Rhizosphere Area Research Articles

Diversity and Plant Growth Properties of Rhizospheric Bacteria Associated with Medicinal Plants.

Microbes in the rhizosphere play a significant role in the growth, development, and efficiency of plants and trees. The rhizospheric area's microbes are reliant on the soil's characteristics and the substances that the plants release. The majority of previous research on medicinal plants concentrated on their bioactive phytochemicals, but this is changing now that it is understood that a large proportion of phytotherapeutic substances are actually created by related microorganisms or through contact with their host. The roots of medicinal plants secrete a large number of secondary metabolites that determine the diversity of microbial communities in their rhizosphere. The dominant bacteria isolated from a variety of medicinal plants include various species of Bacillus,Rhizobium,Pseudomonas,Azotobacter,Burkholderia,Enterobacte,Microbacterium, Serratia,Burkholderia, andBeijerinckia. Actinobacteria also colonize the rhizosphere of medicinal plants that release low molecular weight organic solute that facilitate the solubilisation of inorganic phosphate. Root exudates of medicinal plants resist abiotic stress and accumulate in soil to produce autotoxic effects that exhibit strong obstacles to continuous cropping. Although having a vast bioresource that may be used in agriculture and modern medicine, medicinal plants' microbiomes are largely unknown. The purpose of this review is to (i) Present new insights into the plant microbiome with a focus on medicinal plants, (ii) Provide information about the components of medicinal plants derived from plants and microbes, and (iii) Discuss options for promoting plant growth and protecting plants for commercial cultivation of medicinal plants. The scientific community has paid a lot of attention to the use of rhizobacteria, particularly plant growth-promoting rhizobacteria (PGPR), as an alternative to chemical pesticides. By a variety of processes, these rhizobacteria support plant growth, manage plant pests, and foster resilience to a range of abiotic challenges. It also focuses on how PGPR inoculation affects plant growth and survival in stressful environments.

Seagrass-mediated rhizosphere redox gradients are linked with ammonium accumulation driven by diazotrophs.

Seagrasses are important marine habitats providing several ecosystem services in coastal waters worldwide, such as enhancing marine biodiversity and mitigating climate change through efficient carbon sequestration. Notably, the fitness of seagrasses is affected by plant-microbe interactions. However, these microscale interactions are challenging to study and large knowledge gaps prevail. Our study shows that redox microgradients in the rhizosphere of seagrass select for a unique microbial community that can enhance the ammonium availability for seagrass. We provide first experimental evidence that Rhizobia, including the symbiotic N2-fixing bacteria Bradyrhizobium, can contribute to the bacterial ammonium production in the seagrass rhizosphere. The release of O2 from rhizomes and roots also caused gradients of sulfide in rhizosphere areas with enhanced nifH transcription by sulfate-reducing bacteria. O2 release from seagrass root systems thus seems crucial for ammonium production in the rhizosphere via stimulation of multiple diazotrophic associations.

Isolation and Characterization of Phosphate Solubilizing Bacteria from Upland Rice Cultivation Areas in Bangka Regency

The availability of phosphorus (P) in ultisol acid soils presents a significant challenge due to its attachment to aluminum (Al) or iron (Fe) compounds. A potential solution to address this issue is the utilization of phosphate solubilizing bacteria (PSB). Therefore, this study aimed to analyze the potential of PSB originating from upland rice cultivation on ultisol soils. The bacterial isolates were obtained from soil samples taken from the rhizosphere area and root tissue of upland rice plants cultivated in Payabenua and Saing Villages, Bangka Regency. The pathogenicity testing encompassed hypersensitivity and hemolysis tests, while the P solubilization included the evaluation of the phosphate solubilizing index (PSI) and P dissolution. Subsequently, the selected isolates were subjected to phosphatase enzyme and organic acid content assessment. The results showed a total of 120 isolates, predominantly distributed in the Payabenua area and primarily consisting of endophytic bacteria. Among the six selected isolates, genus Burkholderia dominated four isolates, while the remaining isolates belonged to genus Serratia. Furthermore, in Burkholderia vietnamiensis, the solubility value of P in AlPO4 and Ca3(PO4)2 liquid media exhibited a range of 0.0013 to 0.0344% and 0.0008 to 0.1842%, respectively.

High potential low-cost crude enzymes from Algerian fungal strains for plant polysaccharides hydrolysis

Fungi secrete large enzyme sets, such as glycosyl hydrolases (GH) capable of targeting plant polymers, making them a valuable enzymes source. In this study, three fungal strains were isolated from the rhizosphere area and identified as Trichoderma harzianum, Aspergillus tubingensis and Aspergillus tamarii by molecular analysis. The strains were able to grow on mono-, di- and polysaccharides as sole carbon sources, and even on D-galactose and cellulose which is rare for Aspergillus species. Besides, GH activities such as cellobiohydrolase, β-1,4-D-galactosidase, β-mannosidase glucoamylase and β-1,4-D-galactosidase were revealed in secretome of the strains cultivated on wheat bran with optimum obtained between 4th and 7th day. Furthermore, hydrolysis of wheat bran with T. harzianum, A. tubingensis and A. tamarii culture supernatant resulted in the release of 4.6, 5.5 and6.8 g/L of glucose, respectively. The yield increased two-fold by applying a mix of T. harzianum and A. tubingensis enzymes extracts at a ratio 1:1. In addition, the combination of the crude enzymes with commercial cellulase enhanced 3 times the glucose content. The results present enzyme extracts with high yield in saccharification of complex substrates with a potential application in bioethanol production.

Diversity and community structure of rhizosphere bacteria in shallot treated with Rhizophagus intraradices and Trichoderma asperellum

Abstract. Artanti H, Joko T, Suryanti. 2023. Diversity and community structure of rhizosphere bacteria in shallot treated with Rhizophagus intraradices and Trichoderma asperellum. Biodiversitas 24: 6248-6255. The rhizosphere is an area rich in nutrients and has high microbial activity. The condition of the rhizosphere area can influence plant growth and resistance to pathogens. This study aimed to determine the effect of the application of Rhizophagus intraradices and Trichoderma asperellum on the diversity and community structure of shallot rhizosphere bacteria as well as on the growth and health of shallots. Metagenomic analysis of the shallot rhizosphere was used to determine the diversity and structure of the bacterial community in shallots treated with R. intraradices, T. asperellum, control, and bulk soil. The results showed that the application of R. intraradices and T. asperellum affected the composition and diversity of rhizosphere bacteria and the number of rhizobacteria species. The structure of rhizosphere bacteria was not affected by the application of these two fungi. The diversity and number of rhizosphere bacterial species were able to increase plant growth and resistance, especially triggered by R. intraradices.

Environmental quality assessment of soil as a component of green spaces in parks of the megalopolis

Intensive land degradation occurs under conditions of accelerated urbanization; it is strongly associated with the loss of soil natural capital, primarily animals, plant cover, and biological diversity in general. The creation and functioning of parks, in particular green spaces, in the urbanized areas is an effective mechanism for optimizing the ecological situation within the cities and preventing desertification. The soils of parks are an integral component of green infrastructure; they determine the conditions for the growth and development of both individual plants and green spaces as a whole. The soil buffering capacity actively participates in the mechanisms of implementation of the development and stabilization of soil fertility potentials. The buffering capacity determines the proportion of the soil potential that controls the processes of immobilization (deposition) and mobilization (release, loss) of a particular element of fertility: first of all, mineral nutrients for plant growth, productive moisture, thermal energy in soil, gas composition of soil air, and acidity. We collected soil samples beneath the crowns of trees growing in the territory of the Taras Shevchenko Central Culture and Leisure Park, as one of the largest parks in the city of Dnipro (Ukraine). The soil samples were collected in order to assess the soil acid-base (pH) buffering capacity (pHBC) and determine the direction of microbiological processes in urban soils of the park area afforested with stands from such introduced tree species as green ash (Fraxinus pennsylvanica), black locust (Robinia pseudoacacia), northern red oak (Quercus rubra), tree of heaven (Ailanthus altissima), Kentucky coffee tree (Gymnocladus dioica), and box elder (Acer negundo). The acid-base buffering capacity of the urban soil was determined using the Arrhenius method and estimated according to the buffering area within the acid-base range, calculated using the Simpson formula. Direction of microbial processes in the soil was determined according to the indexes of mineralization-immobilization, pedotrophicity, and oligotrophicity. The output was processed using statistical methods (arithmetic mean and standard deviation were calculated; the difference in the means was found according to the Tukey’s comparison test; interdependencies were determined by linear correlation). We have found significant, strong positive correlations between the pH level of urban soils in the rhizosphere area of the introduced species of park dendroflora and the buffering area within the acid and acid-base (total) range of external influence, as well as a strong negative correlation between pH and buffering area in the alkaline range of external influence. We identified weak mineralization signs according to the ratio of functional groups of microbiota in the studied sites forested with Fraxinus pennsylvanica and Acer negundo.

The role of plant growth promoting rhizobacteria in strengthening plant resistance to fluoride toxicity: a review.

A wide variety of bacteria are present in soil but in rhizospheric area, the majority of microbes helps plant in defending diseases and facilitate nutrient uptake. These microorganisms are supported by plants and they are known as plant growth-promoting rhizobacteria (PGPR). The PGPRs have the potential to replace chemical fertilizers in a way that is more advantageous for the environment. Fluoride (F) is one of the highly escalating, naturally present contaminants that can be hazardous for PGPRs because of its antibacterial capacity. The interactions of F with different bacterial species in groundwater systems are still not well understood. However, the interaction of PGPR with plants in the rhizosphere region reduces the detrimental effects of pollutants and increases plants' ability to endure abiotic stress. Many studies reveal that PGPRs have developed F defense mechanisms, which include efflux pumps, Intracellular sequestration, enzyme modifications, enhanced DNA repair mechanism, detoxification enzymes, ion transporter/antiporters, F riboswitches, and genetic mutations. These resistance characteristics are frequently discovered by isolating PGPRs from high F-contaminated areas or by exposing cells to fluoride in laboratory conditions. Numerous studies have identified F-resistant microorganisms that possess additional F transporters and duplicates of the well-known targets of F. Plants are prone to F accumulation despite the soil's low F content, which may negatively affect their growth and development. PGPRs can be used as efficient F bioremediators for the soil environment. Environmental biotechnology focuses on creating genetically modified rhizobacteria that can degrade F contaminants over time. The present review focuses on a thorough systemic analysis of contemporary biotechnological techniques, such as gene editing and manipulation methods, for improving plant-microbe interactions for F remediation and suggests the importance of PGPRs in improving soil health and reducing the detrimental effects of F toxicity. The most recent developments in the realm of microbial assistance in the treatment of F-contaminated environments are also highlighted.

Patters of reactive nitrogen removal at the waters in the semi-constructed wetland

Protection and rectification patters of urban wetlands have been considered in strategies to balance services to society and negative consequences of excess reactive nitrogen (Nr) loading. However, the knowledge about strategies of semi-constructed wetlands on nitrogen (N) cycling pathways and removal Nr from the overlying water is limited. This study aimed to reveal considerable differences among rectification patterns of the typical semi-constructed wetland (Xixi wetland), comprising rational exploitation area (REA), rehabilitation and reconstruction area (RRA), and conservation area (CA) by analyzing the N distribution and N protentional pathways among them. Results pointed out that both NH4+ and NO3− concentration were prominently higher in REA, as opposed to CA and RRA. Sediments in RRA had relatively higher NH4+ content, indicating the efficiency of dissimilatory nitrate reduction (DNRA) in RRA. Moreover, there was a significant shift in the microbial community structure across different sites and sediments. Metagenomic analysis distinguished the N cycling pathways, with nitrification (M00804), denitrification (M00529), and DNRA (M00530) being the crucial pathways in the semi-constructed wetland. The relative abundance of N metabolic pathways (ko00910) varied among different types of sediments, being more abundant in shore and rhizosphere areas and less abundant in bottom sediments. Methylobacter and Nitrospira were the predominant nitrifiers in shore sediments, while Methylocystis was enriched in the bottom sediments and rhizosphere soils. Furthermore, Anaeromyxobacter, Anaerolinea, Dechloromonas, Nocardioides, and Methylocystis were identified as the primary denitrifiers with N reductase genes (nirK, nirS, or nosZ). Among these, Anaeromyxobacter, Dechloromonas, and Methylocystis were the primary contributors containing the nosZ gene in semi-constructed wetlands, driving the conversion of N2O to N2. This study provides important insights into rectification-dependent Nr removal from the overlying water in terms of N distribution and N metabolic functional microbial communities in the semi-constructed wetlands.

Screening of indigenous Rhizobacteria isolates from Patchouli Rhizosphere producing HCN, Siderophores and Chitinolytic Enzymes

The consortium of bacteria that inhabit the rhizosphere, acting as plant growth promoting rhizobacteria is known as indigenous rhizobacteria. Rhizobacteria can produce chemical compounds that can protect plants from pathogens and various plant-disturbing organisms. Optimization of the growth and yield of patchouli can be done by utilizing the potential of rhizobacteria derived from patchouli rhizosphere. This study aims to obtain rhizobacteria capable of producing secondary metabolites of HCN compounds, siderophores and chitinolytic enzymes which are thought of as biocontrol agents in plant protection. The soil samples used were taken from patchouli rhizosphere areas in three locations, namely Alue Abed, Aceh Jaya and Krueng Itam and Purwosari, Nagan Raya. The exploration results obtained 4 isolates of rhizobacteria from Alue Abed, Calang, 8 isolates from Krueng Itam, Nagan Raya and 37 isolates from Purwosari, Nagan Raya. Based on the test results of qualitative and quantitative physiological properties, 34 isolates were able to produce HCN, 49 isolates produced siderophores and 42 isolates were able to carry out chitinolytic enzyme activity. Rhizobacteria isolate producing HCN, siderophores and chitinolytic enzymes are potential indigenous rhizobacteria candidates and potential for future testing as bio-protections of plants from pathogen attack.

Microbial community in garlic plants under different applications of organic fertilizer

Indonesia is one of the biggest importers of garlic based on the FAO database in 2014-2018 and has continued up until now. Sustainable efforts to supply high domestic demand must be led to change this paradigm. Bacterial community study is important to identify soil health problems and provide insight and basic information to achieve sustainable agricultural management and increase production. This study aims to investigate the bacterial community around Garlic soil, which were treated with different manures (husk and goat’s dunk). Bacterial population enumeration was conducted by specific media and Amplicon sequencing analyses by Illumina was done to analyse bacterial community on some samples. Results showed that in general, highest population of bacteria which has plant growth promoting traits was shown in rhizosphere area with added organic material and bio fertilizer. Moreover, we observed that fertilization influences the bacterial diversity and composition in the rhizosphere, as bacterial taxa such as Rhodanobacter and Chuijabacter had higher abundance in the goat manure-treated plant in comparison to the plant grown in sandy soil.

Studies on Am Fungi Associated With Andrographis Paniculata (Burm.F.) Nees From Tapowan, Amravati

The current day emphasis is on sustainable agriculture, which uses less of chemical inputs like fertilizers and pesticides having adverse effect on soil health, fertility and environment. Thus, use of microbial inoculants plays an important role in sustainable agriculture. AM fungi are known to improve the nutritional status, growth and development of plants. Asian countries are very rich in medicinal plant species and are the major exporters of these plants and their products. These medicinal plants can be popularized and used to improve the economy of low-income countries of Asia and create livelihoods for its people. Kalmegh (Andrographis paniculata Nees.) is such a wonder plant which has numerous medicinal properties. Hence, the purpose of this research was to isolate and identify Arbuscular Mycorrhizal Fungi (AMF) associated with the rhizosphere soils of Andrographis paniculata and mass propagate the native dominant species for further studies. The soil samples were collected from Tapowan area of Amravati, Maharashtra. These samples from rhizosphere area of Andrographis paniculata were wet sieved, and AMF spores were isolated and identified morphotaxonomically. In all five species of Glomus were observed e.g., Glomus leptotichum, Glomus aggregatum, Glomus fasciculatum, Glomus maculosum. The most dominant were of Glomus aggregatum. This dominant species will be mass multiplied and applied in further studies to study growth parameters of Kalmegh. The authors believe that, as this technology being simple can easily be adapted by farmers cultivating this medicinal crop.

Potential Effect of Biochar on Soil Properties, Microbial Activity and Vicia faba Properties Affected by Microplastics Contamination

Microplastics (MPs) contamination is an emerging issue globally; however, adverse impacts of MPs on soil, plants and microbial activity have not been intensively studied. In this study, the potential effect of different levels of MPs (1.5, 7.5, 15%) has been investigated on soil properties, plant properties (Vicia Faba) and microbial activities through a pot experiment. The effect of biochar (BC: 2%) to mitigate the adverse effects of MP has also been examined. Soil properties (pH, EC, OM, CaCO3 and some elements) have significantly differed due to contamination of soil by MPs as well as by adding BC to the soil. The pH and CaCO3 were significantly increased more than in the control, while EC, TDS, available P, Mn and Fe were significantly decreased lower than the control, which implies adsorption on microplastic. Plant properties, such as enzymes, chlorophyll and fresh and dry weight in roots, were adversely affected by MPs contamination; however, BC mitigated this effect, especially with low contamination levels of MPs. The fresh and dry weight of the shoot was not significantly affected by MPs. The cytogenetic analysis showed that the mitotic index was significantly reduced compared to the control (9.39%), while BC increased the mitotic index at 1.5% MPs (7.11%) although it was less than the control. The percentage of abnormalities of V. faba root tip cells under different levels of MPs was significantly increased more than the control; however, BC mitigated this effect, especially at 7.5% MPs. The total count of bacteria and fungi even in soil or in the rhizosphere area did not follow a clear trend; however, the effect of BC was clear in increasing their activities. Microbial biomass carbon and nitrogen were also significantly affected by MPs and BC. In this study, the BC level was low, however, it mitigated some adverse effects of MPs, especially at 1.5 and 7.5% of MPs. Thus, the BC could be promising in mitigating the negative impacts of MPs when applied with suitable levels that need more future studies.

Rhizosphere-Associated Microbiome Profile of Agricultural Reclaimed Lands in Egypt

Plants especially in their natural habitat are considered part of a rich ecosystem that includes many various microorganisms in the soil. The current study aimed to identify the bacterial profile of agriculture-related soil samples using the metabarcoding technique to compare and explore relevant rhizosphere bacteria associated with plant cultivations in newly reclaimed land and habitual cultivated ones. The total environmental DNA was extracted from rhizosphere and noncultivated samples derived from three land types in Egypt. The bacterial 16S rDNA was amplified and sequenced by NGS technology to profile each sample. The microbial profile was characterized by statistical and literature-based methods. Among all samples, the most identified phyla were Actinobacteriota (28%), followed by Proteobacteriota (26%), Firmicutes (14%), Acidobacteriota and Chloroflexi (7%), Gemmatimonadota (5%), Bacteriodota and Crenarchaeota (3%), and Myxococcota (2%), in addition to 37 other phyla with <1% counts. A total of 74 OTUs were unique to the plant rhizosphere area and classified as Bacteriodota (5.1%:0.3%), Firmicutes (2.4%:0.1%), and Proteobacteria (3.5%:2%) phyla in agricultural and reclaimed lands, respectively. Moreover, the rhizosphere profile included a large portion of uncultured and unidentified bacterial species, which opened a window to further analysis. Our analysis provides a key knowledge about the rhizosphere microbiome and highlights its possible use to create microbial-based biofertilizers targeting plant performance in contrast to traditional fertilizers and their side effect on the agriculture sector.

Seasonal variation of distribution and removal of high-risk tetracycline resistance genes in constructed wetland.

Livestock wastewater is an important reservoir of antibiotic resistance genes (ARGs), with high environmental risks. We investigated the seasonal variations of distribution and removal of swine wastewater originated high-risk tetracycline resistance genes (TRGs) in horizontal subsurface flow constructed wetlands. The effects of exogenous addition of tetracycline (TC) and copper ion (Cu2+) on the abundance of TRGs in effluent with single and combined pollution of antibiotic and heavy metal were studied. The results showed that all the three high-risk TRGs (tetM, tetO and tetW) were detected in swine wastewater. Wetlands could effectively reduce the ARGs, with the absolute abundance of TRGs in effluent being decreased by 1.1-2.4 and 1.7-2.9 orders of magnitude in summer and winter compared with the influent, respectively. The abundance of TRGs in wetland soils showed the characte-ristics that the outflow side was lower than the inflow side, the non-rhizosphere area was lower than the rhizosphere area, and lower in winter than in summer. In summer and winter, single and combined pollution of TC and Cu2+ in swine wastewater would increase the abundance of TRGs in effluent compared with that in the control. The constructed wetland is suitable for controlling the environmental diffusion of ARGs in livestock wastewater.

ISOLASI DAN IDENTIFIKASI Trichoderma spp. DARI RHIZOSFER TANAMAN JATI (Tectona grandis Linn.) DI TAMAN HUTAN RAYA PROF. IR. HERMAN YOHANES, DESA KOTABES, KECAMATAN AMARASI KABUPATEN KUPANG

Teak (Tectona grandis Linn.) is a type of forestry plants that has high economic value. Trichoderma spp. is a soil microorganism that is naturally capable of attacking pathogenic fungi and beneficially for plants. This study aims to identify and find out the types of Trichoderma spp. as a biological control agent in the rhizosphere area of teak plants (Tectona grandis Linn.), in Prof. Ir. Herman Yohanes Forest Park, Kotabes Village, Amarasi District, Kupang Regency. This research took place from May to September 2021. Sample tree selection is done using the purposive sampling method, by determining the sample point on a healthy plant. 5 trees were taken as samples and each sample tree is taken 4 points just below the canopy as a soil sampling point. Isolation and identification were carried out at the Laboratotium of Plant Diseases, Faculty of Agriculture, University of Nusa Cendana. Fungal inoculums observed their culture characteristics macroscopically and morphological characteristics microscopically. Cultural and morphological characteristic data are analyzed descriptively and presented in the form of descriptions and images compared to literature to ascertain their identity. The results found 2 species of Trichoderma namely T. citrinoviride, T. reesei.

Biosorption of Pb2+ using Fusarium sp. RS01, a Hg2+ and Pb2+-Resistant Indigenous Fungus of an Abandoned Illegal Gold Mining Site

This study aims to identify and characterize Hg2+ and Pb2+-resistant indigenous fungi that originated in Mandor, an abandoned illegal gold mining site in West Kalimantan, Indonesia. The resistant fungus which has the highest ability in uptaking Pb2+ is then further examined for its biosorption characteristics towards Pb2+. Three different samples consisted of samples taken in the sand area (RP), rhizosphere area (RR) and sediment area (RS) were collected as the sources of fungi. The three types of samples were inoculated in a potato dextrose agar (PDA) medium supplemented with 7.4 ppm of HgCl2 and 7.5 ppm of PbCl2 for screening Hg2+ and Pb2+-resistant fungi, respectively. Each screened fungus was identified macroscopically and microscopically. The tolerant index (TI) towards Hg2+ and Pb2+ was checked by measuring the fungal growth diameter in a PDA medium without or with the presence of different HgCl2 or PbCl2 concentrations. From six identified fungi, five of them showed resistance towards Hg2+ and Pb2+ to maximum concentrations of 200 ppm of HgCl2 and 2085 ppm of PbCl2, respectively. The five identified fungi were Penicillium sp. RR01, Aspergillus sp. RR02, Aspergillus sp. RR03, Aspergillus niger RP01, and Fusarium sp. RS01. At the optimum condition of pH 6 and adsorption time 15 min, the application of 200 ppm of Fusarium sp. was able to remove 9.5 ppm of Pb2+. This Pb2+ biosorption followed well Freundlich isotherm model indicating that the Fusarium sp. RS01 had heterogenous active sites for the adsorption.

ACTIVITY OF THYME ESSENTIAL OILS AGAINST PLANT PATHOGENIC FUNGI AND ITS POTENTIAL USE AS SEED DISINFECTANT

One potential application of essential oils as low-risk biopesticides is as seeds disinfectant. The main goal of this study was to test the activity of thyme essential oil on four strains of seed/soilborne plant pathogenic fungi, Fusarium graminearum, Botrytis allii, Rhizoctonia solani, and Pythium ultimum, and to evaluate the effect of the inhibitory doses on plant seed germination. The direct application of thyme essential oil on seeds demonstrates a lack of selectivity. The main effects were related to radicle architecture and development of the primary and lateral roots, both in monocotyl, sorghum (Sorghum saccharatum), and in the dicotyls garden cress (Lepidium sativum) and white mustard (Sinapis alba). One potential solution to the lack of selectivity of direct application of the essential oils is biofumigation, i.e., application by volatilization in the rhizosphere area. Our paper raises this issue of compatibility between the necessary doses to inhibit the plant pathogenic fungi and the effects on plant seeds. Formulation of essential oils as slow-release nanoformulation could reduce phytotoxicity while maintaining and even enhancing the activity against plant pathogens.

Effects of long-term (10 years) remediation of Caragana on soil enzyme activities, heavy metals, microbial diversity and metabolic spectrum of coal gangue

Phytoremediation is a means of remediation of coal gangue pollution. However, the molecular mechanism of the effect of long-term plant restoration on soil microecology has not been elucidated. This study explored the mechanism of soil-microbe-metabolite interaction after long-term recovery of Caragana korshinskii Kom. We analyzed the physical and chemical properties, enzyme activities, microbial community structure, metabolome and ionomics of the shallow (10 cm), middle (50 cm) and deep (100 cm) rhizosphere and bulk soils after C. korshinskii restoration for 10 years. The activities of soil urease, sucrase, and acid phosphatase mainly increased in the rhizosphere area of C. korshinskii. The microbial abundance increased by 8.5%, 25.0%, and 15.2% in the shallow, middle, and deep levels, respectively. The ionomics results showed that the total Sr, Mn, Fe, Th, Rb, Bi, S, Se, Pb, U, Ni, Ba content in the rhizosphere soil decreased by 0.10–1.06 times (Log2 FC), and the effective state elements increased by 0.21–2.24 times (Log2 FC), there is still a risk of metal pollution in the gangue area. Metabolomics shows that lipids and lipid molecules, organic acids, phenylpropane and polyketides are the main differential metabolites; C. korshinskii repair stimulates the circulation pathways of terpenoids, lipids, amino acids, and carbohydrates. S, Fe, Mn and lipids, organic acids, and organic oxygen compound metabolites drive Acidthiobacillus, Sulfurifustis, Deferrobacterium, Pseudomonas and Sphingomonas to become dominant strains, regulates element metabolism and accelerates the process of environmental restoration.

Diversity of potassium solving microbes on andisol soil affected by the eruption of Mount Sinabung, North Sumatra, Indonesia

Abstract. Sembiring M, Sabrina T. 2022. Diversity of potassium solving microbes on andisol soil affected by the eruption of Mount Sinabung, North Sumatra, Indonesia. Biodiversitas 23: 1759-1764. Potassium (K) is one of the macronutrients needed by plants for seeds' growth, development, and quality. Andisols covered by volcanic ash from Mount Sinabung contain potassium ranging from 0.39-0.58 me/100g. The use of microbes is one of the alternatives methods to increase the availability of potassium in the soil that can be absorbed by plants. This study aimed to find environment-specific superior potassium-solvent microbes. Soil sampling was carried out in Kutarayat Village, Nama Teran Sub-district, Karo District, North Sumatra, Indonesia. The method used is random composite sampling by taking samples from 4 different locations. Sampling points were taken on Andisol soil that had been processed, covered with thin, medium, and thick ash. Sampling was carried out at a depth of 0-20 cm from the ground surface around the rhizosphere area. Isolation of bacteria and fungi was carried out by using multilevel dilutions. The microbes obtained after using the pour plate method were identified at molecular level by using PCR. Microbial potential test was carried out by using andisol soil which was incubated for 30 days. Parameters observed were soil pH, exchangeable potassium, soil organic carbon, and microbial population. 7 bacterial isolates and 3 potassium solubilizing fungi were isolated and identified during the present study. All bacterial and fungal isolates obtained were able to increase the availability of potassium soil exchange. The research results show that Talaromyces pinophilus can increase potassium soil exchange up to 102.94%.

Bakteri Tanah Di Sekitar Rhizosfer Tumbuhan Pioner Pada Lahan Bekas Tambang Kapur

Pioneer plants are plants with high adaptability, so they can grow in disturbed environments, such as ex-limestone mining areas. This adaptability is supported by the ability of these plants to associate with soil bacteria in their rhizosphere area. The presence of these bacteria can support the growth of pioneer plants on disturbed land. The purpose of this study was to characterize the soil bacteria around the rhizosphere of pioneer plants in the former limestone mining areas. Soil samples in the rhizosphere area of 5 pioneer plants from ex-mining lime were then isolated using the Pour plate method to obtain bacterial isolates. The bacterial isolates obtained were then identified their colony morphology. Based on the results of colony morphological identification, 21 isolates were obtained from the rhizosphere of 5 pioneer plants from the former limestone mining area. The highest number of isolates was obtained from the rhizosphere of the Waltheria indica with 9 isolates, 8 isolates of each Lamium barbatum and Digitaria sanguinalis , 7 isolates of Chromoleana odoratum , and 5 isolates of Tridax procumbens .