Differences in microbial diversity and environmental factors in ploughing-treated tobacco soil

Bacterial communities and soil functionality in artificially remediated vegetation of the three gorges reservoir zone

Riparian zones maintain biodiversity, cyclic nutrients, and regulate water quality. However, their stability is increasingly threatened by human activities such as dam construction and climate variability. This study focuses on the riparian zones of the Three Gorges Dam Reservoir (TGDR), a region marked by fluctuating water levels and a subtropical southeast monsoon climate. We investigated the seasonal and vegetation-specific dynamics of soil properties and microbial communities in riparian zones dominated by artificially remediated plants (ARPs) in the TGDR. The selected ARP species included the herbaceous Cynodon dactylon (CD) and Hemarthria altissima (HA), known for their capacity for rapid soil stabilization, and the tree species Salix matsudana (SM) and Taxodium distichum (TD), which enhance nutrient cycling through litter inputs and root exudates. These species were evaluated across spring (T1), summer (T2), and autumn (T3). Our analysis of 360 soil samples led to the generation of high-quality sequences that provided insights into microbial diversity. Principal component analysis identified organic matter, ammonium nitrogen, and total nitrogen as the main contributors to soil property variance, explaining 53.68% in T1, 51.52% in T2, and 56.37% in T3 of the variance (p < 0.01). Correlation analysis highlighted a positive relationship between soil pH and Nitrospirae (r = 0.603) and Proteobacteria (r = 0.558). Enzyme activity varied by season, with acid phosphatase activity peaking in T3 and invertase activity highest in T1. This study also made functional predictions and identified pathways pertinent to metabolism, genetic information processing, and environmental signal transduction. There were seasonal shifts in metabolic pathways, such as an increase in carbohydrate metabolism in T3 via TD. In addition, there was a rise in amino acid metabolism in T3 via CD. Our assessment of microbial diversity uncovered 68 bacterial phyla, with Proteobacteria and Acidobacteria emerging as the dominant taxa. The results indicate that ARPs positively influence microbial health, nutrient cycling, and overall ecosystem integrity. These findings hold significant implications for riparian ecosystem restoration in regions experiencing environmental changes.

Increasing Productivity and Recovering Nutritional, Organoleptic, and Nutraceutical Qualities of Major Vegetable Crops for Better Dietetics

The intensive use of chemical fertilizers for vegetable cultivation to achieve higher productivity causes soil degradation, resulting in an alarming decline (25-50%) in nutritional quality and a reduction in a wide variety of nutritionally essential minerals and nutraceutical compounds in high-yielding vegetable crops over the last few decades. To restore the physio-chemical and biological qualities of soil as well as the nutritional and nutraceutical qualities of fresh produce, there is a growing desire to investigate the remedial impacts of organic sources of nutrition. This study specifically focused on the impact of six different ratios of chemical fertilizers and organic sources with microbial inoculation on vegetable productivity, nutrition quality, and soil health parameters. Results show that replacing chemical fertilizers with organic sources in the presence of a microbial consortium supports the proliferation of the microbial population in the soil rhizosphere and improves the nutritional status and physico-chemical quality of soil, which is the area around the roots of plants where maximum nutrient uptake occurs. This combination of factors significantly recovers overall soil quality, increasing crop productivity by 13.58 to 18.32 percent in tomato, brinjal, and okra. Experimental findings likewise indicate that an assortment of organic sources with a microbial consortium significantly recovers the abundance of beneficial microbes and earthworms in the rhizosphere, which leads to an improvement in nutritional, organoleptic, and nutraceutical quality, with higher antioxidant contents in all three vegetables grown in arid climate conditions.

Investigating the impact of long-term bristlegrass coverage on rhizosphere microbiota, soil metabolites, and carbon-nitrogen dynamics for pear agronomic traits in orchards

Background

Grass coverage (GC) under no-tillage systems in orchards signifcantly infuences underground carbon (C) and nitrogen (N) sequestration, primarily through promoting mineral nutrient utilization by rhizospheric microorganisms. However, the comprehensive impact of GC on microbial communities and plant responses using soil metabolomics remains inadequately recognized.

Methods

We investigated two rhizosphere types established since 2002: bristlegrass (Setaria viridis (L.) P. Beauv.) coverage (SC) and clean cultivation (CC) to assess their efects on soil parameters, enzyme activities, and key pear agronomic traits, including yield (single fruit weight (SFW)) and qualities (soluble solids content (SSC), and total soluble sugar (TSS)). We combined microbiological analysis (16S rRNA sequencing) and non-targeted metabolomics (UPLC-MS/MS and GC-MS) to explore how microbial communities infuence fruit agronomic traits and soil nutrient dynamics in pear orchards under SC conditions.

Results

Our fndings indicate that SC signifcantly enhances soil organic carbon (SOC), soil organic nitrogen (SON), the C:N ratio, and available nitrogen (AN). Moreover, SC leads to pronounced increases in soil enzyme activities involved in the C cycle and storage, including soil sucrase, β-glucosidase, polyphenol oxidase and cellulase. Microbiome analysis revealed substantial diferences in microbial community composition and diversity indices between SC and CC rhizosphere soils within the 0-40 cm depth. Metabolomic analysis demonstrated significant alterations in metabolite profiles across both the 0-20 cm and 20-40 cm layers under SC conditions. The identifed metabolites primarily involve sugar and amino acid-related metabolic pathways, refecting perturbations in C and N metabolism consistent with shifts in bacterial community structure. Several plant growth-promoting rhizobacteria (PGPRs) taxa (e.g., Haliangium, Bacteroides, mle1-7, Subgroup_22, Ellin6067, MND1, Flavobacterium, and Cellvibrio) were enriched under SC, associated with metabolites such as sucrose, N-acetyl-D-glucosamine, N-acetyl-L-glutamic acid, rhamnose, UDP-GlcNAc and D-maltose. These fndings suggest their roles in promoting C and N sequestration processes through sucrose synthesis and glycolytic pathways in the soil, which was signifcantly correlated with the formation of agronomic traits such as fruit yield, SFW SSC and TSS (p<0.05), and SC treatments signifcantly increased yields by 35.40-62.72% and sucrose content in TSS by 2.43-3.96 times than CC treatments.

Conclusion

This study provides valuable insights into the efects of SC on soil microbial communities and plant physiology, enhancing our understanding of their implications for sustainable orchard management.

Continuous cropping system altered soil microbial communities and nutrient cycles

Understanding the response of microbial communities and their potential functions is essential for sustainability of agroecosystems under long-term continuous cropping. However, limited research has focused on investigating the interaction between soil physicochemical factors and microbial community dynamics in agroecosystems under long-term continuous cropping. This study probed into the physicochemical properties, metabolites, and microbial diversity of tobacco rhizosphere soils cropped continuously for 0, 5, and 20 years. The relative abundance of bacterial genera associated with nutrient cycling (e.g., Sphingomonas) increased while potential plant pathogenic fungi and beneficial microorganisms showed synergistic increases with the duration of continuous cropping. Variations in soil pH, alkeline nitrogen (AN) content, and soil organic carbon (SOC) content drove the shifts in soil microbial composition. Metabolites such as palmitic acid, 3-hydroxypropionic acid, stearic acid, and hippuric acid may play a key role in soil acidification. Those results enhance our ability to predict shifts in soil microbial community structure associated with anthropogenic continuous cropping, which can have long-term implications for crop production.

Temperature and phosphorus: the main environmental factors affecting the seasonal variation of soil bacterial diversity in Nansi Lake Wetland

Introduction

The soil bacteria promote the circulation conversion of lake nutrients and play an important role in maintaining the balance of the lake ecosystem. Few studies have investigated the association of seasonal variation in bacteria and environmental factors in inland freshwater lake wetlands. Nansi Lake is a large shallow freshwater lake in northern China. It is an important hub of the eastern route of the South-to-North Water Diversion Project.

Methods

In this study, bacterial 16S rRNA genes were used to analyze the variation of soil bacterial community diversity in Nansi Lake Wetland and its influencing factors in different seasons.

Results

It is showed that the phylum, family, and genus with the largest relative abundance in the soil of Nansi Lake Wetland are Proteobacteria, Nitrosomonadaceae, and MND1, respectively. There were significant seasonal differences in soil bacterial diversity in Nansi Lake Wetland, which was significantly higher in summer than in winter. Seasonal variation in environmental factors was significantly correlated with the variation in bacterial communities. Temperature and the content of available phosphorus may be the key factors influencing seasonal variation in bacterial diversity.

Discussion

The results of this study further enhance our understanding of the relationship between bacterial community diversity and environmental factors in the lake wetland ecosystem, which can provide scientific data for the conservation of Nansi Lake Wetland.

Revealing the role of the rhizosphere microbiota in reproductive growth for fruit productivity when inorganic fertilizer is partially replaced by organic fertilizer in pear orchard fields

In order to address the global crisis in pear productivity, there has been increased attention given to advocating for the use of organic fertilizers. As part of this effort, researchers have been investigating the microbial properties of organic fertilizers to better understand their potential impact on fruit productivity. Our research focused specifically on the impact of four different ratios of sheep manure (SM) and chemical fertilizers (CF) on pear productivity. We found that replacing CF with SM resulted in a proliferation of gammaproteobacteria, Chlamydiae, Bastocatellia and Clostridia in the soil rhizosphere, which is the region around the roots of plants where most nutrient uptake occurs. Using redundancy analysis, we were able to determine that SM was particularly effective at promoting the growth of gammaproteobacteria and clostridia, which were associated with C:N ratios around 14:1 as well as the availability of K, Fe, Zn and Cu. This combination of factors was conducive to a transition from vegetative growth to reproductive growth, resulting in an increase in pear production from 43 to 56 tons per hectare. We also discovered that Blastociella acts as a buffering system in regulating soil acidity. Taken together, our findings indicate that a combination of SM and CF can improve the abundance of beneficial bacteria in the rhizosphere, leading to an increase in pear productivity.

Characterizing bacterial communities in Phragmites australis rhizosphere and non-rhizosphere sediments under pressure of antibiotics in a shallow lake

Introduction

Antibiotics are ubiquitous pollutants and widely found in aquatic ecosystems, which of rhizosphere sediment and rhizosphere bacterial communities had certain correlation. However, the response of bacterial communities in Phragmites australis rhizosphere and non-rhizosphere sediments to antibiotics stress is still poorly understood.

Methods

To address this knowledge gap, the samples of rhizosphere (R) and non-rhizosphere (NR) sediments of P. australis were collected to investigate the differences of bacterial communities under the influence of antibiotics and key bacterial species and dominate environmental factors in Baiyangdian (BYD) Lake.

Results

The results showed that the contents of norfloxacin (NOR), ciprofloxacin (CIP) and total antibiotics in rhizosphere sediments were significantly higher than that in non-rhizosphere sediments, meanwhile, bacterial communities in non-rhizosphere sediments had significantly higher diversity (Sobs, Shannon, Simpsoneven and PD) than those in rhizosphere sediments. Furthermore, total antibiotics and CIP were found to be the most important factors in bacterial diversity. The majority of the phyla in rhizosphere sediments were Firmicutes, Proteobacteria and Campilobacterota, while Proteobacteria, Chloroflexi was the most abundant phyla followed by Bacteroidota, Actinobacteriota in non-rhizosphere sediments. The dominate factors of shaping the bacterial communities in rhizosphere were total antibiotics, pH, sediment organic matter (SOM), and NH₄-N, while dissolved organic carbon (DOC), NO₃-N, pH, and water contents (WC) in non-rhizosphere sediments.

Discussion

It is suggested that antibiotics may have a substantial effect on bacterial communities in P. australis rhizosphere sediment, which showed potential risk for ARGs selection pressure and dissemination in shallow lake ecosystems.