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Molecular Plant Pathology May 2011Burkholderia glumae causes bacterial panicle blight of rice, which is an increasingly important disease problem in global rice production. Toxoflavin and lipase are... (Review)
Review
UNLABELLED
Burkholderia glumae causes bacterial panicle blight of rice, which is an increasingly important disease problem in global rice production. Toxoflavin and lipase are known to be major virulence factors of this pathogen, and their production is dependent on the TofI/TofR quorum-sensing system, which is mediated by N-octanoyl homoserine lactone. Flagellar biogenesis and a type III secretion system are also required for full virulence of B. glumae. Bacterial panicle blight is thought to be caused by seed-borne B. glumae; however, its disease cycle is not fully understood. In spite of its economic importance, neither effective control measures for bacterial panicle blight nor rice varieties showing complete resistance to the disease are currently available. A better understanding of the molecular mechanisms underlying B. glumae virulence and of the rice defence mechanisms against the pathogen would lead to the development of better methods of disease control for bacterial panicle blight.
TAXONOMY
Bacteria; Proteobacteria; Betaproteobacteria; Burkholderiales; Burkholderiaceae; Burkholderia.
MICROBIOLOGICAL PROPERTIES
Gram-negative, capsulated, motile, lophotrichous flagella, pectolytic.
DISEASE SYMPTOMS
Aborted seed, empty grains as a result of failure of grain filling, brown spots on panicles, seedling rot.
DISEASE CONTROL
Seed sterilization, planting partially resistant lines (no completely resistant line is available). KNOWN VIRULENCE FACTORS: Toxoflavin, lipase, type III effectors.
Topics: Bacterial Proteins; Burkholderia; Oryza; Virulence
PubMed: 21453428
DOI: 10.1111/j.1364-3703.2010.00676.x -
The ISME Journal Jun 2019In the symbiosis of the bean bug Riptortus pedestris with Burkholderia insecticola, the bacteria occupy an exclusive niche in the insect midgut and favor insect... (Comparative Study)
Comparative Study
In the symbiosis of the bean bug Riptortus pedestris with Burkholderia insecticola, the bacteria occupy an exclusive niche in the insect midgut and favor insect development and reproduction. In order to understand how the symbiotic bacteria stably colonize the midgut crypts and which services they provide to the host, we compared the cytology, physiology, and transcriptomics of free-living and midgut-colonizing B. insecticola. The analyses revealed that midgut-colonizing bacteria were smaller in size and had lower DNA content, they had increased stress sensitivity, lost motility, and an altered cell surface. Transcriptomics revealed what kinds of nutrients are provided by the bean bug to the Burkholderia symbiont. Transporters and metabolic pathways of diverse sugars such as rhamnose and ribose, and sulfur compounds like sulfate and taurine were upregulated in the midgut-colonizing symbionts. Moreover, pathways enabling the assimilation of insect nitrogen wastes, i.e. allantoin and urea, were also upregulated. The data further suggested that the midgut-colonizing symbionts produced all essential amino acids and B vitamins, some of which are scarce in the soybean food of the host insect. Together, these findings suggest that the Burkholderia symbiont is fed with specific nutrients and also recycles host metabolic wastes in the insect gut, and in return, the bacterial symbiont provides the host with essential nutrients limited in the insect food, contributing to the rapid growth and enhanced reproduction of the bean bug host.
Topics: Animals; Bacterial Proteins; Burkholderia; Culture Media; Gastrointestinal Tract; Heteroptera; Symbiosis; Transcriptome
PubMed: 30742016
DOI: 10.1038/s41396-019-0361-8 -
Applied and Environmental Microbiology Mar 2017During routine screening for from water wells in northern Australia in areas where it is endemic, Gram-negative bacteria (strains MSMB43, MSMB121, and MSMB122) with a...
During routine screening for from water wells in northern Australia in areas where it is endemic, Gram-negative bacteria (strains MSMB43, MSMB121, and MSMB122) with a similar morphology and biochemical pattern to and were coisolated with on Ashdown's selective agar. To determine the exact taxonomic position of these strains and to distinguish them from and , they were subjected to a series of phenotypic and molecular analyses. Biochemical and fatty acid methyl ester analysis was unable to distinguish sp. nov. from closely related species. With matrix-assisted laser desorption ionization-time of flight analysis, all isolates grouped together in a cluster separate from other spp. 16S rRNA and sequence analyses demonstrated phylogenetic placement for sp. nov. in a novel clade within the group. Multilocus sequence typing (MLST) analysis of the three isolates in comparison with MLST data from 3,340 strains and related taxa revealed a new sequence type (ST318). Genome-to-genome distance calculations and the average nucleotide identity of all isolates to both and , based on whole-genome sequences, also confirmed sp. nov. as a novel species within the complex. Molecular analyses clearly demonstrated that strains MSMB43, MSMB121, and MSMB122 belong to a novel species for which the name sp. nov. is proposed, with the type strain MSMB43 (American Type Culture Collection BAA-2767; Belgian Co-ordinated Collections of Microorganisms LMG 29471; DDBJ accession numbers CP013380 to CP013382). is a soil-dwelling bacterium and the causative agent of melioidosis. The genus consists of a diverse group of species, with the closest relatives of referred to as the complex. A proposed novel species, sp. nov., was isolated from a bore water sample from the Northern Territory in Australia. sp. nov. is phylogenetically distinct from and other members of the complex, making it the fifth member of this important group of bacteria.
Topics: Animals; Australia; Bacterial Typing Techniques; Burkholderia; Burkholderia Infections; Burkholderia pseudomallei; DNA, Bacterial; Disease Models, Animal; Fatty Acids; Genes, Bacterial; Genome, Bacterial; Melioidosis; Mice; Mice, Inbred BALB C; Microbial Sensitivity Tests; Multilocus Sequence Typing; Northern Territory; Phenotype; Phylogeny; RNA, Ribosomal, 16S; Rec A Recombinases; Sequence Analysis, DNA; Species Specificity; Virulence; Water Microbiology
PubMed: 27986727
DOI: 10.1128/AEM.02802-16 -
The American Journal of Tropical... Nov 2020Melioidosis is a neglected tropical disease caused by the Gram-negative soil bacterium Current antibiotic regimens used to treat melioidosis are prolonged and...
Melioidosis is a neglected tropical disease caused by the Gram-negative soil bacterium Current antibiotic regimens used to treat melioidosis are prolonged and expensive, and often ineffective because of intrinsic and acquired antimicrobial resistance. Efforts to develop new treatments for melioidosis are limited by the risks associated with handling pathogenic , which restricts research to facilities with biosafety level three containment. Closely related nonpathogenic can be investigated under less stringent biosafety level two containment, and we hypothesized that they could be used as model organisms for developing therapies that would also be effective against . We used microbroth dilution assays to compare drug susceptibility profiles of three strains and five nonpathogenic strains. , , and had similar susceptibility profiles to pathogenic that support their potential as safer in vitro models for developing new melioidosis therapies.
Topics: Anti-Bacterial Agents; Burkholderia; Drug Resistance, Bacterial; Humans; Melioidosis; Species Specificity
PubMed: 32975176
DOI: 10.4269/ajtmh.20-0248 -
Journal of Bacteriology Nov 2022Burkholderia thailandensis is a member of the Burkholderia pseudomallei complex. It encodes the transcription factor MftR, which is conserved among the more pathogenic...
Burkholderia thailandensis is a member of the Burkholderia pseudomallei complex. It encodes the transcription factor MftR, which is conserved among the more pathogenic spp. and previously shown to be a global regulator of gene expression. We report here that a B. thailandensis strain in which the gene is disrupted is more virulent in both Caenorhabditis elegans and onion. The Δ strain exhibits a number of phenotypes associated with virulence. It is more proficient at forming biofilm, and the gene cluster, which has been linked to anaerobic survival and fitness within a biofilm, is upregulated. Swimming and swarming motility are also elevated in Δ cells. We further show that MftR is one of several transcription factors which control production of the siderophore malleobactin. MftR binds directly to the promoter driving expression of , which encodes the extracytoplasmic function sigma factor MbaS that is required for malleobactin production. Malleobactin is a primary siderophore in B. thailandensis as evidenced by reduced siderophore production in ::Tc cells, in which is disrupted. Expression of is increased ~5-fold in Δ cells, and siderophore production is elevated. Under iron-limiting conditions, expression is increased ~150-fold in both wild-type and Δ cells, respectively, reflecting regulation by the ferric uptake regulator (Fur). The expression profiles also point to repression by a separate, ligand-responsive transcription factor, possibly ScmR. Taken together, these data indicate that MftR controls a number of phenotypes, all of which promote bacterial survival in a host environment. Bacterial pathogens face iron limitation in a host environment. To overcome this challenge, they produce siderophores, small iron-chelating molecules. Uptake of iron-siderophore complexes averts bacterial iron limitation. In spp., malleobactin or related compounds are the primary siderophores. We show here that genes encoding proteins required for malleobactin production in B. thailandensis are under the direct control of the global transcription factor MftR. Repression of gene expression by MftR is relieved when MftR binds xanthine, a purine metabolite present in host cells. Our work therefore identifies a mechanism by which siderophore production may be optimized in a host environment, thus contributing to bacterial fitness.
Topics: Siderophores; Virulence; Bacterial Proteins; Burkholderia; Iron; Transcription Factors; Gene Expression Regulation, Bacterial
PubMed: 36286517
DOI: 10.1128/jb.00237-22 -
Proceedings of the National Academy of... Nov 2019Despite the omnipresence of specific host-symbiont associations with acquisition of the microbial symbiont from the environment, little is known about how the...
Despite the omnipresence of specific host-symbiont associations with acquisition of the microbial symbiont from the environment, little is known about how the specificity of the interaction evolved and is maintained. The bean bug acquires a specific bacterial symbiont of the genus from environmental soil and harbors it in midgut crypts. The genus consists of over 100 species, showing ecologically diverse lifestyles, and including serious human pathogens, plant pathogens, and nodule-forming plant mutualists, as well as insect mutualists. Through infection tests of 34 species and 18 taxonomically diverse bacterial species, we demonstrate here that nonsymbiotic and even its outgroup could stably colonize the gut symbiotic organ and provide beneficial effects to the bean bug when inoculated on aposymbiotic hosts. However, coinoculation revealed that the native symbiont always outcompeted the nonnative bacteria inside the gut symbiotic organ, explaining the predominance of the native symbiont in natural bean bug populations. Hence, the abilities for colonization and cooperation, usually thought of as specific traits of mutualists, are not unique to the native symbiont but, to the contrary, competitiveness inside the gut is a derived trait of the native symbiont lineage only and was thus critical in the evolution of the insect gut symbiont.
Topics: Animals; Burkholderia; Heteroptera; Host-Pathogen Interactions; Intestines; Models, Biological; Symbiosis
PubMed: 31636183
DOI: 10.1073/pnas.1912397116 -
Applied and Environmental Microbiology Nov 2020The bacterium produces an arsenal of secondary metabolites that have diverse structures and roles in the ecology of this soil-dwelling bacterium. In coculture...
The bacterium produces an arsenal of secondary metabolites that have diverse structures and roles in the ecology of this soil-dwelling bacterium. In coculture experiments, strain E264 secretes an antimicrobial that nearly eliminates another soil bacterium, strain 168. To identify the antimicrobial, we used a transposon mutagenesis approach. This screen identified antimicrobial-defective mutants with insertions in the , , and genes involved in biosynthesis of a family of 2-alkyl-4(1)-quinolones called 4-hydroxy-3-methyl-2-alkenylquinolines (HMAQs), which are closely related to the 4-hydroxy-2-alkylquinolines (HAQs). Insertions also occurred in the previously uncharacterized gene BTH_II1576 (""). The results confirm that BTH_II1576 is involved in generating -oxide derivatives of HMAQs (HMAQ-NOs). Synthetic HMAQ-NO is active against 168, showing ∼50-fold more activity than HMAQ. Both the methyl group and the length of the carbon side chain account for the high activity of HMAQ-NO. The results provide new information on the biosynthesis and activities of HMAQs and reveal new insight into how these molecules might be important for the ecology of The soil bacterium produces 2-alkyl-4(1)-quinolones that are mostly methylated 4-hydroxyalkenylquinolines, a family of relatively unstudied metabolites similar to molecules also synthesized by Several of the methylated 4-hydroxyalkenylquinolines have antimicrobial activity against other species. We show that strain 168 is particularly susceptible to -oxidated methylalkenylquinolines (HMAQ-NOs). We confirmed that HMAQ-NO biosynthesis requires the previously unstudied protein HmqL. These results provide new information about the biology of 2-alkyl-4(1)-quinolones, particularly the methylated 4-hydroxyalkenylquinolines, which are unique to This study also has importance for understanding secondary metabolites and has implications for potential therapeutic development.
Topics: Anti-Infective Agents; Burkholderia; Methylation; Quinolones
PubMed: 33008823
DOI: 10.1128/AEM.01452-20 -
Microbiology Spectrum Feb 2022Bacteria have developed unique mechanisms to adapt to environmental stresses and challenges of the immune system. Here, we report that Burkholderia pseudomallei, the...
Bacteria have developed unique mechanisms to adapt to environmental stresses and challenges of the immune system. Here, we report that Burkholderia pseudomallei, the causative agent of melioidosis, and its laboratory surrogate, Burkholderia thailandensis, utilize distinct mechanisms for surviving starvation at different incubation temperatures. At 21°C, are present as short rods which can rapidly reactivate and form colonies on solid media. At 4°C, convert into coccoid forms that cannot be cultured on solid agar but can be resuscitated in liquid media supplemented with supernatant obtained from logarithmic phase cultures of B. thailandensis, or catalase and Tween 80, thus displaying characteristics of differentially culturable bacteria (DCB). These DCB have low intensity fluorescence when stained with SYTO 9, have an intact cell membrane (propidium iodide negative), and contain 16S rRNA at levels comparable with growing cells. We also present evidence that lytic transglycosylases, a family of peptidoglycan-remodeling enzymes, are involved in the generation of coccoid forms and their resuscitation to actively growing cells. A B. pseudomallei Δ mutant with four genes deleted did not produce coccoid forms at 4°C and could not be resuscitated in the liquid media evaluated. Our findings provide insights into the adaptation of to nutrient limitation and the generation of differentially culturable bacteria. Bacterial pathogens exhibit physiologically distinct forms that enable their survival in an infected host, the environment and following exposure to antimicrobial agents. B. pseudomallei causes the disease melioidosis, which has a high mortality rate and is difficult to treat with antibiotics. The bacterium is endemic to several countries and detected in high abundance in the environment. Here, we report that during starvation at low temperature, B. pseudomallei produces coccoid forms that cannot grow in standard media and which, therefore, can be challenging to detect using common tools. We provide evidence that the formation of these cocci is mediated by cell wall-specialized enzymes and lytic transglycosylases, and that resuscitation of these forms occurs following the addition of catalase and Tween 80. Our findings have important implications for the disease control and detection of B. pseudomallei, an agent of both public health and defense interest.
Topics: Burkholderia; Burkholderia pseudomallei; Cell Culture Techniques; Humans; Melioidosis; Peptidoglycan; RNA, Ribosomal, 16S; Temperature
PubMed: 34985335
DOI: 10.1128/spectrum.02110-21 -
PloS One 2020The opportunistic pathogens Burkholderia cepacia and Burkholderia contaminans, both genomovars of the Burkholderia cepacia complex (BCC), are frequently cultured from...
The opportunistic pathogens Burkholderia cepacia and Burkholderia contaminans, both genomovars of the Burkholderia cepacia complex (BCC), are frequently cultured from the potable water dispenser (PWD) of the International Space Station (ISS). Here, we sequenced the genomes and conducted phenotypic assays to characterize these Burkholderia isolates. All recovered isolates of the two species fall within monophyletic clades based on phylogenomic trees of conserved single-copy core genes. Within species, the ISS-derived isolates all demonstrate greater than 99% average nucleotide identity (with 95-99% of genomes aligning) and share around 90% of the identified gene clusters from a pangenomic analysis-suggesting that the two groups are each composed of highly similar genomic lineages and their members may have all stemmed from the same two founding populations. The differences that can be observed between the recovered isolates at the pangenomic level are primarily located within putative plasmids. Phenotypically, macrophage intracellularization and lysis occurred at generally similar rates between all ISS-derived isolates, as well as with their respective type-terrestrial strain references. All ISS-derived isolates exhibited antibiotic sensitivity similar to that of the terrestrial reference strains, and minimal differences between isolates were observed. With a few exceptions, biofilm formation rates were generally consistent across each species. And lastly, though isolation date does not necessarily provide any insight into how long a given isolate had been aboard the ISS, none of the assayed physiology correlated with either date of isolation or distances based on nucleotide variation. Overall, we find that while the populations of Burkholderia present in the ISS PWS each maintain virulence, they are likely are not more virulent than those that might be encountered on planet and remain susceptible to clinically used antibiotics.
Topics: Burkholderia; Burkholderia Infections; Burkholderia cepacia; Drinking Water; Phylogeny; Spacecraft; Virulence
PubMed: 32074104
DOI: 10.1371/journal.pone.0227152 -
PloS One 2018Burkholderia pseudomallei is the causative agent of melioidosis and regarded as a bioterrorism threat. It can adapt to the nutrient-limited environment as the bacteria...
Impact of nutritional stress on drug susceptibility and biofilm structures of Burkholderia pseudomallei and Burkholderia thailandensis grown in static and microfluidic systems.
Burkholderia pseudomallei is the causative agent of melioidosis and regarded as a bioterrorism threat. It can adapt to the nutrient-limited environment as the bacteria can survive in triple distilled water for 16 years. Moreover, B. pseudomallei exhibits intrinsic resistance to diverse groups of antibiotics in particular while growing in biofilms. Recently, nutrient-limited condition influenced both biofilm formation and ceftazidime (CAZ) tolerance of B. pseudomallei were found. However, there is no information about how nutrient-limitation together with antibiotics used in melioidosis treatment affects the structure of the biofilm produced by B. pseudomallei. Moreover, no comparative study to investigate the biofilm architectures of B. pseudomallei and the related B. thailandensis under different nutrient concentrations has been reported. Therefore, this study aims to provide new information on the effects of four antibiotics used in melioidosis treatment, viz. ceftazidime (CAZ), imipenem (IMI), meropenem (MEM) and doxycycline (DOX) on biofilm architecture of B. pseudomallei and B. thailandensis with different nutrient concentrations under static and flow conditions using confocal laser scanning microscopy. Impact of nutritional stress on drug susceptibility of B. pseudomallei and B. thailandensis grown planktonically or as biofilm was also evaluated. The findings of this study indicate that nutrient-limited environment enhanced survival of B. pseudomallei in biofilm after exposure to the tested antibiotics. The shedding planktonic B. pseudomallei and B. thailandensis were also found to have increased CAZ tolerance in nutrient-limited environment. However, killing activities of MEM and IMI were stronger than CAZ and DOX on B. pseudomallei and B. thailandensis both in planktonic cells and in 2-day old biofilm. In addition, MEM and IMI were able to inhibit B. pseudomallei and B. thailandensis biofilm formation to a larger extend compared to CAZ and DOX. Differences in biofilm architecture were observed for biofilms grown under static and flow conditions. Under static conditions, biofilms grown in full strength modified Vogel and Bonner's medium (MVBM) showed honeycomb-like architecture while a knitted-like structure was observed under limited nutrient condition (0.1×MVBM). Under flow conditions, biofilms grown in MVBM showed a multilayer structure while merely dispersed bacteria were found when grown in 0.1×MVBM. Altogether, this study provides more insight on the effect of four antibiotics against B. pseudomallei and B. thailandensis in biofilm under different nutrient and flow conditions. Since biofilm formation is believed to be involved in disease relapse, MEM and IMI may be better therapeutic options than CAZ for melioidosis treatment.
Topics: Anti-Bacterial Agents; Biofilms; Burkholderia; Burkholderia pseudomallei; Ceftazidime; Doxycycline; Drug Resistance, Bacterial; Food; Meropenem; Microbial Sensitivity Tests; Microfluidics; Microscopy, Confocal; Thienamycins; Time-Lapse Imaging
PubMed: 29579106
DOI: 10.1371/journal.pone.0194946