause a wide range of effects. In this review, we show that a large variety of plant pathogens are inhibited by microbial VOCs with a focus on the in vitro and in vivo inhibition of phytopathogens of greater scientific and economic importance in agriculture, such as Ralstonia solanacearum, Botrytis cinerea, Xanthomonas and Fusarium species. In this scenario, some genera of VOC-producing microorganisms stand out as antagonists, including Bacillus, Pseudomonas, Serratia and Streptomyces. We also highlight the known molecular and physiological mechanisms by which VOCs inhibit the growth of phytopathogens. Microbial VOCs can provoke many changes in these microorganisms, such as vacuolization, fungal hyphal rupture, loss of intracellular components, regulation of metabolism and pathogenicity genes, plus the expression of proteins important in the host response. Furthermore, we demonstrate that there are aspects to investigate by discussing questions that are still not very clear in this research area, especially those that are essential for the future use of such beneficial microorganisms as biocontrol products in field crops. Therefore, we bring to light the great biotechnological potential of VOCs to help make agriculture more sustainable.

Pulmonary microbiota intervention alleviates fine particulate matter-induced lung inflammation in broilers.

Fine particulate matter (PM2.5) released during the livestock industry endangers the respiratory health of animals. Our previous findings suggested that broilers exposed to PM2.5 exhibited lung inflammation and changes in the pulmonary microbiome. Therefore, this study was to investigate whether the pulmonary microbiota plays a causal role in the pathogenesis of PM2.5-induced lung inflammation. We first used antibiotics to establish a pulmonary microbiota intervention broiler model, which showed a significantly reduced total bacterial load in the lungs without affecting the microbiota composition or structure. Based on it, 45 AA broilers of similar body weight were randomly assigned to three groups: control (CON), PM2.5 (PM), and pulmonary microbiota intervention (ABX-PM). From 21 d of age, broilers in the ABX-PM group were intratracheally instilled with antibiotics once a day for 3 d. Meanwhile, broilers in the other two groups were simultaneously instilled with sterile saline. On 24 and 26 d of age, broilers in the PM and ABX-PM groups were intratracheally instilled with PM2.5 suspension to induce lung inflammation, and broilers in the CON group were simultaneously instilled with sterile saline. The lung histomorphology, inflammatory cytokines' expression levels, lung microbiome, and microbial growth conditions were analyzed to determine the effect of the pulmonary microbiota on PM2.5-induced lung inflammation. Broilers in the PM group showed lung histological injury, while broilers in the ABX-PM group had normal lung histomorphology. Furthermore, microbiota intervention significantly reduced mRNA expression levels of interleukin-1β, tumor necrosis factor-α, interleukin-6, interleukin-8, toll-like receptor 4 and nuclear factor kappa-B. PM2.5 induced significant changes in the β diversity and structure of the pulmonary microbiota in the PM group. However, no significant changes in microbiota structure were observed in the ABX-PM group. Moreover, the relative abundance of Enterococcus cecorum in the PM group was significantly higher than that in the CON and ABX-PM groups. And sterile bronchoalveolar lavage fluid from the PM group significantly promoted the growth of E. cecorum, indicating that PM2.5 altered the microbiota's growth condition. In conclusion, pulmonary microbiota can affect PM2.5-induced lung inflammation in broilers. PM2.5 can alter the bacterial growth environment and promote dysbiosis, potentially exacerbating inflammation.

Deforestation for agriculture increases microbial carbon use efficiency in subarctic soils

Agriculture is likely to expand poleward with climate change, encouraging deforestation for agriculture in subarctic regions, which alters soil physical, chemical and biological properties and potentially affects microbial metabolic efficiency. Deciphering how and by which mechanisms land-use change affects microbial carbon use efficiency (CUE) will enable the development of mitigation strategies to alleviate C losses. We assessed CUE using 18O-labelled water in a paired-plot approach on soils collected from 19 farms across the subarctic region of Yukon, Canada, comprising 14 pairs of forest-to-grassland conversion and 15 pairs of forest-to-cropland conversion. Microbial CUE significantly increased following conversion to grassland and cropland. Land-use conversion resulted in a lower estimated abundance of fungi, while the archaeal abundance increased. Interestingly, structural equation modelling revealed that increases in CUE were mediated by a rise in soil pH and a decrease in soil C:N ratio rather than by shifts in microbial community composition, i.e. the ratio of fungi, bacteria and archaea. Our findings indicate a direct control of abiotic factors on microbial CUE via improved nutrient availability and facilitated conditions for microbial growth. Overall, this implies that to a certain extent CUE can be managed to achieve a more efficient build-up of stabilised soil organic C (SOC), as reflected in increased mineral-associated organic C under agricultural land use. These insights may also help constrain SOC models that generally struggle to predict the effects of deforestation, something that is likely to take place more frequently in the subarctic.