Newly isolated Brevundimonas naejangsanensis as a biocontrol agent against Fusarium redolens the causal of Fusarium yellows of chickpea

Three endophytic bacteria, namely BvV, BvP and BvL, were newly isolated from the root nodules of bean, pea and lentil plants respectively cultivated in Mascara the northwest of Algeria, and identified by 16S ribosomal RNA gene sequencing as Brevundimonas naejangsanensis. These strains were able to produce hydrolytic enzymes and hydrogen cyanide. All strains produced a growth-promoting hormone, indole acetic acid, varying in concentration from 83.2 to 171.7 µg/mL. The phosphate solubilizing activity of BvV, BvP and BvL varied from 25.5 to 42.02 µg/mL for tricalcium phosphate. The three antagonistic Brevundimonas spp. showed in vitro the most inhibitory effect on mycelial growth of Fusarium redolens FRC (from 78.33 to 85.55%). Strain BvV, BvP and BvL produced also volatile metabolites which inhibited mycelial FRC growth up to 39.2%. All strains showed significant disease reduction in pot experiments. Chickpea Fusarium yellows severity caused by FRC was reduced significantly from 89.3 to 96.6% in the susceptible cultivar ILC 482 treated with antagonistic B. naejangsanensis. The maximum stimulatory effect on chickpea plants growth was observed by inoculation of strain BvV. This treatment resulted in a 7.40-26.21% increase in shoot height as compared to the control plants. It is concluded that the endophytic bacterial strains of B. naejangsanensis having different plant growth promoting (PGP) activities can be considered as beneficial microbes for sustainable agriculture. To our knowledge, this is the first report to use B. naejangsanensis strains as a new biocontrol agent against F. redolens, a new pathogen of chickpea plants causing Fusarium yellows disease in Algeria.

Selective Isolation and Identification of Microorganisms with Dual Capabilities: Leather Biodegradation and Heavy Metal Resistance for Industrial Applications

Tanning, crucial for leather production, relies heavily on chromium yet poses risks due to chromium's oxidative conversion, leading to significant wastewater and solid waste generation. Physico-chemical methods are typically used for heavy metal removal, but they have drawbacks, prompting interest in eco-friendly biological remediation techniques like biosorption, bioaccumulation, and biotransformation. The EU Directive (2018/850) mandates alternatives to landfilling or incineration for industrial textile waste management, highlighting the importance of environmentally conscious practices for leather products' end-of-life management, with composting being the most researched and viable option. This study aimed to isolate microorganisms from tannery wastewater and identify those responsible for different types of tanned leather biodegradation. Bacterial shifts during leather biodegradation were observed using a leather biodegradation assay (ISO 20136) with tannery and municipal wastewater as the inoculum. Over 10,000 bacterial species were identified in all analysed samples, with 7 bacterial strains isolated from tannery wastewaters. Identification of bacterial genera like Acinetobacter, Brevundimonas, and Mycolicibacterium provides insights into potential microbial candidates for enhancing leather biodegradability, wastewater treatment, and heavy metal bioremediation in industrial applications.

Unlocking water potential in drylands: Quicklime and fly ash enhance soil microbiome structure, ecological networks and function in acid mine drainage water-irrigated agriculture

In water-stressed regions, treated acid mine drainage (AMD) water for irrigated agriculture is a potential solution to address freshwater scarcity. However, a significant knowledge gap exists on the short and long-term effects of treated AMD water on soil health. This study used high-throughput Illumina sequencing and predictive metagenomic profiling to investigate the impact of untreated AMD (AMD), quicklime- (A1Q and A2Q) and quicklime and fly ash-treated AMD water (AFQ) irrigation on soil bacterial diversity, co-occurrence networks and function. Results showed that untreated AMD water significantly increased soil acidity, electrical conductivity (EC), sulfate (SO42-), and heavy metals (HM), including reduced microbial diversity, disrupted interaction networks, and functional capacity. pH, EC, Cu, and Pb were identified as key environmental factors shaping soil microbial diversity and structure. Predominantly, Pseudomonas, Ralstonia picketti, Methylotenera KB913035, Brevundimonas vesicularis, and Methylobacteriumoryzae, known for their adaptability to acidic conditions and metal resistance, were abundant in AMD soils. However, soils irrigated with treated AMD water exhibited significantly reduced acidity (pH > 6.5), HM and SO42- levels, with an enrichment of a balanced bacterial taxa associated with diverse functions related to soil health and agricultural productivity. These taxa included Sphingomonas, Pseudoxanthomonas, Achromobacter, Microbacterium, Rhodobacter, Clostridium, Massillia, Rhizobium, Paenibacillus, and Hyphomicrobium. Moreover, treated AMD water contributed to higher connectivity and balance within soil bacterial co-occurrence networks compared to untreated AMD water. These results show that quicklime/fly ash treatments can help lessen impacts of AMD water on soil microbiome and health, suggesting its potential for irrigated agriculture in water-scarce regions.

Chromium contamination accentuates changes in the microbiome and heavy metal resistome of a tropical agricultural soil

The impacts of hexavalent chromium (Cr) contamination on the microbiome, soil physicochemistry, and heavy metal resistome of a tropical agricultural soil were evaluated for 6 weeks in field-moist microcosms consisting of a Cr-inundated agricultural soil (SL9) and an untreated control (SL7). The physicochemistry of the two microcosms revealed a diminution in the total organic matter content and a significant dip in macronutrients phosphorus, potassium, and nitrogen concentration in the SL9 microcosm. Heavy metals analysis revealed the detection of seven heavy metals (Zn, Cu, Fe, Cd, Se, Pb, Cr) in the agricultural soil (SL7), whose concentrations drastically reduced in the SL9 microcosm. Illumina shotgun sequencing of the DNA extracted from the two microcosms showed the preponderance of the phyla, classes, genera, and species of Actinobacteria (33.11%), Actinobacteria_class (38.20%), Candidatus Saccharimonas (11.67%), and Candidatus Saccharimonas aalborgensis (19.70%) in SL7, and Proteobacteria (47.52%), Betaproteobacteria (22.88%), Staphylococcus (16.18%), Staphylococcus aureus (9.76%) in SL9, respectively. Functional annotation of the two metagenomes for heavy metal resistance genes revealed diverse heavy metal resistomes involved in the uptake, transport, efflux, and detoxification of various heavy metals. It also revealed the exclusive detection in SL9 metagenome of resistance genes for chromium (chrB, chrF, chrR, nfsA, yieF), cadmium (czcB/czrB, czcD), and iron (fbpB, yqjH, rcnA, fetB, bfrA, fecE) not annotated in SL7 metagenome. The findings from this study revealed that Cr contamination induces significant shifts in the soil microbiome and heavy metal resistome, alters the soil physicochemistry, and facilitates the loss of prominent members of the microbiome not adapted to Cr stress.

Dark Side of Ammonium Nitrogen in Paddy Soil with Low Organic Matter: Stimulation of Microbial As(V) Reduction and As(III) Transfer from Soil to Rice Grains

The bioavailability of arsenic (As) is influenced by ammonium (NH₄⁺-N) fertilization, but the underlying mechanisms controlling As transformation in soil-rice systems are still not fully understood. The effects of two NH₄⁺-N fertilizers, urea and NH₄HCO₃, on the transformation of As in a paddy soil with low organic matter content and transfer in rice plants were investigated. Treatments with urea and NH₄HCO₃ significantly increased arsenite (As(III)) concentration in porewater, bioavailable As in rhizosphere soil, and the relative abundance of the As(V) respiratory reductase gene (arrA) and As(III) methyltransferase gene (arsM). Furthermore, the relative expression of As transporter genes in rice roots, such as OsLsi1, OsLsi2, and OsLsi3, was upregulated, and the translocation efficiency of As(III) from rice roots to brown rice was promoted. Subsequently, As(III) accumulation in brown rice significantly increased. Therefore, attention should be paid to As-contaminated paddy fields with NH₄⁺-N fertilization.

Identification of heavy metals tolerant Brevundimonas sp. from rhizospheric zone of Saccharum munja L. and their efficacy in in-situ phytoremediation

Heavy metals phytoremediation from pulp and paper industry (PPI) sludge was conducted by employing root-associated Brevundimonas sp (PS-4 MN238722.1) in rhizospheric zone of Saccharum munja L. for its detoxification. The study was aimed to investigate the efficiency of Saccharum munja L. for the removal of heavy metals along with physico-chemical parameters through bacterial interactions. Physico-chemical examination of PPI sludge showed biochemical oxygen demand (8357 ± 94 mg kg^-1), electrical conductivity (2264 ± 49 μmhoscm^-1), total phenol (521 ± 24 mg kg^-1), total dissolve solid (1547 ± 23 mg kg^-1), total nitrogen (264 ± 2.13 mg kg^-1), pH (8.2 ± 0.11), chemical oxygen demand (34756 ± 214 mg kg^-1), color (2434 ± 45 Co-Pt), total suspended solid (76 ± 0.67 mg kg^-1), sulphate (2462 ± 13 mg kg^-1), chlorolignin (597 ± 13.01 mg kg^-1), K⁺ (21.04 ± 0.26 mg kg^-1), total solid (1740 ± 54 mg kg^-1), phosphorous, Cl^-, and Na⁺. Heavy metals, such as Fe followed by Zn, Mn, Cd, Cu, Ni, Pb, As, Cr and Hg were above the permissible limit. Root and shoot of Saccharum munja L. revealed highest concentrations of Cd followed by Mn, Ni, Fe, Zn, Cu, As, Cr, Hg, and Pb. Tested metals (Fe, Mn, Pb, Cd, Cr, Cu, Zn, Ni, As, and Hg) bioaccumulation and translocation factors were also revealed to be < 1 and >1, respectively, demonstrating that these plants have considerable absorption and translocation abilities. Plant growth-promoting activity, such as ligninolytic enzymes, hydrolytic enzymes, indole acetic acid, and siderophore production activity of Brevundimonas sp. (PS-4 MN238722.1) were also noted to be higher. These findings support the use of Brevundimonas sp (PS-4 MN238722.1) in combination with Saccharum munja L. plant as interdisciplinary management of industrial sludge at polluted areas for the prevention of soils near the industrial site.

Metagenomic insights into the microbial community structure and resistomes of a tropical agricultural soil persistently inundated with pesticide and animal manure use

Persistent use of pesticides and animal manure in agricultural soils inadvertently introduced heavy metals and antibiotic/antibiotic resistance genes (ARGs) into the soil with deleterious consequences. The microbiome and heavy metal and antibiotic resistome of a pesticide and animal manure inundated agricultural soil (SL6) obtained from a vegetable farm at Otte, Eiyenkorin, Kwara State, Nigeria, was deciphered via shotgun metagenomics and functional annotation of putative ORFs (open reading frames). Structural metagenomics of SL6 microbiome revealed 29 phyla, 49 classes, 94 orders, 183 families, 366 genera, 424 species, and 260 strains with the preponderance of the phyla Proteobacteria (40%) and Actinobacteria (36%), classes Actinobacteria (36%), Alphaproteobacteria (18%), and Gammaproteobacteria (17%), and genera Kocuria (16%), Sphingobacterium (11%), and Brevundimonas (10%), respectively. Heavy metal resistance genes annotation conducted using Biocide and Metal Resistance Gene Database (BacMet) revealed the detection of genes responsible for the uptake, transport, detoxification, efflux, and regulation of copper, cadmium, zinc, nickel, chromium, cobalt, selenium, tungsten, mercury, and several others. ARG annotation using the Antibiotic Resistance Gene-annotation (ARG-ANNOT) revealed ARGs for 11 antibiotic classes with the preponderance of β-lactamases, mobilized colistin resistance determinant (mcr-1), macrolide-lincosamide-streptogramin (MLS), glycopeptide, and aminoglycoside resistance genes, among others. The persistent use of pesticide and animal manure is strongly believed to play a major role in the proliferation of heavy metal and antibiotic resistance genes in the soil. This study revealed that agricultural soils inundated with pesticide and animal manure use are potential hotspots for ARG spread and may accentuate the spread of multidrug resistant clinical pathogens.