Strain B2 Research Articles

The complete genome sequences of Bacillus velezensis B26: a promising biocontrol agent and biofertilizer

Bacillus velezensis is a bacterium widely recognized for its biocontrol properties and ability to promote plant growth. This study presents the whole-genome sequence of B. velezensis B26, a newly identified strain isolated from chicken carcass soil in Udupi, India. The bacterium showed strong activity against fungal pathogens and exhibited diverse enzymatic activities. The whole-genome sequencing was executed using Illumina technologies. Assembly revealed that strain B26 possesses a genome of 3,946,698-bp with a G+C content of 46.3%. Genome annotation identified 3776 protein-coding genes, 1 rRNA gene, 50 tRNA genes, 5 ncRNA genes, and 59 pseudogenes. Functional analysis of the B. velezensis B26 genome revealed 216 genes involved in carbohydrate metabolism, 3 genes in potassium metabolism, 148 genes linked for cofactors, vitamins, prosthetic groups and pigments, 10 genes involved in phosphorus metabolism, 24 genes associated with iron acquisition and metabolism, 20 genes for nitrogen metabolism, 6 genes involved in sulfur metabolism, 6 genes in secondary metabolism, 12 genes associated with metabolism of aromatic compounds, 43 genes involved in stress response and 36 genes associated with virulence, disease and defence. The raw sequence data generated in this work have been deposited in the NCBI database and the genome sequence is available under the accession number JAYKOV000000000. These genomic data provide insight into the biocontrol ability and plant-growth promoting capabilities of B. velezensis B26.

Risk to UK Consumers From Meat, Mince and Offal From Beef, in the Hypothetical Scenario That Highly Pathogenic Avian Influenza H5N1 Strain B3.13 Is Found in UK Beef and Dairy Cattle

Risk to UK Consumers From Meat, Mince and Offal From Beef, in the Hypothetical Scenario That Highly Pathogenic Avian Influenza H5N1 Strain B3.13 Is Found in UK Beef and Dairy Cattle

Effects of hap2 deletion on mnp/vp transcription in Pleurotus ostreatus grown on lignocellulosic substrates

The regulatory mechanisms governing expression of genes encoding lignin-modifying enzymes (LME) in white-rot fungi remain largely unexplored. Although molecular cloning has identified CCAAT-boxes frequently located 5′-upstream of these genes, their role in transcriptional regulation is not well understood. This study examines the function of hap2, a gene encoding a hypothetical protein homologous to a component of the CCAAT-binding Hap complex, in the white-rot fungus Pleurotus ostreatus. Deletion of hap2 resulted in significantly reduced Mn2+-dependent peroxidase activity and lignin-degrading capacity compared to the parental strain 20b grown on beech wood sawdust (BWS) medium. Real-time PCR revealed that vp2 transcript levels were significantly lower in hap2 deletants than in 20b grown when cultured on the three solid media consisting of BWS, holocellulose, or Avicel, but not on yeast-malt-glucose (YMG) agar plates. Additionally, glutathione S-transferase (GST) pulldown and electrophoretic mobility shift assays demonstrated that recombinant P. ostreatus Hap2, Hap3, and Hap5 expressed in Escherichia coli form a complex capable of binding to the CCAAT sequence 5′-upstream of vp2 in vitro. These results suggest that Hap2, as part of the CCAAT-binding complex, is essential for transcriptional upregulation of vp2 in P. ostreatus growing on lignocellulosic substrates.Key points• P. ostreatus hap2 deletants were generated.• Lignin-degrading capacity was significantly reduced in the hap2 deletants.• vp2 was significantly downregulated upon hap2 deletion.

Screening of oxytetracycline-degrading strains in the intestine of the black soldier fly larvae and their degradation characteristics

The presence of excessive antibiotic residues poses a significant threat to human health and the environment. This study was designed to identify an effective oxytetracycline (OTC)-degrading strain through the screening of the intestine of black soldier fly larvae (BSFL). A strain designated “B2” was selected using a series of traditional microbial screening methods. It could be identified as Enterococcus faecalis by Gram staining and 16S rDNA sequencing, with a similarity of 99.93%. Its ability to degrade OTC was then assessed using high-performance liquid chromatography (HPLC). The degradation of the strain was characterized using a one-way test to assess the effects of the substrate concentration, inoculum amount, and initial pH on the degrading bacteria. The results indicate that strain B2 exhibited optimal OTC-degrading performance at a substrate concentration of 50 mg/L, with an inoculum amount of 6% and a pH value of 5.0. Specifically, strain B2 achieved degradation rates of 71.11%, 56.14%, and 45.03%. These findings demonstrate the effectiveness of strain B2 in degrading OTC, indicating its potential for use in environmental remediation efforts.

Isolation and characterization of a strain Clostridium butyricum B3 from the intestine of Pelteobagrus fulvidraco and its potential probiotic roles

The use of host-associated probiotics in aquaculture have been limited due to difficulties in their isolation from the host gastrointestinal tract and validation of their biological function. Here, anaerobic Clostridium butyricum strain B3 was isolated for the first time from the intestines of yellow catfish (Pelteobagrus fulvidraco). Alignment of 16 S rDNA sequences revealed 99 % identify between strain B3 and wild-type C. butyricum. C. butyricum B3 was found to tolerate a wide range of temperature (up to 80 °C) and pH (1 to 13) levels. In vitro microbial growth experiments revealed that C. butyricum B3 produced acetic acid (890.00 ± 23.00 mg/L) and butyric acid (672.67 ± 51.67 mg/L) highly productively within 24 h. Further in vitro characterization findings also suggested that C. butyricum B3 is sensitive to several antibiotics, including ampicillin and chloramphenicol, and potently inhibits the growth of pathogenic bacteria such as Aeromonas hydrophila. In a feeding experiments, 30 days of dietary supplementation with 3.0 × 107 to 109 CFU/g B3 significantly increased the specific growth rates of yellow catfish juveniles by more than 61.5 %. Activities of trypsin, α-amylase and lipase were significantly enhanced in group fed with 3.0 × 107 B3 compared to the control group (P < 0.05). Furthermore, ACP activity was significantly increased by more than 25.0 %, whereas malondialdehyde content significantly decreased by at least 38.5 % in all B3 feeding groups (P < 0.05). In addition, hepatocyte density increased, and goblet cells in the intestinal epithelial cells expanded. Meanwhile, C. butyricum B3 feeding significantly activated genes (such as grhpr and enpp2) involved in lipid metabolism and proliferator-activated receptor signaling pathway, increased bacterial diversity, and reduced the bacterial richness of the gut microbiota (P < 0.05). In conclusion, dietary inclusion of 3.0 × 107 CFU/g of C. butyricum B3 enhanced the growth performance, immune response, and lipid metabolism of P. fulvidraco.

Feed supplementation with quorum quenching probiotics improved growth response, immune response, and resistance in the giant mottled eel, Anguilla marmorata

This study aimed to evaluate the effect of feed supplementation with quorum quenching (QQ) probiotic bacteria on growth performance, hematology, immune response, and disease resistance in giant mottled eels. The feed used was supplemented with 45 ± 2.3 g/individual QQ bacteria using the following treatments, namely Bacillus cereus strain B8, Pseudomonas putida strain BPA1, Bacillus cereus strain HPC 576, and control (no QQ). A total of 420 eels (average weight 45 ± 2.3 g/ind.) were randomly reared in 12 open tarpaulin ponds of 2 x 1 x 1 (W x L x D) m and 1000-L volume for 8 weeks. Feed was given three times per day at 5% of the body weight. Water was changed daily at 25%, and shelters were provided using 3-inch diameter PVC pipes. The results showed that the feed containing QQ bacteria improved the growth, hematology, immunity, and disease resistance of the eels compared to the control (P < 0.05). Furthermore, among the QQ bacteria tested, the feed with B. cereus strain HPC 576 had the highest performance in all tested parameters.

Bacillus Species’ Gaseous Metabolites Prolong the Shelf Life of Apples and Grapes

In view of the threat to the environment posed by the widely used plant and fruit preservation chemicals in current agricultural practices, and the indispensability of fruit and plant preservatives in ensuring the yield of agricultural products, it is urgent to explore environmentally friendly and efficient preservative alternatives. Against this backdrop, bacterial preservatives stand out as a potential green solution. In this study, 12 strains of Bacillus derived from different ecological niches were carefully screened to evaluate the inhibitory efficacy of their gaseous metabolites against Anthracnose colloidospora, a common fruit pathogen, by bisectional method. The results showed that the bacterial suspension of strain B4 was the most prominent in inhibiting the growth of Colloidosporum anthracnose, and it significantly narrowed the growth circle of pathogenic bacteria, so it was selected as the object for further optimization and application. Subsequently, we designed a practical application test for fruit preservation, in which the bacteria of strain B4 were directly placed in the same environment as the fruit to be preserved, and the observation was continued for five days. By comparing and analyzing the fruit state before and after treatment, we were pleased to find that strain B4 showed a positive effect on inhibiting fruit rot, indicating its great potential as a natural fruit preservative. This discovery not only provides a scientific basis for reducing the use of chemical preservatives, but also contributes to the sustainable development of agriculture and the protection of the ecological environment.

De novo biosynthesis of anthocyanins in Saccharomyces cerevisiae using metabolic pathway synthases from blueberry

BackgroundAnthocyanins are water-soluble flavonoids in plants, which give plants bright colors and are widely used as food coloring agents, nutrients, and cosmetic additives. There are several limitations for traditional techniques of collecting anthocyanins from plant tissues, including species, origin, season, and technology. The benefits of using engineering microbial production of natural products include ease of use, controllability, and high efficiency.ResultsIn this study, ten genes encoding enzymes involved in the anthocyanin biosynthetic pathway were successfully cloned from anthocyanin-rich plant materials blueberry fruit and purple round eggplant rind. The Yeast Fab Assembly technology was utilized to construct the transcriptional units of these genes under different promoters. The transcriptional units of PAL and C4H, 4CL and CHS were fused and inserted into Chr. XVI and IV of yeast strain JDY52 respectively using homologous recombination to gain Strain A. The fragments containing the transcriptional units of CHI and F3H, F3’H and DFR were inserted into Chr. III and XVI to gain Strain B1. Strain B2 has the transcriptional units of ANS and 3GT in Chr. IV. Several anthocyanidins, including cyanidin, peonidin, pelargonidin, petunidin, and malvidin, were detected by LC-MS/MS following the predicted outcomes of the de novo biosynthesis of anthocyanins in S. cerevisiae using a multi-strain co-culture technique.ConclusionsWe propose a novel concept for advancing the heterologous de novo anthocyanin biosynthetic pathway, as well as fundamental information and a theoretical framework for the ensuing optimization of the microbial synthesis of anthocyanins.

Draft genome sequence of Penicillium citrinum B9, a plant growth-promoting symbiont from barley rhizosphere.

Penicillium citrinum strain B9 is a plant growth-promoting fungus isolated from Barley (Hordeum vulgare) rhizosphere. We report the first draft genome of P. citrinum B9 assembled using single-molecule real-time sequencing and Illumina reads. The assembled genome spans 31.3 Mb comprising nine contigs and 10,106 protein-encoding genes.

The different effects of molybdate on Hg(II) bio-methylation in aerobic and anaerobic bacteria.

In nature, methylmercury (MeHg) is primarily generated through microbial metabolism, and the ability of bacteria to methylate Hg(II) depends on both bacterial properties and environmental factors. It is widely known that, as a metabolic analog, molybdate can inhibit the sulfate reduction process and affect the growth and methylation of sulfate-reducing bacteria (SRB). However, after it enters the cell, molybdate can be involved in various intracellular metabolic pathways as a molybdenum cofactor; whether fluctuations in its concentration affect the growth and methylation of aerobic mercury methylating strains remains unknown. To address this gap, aerobic γ-Proteobacteria strains Raoultella terrigena TGRB3 (B3) and Pseudomonas putida TGRB4 (B4), as well as an obligate anaerobic δ-Proteobacteria strain of the SRB Desulfomicrobium escambiense CGMCC 1.3481 (DE), were used as experimental strains. The growth and methylation ability of each strain were analyzed under conditions of 500 ng·L-1 Hg(II), 0 and 21% of oxygen, and 0, 0.25, 0.50, and 1 mM of MoO4 2-. In addition, in order to explore the metabolic specificity of aerobic strains, transcriptomic data of the facultative mercury-methylated strain B3 were further analyzed in an aerobic mercuric environment. The results indicated that: (a) molybdate significantly inhibited the growth of DE, while B3 and B4 exhibited normal growth. (b) Under anaerobic conditions, in DE, the MeHg content decreased significantly with increasing molybdate concentration, while in B3, MeHg production was unaffected. Furthermore, under aerobic conditions, the MeHg productions of B3 and B4 were not influenced by the molybdate concentration. (c) The transcriptomic analysis showed several genes that were annotated as members of the molybdenum oxidoreductase family of B3 and that exhibited significant differential expression. These findings suggest that the differential expression of molybdenum-binding proteins might be related to their involvement in energy metabolism pathways that utilize nitrate and dimethyl sulfoxide as electron acceptors. Aerobic bacteria, such as B3 and B4, might possess distinct Hg(II) biotransformation pathways from anaerobic SRB, rendering their growth and biomethylation abilities unaffected by molybdate.

Seed endophytes reshape rhizosphere microbiota to promote the growth of Eucommia ulmoides seedlings

Plant seeds harbor numerous beneficial endophytes that can be vertically transmitted across generations, positively influencing plant growth. This study aimed to enhance our understanding of the functions of endophytes in Eucommia ulmoides seeds and investigate their potential mechanisms for promoting E. ulmoides seedling growth. Preliminary screening for seed endophytes that increase E. ulmoides seedling growth was conducted using microbe–seedling co-culture experiments. Subsequently, the two strains with the most pronounced growth-promoting effects were tested in pot experiments. The mechanism underlying their effects on E. ulmoides growth was elucidated through high-throughput sequencing analysis of rhizosphere soil. The bacterium Cytobacillus gottheilii B7 and the fungus Cladosporium halotolerans Z27 had the most significant growth-promoting effects on E. ulmoides seedlings. Inoculation of these strains into the soil led to substantial improvements in physiological indicators in E. ulmoides. Notably, strain B7 showed a superior effect compared to strain Z27. Although strain B7 inoculation reduced rhizosphere bacterial α-diversity, it strengthened the network interactions among rhizosphere microorganisms and selectively recruited specific rhizosphere microbial taxa, including Ilumatobacter, Algoriphagus and OLB13, while inhibiting the growth of Subulicystidium and Symmetrospora. Functional annotation suggested that strain B7 inoculation enhanced plant nitrite respiratory metabolism and inhibited plant pathogen. Similarly, strain Z27 inoculation recruited genera such as Flavihumibacter, Pseudoxanthomonas, and Myriococcum, while inhibiting Symmetrospora. These results provide scientific data for a comprehensive analysis of seed endophytes in the future and valuable resources for the development and application of microbial inoculants.

Toxicity of Beauveria bassiana to Bactrocera dorsalis and effects on its natural predators.

Entomopathogenic fungi (EPF) are economical and environmentally friendly, forming an essential part of integrated pest management strategies. We screened six strains of Beauveria bassiana (B1-B6) (Hypocreales: Cordycipitaceae), of which B4 was the most virulent to Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). We further assessed the biological characteristics of strain B4 and the environmental factors influencing its ability to infect B. dorsalis. We also evaluated the effects of B4 on two of the natural predators of B. dorsalis. We found that strain B4 was the most virulent to 3rd instar larvae, pupae, and adult B. dorsalis, causing mortality rates of 52.67, 61.33, and 90.67%, respectively. B4 was not toxic to B. dorsalis eggs. The optimum B4 effects on B. dorsalis were achieved at a relative humidity of 91-100% and a temperature of 25°C. Among the six insecticides commonly used for B. dorsalis control, 1.8% abamectin emulsifiable concentrate had the strongest inhibitory effect on B4 strain germination. B4 spraying affected both natural enemies (Amblyseius cucumeris and Anastatus japonicus), reducing the number of A. cucumeris and killing A. japonicus adults. We found a valuable strain of EPF (B4) that is virulent against many life stages of B. dorsalis and has great potential for the biological control of B. dorsalis. We also provide an important theoretical and practical base for developing a potential fungicide to control B. dorsalis.

ПОЧВЕННЫЕ БАКТЕРИИ ИЗ АВТОХТОННЫХ МИКРОБНЫХ СООБЩЕСТВ ЦЕНТРАЛЬНОЙ СИБИРИ В БИОЛОГИЧЕСКОЙ ЗАЩИТЕ ПШЕНИЦЫ ОТ ALTERNARIA TENUISSIMA

The aim of the study is to find the strongest soil microorganisms from autochthonous microbial communities of Central Siberia against phytopathogenic micromycetes Alternaria tenuissima. The object of the study is autochthonous soil bacteria isolated from the soils of the Krasnoyarsk forest-steppe in the Sukhobuzimsky District. Soil samples were taken from under spring wheat Novosibirskaya 15 and from under perennial grasses. The soil cover is represented by ordinary leached chernozem. Ammonium nitrate was used (34.7 kg/ha active ingredient). The climatic conditions are moderately dry and continental. The studies were carried out in 2022–2023. Antagonistic activity was measured on the GRM Saburo. With a general growth of the test culture and soil bacteria, the strongest antagonists were found in the suppression zone of Alternaria tenuissima. The identification of the most powerful bacterial antagonists in reducing the intensity and prevalence of root rot was carried out using the method of artificial infection with Alternaria tenuissima. Before infection with micromycete, bacterization of spring wheat seeds Novosibirskaya 15 with the studied bacterial isolates was carried out. Mathematical processing of the obtained results was carried out by one-way variance analysis and two-sample F-test for variance. The results of the study on the use of soil autochthonous antagonist microorganisms in biological protection of spring wheat from the causative agents of root rot Alternaria tenuissima showed that the studied bacterial isolates statistically significantly (p &lt; 0.01) reduced the intensity and prevalence of this disease. The maxi-mum effect in reducing the intensity and prevalence of the disease was shown by isolates B2 and B4. Also, the studied bacterial strains showed a significant effect (p &lt; 0.001) on the length of sprouts. The greatest increase in length in spring wheat sprouts was in the experimental variant with strain B2. This strain can be recommended not only for protection against Alternaria tenuissima, but also for stimuli-ting wheat growth.

Efficacy of Novel Fungicides against the Fusarium oxysporum f.sp. cubense Causing Panama wilt of Banana

Panama wilt of banana caused by Fusarium oxysporum f.sp. cubense TR4 is considered as most devastating disease of bananas. In Bihar, this disease became a menace to banana growers of Bihar due to introduction of new highly virulent strains i.e.TR 4 strain B2. The objectives of this study were to evaluate newly available fungicides under in vitro and in vivo conditions for the efficient management of the Panama wilt of banana. Fourteen different fungicides and novel chemicals were tested in vitro as well as in vivo conditions. Native (tebuconazole 50% + trifloxystrobin 25%) was found to exhibit 100% inhibition over control in vitro whereas in pot conditions 86.2% inhibition over control was observed against Fusarium oxysporum f.sp. cubense TR 4 strain B2 in cultivar Alpan (AAB).

Biological Management of Panama Wilt of Banana Caused by Fusarium oxysporum f. sp. Cubense

Bananas are one of the most important fruit crops grown in tropical and sub-tropical regions of the world. It contributes to the livelihood of many growers and constitutes a larger proportion of fruit orchards in India. Panama wilt of banana is a major fungal disease affecting banana cultivations and farmers facing huge economic losses after the introduction of Fusarium oxysporum f.sp.cubense Foc TR4 strain B2 in Bihar .In the present investigation, native and commercial isolates of Trichoderma viride and Trichoderma harzianum are tested against the all isolates of Fusarium oxxysporum f.sp. cubense. Both the biocontrol agents were found highly effective against the Iso. M, Iso A and Iso.K under in vitro as well as under natural pot conditions. But in the case of Iso.G (Foc TR 4 strain B2), these bioagents were found moderately effective under in vivo and in vitro conditions.

Genome analysis of Pseudomonas strain 4B with broad antagonistic activity against toxigenic fungi.

Pseudomonas sp. 4B isolated from the effluent pond of a bovine abattoir was investigated as antifungal against toxigenic fungi. The complete genome of Pseudomonas 4B was sequenced using the Illumina MiSeq platform. Phylogenetic analysis and genome comparisons indicated that the strain belongs to the Pseudomonas aeruginosa group. In silico investigation revealed gene clusters associated with the biosynthesis of several antifungals, including pyocyanin, rhizomide, thanamycin, and pyochelin. This bacterium was investigated through antifungal assays, showing an inhibitory effect against all toxigenic fungi tested. Bacterial cells reduced the diameter of fungal colonies, colony growth rate, and sporulation of each indicator fungi in 10-day simultaneous growing tests. The co-incubation of bacterial suspension and fungal spores in yeast extract-sucrose broth for 48h resulted in reduced spore germination. During simultaneous growth, decreased production of aflatoxin B1 and ochratoxin A by Aspergillus flavus and Aspergillus carbonarius, respectively, was observed. Genome analysis and in vitro studies showed the ability of P. aeruginosa 4B to reduce fungal growth parameters and mycotoxin levels, indicating the potential of this bacterium to control toxigenic fungi. The broad antifungal activity of this strain may represent a sustainable alternative for the exploration and subsequent use of its possible metabolites in order to control mycotoxin-producing fungi.

Combined application of biochar and metal-tolerant bacteria alleviates cadmium toxicity by modulating the antioxidant defense mechanism and physicochemical attributes in rice (Oryza sativa L.) grown in cadmium-contaminated soil

Agricultural soil contamination by heavy metal (cadmium) is a widespread issue and causes deleterious effects on crops. One of the most effective and ecofriendly methods for cadmium detoxification is microbe-assisted phytoremediation and soil amendment with biochar. The current study investigated the combined effect of biochar (Parthenium hysterophorus L.) and microbes (Bacillus cereus strain B2) in alleviating cadmium toxicity in rice grown in cadmium-contaminated soil (0, 10, 15, and 20 mg/kg). Results revealed that cadmium caused damage to plant health. Maximum reduction in plant biomass, gas exchange parameters, and chlorophyll content was observed on cadmium 20 mg/kg. As compared with the sole application of biochar (2 %) and microbes, the greatest plant height (33.68%), photosynthetic rate (23.52 %), stomatal conductance (48.93 %), water use efficiency (21.41 %), transpiration rate (58.87 %), chlorophyll a (74.81 %), chlorophyll b (31.28 %), total chlorophyll (60.53 %), and carotenoids (26.97 %) were recorded with combined application of biochar and microbes. Similarly, superoxidase (SOD), catalase (CAT), peroxidase (POD), and absorbate peroxidase (APX) activity was significantly boosted by combined application of microbes and biochar (2 %), which were 33.90 %, 24.18 %, 51.70 %, and 19.06 %, respectively, while significant reduction was found in the ROS (16.60 %), (20.06 %) and MDA (26.08 %) content in rice plants. However, cadmium concentrations in different parts of plant were decreased at higher concentrations of biochar (2 %) with microbes. These findings indicate that combined application of Bacillus cereus strain B2 and biochar could be a promising strategy for reducing rice crop cadmium toxicity and boosting its growth, physiology, and defense system efficiently as compared with sole application.

Lonicera japonica protects Pelodiscus sinensis by inhibiting the biofilm formation of Aeromonas hydrophila.

Aquaculture has suffered significant financial losses as a result of the infection of zoonotic Aeromonas hydrophila, which has a high level of resistance to classic antibiotics. In this study, we isolated an A. hydrophila strain B3 from diseased soft-shelled turtle (Pelodiscus sinensis), which is one of the most commercially significant freshwater farmed reptiles in East Asia, and found that A. hydrophila was its dominant pathogen. To better understand the inhibition effect and action mechanism of Chinese herbs on A. hydrophila, we conducted Chinese herbs screening and found that Lonicera japonica had a significant antibacterial effect on A. hydrophila B3. Experimental therapeutics of L. japonica on soft-shelled turtle showed that the supplement of 1% L. japonica to diet could significantly upregulate the immunity-related gene expression of soft-shelled turtle and protect soft-shelled turtle against A. hydrophila infection. Histopathological section results validated the protective effect of L. japonica. As the major effective component of L. japonica, chlorogenic acid demonstrated significant inhibitory effect on the growth of A. hydrophila with MIC at 6.4 mg/mL. The in vitro assay suggested that chlorogenic acid could inhibit the hemolysin/protease production and biofilm formation of A. hydrophila and significantly decrease the expression of quorum sensing, biofilm formation, and hemolysin-related genes in A. hydrophila. Our results showed that the Chinese herb L. japonica would be a promising candidate for the treatment of A. hydrophila infections in aquaculture, and it not only improves the immune response of aquatic animals but also inhibits the virulence factor (such as biofilm formation) expression of A. hydrophila. KEY POINTS: • A. hydrophila was the dominant pathogen of the diseased soft-shelled turtle. • L. japonica can protect soft-shelled turtle against A. hydrophila infection. • Chlorogenic acid inhibits the growth and biofilm formation of A. hydrophila.

Inhibitory Potential of Actinobacteria Isolated from Neelum Valley, Kashmir, Pakistan Against Typhoidal Salmonella

Given the emerging antimicrobial resistance (AMR), finding new antimicrobials and chemotherapeutics is a need of the hour. The under-explored habitats harbouring untapped microbial diversity are considered attractive targets to look for new potent bioactive compounds. In this study, N=32 actinobacteria strains were recovered from the soil of Neelum Valley, Kashmir, Pakistan, to screen their inhibitory activity and metabolomic potential against MDR typhoidal Salmonella. The TLC pattern and HPLC-UV-MS analysis of the extracts of isolated strains showed the presence of a variety of bioactive compounds. The actinobacteria strains B6, D13, B11.2 and others were found to be the most prolific producers of diverse secondary metabolites. In the screening for inhibitory activity against MDR typhoidal Salmonella, the extracts of strains B6, B16, B21 and D13 were found to be the most active exhibiting up to 20 mm zone of inhibition. Similarly, the cytotoxicity potential of the extracts against Artemiasalina by determining %larval mortality, the extract of strain Kel 1311A showed 91% mortality followed by the extracts of strains AzB1, kel 1391, B13, B8, and B4 showed % mortality up to 87.3%. 90%, 88% and 85.41% respectively. The HPLC-UV/MS analysis revealed the presence of a varietyof compounds with molecular weights of 400, 510 and 519 Daltons in the extract of strain B4 and 651, 356, 378 and 400 Daltons in the extracts of strain D13. The study suggested that actinobacteria living in the soil of Neelum Valley Kashmir are a rich source of novel bio-active, cytotoxic and anti-microbial compounds.

PGPR-Soil Microbial Communities' Interactions and Their Influence on Wheat Growth Promotion and Resistance Induction against Mycosphaerella graminicola.

The efficiency of plant-growth-promoting rhizobacteria (PGPR) may not be consistently maintained under field conditions due to the influence of soil microbial communities. The present study aims to investigate their impact on three PGPR-based biofertilizers in wheat. We used the PGPR Paenibacillus sp. strain B2 (PB2), PB2 in co-inoculation with Arthrobacter agilis 4042 (Mix 2), or with Arthrobacter sp. SSM-004 and Microbacterium sp. SSM-001 (Mix 3). Inoculation of PB2, Mix 2, and Mix 3 into non-sterile field soil had a positive effect on root and aboveground dry biomass, depending on the wheat cultivar. The efficiency of the PGPR was further confirmed by the protection they provided against Mycosphaerella graminicola, the causal agent of Septoria leaf blotch disease. PB2 exhibited protection of ≥37.8%, while Mix 2 showed ≥47.9% protection in the four cultivars tested. These results suggest that the interactions between PGPR and native soil microbial communities are crucial for promoting wheat growth and protection. Additionally, high-throughput sequencing of microbial communities conducted 7 days after PGPR inoculations revealed no negative effects of PB2, Mix 2, and Mix 3 on the soil microbial community structure. Interestingly, the presence of Arthrobacter spp. appeared to mitigate the potential negative effect of PB2 on bacterial community and foster root colonization by other beneficial bacterial strains.