Pseudomonas Koreensis Research Articles

Pseudomonas koreensis AB36 from a gold mine: genomic insights into adaptation to extreme conditions and potential plant growth promotion

AbstractThe genus Pseudomonas is one of the most varied and widespread bacterial genera, with species found in most environment. They are known to degrade organic and inorganic compounds, produce secondary metabolites, and enhance plant growth. The genome of Pseudomonas koreensis AB36, a heavy metal resistant organism isolated from a gold mine was sequenced to unveil the versatile metabolic potential of the organism. The genome is a single circular chromosome of 5,902,614 bp, with G + C content of 60.1%. There are 4154 similar orthologous gene clusters shared among strain AB36 and other sequenced P. koreensis strains with 7 clusters found alone in the genome of strain AB36. Genome mining of the organism predicted 8 biosynthetic gene clusters using antiSMASH including three non-ribosomal peptide synthethase (NRPS) clusters, arylpolyene and bacteriocin. The genome contains putative genes for heavy metal transport/resistance. These results show the heavy metal resistance ability and degradation of xenobiotic compounds of strain AB36 as well as its potential to adapt to various environments.

Role of the Pseudomonas koreensis BB2.A.1 and Serratia liquefaciens BB2.1.1 Bacterial Strains in Maize Trace Metal Stress Management.

Plant-growth-promoting rhizobacteria (PGPR), in addition to their well-known direct effects on plant growth and development, have been reported to be effective in plant abiotic (trace metal, drought, etc.) and biotic (phytopathogens, insects, etc.) stress management. PGPRs are involved in shaping the fate of trace metals in the rhizosphere and plants and thus may also reduce trace metal stress in plants. The aims of our study were to isolate and select indigenous trace-metal-resistant PGP strains and investigate their effects on maize germination and early development. The roles of the two selected strains, Pseudomonas koreensis and Serratia liquefaciens isolated from trace-metal-contaminated soil were investigated to mitigate trace metal stress in 21-day-old Zea mays seedlings. In the present study, 13 bacterial strains were isolated and screened for PGP traits under normal and trace metal stress conditions. The effect of two selected strains was further studied on plant experiments. The germination process, plant growth parameters (length, weight, dry matter content), photosynthetic activity, GPOX activity, trace metal accumulation, and translocation in microbes inoculated Cd (0.5 mM), Zn (1 mM), and Cd + Zn (0.1 + 0.5 mM) treated maize plants was studied. Our results revealed that trace metal toxicity, in terms germination and growth parameters and antioxidant enzyme activity, was enhanced upon inoculation with Pseudomonas koreensis BB2.A.1. Chlorophyll content and accumulation studies showed enhanced results following inoculation with Serratia liquefaciens BB2.1.1. Therefore, both bacterial strains possessed beneficial traits that enabled them to reduce metal toxicity in maize.

Selection of vaccine candidates against Pseudomonas koreensis using reverse vaccinology and a preliminary efficacy trial in Empurau (Tor tambroides)

This study marks the first utilization of reverse vaccinology to develop recombinant subunit vaccines against Pseudomonas koreensis infection in Empurau (Tor tambroides). The proteome (5538 proteins) was screened against various filters to prioritize proteins based on features that are associated with virulence, subcellular localization, transmembrane helical structure, antigenicity, essentiality, non-homology with the host proteome, molecular weight, and stability, which led to the identification of eight potential vaccine candidates. These potential vaccine candidates were cloned and expressed, with six achieving successful expression and purification. The antigens were formulated into two distinct vaccine mixtures, Vac A and Vac B, and their protective efficacy was assessed through in vivo challenge experiments. Vac A and Vac B demonstrated high protective efficacies of 100 % and 81.2 %, respectively. Histological analyses revealed reduced tissue damage in vaccinated fish after experimental infection, with Vac A showing no adverse effects, whereas Vac B exhibited mild degenerative changes. Quantitative real-time PCR results showed a significant upregulation of TNF-α and downregulation of IL-1β in the kidneys, spleen, gills, and intestine in both Vac A- and Vac B-immunized fish after challenged with P. koreensis. Additionally, IL-8 exhibits tissue-specific differential expression, with significant upregulation in the kidney, gills, and intestine, and downregulation in the spleen, particularly notable in Vac A-immunized fish. The research underscores the effectiveness of the reverse vaccinology approach in fish and demonstrates the promising potential of Vac A and Vac B as recombinant subunit vaccines.

Essential amino acid residues and catalytic mechanism of trans-epoxysuccinate hydrolase for production of meso-tartaric acid.

This study aimed to discuss the essential amino acid residues and catalytic mechanism of trans-epoxysuccinate hydrolase from Pseudomonas koreensis for the production of meso-tartaric acid. The optimum conditions of the enzyme were 45°C and pH 9.0, respectively. It was strongly inhibited by Zn2+, Mn2+ and SDS. Michaelis-Menten enzyme kinetics analysis gave a Km value of 3.50mM and a kcat of 99.75s-1, with an exceptional EE value exceeding 99.9%. Multiple sequence alignment and homology modeling revealed that the enzyme belonged to MhpC superfamily and possessed a typical α/β hydrolase folding structure. Site-directed mutagenesis indicated H34, D104, R105, R108, D128, Y147, H149, W150, Y211, and H272 were important catalytic residues. The 18O-labeling study suggested the enzyme acted via two-step catalytic mechanism. The structure and catalytic mechanism of trans-epoxysuccinate hydrolase were first reported. Ten residues were critical for its catalysis and a two-step mechanism by an Asp-His-Asp catalytic triad was proposed.

Isolation, identification and characterisation of Pseudomonas koreensis CM-01 isolated from diseased Malaysian mahseer (Tor tambroides)

Pseudomonas species are one of the most threatening fish pathogens which reside a wide range of environments. In this study, the dominant bacteria were isolated from diseased Malaysian mahseer (Tor tambroides) and tentatively named CM-01. It was identified as Pseudomonas koreensis based on its biochemical, morphological, genetic and physiological information. Its pathogenicity was found to be correlated with twelve virulence genes identified including iron uptake, protease, acylhomoserine lactone synthase gacS/gacA component regulation system, type IV secretion system, hydrogen cyanide production, exolysin, alginate biosynthesis, flagella and pili. The median lethal dose (LD50) for the CM-01 isolate on Malaysian mahseer was documented at 5.01 × 107 CFU/mL. The experimental infection revealed that CM-01 led to significant histological lesions in the fish, ultimately resulting in death. These lesions comprise necrosis, tissue thickening and aggregation. Drug sensitivity tests had shown its susceptibility to beta-lactam combination agents and further suggest its drug of choice. Its growing features had shown its growth at optimal temperature and pH. To the best of our knowledge, this is the first report of P. koreensis linked to diseased T. tambroides. Statement of relevanceIn this research, a novel strain of Pseudomonas koreensis, CM-01 was isolated from diseased T. tambroides for the first time. The antimicrobial susceptibility, pathogenicity, virulence genes and growth characteristics of CM-01 were studied. These findings established a scientific foundation for the recognition of P. koreensis and the management of fish infections caused by this pathogen.

The interaction between intratumoral bacteria and metabolic distortion in hepatocellular carcinoma

BackgroundIntratumoral bacteria might play essential roles in tumorigenesis in different cancer types. However, its features and potential roles in hepatocellular carcinoma (HCC) are largely unknown.MethodsIn this study, we assessed bacterial RNA by 16S rRNA fluorescence in situ hybridization and detected bacterial lipopolysaccharide (LPS) via immunohistochemistry. Hepa1-6 cells were used to establish orthotopic HCC models in mice. 2bRAD sequencing for microbiome was performed to determine the intratumoral bacterial characteristics, and liquid chromatography-mass spectrometry was conducted to explore the metabolic profile. The potential association between different intratumoral microbiota and metabolites were evaluated.ResultsWe detected bacterial 16S rRNA and LPS in HCC tissues from the patients with HCC. In HCC mouse model, we found that the intratumor bacteria in HCC tissues were significantly different to adjacent nontumor tissues. Furthermore, we observed different metabolites in HCC tissues and adjacent nontumor tissues, such as N-acetyl-D-glucosamine and a-lactose. Our results showed that several bacteria were significantly associated with metabolites, such as Pseudomonas koreensis, which was positively correlated with N-acetyl-D-glucosamine and negatively correlated with citrulline.ConclusionsThis study confirmed the close association between different bacteria and metabolites, which might provide novel opportunities for developing new biomarkers and therapeutic targets for HCC.

Nitric oxide synthase expression in Pseudomonas koreensis MME3 improves plant growth promotion traits

The development of novel biotechnologies that promote a better use of N to optimize crop yield is a central goal for sustainable agriculture. Phytostimulation, biofertilization, and bioprotection through the use of bio-inputs are promising technologies for this purpose. In this study, the plant growth–promoting rhizobacteria Pseudomonas koreensis MME3 was genetically modified to express a nitric oxide synthase of Synechococcus SyNOS, an atypical enzyme with a globin domain that converts nitric oxide to nitrate. A cassette for constitutive expression of synos was introduced as a single insertion into the genome of P. koreensis MME3 using a miniTn7 system. The resulting recombinant strain MME3:SyNOS showed improved growth, motility, and biofilm formation. The impact of MME3:SyNOS inoculation on Brachypodium distachyon growth and N uptake and use efficiencies under different N availability situations was analyzed, in comparison to the control strain MME3:c. After 35 days of inoculation, plants treated with MME3:SyNOS had a higher root dry weight, both under semi-hydroponic and greenhouse conditions. At harvest, both MME3:SyNOS and MME3:c increased N uptake and use efficiency of plants grown under low N soil. Our results indicate that synos expression is a valid strategy to boost the phytostimulatory capacity of plant-associated bacteria and improve the adaptability of plants to N deficiency.Key points• synos expression improves P. koreensis MME3 traits important for rhizospheric colonization• B. distachyon inoculated with MME3:SyNOS shows improved root growth• MME3 inoculation improves plant N uptake and use efficiencies in N-deficient soil

Surface colonization by Flavobacterium johnsoniae promotes its survival in a model microbial community.

Microbial communities direct key environmental processes through multispecies interactions. Understanding these interactions is vital for manipulating microbiomes to promote health in human, environmental, and agricultural systems. However, microbiome complexity can hinder our understanding of the underlying mechanisms in microbial community interactions. As a first step toward unraveling these interactions, we explored the role of surface colonization in microbial community interactions using The Hitchhikers Of the Rhizosphere (THOR), a genetically tractable model community of three bacterial species, Flavobacterium johnsoniae, Pseudomonas koreensis, and Bacillus cereus. We identified F. johnsoniae genes important for surface colonization in solitary conditions and in the THOR community. Understanding the mechanisms that promote the success of bacteria in microbial communities brings us closer to targeted manipulations to achieve outcomes that benefit agriculture, the environment, and human health.

Study of the microbiome associated with stem crown galls of grapes

The work investigated the species composition of the bacterial microbiome associated with stem crown galls on the grape variety Kishmish radiant (Cardinal x Kishmish pink). The result of the identification of bacterial isolates using MALDI-TOF mass spectrometry, molecular genetic analysis, and the cultural method on nutrient media made it possible to identify them in stem crown galls of grapes is presented. The following microorganisms were identified: Pseudomonas koreensis, Roaultella planticola, Enterobacter cloacae, Pseudomonas fulva, Xanthomonas bonasiae, Winslowiella toletana. Using a biological test on carrots, the pathogenicity of two species Xanthomonas bonasiae, Winslowiella toletana was determined by the ability to form galls, while no virulence genes were detected by PCR analysis using specific primer pairs of genes.

Biodegradation of crystal violet by newly isolated bacteria.

Confronting the environmental threat posed by textile dyes, this study highlights bioremediation as a pivotal solution to mitigate the impacts of Crystal Violet, a widely-utilized triphenylmethane dye known for its mutagenic and mitotic toxicity. We isolated and identified several bacterial strains capable of degrading Crystal Violet under various environmental conditions. Newly identified strains, including Mycolicibacterium nivoides, Chryseobacterium sp., Agrobacterium rhizogenes, Pseudomonas crudilactis, and Pseudomonas koreensis demonstrated significant decolorization activity of Crystal Violet, complementing the already known capabilities of Stenotrophomonas maltophilia. Initial experiments using crude extracts confirmed their degradation potential, followed by detailed studies that investigated the impact of different pH levels and temperatures on some strains' degradation efficiency. Depending on the bacteria, the degree of activity change according to pH and temperature was different. At 37 °C, Chryseobacterium sp. and Stenotrophomonas maltophilia exhibited higher degradation activity compared to 25 °C, while Pseudomonas crudilactis and Mycolicibacterium nivoides did not exhibit a statistically significant difference between the two temperatures. Mycolicibacterium nivoides performed optimally at pH 8, while Pseudomonas crudilactis showed high activity at pH 5. Stenotrophomonas maltophilia's activity remained consistent across the pH range. These findings not only underscore the effectiveness of these bacteria as agents for Crystal Violet degradation but also pave the way for their application in large-scale bioremediation processes for the treatment of textile effluents, marking them as vital to environmental sustainability efforts.

IMPACT OF RHIZOSPHERIC, NODULATION AND SOIL MICROBIOME ON SOYBEAN AND RICE GROWTH FOR SUSTAINABLE AGRICULTURE

Microorganisms are critical for the survival of life on Earth, but we know very little about the vast majority ofmicrobes. We studied the culturable soybean root, soil, and nodules microbiome here. Thirty bacterial sampleswere isolated from different localities of soybean crops, including soil, root, and nodules, to assess their abilityfor plant growth promotion. To evaluate the richness and diversity in the root and soil, we performed the mostprobable number (MPN) test. Seven of the bacterial isolates were able to produce cellulase, in which JSW1 andJSW6 were most efficient with 2.56 and 2.05 cellulolytic index. All isolates were able to grow and utilizedpectin, in which JSW2 and JSW3 were most efficient with 0.8 and 0.66 pectinolytic index. Pikovskaya mediamodified with TCP JSW1 and JSW2 showed a 3.0 and 2.33 solubility index, and on CaCO 3 media, the JSW1strain produced a 1.58 solubilization index. All bacterial isolates were phylogenetically identified by sequencingand analyzing the 16S rRNA gene. Under controlled conditions, consortia, Pantoea dispersa, and Rhizobiumsp. isolates considerably improved rice root dry weight by 53%, 75%, and 69% and shoot dry weight by 85%,71%, and 76%. Based on in vitro characterization, the potential bacteria Pantoea dispersa, Pseudomonaskoreensis, and Rhizobium sp. were selected to be evaluated for plant growth, nodulation, and grain yield underfield experiment. Under field conditions, Rhizobium sp and Pseudomonas koreensis were found best as singleinoculation by improving 53% and 49% grain yield, respectively. These potential bacteria could be used asbiofertilizers for soybean crop productivity.

Screening and characterization of heavy metal tolerant rhizobacteria from wild Musa rhizosphere from coal mining area of Changki, Nagaland, India and assessment of their growth promoting potential under Cd/Cu contaminated conditions

In soils polluted with heavy metals, plant growth promoting rhizobacteria (PGPR) with heavy metal tolerance can aid plants to adapt to heavy metal contaminated conditions. Heavy metal tolerant rhizobacteria were isolated from Musa rhizosphere growing the Tsurang Riverbank, Nagaland, India, a coal mining area. A total of 26 bacterial isolates/strains were tested for heavy metals and salt tolerance and some growth-promoting traits like IAA, siderophore production and phosphate solubilisation. Of the 26 strains, 7 strains (TSU1, TSU11, TSU12, TSU3, TSU4, TSU7, and TSU8) supported better plant growth. Different isolates displayed variable heavy metal tolerance (30 to 8070 μg/ml). Strains TSU8 and TSU4 exhibited the highest salt tolerance (12 %). Based on the 16S rRNA sequencing, the isolates were identified as TSU3 (Bacillus cereus) (OQ547230), TSU4 (Bacillus safensis) (OQ547231), TSU8 (Bacillus pumilus) (OQ547232), TSU11 (Klebsiella variicola) (OQ947091), TSU12 (Lelliottia amnigena) (OQ947097), TSU7 (Pseudomonas koreensis) (OQ947088) and TSU1 (Serratia marcescens) (OQ726408). A successful consortium of bacterial isolates was formulated and inoculated on Brassica juncea and Helianthus annuus with heavy metal Cd/Cu (150 µgml−1) in the potted soil. This consortium improved growth performance significantly in both fresh and dry weight basis. In B. juncea, enhancement in root length and weight were recorded by 53 and 93 % respectively against control, while, fresh weight of shoot was improved by 72 % on soil adjunct with PGPR and 67 % with PGPR in heavy metal contaminated condition. Similar trend was also registered on dry weight basis. Whereas, PGPR consortia treated H. annuus registered increased shoot and root lengths both fresh and dry weight basis. This consortium with these seven bacterial isolates may contribute to microbe assisted phytoremediation under heavy metal polluted area.

Isolation, identification and pathogenicity of local entomopathogenic bacteria as biological control agents against the wild cochineal Dactylopius opuntiae (Cockerell) on cactus pear in Morocco

The Opuntia ficus-indica (L.) cactus, a crucial crop in Morocco, is threatened by the wild cochineal, Dactylopius opuntiae (Cockerell). The aim of this research was to investigate the efficacy of nine bacterial strains against both D. opuntiae nymphs and adults females applied individually or after black soap in the laboratory, greenhouse, and field conditions. Using the partial 16S ribosomal DNA, the bacterial isolates were identified as Pseudomonas koreensis, Pseudomonas sp., Burkholderia sp. and Bacillus sp. Under laboratory conditions, the insecticidal activity of P. koreensis strain 66Ms.04 showed the level mortality (88%) of adult females’ at 108 CFU/mL, 7 days after application. At a concentration of 108 CFU/mL, P. koreensis strain 66Ms.04 and Pseudomonas sp. (strains 37 and 5) caused 100% nymphs mortality rate three days after application. Under greenhouse conditions, the use of P. koreensis strain 66Ms.04 at 108 CFU/mL following the application of black soap (60 g/L) demonstrated the maximum levels of females and nymphs’ mortalities with 80 and 91.25%, respectively, after 8 days of treatment. In field conditions, the combined application of the P. koreensis strain 66Ms.04 at 108 CFU/mL with black soap at 60 g/L, for an interval of 7 days, significantly increased the mortality of adult females to 93.33% at 7 days after the second application. These findings showed that the combined treatment of P. koreensis strain 66Ms.04 with black soap can be a potent and eco-friendly pesticide against D. opuntiae.

Bacteria existing in pre-pollinated styles (silks) can defend the exposed male gamete fertilization channel of maize against an environmental Fusarium pathogen.

In flowering plants, fertilization requires exposing maternal style channels to the external environment to capture pollen and transmit its resident sperm nuclei to eggs. This results in progeny seed. However, environmental fungal pathogens invade developing seeds through the style. We hypothesized that prior to environmental exposure, style tissue already possesses bacteria that can protect styles and seed from such pathogens. We further hypothesized that farmers have been inadvertently selecting immature styles over many generations to have such bacteria. We tested these hypotheses in maize, a wind-pollinated crop, which has unusually long styles (silks) that are invaded by the economically-important fungal pathogen Fusarium graminearum (Fg). Here, unpollinated silk-associated bacteria were cultured from a wild teosinte ancestor of maize and diverse maize landraces selected by indigenous farmers across the Americas, grown in a common Canadian field for one season. The bacteria were taxonomically classified using 16S rRNA sequencing. In total, 201 bacteria were cultured, spanning 29 genera, 63 species, and 62 unique OTUs, dominated by Pseudomonas, Pantoea and Microbacterium. These bacteria were tested for their ability to suppress Fg in vitro which identified 10 strains belonging to 6 species: Rouxiella badensis, Pantoea ananatis, Pantoea dispersa, Pseudomonas koreensis, Rahnella aquatilis, and Ewingella americana. Two anti-Fg strains were sprayed onto silks before/after Fg inoculation, resulting in ≤90% reductions in disease (Gibberella ear rot) and 70-100% reductions in associated mycotoxins (deoxynivalenol and zearalenone) in progeny seeds. These strains also protected progeny seeds post-harvest. Confocal fluorescent imaging showed that one silk bacterium (Rouxiella AS112) colonized susceptible entry points of Fg on living silks including stigmatic trichomes, wounds, and epidermal surfaces where they formed thick biofilms. Post-infection, AS112 was associated with masses of dead Fg hyphae. These results suggest that the maize style (silk) is endowed with potent bacteria from the mother plant to protect itself and progeny from Fusarium. The evidence suggests this trait may have been selected by specific indigenous peoples, though this interpretation requires further study.

Activity of biocontrol agents against the grapevine pathogen Fomitiporia mediterranea

Biological control agents (BCAs) have shown efficacy against several pathogens associated with Esca of grapevines, but their effects on the white rot pathogen Fomitiporia mediterranea (Fmed) have not been extensively studied. An assessment of several potential BCAs evaluated activity against Fmed. This included isolates of Trichoderma simmonsii, T. citrinoviride, T. atroviride, Bacillus subtilis, B. amyloliquefaciens/velezensis and Pseudomonas koreensis, all obtained from grapevines in Austria. Effects of the BCAs on Fmed growth were assessed in dual culture assays and in assays with fresh and autoclaved grapevine wood disks. In the dual culture assays, all the BCAs reduced growth of Fmed compared to experimental controls. In the Trichoderma experiments, Fmed growth only marginally exceeded the size of the initial mycelium plugs, and growth inhibition for all Fmed isolates and strains was 91 to 97%. Growth of Fmed was inhibited by 55 to 66% by B. amyloliquefaciens/velezensis isolates, by 41 to 49% by B. subtilis isolates, and by 55 to 66% by P. koreensis. In the wood disc assays, Fmed colonized fresh and autoclaved wood. All the Trichoderma isolates almost completely suppressed Fmed growth on fresh and autoclaved wood. Less but statistically significant inhibition was recorded for an isolate of B. amyloliquefaciens/velezensis and one of P. koreensis.

Unlocking the potential of rhizobacteria in Moroccan vineyard soils: Biocontrol of grapevine trunk diseases and plant growth promotion

Rhizospheric bacteria isolated from the root system of Vitis vinifera plants in Morocco were evaluated for their activities against fungi associated with grapevine trunk diseases namely Diplodia mutila, Neoscytalidium dimidiatum, Trichothecium roseum, and Neopestalotiopsis vitis. Those pathogens cause grapevine decline and impede growth and are known as the greatest threat to production worldwide. Among a collection of 196 rhizobacteria, twenty-four isolates exhibited potential antifungal activity against all the tested fungal pathogens. Based on the partial 16S rDNA genes, different genera were identified namely Bacillus, Pseudomonas, Achromobacter, Ensifer, and Brucella. In particular, Bacillus halotolerans (JFM-64 and JMS-14), Pseudomonas koreensis (JRSK-45), and Ensifer adhaerens (JRSK-84) were found to be the most effective strains. Furthermore, the potential of bacterial isolates to promote plant growth was assessed. The funding revealed that of twenty-four antagonist rhizobacteria, seventeen displayed protease and chitinase production, while fifteen, thirteen, and twelve bacteria demonstrated the production of amylase, cellulase, and pectinase respectively. Furthermore, thirteen bacterial isolates produced hydrocyanic acid (HCN), sixteen isolates harbor the ability to solubilize tricalcium phosphate and seventeen were able to produce siderophores and indole acetic acid (IAA). The results of the current study showed that the most effective bacterial isolates could exhibit traits other than Plant Growth-Promoting Rhizobacteria (PGPR). Our results showed that the bacterization of B. napus seedlings with the selected bacteria improved plant growth when compared to untreated controls. Autoclaved grape wood assays were used to further confirm the in vitro results. The growth of Diplodia mutila, Neopestalotiopsis vitis, Neoscytalidium dimidiatum, and Trichothecium roseum was effectively reduced by rhizobacterial isolate Pseudomonas koreensis (JRSK-45) by 97.31, 97.14, 94.17, and 91.91%, respectively. This study highlights the potential of specific rhizobacteria as a promising approach to controlling fungal trunk pathogens associated with grapevine decline.

Suppression of tomato bacterial speck disease (Pseudomonas syringae pv. tomato (Okabe) Young, Dye, & Wilkie) via induced systemic resistance by Pseudomonas and Bacillus strains

Bacterial speck Pseudomonas syringae pv. tomato (Pst) (Okabe) Young, Dye, & Wilkie is a widespread disease in tomato plants. Four plant growth-promoting rhizobacterial (PGPR) strains 5(3), 68(2), 36(1), and 47(3) played a significant role (50% and higher) in reducing spot disease severity. Selected strains were identified as Pseudomonas koreensis 5(3), Bacillus mycoides 68(2), Bacillus mojavensis 36(1), and Bacillus simplex 47(3) using the MALDI Biotyper classification system. In planta assay using tomato seedlings were inoculated with the bacterial strains alone or in dual combination. Pseudomonas koreensis 5(3) (51.9%–74.29%) and Bacillus mycoides 68(2) (36.70%–65.56%) both provided a significant reduction in foliar severity caused by bacterial speck disease agent Pseudomonas syringae pv. tomato (Okabe) Young, Dye, & Wilkie. Bacillus simplex 47(3) and Bacillus mojavensis 36(1) were successful only in combined treatments. Defense enzymes Proline, Peroxidase, and Catalase were induced by PGPR strains in comparison with those of control plants. Hydrogen peroxide (H2O2) and callose deposition were evident at reaction sites induced by PGPR strains. The accumulation of callose, H2O2, and high levels of defense enzymes via the treatment of PGPRs might play a significant role in a practical, safe, and effective way to control Pseudomonas syringae pv. tomato.

Whole-Genome Sequencing of Pseudomonas koreensis Isolated from Diseased Tor tambroides.

Unlike environmental P. koreensis isolated from soil, which has been studied extensively for its role in promoting plant growth, pathogenic P. koreensis isolated from fish has been rarely reported. Therefore, we investigated and isolated the possible pathogen that is responsible for the diseased state of Tor tambroides. Herein, we reported the morphological and biochemical characteristics, as well as whole-genome sequences of a newly identified P. koreensis strain. We assembled a high-quality draft genome of P. koreensis CM-01 with a contig N50 value of 233,601bp and 99.5% BUSCO completeness. The genome assembly of P. koreensis CM-01 is consists of6,171,880bp with aG+C content of 60.5%. Annotation of the genome identified 5538 protein-coding genes, 3 rRNA genes, 54 tRNAs, and no plasmids were found. Besides these, 39 interspersed repeat and 141 tandem repeat sequences, 6 prophages, 51 genomic islands, 94 insertion sequences, 4 clustered regularly interspaced short palindromic repeats, 5 antibiotic-resistant genes, and 150 virulence genes were alsopredicted in the P. koreensis CM-01 genome. Culture-based approach showed thatCM-01 strain exhibited resistance against ampicillin, aztreonam, clindamycin, and cefoxitinwith a calculated multiple antibiotic resistance (MAR) index value of 0.4. In addition, the assembled CM-01 genome was successfully annotated against the Cluster of Orthologous Groups of proteins database, Gene Ontology database, and Kyoto Encyclopedia of Genes and Genome pathway database. A comparative analysis of CM-01 with three representative strains of P. koreensis revealed that 92% of orthologous clusters were conserved among these four genomes, and only the CM-01 strain possesses unique elements related to pathogenicity and virulence. This study provides fundamental phenotypic and genomic information for the newly identified P. koreensis strain.

Plant growth-promoting rhizobacteria’s (PGPR) effects on Medicago sativa growth, arbuscular mycorrhizal colonisation, and soil enzyme activities

ABSTRACT Plant growth-promoting rhizobacteria (PGPR) can ameliorate soil fertility and boost crop yields. This paper reports a study of the effect of PGPR inoculation on Medicago sativa plants. Sixteen indigenous PGPR were isolated and screened for PGP traits. Their influence was assessed on the growth of M. sativa plants, root colonisation by arbuscular mycorrhizal fungi (AMF), and soil enzyme activities (SEA). The bacterial isolates showed interesting PGP traits. They increased the plant’s shoot and root dry weights, AM colonisation, and SEA. Two bacteria assigned to Pseudomonas koreensis and Alcaligenes faecalis were selected as effective inoculants for M. sativa plants. These PGPR may represent suitable candidates as bio-enhancers and biofertilizers in sustainable agricultural systems.

Developing eco‐friendly endophytic bioinoculants for enhancing productivity and soil fertility in wheat

AbstractThe main aim of this study was to explore the potential role of wheat endophytic bacteria on wheat (Triticum aestivum L.) production and soil health management under pot and field trials. Seven plant growth‐promoting putative endophytes were isolated from different wheat plant parts (root, shoot, leaf, and seed). We selected two effective bacterial strains, Pseudomonas sp. BHUJPV‐WRO5 (from the “Pseudomonas koreensis” subgroup) originating from the root and Staphylococcus sp. BHUJPV‐WLE7 isolated from leaf, based on plant growth‐promoting traits like indole‐3‐acetic acid, ammonia, siderophore production, and phosphate solubilization. We conducted pot and field experiments with treatments T1 (uninoculated), T2 (Pseudomonas sp.), and T3 (Staphylococcus sp.). In pots, grain yield was higher with Pseudomonas sp. or S. xylosus than in the control. Similarly, grain yield in the field was increased with Pseudomonas sp. BHUJPV‐WRO5 or Staphylococcus sp. BHUJPV‐WLE7 compared with control. Pseudomonas sp. BHUJPV‐WRO5 also resulted in higher soil electrical conductivity (both pot and field), total organic carbon (in field), soil contents in available N, P, and K (in pot and field), and potential activity in soil of alkaline phosphatase (pot and field), dehydrogenase and β‐glucosidase (in pot). The effects of Staphylococcus sp. BHUJPV‐WLE7 were smaller, with however, higher soil levels for electrical conductivity (in pot), total organic carbon (in field), available P (in pot and field), and higher potential activity of alkaline phosphatase (in pot) than control. Overall, the putative wheat endophytes effectively enhanced plant growth, crop productivity, and soil quality, and Pseudomonas stain is promising as a bio‐inoculant for sustainable wheat production.