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883100.9726Search for biocontrol agents among endophytic lipopeptide-synthesizing bacteria Bacillus spp. to protect wheat plants against Greenbug aphid (Schizaphis graminum). Beneficial endophytic bacteria can suppress the development of insect pests through direct antagonism, with the help of metabolites, or indirectly by the induction of systemic resistance through the regulation of hormonal signaling pathways. Lipopeptides are bacterial metabolites that exhibit direct antagonistic activity against many organisms, including insects. Also, lipopeptides are able to trigger induced systemic resistance (ISR) in plants against harmful organisms, but the physiological mechanisms of their action are just beginning to be studied. In this work, we studied ten strains of bacteria isolated from the tissues of wheat and potatoes. Sequencing of the 16S rRNA gene showed that all isolates belong to the genus Bacillus and to two species, B. subtilis and B. velezensis. The genes for lipopeptide synthetase - surfactin synthetase (Bs_srf ), iturin synthetase (Bs_ituA, Bs_ituB) and fengycin synthetase (Bs_fenD) - were identified in all bacterial isolates using PCR. All strains had high aphicidal activity against the Greenbug aphid (Schizaphis graminum Rond.) due to the synthesis of lipopeptides, which was proven using lipopeptide-rich fractions (LRFs) isolated from the strains. Endophytic lipopeptide-synthesizing strains of Bacillus spp. indirectly affected the viability of aphids, the endurance of plants against aphids and triggered ISR in plants, which manifested itself in the regulation of oxidative metabolism and the accumulation of transcripts of the Pr1, Pr2, Pr3, Pr6 and Pr9 genes due to the synthesis of lipopeptides, which was proven using LRF isolated from three strains: B. subtilis 26D, B. subtilis 11VM, and B. thuringiensis B-6066. We have for the first time demonstrated the aphicidal effect of fengycin and the ability of the fengycin-synthesizing strains and isolates, B. subtilis Ttl2, Bacillus sp. Stl7 and B. thuringiensis B-6066, to regulate components of the pro-/antioxidant system of aphid-infested plants. In addition, this work is the first to demonstrate an elicitor role of fengycin in triggering a systemic resistance to S. graminum in wheat plants. We have discovered new promising strains and isolates of endophytes of the genus Bacillus, which may be included in the composition of new biocontrol agents against aphids. One of the criteria for searching for new bacteria active against phloem-feeding insects can be the presence of lipopeptide synthetase genes in the bacterial genome.202438952706
883010.9723Additive Effect of the Composition of Endophytic Bacteria Bacillus subtilis on Systemic Resistance of Wheat against Greenbug Aphid Schizaphis graminum Due to Lipopeptides. The use of biocontrol agents based on endophytic bacteria against phloem-feeding insects is limited by a lack of knowledge and understanding of the mechanism of action of the endophyte community that makes up the plant microbiome. In this work, the mechanisms of the additive action of endophytic strains B. subtilis 26D and B. subtilis 11VM on the resistance of bread spring wheat against greenbug aphid Schizaphis graminum, was studied. It was shown that B. subtilis 26D secreted lipopeptide surfactin and phytohormones cytokinins, and B. subtilis 11VM produced iturin and auxins into the cultivation medium. Both strains and their lipopeptide-rich fractions showed direct aphicidal activity against greenbug aphid. For the first time, it was shown that B. subtilis 26D and B. subtilis 11VM in the same manner, as well as their lipopeptide-rich fractions, activated the expression of salicylate- and ethylene-dependent PR genes, and influenced plant redox metabolism, which led to an increase in plant endurance against aphids. The composition of endophytic strains B. subtilis 26D + B. subtilis 11VM had an additive effect on plant resistance to aphids due to an increase in the number of endophytic bacterial cells, and, as well as due to the synergistic effect of their mixture of lipopeptides - surfactin + iturin, both on the aphid mortality and on the expression of PR1 and PR3 genes. All these factors can be the reason for the observed increase in the growth of plants affected by aphids under the influence of B. subtilis 26D and B. subtilis 11VM, individually and in composition. The study demonstrates the possibility of creating in the future an artificial composition to enhance plant microbiome with endophytic bacteria, which combines growth-promoting and plant immunity stimulating properties against phloem-feeding insects. This direction is one of the most promising approaches to green pesticide discovery in the future.202336676163
878020.9715Surfactin and fengycin lipopeptides of Bacillus subtilis as elicitors of induced systemic resistance in plants. Multiple strains of Bacillus spp. were demonstrated to stimulate plant defence responses. However, very little is known about the nature of molecular determinants secreted by these Gram-positive bacteria that are responsible for the elicitation of the induced systemic resistance (ISR) phenomenon. This study shows that the lipopeptides surfactins and fengycins may be involved in this elicitation process. In bean, pure fengycins and surfactins provided a significant ISR-mediated protective effect on bean plants, similar to the one induced by living cells of the producing strain S499. Moreover, experiments conducted on bean and tomato plants showed that overexpression of both surfactin and fengycin biosynthetic genes in the naturally poor producer Bacillus subtilis strain 168 was associated with a significant increase in the potential of the derivatives to induce resistance. In tomato cells, key enzymes of the lipoxygenase pathway appeared to be activated in resistant plants following induction by lipopeptide overproducers. To our knowledge, such lipopeptides constitute a novel class of compounds from non-pathogenic bacteria that can be perceived by plant cells as signals to initiate defence mechanisms.200717359279
1830.9714Antivirulence effects of cell-free culture supernatant of endophytic bacteria against grapevine crown gall agent, Agrobacterium tumefaciens, and induction of defense responses in plantlets via intact bacterial cells. BACKGROUND: Crown gall disease caused by Agrobacterium tumefaciens is a very destructive affliction that affects grapevines. Endophytic bacteria have been discovered to control plant diseases via the use of several mechanisms. This research examined the potential for controlling crown gall by three endophytic bacteria that were previously isolated from healthy cultivated and wild grapevines including Pseudomonas kilonensis Ba35, Pseudomonas chlororaphis Ba47, and Serratia liquefaciens Ou55. RESULT: At various degrees, three endophytic bacteria suppressed the populations of A. tumefaciens Gh1 and greatly decreased the symptoms of crown gall. Furthermore, biofilm production and motility behaviors of A. tumefaciens Gh1were greatly inhibited by the Cell-free Culture Supernatant (CFCS) of endophytic bacteria. According to our findings, CFCS may reduce the adhesion of A. tumefaciens Gh1 cells to grapevine cv. Rashe root tissues as well as their chemotaxis motility toward the extract of the roots. When compared to the untreated control, statistical analysis showed that CFCS significantly reduced the swimming, twitching, and swarming motility of A. tumefaciens Gh1. The findings demonstrated that the endophytic bacteria effectively stimulated the production of plant defensive enzymes including superoxide dismutase (SOD), polyphenol oxidase (PPO), peroxidase (POD), phenylalanine ammonia lyase (PAL), and total soluble phenols at different time intervals in grapevine inoculated with A. tumefaciens Gh1. The Ba47 strain markedly increased the expression levels of defense genes associated with plant resistance. The up-regulation of PR1, PR2, VvACO1, and GAD1 genes in grapevine leaves indicates the activation of SA and JA pathways, which play a role in enhancing resistance to pathogen invasion. The results showed that treating grapevine with Ba47 increased antioxidant defense activities and defense-related gene expression, which reduced oxidative damage caused by A. tumefaciens and decreased the incidence of crown gall disease. CONCLUSION: This is the first study on how A. tumefaciens, the grapevine crown gall agent, is affected by CFCS generated by endophytic bacteria in terms of growth and virulence features. To create safer plant disease management techniques, knowledge of the biocontrol processes mediated by CFCS during microbial interactions is crucial.202438336608
54140.9710A Teleost Bactericidal Permeability-Increasing Protein Kills Gram-Negative Bacteria, Modulates Innate Immune Response, and Enhances Resistance against Bacterial and Viral Infection. Bactericidal/permeability-increasing protein (BPI) is an important factor of innate immunity that in mammals is known to take part in the clearance of invading Gram-negative bacteria. In teleost, the function of BPI is unknown. In the present work, we studied the function of tongue sole (Cynoglossus semilaevis) BPI, CsBPI. We found that CsBPI was produced extracellularly by peripheral blood leukocytes (PBL). Recombinant CsBPI (rCsBPI) was able to bind to a number of Gram-negative bacteria but not Gram-positive bacteria. Binding to bacteria led to bacterial death through membrane permeabilization and structural destruction, and the bound bacteria were more readily taken up by PBL. In vivo, rCsBPI augmented the expression of a wide arrange of genes involved in antibacterial and antiviral immunity. Furthermore, rCsBPI enhanced the resistance of tongue sole against bacterial as well as viral infection. These results indicate for the first time that a teleost BPI possesses immunoregulatory effect and plays a significant role in antibacterial and antiviral defense.201627105425
1650.9709A glycoside hydrolase 30 protein BpXynC of Bacillus paralicheniformis NMSW12 recognized as A MAMP triggers plant immunity response. Bacillus spp. has been widely used as a biocontrol agent to control plant diseases. However, little is known about mechanisms of the protein MAMP secreted by Bacillus spp. Herein, our study reported a glycoside hydrolase family 30 (GH30) protein, BpXynC, produced by the biocontrol bacteria Bacillus paralicheniformis NMSW12, that can induce cell death in several plant species. The results revealed that the recombinant protein triggers cell death in Nicotiana benthamiana in a BAK1-dependent manner and elicits an early defense response, including ROS burst, activation of MAPK cascades, and upregulation of plant immunity marker genes. BpXynC was also found to be a glucuronoxylanase that exhibits hydrolysis activity on xlyan. Two mutants of BpXynC which lost the glucuronoxylanase activity still retained the elicitor activity. The qRT-PCR results of defense-related genes showed that BpXynC induces plant immunity responses via an SA-mediated pathway. BpXynC and its mutants could induce resistance in N. benthamiana against infection by Sclerotinia sclerotiorum and tobacco mosaic virus (TMV). Furthermore, BpXynC-treated tomato fruits exhibited strong resistance to the infection of Phytophthora capsica. Overall, our study revealed that GH30 protein BpXynC can induce plant immunity response as MAMP, which can be further applied as a biopesticide to control plant diseases.202438286384
819460.9706Role of the phenazine-inducing protein Pip in stress resistance of Pseudomonas chlororaphis. The triggering of antibiotic production by various environmental stress molecules can be interpreted as bacteria's response to obtain increased fitness to putative danger, whereas the opposite situation - inhibition of antibiotic production - is more complicated to understand. Phenazines enable Pseudomonas species to eliminate competitors for rhizosphere colonization and are typical virulence factors used for model studies. In the present work, we have investigated the negative effect of subinhibitory concentrations of NaCl, fusaric acid and two antibiotics on quorum-sensing-controlled phenazine production by Pseudomonas chlororaphis. The selected stress factors inhibit phenazine synthesis despite sufficient cell density. Subsequently, we have identified connections between known genes of the phenazine-inducing cascade, including PsrA (Pseudomonas sigma regulator), RpoS (alternative sigma factor), Pip (phenazine inducing protein) and PhzI/PhzR (quorum-sensing system). Under all tested conditions, overexpression of Pip or PhzR restored phenazine production while overexpression of PsrA or RpoS did not. This forced restoration of phenazine production in strains overexpressing regulatory genes pip and phzR significantly impairs growth and stress resistance; this is particularly severe with pip overexpression. We suggest a novel physiological explanation for the inhibition of phenazine virulence factors in pseudomonas species responding to toxic compounds. We propose that switching off phenazine-1-carboxamide (PCN) synthesis by attenuating pip expression would favour processes required for survival. In our model, this 'decision' point for promoting PCN production or stress resistance is located downstream of rpoS and just above pip. However, a test with the stress factor rifampicin shows no significant inhibition of Pip production, suggesting that stress factors may also target other and so far unknown protagonists of the PCN signalling cascade.201121030433
1270.9706A Diketopiperazine, Cyclo-(L-Pro-L-Ile), Derived From Bacillus thuringiensis JCK-1233 Controls Pine Wilt Disease by Elicitation of Moderate Hypersensitive Reaction. Pine wilt disease (PWD) caused by the pine wood nematode (PWN) Bursaphelenchus xylophilus is one of the devastating diseases affecting pine forests worldwide. Although effective control measurements are still missing, induction of resistance could represent a possible eco-friendly alternative. In this study, induced resistance-based in vitro and in vivo screening tests were carried out for selection of bacteria with the ability to suppress PWD. Out of 504 isolated bacteria, Bacillus thuringiensis JCK-1233 was selected for its ability to boost pathogenesis-related 1 (PR1) gene expression, a marker of systemic acquired resistance. Moreover, treatment of pine seedlings with B. thuringiensis JCK-1233 resulted in increased expression of other defense-related genes, and significantly inhibited PWD development under greenhouse conditions. However, B. thuringiensis JCK-1233 showed no direct nematicidal activity against B. xylophilus. To identify the effective compound responsible for the induction of resistance in B. thuringiensis JCK-1233, several diketopiperazines (DPKs) including cyclo-(D-Pro-L-Val), cyclo-(L-Pro-L-Ile), cyclo-(L-Pro-L-Phe), and cyclo-(L-Leu-L-Val) were isolated and tested. Foliar treatment of pine seedlings with Cyclo-(L-Pro-L-Ile) resulted in suppression of PWD severity and increased the expression of defense-related genes similarly to B. thuringiensis JCK-1233 treatment. Interestingly, treatment with B. thuringiensis JCK-1233 or cyclo-(L-Pro-L-Ile) showed moderately enhanced expression of PR-1, PR-2, PR-3, PR-4, PR-5, and PR-9 genes following inoculation with PWN compared to that in the untreated control, indicating that they mitigated the burst of hypersensitive reaction in susceptible pine seedlings. In contrast, they significantly increased the expression levels of PR-6 and PR-10 before PWN inoculation. In conclusion, foliar spraying with either B. thuringiensis JCK-1233 culture suspension or DPKs could induce resistance in pine seedlings, thereby alleviating the serious damage by PWD. Taken together, this study supports aerial spraying with eco-friendly biotic or abiotic agents as a valuable strategy that may mark an epoch for the control of PWD in pine forests.202032849672
1380.9701Streptomyces sp. JCK-6131 Protects Plants Against Bacterial and Fungal Diseases via Two Mechanisms. Plant bacterial and fungal diseases cause significant agricultural losses and need to be controlled. Beneficial bacteria are promising candidates for controlling these diseases. In this study, Streptomyces sp. JCK-6131 exhibited broad-spectrum antagonistic activity against various phytopathogenic bacteria and fungi. In vitro assays showed that the fermentation filtrate of JCK-6131 inhibited the growth of bacteria and fungi with minimum concentration inhibitory (MIC) values of 0.31-10% and 0.31-1.25%, respectively. In the in vivo experiments, treatment with JCK-6131 effectively suppressed the development of apple fire blight, tomato bacterial wilt, and cucumber Fusarium wilt in a dose-dependent manner. RP-HPLC and ESI-MS/MS analyses indicated that JCK-6131 can produce several antimicrobial compounds, three of which were identified as streptothricin E acid, streptothricin D, and 12-carbamoyl streptothricin D. In addition, the disease control efficacy of the foliar application of JCK-6131 against tomato bacterial wilt was similar to that of the soil drench application, indicating that JCK-6131 could enhance defense resistance in plants. Molecular studies on tomato plants showed that JCK-6131 treatment induced the expression of the pathogenesis-related (PR) genes PR1, PR3, PR5, and PR12, suggesting the simultaneous activation of the salicylate (SA) and jasmonate (JA) signaling pathways. The transcription levels of PR genes increased earlier and were higher in treated plants than in untreated plants following Ralstonia solanacearum infection. These results indicate that Streptomyces sp. JCK-6131 can effectively control various plant bacterial and fungal diseases via two distinct mechanisms of antibiosis and induced resistance.202134603354
877590.9698Induction of systemic resistance in tomato by N-acyl-L-homoserine lactone-producing rhizosphere bacteria. N-acyl-L-homoserine lactone (AHL) signal molecules are utilized by Gram-negative bacteria to monitor their population density (quorum sensing) and to regulate gene expression in a density-dependent manner. We show that Serratia liquefaciens MG1 and Pseudomonas putida IsoF colonize tomato roots, produce AHL in the rhizosphere and increase systemic resistance of tomato plants against the fungal leaf pathogen, Alternaria alternata. The AHL-negative mutant S. liquefaciens MG44 was less effective in reducing symptoms and A. alternata growth as compared to the wild type. Salicylic acid (SA) levels were increased in leaves when AHL-producing bacteria colonized the rhizosphere. No effects were observed when isogenic AHL-negative mutant derivatives were used in these experiments. Furthermore, macroarray and Northern blot analysis revealed that AHL molecules systemically induce SA- and ethylene-dependent defence genes (i.e. PR1a, 26 kDa acidic and 30 kDa basic chitinase). Together, these data support the view that AHL molecules play a role in the biocontrol activity of rhizobacteria through the induction of systemic resistance to pathogens.200617087474
9026100.9698Citral and its derivatives inhibit quorum sensing and biofilm formation in Chromobacterium violaceum. With an upsurge in multidrug resistant bacteria backed by biofilm defence armours, there is a desperate need of new antibiotics with a non-traditional mechanism of action. Targeting bacteria by misguiding them or halting their communication is a new approach that could offer a new way to combat the multidrug resistance problem. Quorum sensing is considered to be the achilles heel of bacteria that has a lot to offer. Since, both quorum sensing and biofilm formation have been related to drug resistance and pathogenicity, in this study we synthesised new derivatives of citral with antiquorum sensing and biofilm disrupting properties. We previously reported antimicrobial and antiquorum sensing activity of citral and herein we report the synthesis and evaluation of citral and its derivatives (CD1-CD3) for antibacterial, antibiofilm and antiquorum sensing potential against Chromobacterium violaceum using standard methods. Preliminary results revealed that CD1 is the most active of all the derivatives. Qualitative and quantitative evaluation of antiquorum sensing activity at sub-inhibitory concentrations of these compounds also revealed high activity for CD1 followed by CD2, CD3 and citral. These compounds also inhibit biofilm formation at subinhibitory concentrations without causing any bacterial growth inhibition. These results were replicated by RT-qPCR with down regulation of the quorum sensing genes when C. violaceum was treated with these test compounds. Overall, the results are quite encouraging, revealing that biofilm and quorum sensing are interrelated processes and also indicating the potential of these derivatives to impede bacterial communication and biofilm formation.202133392626
8829110.9697VtaA8 and VtaA9 from Haemophilus parasuis delay phagocytosis by alveolar macrophages. Haemophilus parasuis, a member of the family Pasteurellaceae, is a common inhabitant of the upper respiratory tract of healthy pigs and the etiological agent of Glässer's disease. As other virulent Pasteurellaceae, H. parasuis can prevent phagocytosis, but the bacterial factors involved in this virulence mechanism are not known. In order to identify genes involved in phagocytosis resistance, we constructed a genomic library of the highly virulent reference strain Nagasaki and clones were selected by increased survival after incubation with porcine alveolar macrophages (PAM). Two clones containing two virulent-associated trimeric autotransporter (VtaA) genes, vtaA8 and vtaA9, respectively, were selected by this method. A reduction in the interaction of the two clones with the macrophages was detected by flow cytometry. Monoclonal antibodies were produced and used to demonstrate the presence of these proteins on the bacterial surface of the corresponding clone, and on the H. parasuis phagocytosis-resistant strain PC4-6P. The effect of VtaA8 and VtaA9 in the trafficking of the bacteria through the endocytic pathway was examined by fluorescence microscopy and a delay was detected in the localization of the vtaA8 and vtaA9 clones in acidic compartments. These results are compatible with a partial inhibition of the routing of the bacteria via the degradative phagosome. Finally, antibodies against a common epitope in VtaA8 and VtaA9 were opsonic and promoted phagocytosis of the phagocytosis-resistant strain PC4-6P by PAM. Taken together, these results indicate that VtaA8 and VtaA9 are surface proteins that play a role in phagocytosis resistance of H. parasuis.201222839779
746120.9696Novel antimicrobial 3-phenyl-4-phenoxypyrazole derivatives target cell wall lipid intermediates with low mammalian cytotoxicity. The growing crisis of antimicrobial resistance (AMR) underscores the critical need for innovative antimicrobial discoveries. Novel antibiotics targeting the bacterial cell wall remain an attractive area of research, due to their conservation and essentiality in bacteria and their absence in eukaryotic cells. Antibiotics targeting lipid II are of special interest due to the reduced potential for target modification of lipid components and their surface accessibility to inhibitors. In this study, we identified 3-phenyl-4-phenoxypyrazole analogues named PYO12 and PYO12a with bactericidal activity against gram-positive bacteria and low cytotoxicity for different types of mammalian cells. Gram-negative bacteria were resistant to PYO12 activity through extrusion of this compound via efflux pumps. Exposure to PYO12 induces expression of genes involved in resistance to antimicrobials targeting the cell wall, suggesting that PYO12 acts via binding to lipid II or other lipid intermediates involved in peptidoglycan or teichoic acid biosynthesis. Antagonism of PYO12 antibacterial activity by undecaprenyl-pyrophosphate supports the idea that PYO12 may bind to the lipid moiety of lipid II blocking the shuttling of peptidoglycan precursors across the cytoplasmic membrane. These findings open opportunities to further develop these compounds as antibiotics targeting bacterial cell wall synthesis.202541083642
626130.9695Enterococcus faecalis Adapts to Antimicrobial Conjugated Oligoelectrolytes by Lipid Rearrangement and Differential Expression of Membrane Stress Response Genes. Conjugated oligoelectrolytes (COEs) are emerging antimicrobials with broad spectrum activity against Gram positive and Gram negative bacteria as well as fungi. Our previous in vitro evolution studies using Enterococcus faecalis grown in the presence of two related COEs (COE1-3C and COE1-3Py) led to the emergence of mutants (changes in liaF and liaR) with a moderate 4- to16-fold increased resistance to COEs. The contribution of liaF and liaR mutations to COE resistance was confirmed by complementation of the mutants, which restored sensitivity to COEs. To better understand the cellular target of COEs, and the mechanism of resistance to COEs, transcriptional changes associated with resistance in the evolved mutants were investigated in this study. The differentially transcribed genes encoded membrane transporters, in addition to proteins associated with cell envelope synthesis and stress responses. Genes encoding membrane transport proteins from the ATP binding cassette superfamily were the most significantly induced or repressed in COE tolerant mutants compared to the wild type when exposed to COEs. Additionally, differences in the membrane localization of a lipophilic dye in E. faecalis exposed to COEs suggested that resistance was associated with lipid rearrangement in the cell membrane. The membrane adaptation to COEs in EFC3C and EFC3Py resulted in an improved tolerance to bile salt and sodium chloride stress. Overall, this study showed that bacterial cell membranes are the primary target of COEs and that E. faecalis adapts to membrane interacting COE molecules by both lipid rearrangement and changes in membrane transporter activity. The level of resistance to COEs suggests that E. faecalis does not have a specific response pathway to elicit resistance against these molecules and this is supported by the rather broad and diverse suite of genes that are induced upon COE exposure as well as cross-resistance to membrane perturbing stressors.202032117172
9223140.9695De novo evolution of antibiotic resistance to Oct-TriA(1). The rise of antimicrobial resistance as a global health concern has led to a strong interest in compounds able to inhibit the growth of bacteria without detectable levels of resistance evolution. A number of these compounds have been reported in recent years, including the tridecaptins, a small family of lipopeptides typified by the synthetic analogue octyl-tridecaptin A(1). Hypothesizing that prior reports of negligible resistance evolution have been due in part to limitations in the laboratory evolution systems used, we have attempted to select for resistant mutants using a soft agar gradient evolution (SAGE) system developed by our lab. Following optimization of the media conditions by incorporation of the anti-synaeresis agent xanthan gum into the agar matrix, we successfully evolved high-level resistance to both octyl-tridecaptin A(1) as well as the challenging lipopeptide antibiotic polymyxin B. Decreased tridecaptin susceptibility was linked to mutations in outer membrane proteins ompC, lptD and mlaA, with the effect of these genes confirmed through a mix of allelic replacement and knockout studies. Overall, this work demonstrates the robust evolutionary potential of bacteria, even in the face of challenging antimicrobial agents.202539832423
37150.9694N-3-Oxo-Octanoyl Homoserine Lactone Primes Plant Resistance Against Necrotrophic Pathogen Pectobacterium carotovorum by Coordinating Jasmonic Acid and Auxin-Signaling Pathways. Many Gram-negative bacteria use small signal molecules, such as N-acyl-homoserine lactones (AHLs), to communicate with each other and coordinate their collective behaviors. Recently, increasing evidence has demonstrated that long-chained quorum-sensing signals play roles in priming defense responses in plants. Our previous work indicated that a short-chained signal, N-3-oxo-octanoyl homoserine lactone (3OC8-HSL), enhanced Arabidopsis resistance to the hemi-biotrophic bacteria Pseudomonas syringae pv. tomato DC3000 through priming the salicylic acid (SA) pathway. Here, we found that 3OC8-HSL could also prime resistance to the necrotrophic bacterium Pectobacterium carotovorum ssp. carotovorum (Pcc) through the jasmonic acid (JA) pathway, and is dependent on auxin responses, in both Chinese cabbage and Arabidopsis. The subsequent Pcc invasion triggered JA accumulation and increased the down-stream genes' expressions of JA synthesis genes (LOX, AOS, and AOC) and JA response genes (PDF1.2 and VSP2). The primed state was not observed in the Arabidopsis coi1-1 and jar1-1 mutants, which indicated that the primed resistance to Pcc was dependent on the JA pathway. The 3OC8-HSL was not transmitted from roots to leaves and it induced indoleacetic acid (IAA) accumulation and the DR5 and SAUR auxin-responsive genes' expressions in seedlings. When Arabidopsis and Chinese cabbage roots were pretreated with exogenous IAA (10 μM), the plants had activated the JA pathway and enhanced resistance to Pcc, which implied that the JA pathway was involved in AHL priming by coordinating with the auxin pathway. Our findings provide a new strategy for the prevention and control of soft rot in Chinese cabbage and provide theoretical support for the use of the quorum-sensing AHL signal molecule as a new elicitor.202235774826
751160.9694Global transcriptomics and targeted metabolite analysis reveal the involvement of the AcrAB efflux pump in physiological functions by exporting signaling molecules in Photorhabdus laumondii. In Gram-negative bacteria, resistance-nodulation-division (RND)-type efflux pumps, particularly AcrAB-TolC, play a critical role in mediating resistance to antimicrobial agents and toxic metabolites, contributing to multidrug resistance. Photorhabdus laumondii is an entomopathogenic bacterium that has garnered significant interest due to its production of bioactive specialized metabolites with anti-inflammatory, antimicrobial, and scavenger deterrent properties. In previous work, we demonstrated that AcrAB confers self-resistance to stilbenes in P. laumondii TT01. Here, we explore the pleiotropic effects of AcrAB in this bacterium. RNA sequencing of ∆acrA compared to wild type revealed growth-phase-specific gene regulation, with stationary-phase cultures showing significant downregulation of genes involved in stilbene, fatty acid, and anthraquinone pigment biosynthesis, as well as genes related to cellular clumping and fimbrial pilin formation. Genes encoding putative LuxR regulators, type VI secretion systems, two-partner secretion systems, and contact-dependent growth inhibition systems were upregulated in ∆acrA. Additionally, exponential-phase cultures revealed reduced expression of genes related to motility in ∆acrA. The observed transcriptional changes were consistent with phenotypic assays, demonstrating that the ∆acrA mutant had altered bioluminescence and defective orange pigmentation due to disrupted anthraquinone production. These findings confirm the role of stilbenes as signaling molecules involved in gene expression, thereby shaping these phenotypes. Furthermore, we showed that AcrAB contributes to swarming and swimming motilities independently of stilbenes. Collectively, these results highlight that disrupting acrAB causes transcriptional and metabolic dysregulation in P. laumondii, likely by impeding the export of key signaling molecules such as stilbenes, which may serve as a ligand for global transcriptional regulators.IMPORTANCERecent discoveries have highlighted Photorhabdus laumondii as a promising source of novel anti-infective compounds, including non-ribosomal peptides and polyketides. One key player in the self-resistance of this bacterium to stilbene derivatives is the AcrAB-TolC complex, which is also a well-known contributor to multidrug resistance. Here, we demonstrate the pleiotropic effects of the AcrAB efflux pump in P. laumondii TT01, impacting secondary metabolite biosynthesis, motility, and bioluminescence. These effects are evident at transcriptional, metabolic, and phenotypic levels and are likely mediated by the efflux of signaling molecules such as stilbenes. These findings shed light on the multifaceted roles of efflux pumps and open avenues to better explore the complexity of resistance-nodulation-division (RND) pump-mediated signaling pathways in bacteria, thereby aiding in combating multidrug-resistant infections.202540920493
8799170.9693The membrane-active polyaminoisoprenyl compound NV716 re-sensitizes Pseudomonas aeruginosa to antibiotics and reduces bacterial virulence. Pseudomonas aeruginosa is intrinsically resistant to many antibiotics due to the impermeability of its outer membrane and to the constitutive expression of efflux pumps. Here, we show that the polyaminoisoprenyl compound NV716 at sub-MIC concentrations re-sensitizes P. aeruginosa to abandoned antibiotics by binding to the lipopolysaccharides (LPS) of the outer membrane, permeabilizing this membrane and increasing antibiotic accumulation inside the bacteria. It also prevents selection of resistance to antibiotics and increases their activity against biofilms. No stable resistance could be selected to NV716-itself after serial passages with subinhibitory concentrations, but the transcriptome of the resulting daughter cells shows an upregulation of genes involved in the synthesis of lipid A and LPS, and a downregulation of quorum sensing-related genes. Accordingly, NV716 also reduces motility, virulence factors production, and biofilm formation. NV716 shows a unique and highly promising profile of activity when used alone or in combination with antibiotics against P. aeruginosa, combining in a single molecule anti-virulence and potentiator effects. Additional work is required to more thoroughly understand the various functions of NV716.202236008485
8776180.9693Systemic resistance induced by rhizosphere bacteria. Nonpathogenic rhizobacteria can induce a systemic resistance in plants that is phenotypically similar to pathogen-induced systemic acquired resistance (SAR). Rhizobacteria-mediated induced systemic resistance (ISR) has been demonstrated against fungi, bacteria, and viruses in Arabidopsis, bean, carnation, cucumber, radish, tobacco, and tomato under conditions in which the inducing bacteria and the challenging pathogen remained spatially separated. Bacterial strains differ in their ability to induce resistance in different plant species, and plants show variation in the expression of ISR upon induction by specific bacterial strains. Bacterial determinants of ISR include lipopolysaccharides, siderophores, and salicylic acid (SA). Whereas some of the rhizobacteria induce resistance through the SA-dependent SAR pathway, others do not and require jasmonic acid and ethylene perception by the plant for ISR to develop. No consistent host plant alterations are associated with the induced state, but upon challenge inoculation, resistance responses are accelerated and enhanced. ISR is effective under field conditions and offers a natural mechanism for biological control of plant disease.199815012509
226190.9692Resistance mechanisms for Gram-negative bacteria-specific lipopeptides, turnercyclamycins, differ from that of colistin. Bacterial resistance to antibiotics is a crisis. Acinetobacter baumannii is among the CDC urgent threat pathogens in part for this reason. Lipopeptides known as turnercyclamycins are produced by symbiotic bacteria that normally live in marine mollusks, where they may be involved in shaping their symbiotic niche. Turnercyclamycins killed Gram-negative pathogens including drug-resistant Acinetobacter, but how do the mechanisms of resistance compare to other lipopeptide drugs? Here, we define resistance from a truncation of MlaA, a protein involved in regulating bacterial membrane phospholipids. Intriguingly, this resistance mechanism only affected one turnercyclamycin variant, which differed only in two atoms in the lipid tail of the compounds. We could not obtain significant resistance to the second turnercyclamycin variant, which was also effective in an infection model. This study reveals an unexpected subtlety in resistance to lipopeptide antibiotics, which may be useful in the design and development of antibiotics to combat drug resistance.202337882570