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Angewandte Chemie (International Ed. in... Dec 2022Benzoxazolinate is a rare bis-heterocyclic moiety that interacts with proteins and DNA and confers extraordinary bioactivities on natural products, such as C-1027....
Benzoxazolinate is a rare bis-heterocyclic moiety that interacts with proteins and DNA and confers extraordinary bioactivities on natural products, such as C-1027. However, the biosynthetic gene responsible for the key cyclization step of benzoxazolinate remains unclear. Herein, we show a putative acyl AMP-ligase responsible for the last cyclization step. We used the enzyme as a probe for genome mining and discovered that the orphan benzobactin gene cluster in entomopathogenic bacteria prevails across Proteobacteria and Firmicutes. It turns out that Pseudomonas chlororaphis produces various benzobactins, whose biosynthesis is highlighted by a synergistic effect of two unclustered genes encoding enzymes on boosting benzobactin production; the formation of non-proteinogenic 2-hydroxymethylserine by a serine hydroxymethyltransferase; and the types I and II NRPS architecture for structural diversity. Our findings reveal the biosynthetic potential of a widespread benzobactin gene cluster.
Topics: Biological Products; Bacteria; Multigene Family; Peptide Synthases
PubMed: 36198080
DOI: 10.1002/anie.202206106 -
Plant Disease Oct 2022As the excessive use of chemical fertilizers harms organisms and adversely affects the soil environment, the replacement of chemical fertilizers with biological...
As the excessive use of chemical fertilizers harms organisms and adversely affects the soil environment, the replacement of chemical fertilizers with biological fertilizers has attracted widespread attention as an environmental protection strategy. In this study, the effects of rhizosphere bacteria inoculation on growth of var. seedlings, soil parameters, soil microbial community structure, and the biocontrol of damping-off were studied by pot experiments. The results showed that all three rhizosphere bacteria (, , and A07) tested exhibited growth-promoting properties, such as the production of indole-3-acetic acid, hydrolase, siderophores, and hydrogen cyanide; nitrogen fixation; and phosphorus solubilization. The application of the three bacteria increased plant biomass, root structure, and nutrient content and also increased soil nutrient content and enzyme activity. Bacterial inoculation promoted the growth of beneficial bacteria and antagonistic bacteria by adjusting the physicochemical properties of the soil, thereby improving the bacterial community structure. Among the soil features, available nitrogen, total nitrogen, available potassium, and urease activity were the main influencing factors. In addition, it was also found that bacterial inoculation significantly increased the activities of plant superoxide dismutase, catalase, peroxidase, and other defense enzymes; enhanced plant disease resistance; effectively inhibited damping-off; and promoted plant growth. In summary, the application of three rhizosphere bacteria systematically affected the interaction between plants, soil parameters, and soil microbial communities. These results provide a basis for understanding how rhizosphere bacteria promote the growth of var. , thereby offering a promising sustainable alternative to chemical fertilizers.
Topics: Bacteria; Catalase; Fertilizers; Hydrogen Cyanide; Microbiota; Nitrogen; Phosphorus; Pinus sylvestris; Potassium; Rhizoctonia; Seedlings; Siderophores; Soil; Superoxide Dismutase; Urease
PubMed: 36094426
DOI: 10.1094/PDIS-11-21-2562-RE -
Frontiers in Microbiology 2022f. sp. () tropical race 4 (TR4) is threatening banana production because of its increasing spread. Biological control approaches have been widely studied and...
f. sp. () tropical race 4 (TR4) is threatening banana production because of its increasing spread. Biological control approaches have been widely studied and constitute interesting complementary measures to integrated disease management strategies. They have been based mainly on the use of single biological control agents (BCAs). In this study, we moved a step forward by designing a synthetic microbial community (SynCom) for the control of Fusarium wilt of banana (FWB). Ninety-six isolates of spp., spp., spp., and spp. were obtained from the banana rhizosphere and selected for the antagonism against TR4. In pot experiments, a large community such as SynCom 1.0 (44 isolates with moderate to high antagonistic activity) or a small one such as SynCom 1.1 (seven highly effective isolates) provided similar disease control (35% symptom severity reduction). An study of the interactions among SynCom 1.1 isolates and between them and revealed that beneficial microorganisms not only antagonized the pathogen but also some of the SynCom constituents. Furthermore, defended itself by antagonizing the beneficial microbes. We also demonstrated that fusaric acid, known as one of the secondary metabolites of species, might be involved in such an interaction. With this knowledge, SynCom 1.2 was then designed with three isolates: subsp. PS5, BN8.2, and T2C1.4. A non-simultaneous soil application of these isolates (to diminish cross-inhibition) delayed FWB progress over time, with significant reductions in incidence and severity. SynCom 1.2 also performed better than two commercial BCAs, BioPak and T-Gro. Eventually, SynCom 1.2 isolates were characterized for several biocontrol traits and their genome was sequenced. Our data showed that assembling a SynCom for biocontrol is not an easy task. The mere mixtures of antagonists (e.g., SynCom 1.0 and 1.1) might provide effective biocontrol, but an accurate investigation of the interactions among beneficial microorganisms is needed to improve the results (e.g., SynCom 1.2). SynCom 1.2 is a valuable tool to be further developed for the biological control of FWB.
PubMed: 35992653
DOI: 10.3389/fmicb.2022.967885 -
Journal of Applied Microbiology Nov 2022Phenazines, such as phenazine-1-carboxylic acid (PCA), phenazine-1-carboxamide (PCN), 2-hydroxyphenazine-1-carboxylic acid (2-OH-PCA), 2-hydroxyphenazine (2-OH-PHZ), are...
AIMS
Phenazines, such as phenazine-1-carboxylic acid (PCA), phenazine-1-carboxamide (PCN), 2-hydroxyphenazine-1-carboxylic acid (2-OH-PCA), 2-hydroxyphenazine (2-OH-PHZ), are a class of secondary metabolites secreted by plant-beneficial Pseudomonas. Ps. chlororaphis GP72 utilizes glycerol to synthesize PCA, 2-OH-PCA and 2-OH-PHZ, exhibiting broad-spectrum antifungal activity. Previous studies showed that the addition of dithiothreitol (DTT) could increase the phenazines production in Ps. chlororaphis GP72AN. However, the mechanism of high yield of phenazine by adding DTT is still unclear.
METHODS AND RESULTS
In this study, untargeted and targeted metabolomic analysis were adopted to determine the content of metabolites. The results showed that the addition of DTT to GP72AN affected the content of metabolites of central carbon metabolism, shikimate pathway and phenazine competitive pathway. Transcriptome analysis was conducted to investigate the changed cellular process, and the result indicated that the addition of DTT affected the expression of genes involved in phenazine biosynthetic cluster and genes involved in phenazine competitive pathway, driving more carbon flux into phenazine biosynthetic pathway. Furthermore, genes involved in antioxidative stress, phosphate transport system and mexGHI-opmD efflux pump were also affected by adding DTT.
CONCLUSION
This study demonstrated that the addition of DTT altered the expression of genes related to phenazine biosynthesis, resulting in the change of metabolites involved in central carbon metabolism, shikimate pathway and phenazine competitive pathway.
SIGNIFICANCE AND IMPACT OF THE STUDY
This work expands the understanding of high yield of phenazine by the addition of DTT and provides several targets for increasing phenazine production.
Topics: Pseudomonas chlororaphis; Glycerol; Antifungal Agents; Dithiothreitol; Transcriptome; Phenazines; Metabolomics; Gene Expression Profiling; Carbon; Phosphates; Bacterial Proteins
PubMed: 35870153
DOI: 10.1111/jam.15727 -
Microbial Ecology Jul 2023The interaction of plants with bacteria and the long-term success of their adaptation to challenging environments depend upon critical traits that include nutrient...
The interaction of plants with bacteria and the long-term success of their adaptation to challenging environments depend upon critical traits that include nutrient solubilization, remodeling of root architecture, and modulation of host hormonal status. To examine whether bacterial promotion of phosphate solubilization, root branching and the host auxin response may account for plant growth, we isolated and characterized ten bacterial strains based on their high capability to solubilize calcium phosphate. All strains could be grouped into six Pseudomonas species, namely P. brassicae, P. baetica, P. laurylsulfatiphila, P. chlororaphis, P. lurida, and P. extremorientalis via 16S rRNA molecular analyses. A Solibacillus isronensis strain was also identified, which remained neutral when interacting with Arabidopsis roots, and thus could be used as inoculation control. The interaction of Arabidopsis seedlings with bacterial streaks from pure cultures in vitro indicated that their phytostimulation properties largely differ, since P. brassicae and P. laurylsulfatiphila strongly increased shoot and root biomass, whereas the other species did not. Most bacterial isolates, except P. chlororaphis promoted lateral root formation, and P. lurida and P. chlororaphis strongly enhanced expression of the auxin-inducible gene construct DR5:GUS in roots, but the most bioactive probiotic bacterium P. brassicae could not enhance the auxin response. Inoculation with P. brassicae and P. lurida improved shoot and root growth in medium supplemented with calcium phosphate as the sole Pi source. Collectively, our data indicate the differential responses of Arabidopsis seedlings to inoculation with several Pseudomonas species and highlight the potential of P. brassicae to manage phosphate nutrition and plant growth in a more eco-friendly manner.
Topics: Arabidopsis; Pseudomonas; Seedlings; Phosphates; RNA, Ribosomal, 16S; Plant Roots; Indoleacetic Acids; Bacteria
PubMed: 35867140
DOI: 10.1007/s00248-022-02080-y -
IScience Jul 2022Two-partner secretion (TPS) is widespread in the bacterial world. The pore-forming TPS toxin ExlA of is conserved in pathogenic and environmental . While and...
Two-partner secretion (TPS) is widespread in the bacterial world. The pore-forming TPS toxin ExlA of is conserved in pathogenic and environmental . While and displayed ExlA-dependent killing, did not cause damage to eukaryotic cells. ExlA proteins interacted with epithelial cell membranes; however, only ExlA induced the cleavage of the adhesive molecule E-cadherin. ExlA proteins participated in insecticidal activity toward the larvae of and the fly Evolutionary analyses demonstrated that the differences in the C-terminal domains are partly due to horizontal movements of the operon within the genus Reconstruction of the evolutionary history revealed the complex horizontal acquisitions. Together, our results provide evidence that conserved TPS toxins in environmental play a role in bacteria-insect interactions and discrete differences in CTDs may determine their specificity and mode of action toward eukaryotic cells.
PubMed: 35789842
DOI: 10.1016/j.isci.2022.104596 -
Journal of Agricultural and Food... Jun 2022has been demonstrated as a valuable source of antimicrobial metabolites for plant disease biocontrol and biopesticide development. Although phenazine-1-carboxylic acid...
has been demonstrated as a valuable source of antimicrobial metabolites for plant disease biocontrol and biopesticide development. Although phenazine-1-carboxylic acid (PCA) secreted by has been commercialized as an antifungal biopesticide, it shows poor antibacterial activity. Questiomycin A, with versatile antibacterial activities, is mainly discovered in some well-known phenazine-producing strains but not in . Its low titer hinders practical applications. In this work, a metabolite was first identified as Questiomycin A in -derived strain HT66ΔΔ. Subsequently, Questiomycin A has been elucidated to share the same biosynthesis process with PCA by gene deletion and assays. Through rational metabolic engineering, heterologous phenoxazinone synthase introduction, and medium optimization, the titer reached 589.78 mg/L in , the highest production reported to date. This work contributes to a better understanding of Questiomycin A biosynthesis and demonstrates a promising approach to developing a new antibacterial biopesticide in .
Topics: Anti-Bacterial Agents; Bacterial Proteins; Biological Control Agents; Metabolic Engineering; Oxazines; Phenazines; Pseudomonas chlororaphis
PubMed: 35708224
DOI: 10.1021/acs.jafc.2c03216 -
International Microbiology : the... Nov 2022The biocontrol rhizobacterium Pseudomonas chlororaphis is one of the bacterial species of the P. fluorescens group where insecticide fit genes have been found. Fit...
The biocontrol rhizobacterium Pseudomonas chlororaphis is one of the bacterial species of the P. fluorescens group where insecticide fit genes have been found. Fit toxin, supported with other antimicrobial compounds, gives the bacterial the ability to repel and to fight against eukaryotic organisms, such as nematodes and insect larvae, thus protecting the plant host and itself. Pseudomonas chlororaphis PCL1606 is an antagonistic rhizobacterium isolated from avocado roots and show efficient biocontrol against fungal soil-borne disease. The main antimicrobial compound produced by P. chlororaphis PCL606 is 2-hexyl-5-propyl resorcinol (HPR), which plays a crucial role in effective biocontrol against fungal pathogens. Further analysis of the P. chlororaphis PCL1606 genome showed the presence of hydrogen cyanide (HCN), pyrrolnitrin (PRN), and homologous fit genes. To test the insecticidal activity and to determine the bases for such activity, single and double mutants on the biosynthetic genes of these four compounds were tested in a Galleria mellonella larval model using inoculation by injection. The results revealed that Fit toxin and HPR in combination are involved in the insecticide phenotype of P. chlororaphis PCL1606, and additional compounds such as HCN and PRN could be considered supporting compounds.
Topics: Anti-Infective Agents; Hydrogen Cyanide; Insecticides; Pseudomonas chlororaphis; Pyrrolnitrin; Resorcinols; Soil
PubMed: 35670867
DOI: 10.1007/s10123-022-00253-w -
Journal of Basic Microbiology Jul 2022In the present study, nonrhizobial endophytes were isolated from Pisum sativum and Cicer arietinum from Haryana, India. A total of 355 bacterial endophytes were screened...
In the present study, nonrhizobial endophytes were isolated from Pisum sativum and Cicer arietinum from Haryana, India. A total of 355 bacterial endophytes were screened for plant growth promoting traits. Out of all, 96 bacterial endophytes were selected based on morphological characters and multi-PGP traits, and their diversity analyzed by amplified ribosomal DNA restriction analysis. Based on their ARDRA profile, the 25 representative isolates (12 from P. sativum and 13 from C. arietinum), were selected and identified by 16S ribosomal DNA sequencing. Genetic relatedness based on BLAST analysis revealed the similarity of these isolates with members of three prominent phyla, that is, Proteobacteria, Firmicutes, and Actinobacteria. The dominant cluster, Firmicutes, constituted 60% of the isolates, assigned to four different genera, Bacillus, Staphylococcus, Ornithinibacillus, and Lysinibacillus. Phylum α-proteobacteria included two genera, namely Paenochrobactrum and Ochrobactrum and three genera in phylum γ-proteobacteria, namely Pseudomonas, Pantoea and Proteus. The phylum Actinobacteria was constituted of two genera, Microbacterium and Arthrobacter. Bacillus zhangzhouensis, Bacillus safensis, Arthrobacter enclensis from P. sativum and Bacillus haynesii, Paenochrobactrum sp. from C. arietinum are documented as plant growth promoting endophytic bacteria for the first time in the present study. The in vitro and in vivo assessment based on bonitur score revealed that the endophytic isolates Bacillus mojavensis PRN2, Pseudomonas chlororaphis PHN9, B. safensis PRER2, Pseudomonas sp. RCP1, Pseudomonas lini PRN1 and B. haynensii RCP3 from P. sativum and C. arietinum significantly enhanced the plant growth parameters. Therefore, these potential isolates can be further harnessed for preparation of bioformulations to enhance sustainable agriculture.
Topics: Bacteria; Cicer; DNA, Ribosomal; Endophytes; Firmicutes; Pisum sativum; Phylogeny; Plant Roots; Proteobacteria; RNA, Ribosomal, 16S
PubMed: 35655367
DOI: 10.1002/jobm.202100575 -
International Journal of Biological... Jun 2022Enhanced co-production of medium-chain-length polyhydroxyalkanoates (mcl-PHA) and extracellular phenazines was assessed through a high cell density cultivation of...
Enhanced co-production of medium-chain-length polyhydroxyalkanoates and phenazines from crude glycerol by high cell density cultivation of Pseudomonas chlororaphis in membrane bioreactor.
Enhanced co-production of medium-chain-length polyhydroxyalkanoates (mcl-PHA) and extracellular phenazines was assessed through a high cell density cultivation of Pseudomonas chlororaphis subsp. aurantiaca (DSM 19603) in a membrane bioreactor using crude glycerol as a fermentative substrate. A maximum dry cell weight (DCW) of 59.25 ± 0.31 g/L was achieved at 90 h of cultivation with a maximum mcl-PHA and extracellular phenazines concentrations of respectively 19.05 ± 0.04 g/L (32.16% of DCW) and 79.42 ± 0.35 mg/L. mcl-PHA concentration achieved through cell retention culture was 28.43-folds higher than that obtained by batch culture. Fourier transform infrared spectroscopy, gas chromatography-mass spectrometry, and H nuclear magnetic resonance analysis identified the produced PHA as a mcl-PHA copolymer of 3-hydroxyhexanoate (0.68%), 3-hydroxyoctanoate (7.76%), 3-hydroxydecanoate (49.18%), 3-hydroxydodecanoate (4.89%), and 3-hydroxytetradecanoate (37.50%). The mcl-PHA exhibited a highly amorphous structure with low crystallinity index (4.19%) and high thermal stability. This is the first report on the enhanced co-production of mcl-PHA and phenazines in a membrane bioreactor.
Topics: Bioreactors; Cell Count; Glycerol; Phenazines; Polyhydroxyalkanoates; Pseudomonas; Pseudomonas chlororaphis
PubMed: 35577193
DOI: 10.1016/j.ijbiomac.2022.05.089