Repurposing promethazine hydrochloride to inhibit biofilm formation against Burkholderia thailandensis.

Melioidosis is a severe infectious disease caused by Burkholderia pseudomallei, an intracellular pathogen with a high mortality rate and significant antibiotic resistance. The high mortality rate and resistance to antibiotics have drawn considerable attention from researchers studying melioidosis. This study evaluated the effects of various concentrations (75, 50, and 25 µg/mL) of promethazine hydrochloride (PTZ), a potent antihistamine, on biofilm formation and lipase activity after 24 h of exposure to B. thailandensis E264. A concentration-dependent decrease in both biofilm biomass and lipase activity was observed. RT-PCR analysis revealed that PTZ treatment not only made the biofilm structure loose but also reduced the expression of btaR1, btaR2, btaR3, and scmR. Single gene knockouts of quorum sensing (QS) receptor proteins (∆btaR1, ∆btaR2, and ∆btaR3) were successfully constructed. Deletion of btaR1 affected biofilm formation in B. thailandensis, while deletion of btaR2 and btaR3 led to reduced lipase activity. Molecular docking and biological performance results demonstrated that PTZ inhibits biofilm formation and lipase activity by suppressing the expression of QS-regulated genes. This study found that repositioning PTZ reduced biofilm formation in B. thailandensis E264, suggesting a potential new approach for combating melioidosis.

Bacterial esterases reverse lipopolysaccharide ubiquitylation to block host immunity.

Aspects of how Burkholderia escape the host's intrinsic immune response to replicate in the cell cytosol remain enigmatic. Here, we show that Burkholderia has evolved two mechanisms to block the activity of Ring finger protein 213 (RNF213)-mediated non-canonical ubiquitylation of bacterial lipopolysaccharide (LPS), thereby preventing the initiation of antibacterial autophagy. First, Burkholderia's polysaccharide capsule blocks RNF213 association with bacteria and second, the Burkholderia deubiquitylase (DUB), TssM, directly reverses the activity of RNF213 through a previously unrecognized esterase activity. Structural analysis provides insight into the molecular basis of TssM esterase activity, allowing it to be uncoupled from its isopeptidase function. Furthermore, a putative TssM homolog also displays esterase activity and removes ubiquitin from LPS, establishing this as a virulence mechanism. Of note, we also find that additional immune-evasion mechanisms exist, revealing that overcoming this arm of the host's immune response is critical to the pathogen.

Employing Genomic Tools to Explore the Molecular Mechanisms behind the Enhancement of Plant Growth and Stress Resilience Facilitated by a Burkholderia Rhizobacterial Strain.

The rhizobacterial strain BJ3 showed 16S rDNA sequence similarity to species within the Burkholderia genus. Its complete genome sequence revealed a 97% match with Burkholderia contaminans and uncovered gene clusters essential for plant-growth-promoting traits (PGPTs). These clusters include genes responsible for producing indole acetic acid (IAA), osmolytes, non-ribosomal peptides (NRPS), volatile organic compounds (VOCs), siderophores, lipopolysaccharides, hydrolytic enzymes, and spermidine. Additionally, the genome contains genes for nitrogen fixation and phosphate solubilization, as well as a gene encoding 1-aminocyclopropane-1-carboxylate (ACC) deaminase. The treatment with BJ3 enhanced root architecture, boosted vegetative growth, and accelerated early flowering in Arabidopsis. Treated seedlings also showed increased lignin production and antioxidant capabilities, as well as notably increased tolerance to water deficit and high salinity. An RNA-seq transcriptome analysis indicated that BJ3 treatment significantly activated genes related to immunity induction, hormone signaling, and vegetative growth. It specifically activated genes involved in the production of auxin, ethylene, and salicylic acid (SA), as well as genes involved in the synthesis of defense compounds like glucosinolates, camalexin, and terpenoids. The expression of AP2/ERF transcription factors was markedly increased. These findings highlight BJ3's potential to produce various bioactive metabolites and its ability to activate auxin, ethylene, and SA signaling in Arabidopsis, positioning it as a new Burkholderia strain that could significantly improve plant growth, stress resilience, and immune function.

Enhanced removal of 2,4-dichlorophenol by a novel biotic-abiotic hybrid system based on zeolitic imidazolate framework-8.

Biotic-abiotic hybrid systems have recently emerged as a potential technique for stable and efficient removal of persistent contaminants due to coupling of microbial catabolic with abiotic adsorption/redox processes. In this study, Burkholderia vietnamensis C09V (B.V.C09V) was successfully integrated with a Zeolitic Imidazolate Framework-8 (ZIF-8) to construct a state-of-art biotic-abiotic system using polyvinyl alcohol/ sodium alginate (PVA/SA) as media. The biotic-abiotic system (PVA/SA-ZIF-8 @B.V.C09V) was able to remove 99.0 % of 2,4-DCP within 168 h, which was much higher than either PVA/SA, PVA/SA-ZIF-8 or PVA/SA@B.V.C09V (53.8 %, 72.6 % and 67.2 %, respectively). Electrochemical techniques demonstrated that the carrier effect of PVA/SA and the driving effect of ZIF-8 collectively accelerated electron transfer processes associated with enzymatic reactions. In addition, quantitative-PCR (Q-PCR) revealed that ZIF-8 stimulated B.V.C09V to up-regulate expression of tfdB, tfdC, catA, and catC genes (2.40-, 1.68-, 1.58-, and 1.23-fold, respectively), which encoded the metabolism of related enzymes. Furthermore, the effect of key physical, chemical, and biological properties of PVA/SA-ZIF-8 @B.V.C09V on 2,4-DCP removal were statistically investigated by Spearman correlation analysis to identify the key factors that promoted synergistic removal of 2,4-DCP. Overall, this study has created an innovative new strategy for the sustainable remediation of 2,4-DCP in aquatic environments.

Evaluating lignin degradation under limited oxygen conditions by bacterial isolates from forest soil.

Lignin, a heterogeneous aromatic polymer present in plant biomass, is intertwined with cellulose and hemicellulose fibrils, posing challenges to its effective utilization due to its phenolic nature and recalcitrance to degradation. In this study, three lignin utilizing bacteria, Klebsiella sp. LEA1, Pseudomonas sp. LEA2, and Burkholderia sp. LEA3, were isolated from deciduous forest soil samples in Nan province, Thailand. These isolates were capable of growing on alkali lignin and various lignin-associated monomers at 40 °C under microaerobic conditions. The presence of Cu2+ significantly enhanced guaiacol oxidation in Klebsiella sp. LEA1 and Pseudomonas sp. LEA2. Lignin-related monomers and intermediates such as 2,6-dimethoxyphenol, 4-vinyl guaiacol, 4-hydroxybenzoic acid, benzoic acid, catechol, and succinic acid were detected mostly during the late stage of incubation of Klebsiella sp. LEA1 and Pseudomonas sp. LEA2 in lignin minimal salt media via GC-MS analysis. The intermediates identified from Klebsiella sp. LEA1 degradation suggested that conversion and utilization occurred through the ß-ketoadipate (ortho-cleavage) pathway under limited oxygen conditions. The ability of these bacteria to thrive on alkaline lignin and produce various lignin-related intermediates under limited oxygen conditions suggests their potential utility in oxygen-limited processes and the production of renewable chemicals from plant biomass.

Two cadmium-resistant bacteria Burkholderia contaminans HA09 and Arthrobacter humicola improve phytoremediation efficiency of cadmium in Ageratum conyzoides L.

To investigate the impact and mechanism of Cd-tolerant bacteria in soil on promoting Cd accumulation in Ageratum conyzoides L., we verified the impact of inoculating two strains, B-1 (Burkholderia contaminans HA09) and B-7 (Arthrobacter humicola), on Cd accumulation in A. conyzoides through a pot experiment. Additionally, we investigated the dissolution of CdCO3 and nutrient elements, as well as the release of indoleacetic acid (IAA) by the two strains. The results showed that both strains can significantly improve the dissolution of CdCO3. Strains B-1 and B-7 had obvious effect of dissolving phosphorus, which was 5.63 and 2.76 times higher than that of the control group, respectively. Strain B-7 had significant effect of dissolution potassium, which was 1.79 times higher than that of the control group. Strains B-1 and B-7 had significant nitrogen fixation effect, which was 29.53 and 44.39 times higher than that of the control group, respectively. In addition, inoculating with strain B-1 and B-7 significantly increased the Cd extraction efficiency of A. conyzoides (by 114% and 45% respectively) through enhancing Cd accumulation and the biomass of A. conyzoides. Furthermore, the inoculation of strain B-1 and B-7 led to a significant increase in the activities of CAT and SOD, as well as the content of chlorophyll a and total chlorophyll in the leaves of A. conyzoides. To sum up, strain B-1 and B-7 can promote the phytoremediation efficiency of A. conyzoides on Cd by promoting the biomass and Cd accumulation of A. conyzoides.

Prevalence and diversity of TAL effector-like proteins in fungal endosymbiotic Mycetohabitans spp.

Endofungal Mycetohabitans (formerly Burkholderia) spp. rely on a type III secretion system to deliver mostly unidentified effector proteins when colonizing their host fungus, Rhizopus microsporus. The one known secreted effector family from Mycetohabitans consists of homologues of transcription activator-like (TAL) effectors, which are used by plant pathogenic Xanthomonas and Ralstonia spp. to activate host genes that promote disease. These 'Burkholderia TAL-like (Btl)' proteins bind corresponding specific DNA sequences in a predictable manner, but their genomic target(s) and impact on transcription in the fungus are unknown. Recent phenotyping of Btl mutants of two Mycetohabitans strains revealed that the single Btl in one Mycetohabitans endofungorum strain enhances fungal membrane stress tolerance, while others in a Mycetohabitans rhizoxinica strain promote bacterial colonization of the fungus. The phenotypic diversity underscores the need to assess the sequence diversity and, given that sequence diversity translates to DNA targeting specificity, the functional diversity of Btl proteins. Using a dual approach to maximize capture of Btl protein sequences for our analysis, we sequenced and assembled nine Mycetohabitans spp. genomes using long-read PacBio technology and also mined available short-read Illumina fungal-bacterial metagenomes. We show that btl genes are present across diverse Mycetohabitans strains from Mucoromycota fungal hosts yet vary in sequences and predicted DNA binding specificity. Phylogenetic analysis revealed distinct clades of Btl proteins and suggested that Mycetohabitans might contain more species than previously recognized. Within our data set, Btl proteins were more conserved across M. rhizoxinica strains than across M. endofungorum, but there was also evidence of greater overall strain diversity within the latter clade. Overall, the results suggest that Btl proteins contribute to bacterial-fungal symbioses in myriad ways.

Phage-induced efflux down-regulation boosts antibiotic efficacy.

The interactions between a virus and its host vary in space and time and are affected by the presence of molecules that alter the physiology of either the host or the virus. Determining the molecular mechanisms at the basis of these interactions is paramount for predicting the fate of bacterial and phage populations and for designing rational phage-antibiotic therapies. We study the interactions between stationary phase Burkholderia thailandensis and the phage ΦBp-AMP1. Although heterogeneous genetic resistance to phage rapidly emerges in B. thailandensis, the presence of phage enhances the efficacy of three major antibiotic classes, the quinolones, the beta-lactams and the tetracyclines, but antagonizes tetrahydrofolate synthesis inhibitors. We discovered that enhanced antibiotic efficacy is facilitated by reduced antibiotic efflux in the presence of phage. This new phage-antibiotic therapy allows for eradication of stationary phase bacteria, whilst requiring reduced antibiotic concentrations, which is crucial for treating infections in sites where it is difficult to achieve high antibiotic concentrations.

Efficient production of polyhydroxybutyrate using lignocellulosic biomass derived from oil palm trunks by the inhibitor-tolerant strain Burkholderia ambifaria E5-3.

Lignocellulosic biomass is a valuable, renewable substrate for the synthesis of polyhydroxybutyrate (PHB), an ecofriendly biopolymer. In this study, bacterial strain E5-3 was isolated from soil in Japan; it was identified as Burkholderia ambifaria strain E5-3 by 16 S rRNA gene sequencing. The strain showed optimal growth at 37 °C with an initial pH of 9. It demonstrated diverse metabolic ability, processing a broad range of carbon substrates, including xylose, glucose, sucrose, glycerol, cellobiose, and, notably, palm oil. Palm oil induced the highest cellular growth, with a PHB content of 65% wt. The strain exhibited inherent tolerance to potential fermentation inhibitors derived from lignocellulosic hydrolysate, withstanding 3 g/L 5-hydroxymethylfurfural and 1.25 g/L acetic acid. Employing a fed-batch fermentation strategy with a combination of glucose, xylose, and cellobiose resulted in PHB production 2.7-times that in traditional batch fermentation. The use of oil palm trunk hydrolysate, without inhibitor pretreatment, in a fed-batch fermentation setup led to significant cell growth with a PHB content of 45% wt, equivalent to 10 g/L. The physicochemical attributes of xylose-derived PHB produced by strain E5-3 included a molecular weight of 722 kDa, a number-average molecular weight of 191 kDa, and a polydispersity index of 3.78. The amorphous structure of this PHB displayed a glass transition temperature of 4.59 °C, while its crystalline counterpart had a melting point of 171.03 °C. This research highlights the potential of lignocellulosic feedstocks, especially oil palm trunk hydrolysate, for PHB production through fed-batch fermentation by B. ambifaria strain E5-3, which has high inhibitor tolerance.

Burkholderia semiarida as Cause of Recurrent Pulmonary Infection in Immunocompetent Patient, China.

Burkholderia semiarida was previously identified solely as a plant pathogen within the Burkholderia cepacia complex. We present a case in China involving recurrent pneumonia attributed to B. semiarida infection. Of note, the infection manifested in an immunocompetent patient with no associated primary diseases and endured for >3 years.

Discovery and mechanism explanation of a novel green biocatalyst esterase Bur01 from Burkholderia ambifaria for ester synthesis under aqueous phase.

Biocatalyst catalyzing the synthesis of esters under aqueous phase is an alternative with green and sustainable characteristics. Here, a biocatalyst esterase Bur01 was identified through genome sequencing and gene library construction from a Burkholderia ambifaria BJQ0010 with efficient ester synthesis property under aqueous phase for the first time. Bur01 was soluble expressed and the purified enzyme showed the highest activity at pH 4.0 and 40 °C. It had a broad substrate spectrum, especially for ethyl esters. The structure of Bur01 was categorized as a member of α/ß fold hydrolase superfamily. The easier opening of lid under aqueous phase and the hydrophobicity of substrate channel contribute to easier access to the active center for substrate. Molecular docking and site-directed mutation demonstrated that the oxyanion hole Ala22, Met112 and π-bond stacking between His24 and Phe217 played essential roles in catalytic function. The mutants V149A, V149I, L159I and F137I enhanced enzyme activity to 1.42, 1.14, 1.32 and 2.19 folds due to reduced spatial resistance and increased hydrophobicity of channel and ethyl octanoate with the highest conversion ratio of 68.28 % was obtained for F137I. These results provided new ideas for developing green catalysts and catalytic basis of mechanistic studies for ester synthetase under aqueous phase.

Biosynthesis of silver nanoparticles using Burkholderia contaminans ZCC and mechanistic analysis at the proteome level.

The biogenic synthesis of silver nanoparticles (AgNPs) by microorganisms has been a subject of increasing attention. Despite extensive studies on this biosynthetic pathway, the mechanisms underlying the involvement of proteins and enzymes in AgNPs production have not been fully explored. Herein, we reported that Burkholderia contaminans ZCC was able to reduce Ag+ to AgNPs with a diameter of (10±5) nm inside the cell. Exposure of B. contaminans ZCC to Ag+ ions led to significant changes in the functional groups of cellular proteins, with approximately 5.72% of the (C-OH) bonds being converted to (C-C/C-H) (3.61%) and CO (2.11%) bonds, and 4.52% of the CO (carbonyl) bonds being converted to (C-OH) bonds. Furthermore, the presence of Ag+ and AgNPs induced the ability of extracellular electron transfer for ZCC cells via specific membrane proteins, but this did not occur in the absence of Ag+ ions. Proteomic analysis of the proteins and enzymes involved in heavy metal efflux systems, protein secretion system, oxidative phosphorylation, intracellular electron transfer chain, and glutathione metabolism suggests that glutathione S-transferase and ubiquinol-cytochrome c reductase iron-sulfur subunit play importance roles in the biosynthesis of AgNPs. These findings contribute to a deeper understanding of the functions exerted by glutathione S-transferase and ferredoxin-thioredoxin reductase iron-sulfur subunits in the biogenesis of AgNPs, thereby hold immense potential for optimizing biotechnological techniques aimed at enhancing the yield and purity of biosynthetic AgNPs.

Mass Production of Arbuscular Mycorrhizal Fungi on the Sorghum Plants Inoculated with Burkholderia arboris Using Soybean Mill Waste and Vermicompost-Amended Soil-Sand Substrate.

Arbuscular mycorrhizal (AM) fungi are being used as a new generation of biofertilizers to increase plant growth by improving plant nutrition and bio-protection. However, because of the obligatory nature of the plant host, large-scale multiplication of AM propagules is challenging, which limits its applicability. This study evaluates the ability of Burkholderia arboris to increase AM production in soybean mill waste and vermicompost amended by soil-sand mixture planted with sorghum as a host plant. The experiment was conducted in a nursery using a completely randomized design with four inoculation treatments (B. arboris, AM fungi, B. arboris + AM fungi, and control) under sterilized and unsterilized conditions. AM production was investigated microscopically (spore density and root colonization), and biochemically (AM-specific lipid biomarker, 16:1ω5cis derived from neutral lipid fatty acid (NLFA), and phospholipid fatty acid (PLFA) fractions from both soil and roots). Integrating B. arboris with AM fungi in organically amended pots was found to increase AM fungal production by 62.16 spores g-1 soil and root colonization by 80.85%. Biochemical parameters also increased with B. arboris inoculation: 5.49 nmol PLFA g-1 soil and 692.68 nmol PLFA g-1 root and 36.72 nmol NLFA g-1 soil and 3147.57 nmol NLFA g-1 root. Co-inoculation also increased glomalin-related soil protein and root biomass. Principal component analysis (PCA) further supported the higher contribution of B. arboris to AM fungi production under unsterilized conditions. In conclusion, inoculation of AM plant host seeds with B. arboris prior to sowing into organic potting mix could be a promising and cost-effective approach for increasing AM inoculum density for commercial production. Furthermore, efforts need to be made for up-scaling the AM production with different plant hosts and soil-substrate types.

Isolation of a PRD1-like phage uncovers the carriage of three putative conjugative plasmids in clinical Burkholderia contaminans.

The Burkholderia cepacia complex (Bcc) is a group of increasingly multi-drug resistant opportunistic bacteria. This resistance is driven through a combination of intrinsic factors and the carriage of a broad range of conjugative plasmids harbouring virulence determinants. Therefore, novel treatments are required to treat and prevent further spread of these virulence determinants. In the search for phages infective for clinical Bcc isolates, CSP1 phage, a PRD1-like phage was isolated. CSP1 phage was found to require pilus machinery commonly encoded on conjugative plasmids to facilitate infection of Gram-negative bacteria genera including Escherichia and Pseudomonas. Whole genome sequencing and characterisation of one of the clinical Burkholderia isolates revealed it to be Burkholderia contaminans. B. contaminans 5080 was found to contain a genome of over 8 Mbp encoding multiple intrinsic resistance factors, such as efflux pump systems, but more interestingly, carried three novel plasmids encoding multiple putative virulence factors for increased host fitness, including antimicrobial resistance. Even though PRD1-like phages are broad host range, their use in novel antimicrobial treatments shouldn't be dismissed, as the dissemination potential of conjugative plasmids is extensive. Continued survey of clinical bacterial strains is also key to understanding the spread of antimicrobial resistance determinants and plasmid evolution.

Burkholderia ambifaria H8 as an effective biocontrol strain against maize stalk rot via producing volatile dimethyl disulfide.

BACKGROUND: Maize stalk rot (MSR) caused by Fusarium graminearum is the primary factor contributing to the reduction in maize yield and quality. However, this soil-borne disease presents a significant challenge for sustainable control through field management and chemical agents. The screening of novel biocontrol agents can aid in developing innovative and successful strategies for MSR control. RESULTS: A total of 407 strains of bacteria were isolated from the rhizosphere soil of a resistant maize inbred line. One strain exhibited significant antagonistic activity in plate and pot experiments, and was identified as Burkholderia ambifaria H8. The strain could significantly inhibit the mycelial growth and spore germination of F. graminearum, induce resistance to stalk rot, and promote plant growth. The volatile compounds produced by strain H8 and its secondary metabolites in the sterile fermentation broth exhibited antagonistic activity. The primary volatile compound produced by strain H8 was identified as dimethyl disulfide (DMDS) using gas chromatography tandem mass spectrometry. Through in vitro antagonistic activity assays and microscopic observation, it was confirmed that DMDS was capable of inhibiting mycelial growth and disrupting the mycelial structure of F. graminearum, suggesting it may be the major active compound for strain H8. The transcriptome data of F. graminearum further indicated that strain H8 and its volatile compounds could alter pathogenic fungi metabolism, influence the related metabolic pathways, and potentially induce cell apoptosis within F. graminearum. CONCLUSION: Our results showed that B. ambifaria H8 was capable of producing the volatile substance dimethyl disulfide, which influenced the synthesis and permeability of cell membranes in pathogens. Thus, B. ambifaria H8 was found to be a promising biological control agent against MSR. © 2024 Society of Chemical Industry.

Structural and functional insights into the enzymatic activities of lipases from Burkholderia stagnalis and Burkholderia plantarii.

Lipases with high interesterification activity are important enzymes for industrial use. The lipase from Burkholderia stagnalis (BsL) exhibits higher interesterification activity than that from Burkholderia plantarii (BpL) despite their significant sequence similarity. In this study, we determined the crystal structure of BsL at 1.40 Å resolution. Utilizing structural insights, we have successfully augmented the interesterification activity of BpL by over twofold. This enhancement was achieved by substituting threonine with serine at position 289 through forming an expansive space in the substrate-binding site. Additionally, we discuss the activity mechanism based on the kinetic parameters. Our study sheds light on the structural determinants of the interesterification activity of lipase.

The long-chain flavodoxin FldX1 improves the biodegradation of 4-hydroxyphenylacetate and 3-hydroxyphenylacetate and counteracts the oxidative stress associated to aromatic catabolism in Paraburkholderia xenovorans.

BACKGROUND: Bacterial aromatic degradation may cause oxidative stress. The long-chain flavodoxin FldX1 of Paraburkholderia xenovorans LB400 counteracts reactive oxygen species (ROS). The aim of this study was to evaluate the protective role of FldX1 in P. xenovorans LB400 during the degradation of 4-hydroxyphenylacetate (4-HPA) and 3-hydroxyphenylacetate (3-HPA). METHODS: The functionality of FldX1 was evaluated in P. xenovorans p2-fldX1 that overexpresses FldX1. The effects of FldX1 on P. xenovorans were studied measuring growth on hydroxyphenylacetates, degradation of 4-HPA and 3-HPA, and ROS formation. The effects of hydroxyphenylacetates (HPAs) on the proteome (LC-MS/MS) and gene expression (qRT-PCR) were quantified. Bioaugmentation with strain p2-fldX1 of 4-HPA-polluted soil was assessed, measuring aromatic degradation (HPLC), 4-HPA-degrading bacteria, and plasmid stability. RESULTS: The exposure of P. xenovorans to 4-HPA increased the formation of ROS compared to 3-HPA or glucose. P. xenovorans p2-fldX1 showed an increased growth on 4-HPA and 3-HPA compared to the control strain WT-p2. Strain p2-fldX1 degraded faster 4-HPA and 3-HPA than strain WT-p2. Both WT-p2 and p2-fldX1 cells grown on 4-HPA displayed more changes in the proteome than cells grown on 3-HPA in comparison to glucose-grown cells. Several enzymes involved in ROS detoxification, including AhpC2, AhpF, AhpD3, KatA, Bcp, CpoF1, Prx1 and Prx2, were upregulated by hydroxyphenylacetates. Downregulation of organic hydroperoxide resistance (Ohr) and DpsA proteins was observed. A downregulation of the genes encoding scavenging enzymes (katE and sodB), and gstA and trxB was observed in p2-fldX1 cells, suggesting that FldX1 prevents the antioxidant response. More than 20 membrane proteins, including porins and transporters, showed changes in expression during the growth of both strains on hydroxyphenylacetates. An increased 4-HPA degradation by recombinant strain p2-fldX1 in soil microcosms was observed. In soil, the strain overexpressing the flavodoxin FldX1 showed a lower plasmid loss, compared to WT-p2 strain, suggesting that FldX1 contributes to bacterial fitness. Overall, these results suggest that recombinant strain p2-fldX1 is an attractive bacterium for its application in bioremediation processes of aromatic compounds. CONCLUSIONS: The long-chain flavodoxin FldX1 improved the capability of P. xenovorans to degrade 4-HPA in liquid culture and soil microcosms by protecting cells against the degradation-associated oxidative stress.

Molecular characterization and evaluation of novel management options for Burkholderia glumae BG1, the causative agent of panicle blight of rice (Oryza sativa L.).

BACKGROUND: Bacterial panicle blight, incited by Burkholderia glumae, has impacted rice production globally. Despite its significance, knowledge about the disease and the virulence pattern of the causal agent is very limited. Bacterial panicle blight is a major challenge in the rice-growing belts of North-western India, resulting in yield reduction. However, the management of B. glumae has become a challenge due to the lack of proper management strategies. METHODOLOGY AND RESULTS: Twenty-one BG strains have been characterized using the 16S rRNA and the gyrB gene-based sequence approach in the present study. The gyrB gene-based phylogenetic analysis resulted in geographic region-specific clustering of the BG isolates. The virulence screening of twenty-one BG strains by inoculating the pathogenic bacterial suspension of 1 × 10-8 cfu/ml at the booting stage (55 DAT) revealed the variation in the disease severity and the grain yield of rice plants. The most virulent BG1 strain resulted in the highest disease incidence (82.11%) and lowest grain yield (11.12 g/plant), and the least virulent BG10 strain resulted in lowest disease incidence of 18.94% and highest grain yield (24.62 g/plant). In vitro evaluation of various biocontrol agents and nano copper at different concentrations by agar well diffusion method revealed that nano copper at 1000 mg/L inhibited the colony growth of B. glumae. Under net house conditions, nano copper at 1000 mg/L reduced the disease severity to 21.23% and increased the grain yield by 20.91% (31.76 g per plant) compared to the positive control (COC 0.25% + streptomycin 200 ppm). Remarkably, pre-inoculation with nano copper at 1000 mg/L followed by challenge inoculation with B. glumae enhanced the activity of enzymatic antioxidants viz., Phenyl ammonia-lyase (PAL), Polyphenol oxidase (PPO) and Peroxidase (POX) and non-enzymatic antioxidant phenol. Additionally, we observed a substantial transcript level upregulation of six defense-related genes to several folds viz., OsPR2, OsPR5, OsWRKY71, OsPAL1, OsAPX1, and OsPPO1 in comparison to the pathogen control and healthy control. CONCLUSIONS: Overall, our study provides valuable insights into the potential and practical application of nano copper for the mitigation of bacterial panicle blight, offering promising prospects for commercial utilization in disease management.

Burkholderia thailandensis uses a type VI secretion system to lyse protrusions without triggering host cell responses.

To spread within a host, intracellular Burkholderia form actin tails to generate membrane protrusions into neighboring host cells and use type VI secretion system-5 (T6SS-5) to induce cell-cell fusions. Here, we show that B. thailandensis also uses T6SS-5 to lyse protrusions to directly spread from cell to cell. Dynamin-2 recruitment to the membrane near a bacterium was followed by a short burst of T6SS-5 activity. This resulted in the polymerization of the actin of the newly invaded host cell and disruption of the protrusion membrane. Most protrusion lysis events were dependent on dynamin activity, caused no cell-cell fusion, and failed to be recognized by galectin-3. T6SS-5 inactivation decreased protrusion lysis but increased galectin-3, LC3, and LAMP1 accumulation in host cells. Our results indicate that B. thailandensis specifically activates T6SS-5 assembly in membrane protrusions to disrupt host cell membranes and spread without alerting cellular responses, such as autophagy.