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Frontiers in Cellular and Infection... 2017is a Gram-negative intracellular pathogen and the causative agent of melioidosis, a severe disease of both humans and animals. Melioidosis is an emerging disease which... (Review)
Review
is a Gram-negative intracellular pathogen and the causative agent of melioidosis, a severe disease of both humans and animals. Melioidosis is an emerging disease which is predicted to be vastly under-reported. Type III Secretion Systems (T3SSs) are critical virulence factors in Gram negative pathogens of plants and animals. The genome of encodes three T3SSs. T3SS-1 and -2, of which little is known, are homologous to Hrp2 secretion systems of the plant pathogens and . T3SS-3 is better characterized and is homologous to the Inv/Mxi-Spa secretion systems of spp. and , respectively. Upon entry into the host cell, requires T3SS-3 for efficient escape from the endosome. T3SS-3 is also required for full virulence in both hamster and murine models of infection. The regulatory cascade which controls T3SS-3 expression and the secretome of T3SS-3 have been described, as well as the effect of mutations of some of the structural proteins. Yet only a few effector proteins have been functionally characterized to date and very little work has been carried out to understand the hierarchy of assembly, secretion and temporal regulation of T3SS-3. This review aims to frame current knowledge of T3SSs in the context of other well characterized model T3SSs, particularly those of and .
Topics: Animals; Bacterial Proteins; Burkholderia pseudomallei; Cricetinae; Gene Expression Regulation, Bacterial; Humans; Melioidosis; Mice; Molecular Chaperones; Mutation; Plant Diseases; Salmonella; Shigella flexneri; Type III Secretion Systems; Virulence Factors
PubMed: 28664152
DOI: 10.3389/fcimb.2017.00255 -
BMC Microbiology May 2021Burkholderia pseudomallei, a facultative intracellular bacterium, is the aetiological agent of melioidosis that is responsible for up to 40% sepsis-related mortality in...
BACKGROUND
Burkholderia pseudomallei, a facultative intracellular bacterium, is the aetiological agent of melioidosis that is responsible for up to 40% sepsis-related mortality in epidemic areas. However, no effective vaccine is available currently, and the drug resistance is also a major problem in the treatment of melioidosis. Therefore, finding new clinical treatment strategies in melioidosis is extremely urgent.
RESULTS
We demonstrated that tauroursodeoxycholic acid (TUDCA), a clinically available endoplasmic reticulum (ER) stress inhibitor, can promote B. pseudomallei clearance both in vivo and in vitro. In this study, we investigated the effects of TUDCA on the survival of melioidosis mice, and found that treatment with TUDCA significantly decreased intracellular survival of B. pseudomallei. Mechanistically, we found that B. pseudomallei induced apoptosis and activated IRE1 and PERK signaling ways of ER stress in RAW264.7 macrophages. TUDCA treatment could reduce B. pseudomallei-induced ER stress in vitro, and TUDCA is protective in vivo.
CONCLUSION
Taken together, our study has demonstrated that B. pseudomallei infection results in ER stress-induced apoptosis, and TUDCA enhances the clearance of B. pseudomallei by inhibiting ER stress-induced apoptosis both in vivo and in vitro, suggesting that TUDCA could be used as a potentially alternative treatment for melioidosis.
Topics: Animals; Apoptosis; Burkholderia pseudomallei; Cell Line; Endoplasmic Reticulum Stress; Melioidosis; Mice; Signal Transduction; Survival Analysis; Taurochenodeoxycholic Acid
PubMed: 33947331
DOI: 10.1186/s12866-021-02199-x -
PloS One 2020Identification of bacterial virulence factors is critical for understanding disease pathogenesis, drug discovery and vaccine development. In this study we used two...
Identification of bacterial virulence factors is critical for understanding disease pathogenesis, drug discovery and vaccine development. In this study we used two approaches to predict virulence factors of Burkholderia pseudomallei, the Gram-negative bacterium that causes melioidosis. B. pseudomallei is naturally antibiotic resistant and there are no clinically available melioidosis vaccines. To identify B. pseudomallei protein targets for drug discovery and vaccine development, we chose to search for substrates of the B. pseudomallei periplasmic disulfide bond forming protein A (DsbA). DsbA introduces disulfide bonds into extra-cytoplasmic proteins and is essential for virulence in many Gram-negative organism, including B. pseudomallei. The first approach to identify B. pseudomallei DsbA virulence factor substrates was a large-scale genomic analysis of 511 unique B. pseudomallei disease-associated strains. This yielded 4,496 core gene products, of which we hypothesise 263 are DsbA substrates. Manual curation and database screening of the 263 mature proteins yielded 81 associated with disease pathogenesis or virulence. These were screened for structural homologues to predict potential B-cell epitopes. In the second approach, we searched the B. pseudomallei genome for homologues of the more than 90 known DsbA substrates in other bacteria. Using this approach, we identified 15 putative B. pseudomallei DsbA virulence factor substrates, with two of these previously identified in the genomic approach, bringing the total number of putative DsbA virulence factor substrates to 94. The two putative B. pseudomallei virulence factors identified by both methods are homologues of PenI family β-lactamase and a molecular chaperone. These two proteins could serve as high priority targets for future B. pseudomallei virulence factor characterization.
Topics: Amino Acid Sequence; Bacterial Proteins; Bacterial Vaccines; Burkholderia pseudomallei; Cysteine; Epitopes, B-Lymphocyte; Gene Ontology; Genome, Bacterial; Models, Molecular; Sequence Homology, Amino Acid; Substrate Specificity; Virulence Factors
PubMed: 33216758
DOI: 10.1371/journal.pone.0241306 -
Molecular Biology and Evolution Jan 2022The soil bacterium Burkholderia pseudomallei is the causative agent of melioidosis and a significant cause of human morbidity and mortality in many tropical and...
The soil bacterium Burkholderia pseudomallei is the causative agent of melioidosis and a significant cause of human morbidity and mortality in many tropical and subtropical countries. The species notoriously survives harsh environmental conditions but the genetic architecture for these adaptations remains unclear. Here we employed a powerful combination of genome-wide epistasis and co-selection studies (2,011 genomes), condition-wide transcriptome analyses (82 diverse conditions), and a gene knockout assay to uncover signals of "co-selection"-that is a combination of genetic markers that have been repeatedly selected together through B. pseudomallei evolution. These enabled us to identify 13,061 mutation pairs under co-selection in distinct genes and noncoding RNA. Genes under co-selection displayed marked expression correlation when B. pseudomallei was subjected to physical stress conditions, highlighting the conditions as one of the major evolutionary driving forces for this bacterium. We identified a putative adhesin (BPSL1661) as a hub of co-selection signals, experimentally confirmed a BPSL1661 role under nutrient deprivation, and explored the functional basis of co-selection gene network surrounding BPSL1661 in facilitating the bacterial survival under nutrient depletion. Our findings suggest that nutrient-limited conditions have been the common selection pressure acting on this species, and allelic variation of BPSL1661 may have promoted B. pseudomallei survival during harsh environmental conditions by facilitating bacterial adherence to different surfaces, cells, or living hosts.
Topics: Adhesins, Bacterial; Alleles; Biological Evolution; Burkholderia pseudomallei; Selection, Genetic; Stress, Physiological
PubMed: 34662416
DOI: 10.1093/molbev/msab306 -
MSphere Feb 2021is a Gram-negative bacterium that causes the sapronotic disease melioidosis. An outbreak in 2003 in the state of Ceara, Brazil, resulted in subsequent surveillance and...
is a Gram-negative bacterium that causes the sapronotic disease melioidosis. An outbreak in 2003 in the state of Ceara, Brazil, resulted in subsequent surveillance and environmental sampling which led to the recognition of as an endemic pathogen in that area. From 2003 to 2015, 24 clinical and 12 environmental isolates were collected across Ceara along with one from the state of Alagoas. Using next-generation sequencing, multilocus sequence typing, and single nucleotide polymorphism analysis, we characterized the genomic diversity of this collection to better understand the population structure of associated with Ceara. We found that the isolates in this collection form a distinct subclade compared to other examples from the Western Hemisphere. Substantial genetic diversity among the clinical and environmental isolates was observed, with 14 sequence types (STs) identified among the 37 isolates. Of the 31,594 core single-nucleotide polymorphisms (SNPs) identified, a high proportion (59%) were due to recombination. Because recombination events do not follow a molecular clock, the observation of high occurrence underscores the importance of identifying and removing recombination SNPs prior to evolutionary reconstructions and inferences in public health responses to outbreaks. Our results suggest long-term prevalence in this recently recognized region of melioidosis endemicity. causes significant morbidity and mortality, but its geographic prevalence and genetic diversity are not well characterized, especially in the Western Hemisphere. A better understanding of the genetic relationships among clinical and environmental isolates will improve knowledge of the population structure of this bacterium as well as the ability to conduct epidemiological investigations of cases of melioidosis.
Topics: Bacterial Typing Techniques; Brazil; Burkholderia pseudomallei; DNA, Bacterial; Disease Outbreaks; Genetic Variation; Genome, Bacterial; Genomics; Genotype; Humans; Male; Melioidosis; Phylogeny; Sequence Analysis, DNA
PubMed: 33536328
DOI: 10.1128/mSphere.01259-20 -
BMC Microbiology Mar 2022Burkholderia pseudomallei (B. pseudomallei), as a highly pathogenic organism, causes melioidosis, which is a disease of public health importance in many tropical...
BACKGROUND
Burkholderia pseudomallei (B. pseudomallei), as a highly pathogenic organism, causes melioidosis, which is a disease of public health importance in many tropical developing countries. Here, we present and validate a novel detection technique, termed multiple cross displacement amplification combined with nanoparticles-based lateral flow biosensor (MCDA-NB), for identifying B. pseudomallei and diagnosing melioidosis.
RESULTS
B. pseudomallei-MCDA targets the TTS1 (Type III secretion system gene cluster 1) to specifically design ten MCDA primers. The nanoparticles-based biosensor (NB) can be combined with B. pseudomallei-MCDA for visually, objective, simply and rapidly reporting reaction results. The optimal amplification conditions of B. pseudomallei-MCDA were 66 °C for 30 min. Assay's sensitivity was 100 fg of genomic DNA in the pure cultures, and the analytical specificity was 100% by the examination of 257 strains, including 228 B. pseudomallei and 29 non-B. pseudomallei. As a result, the whole detection procedure was completed within 50 min, including 15 min for genomic DNA preparation, 30 min for l MCDA reaction, and 2 min for the interpretation of the results visually by biosensor.
CONCLUSIONS
B. pseudomallei-MCDA assay is a rapid, sensitive and specific method for the detection of B. pseudomallei, and can be used as a potential tool for melioidosis diagnose in basic, field and clinical laboratories.
Topics: Biosensing Techniques; Burkholderia pseudomallei; Humans; Melioidosis; Nucleic Acid Amplification Techniques; Sensitivity and Specificity
PubMed: 35272632
DOI: 10.1186/s12866-022-02485-2 -
PLoS Pathogens May 2021Burkholderia pseudomallei, the etiological agent of melioidosis in humans and animals, often occupies environmental niches and infection sites characterized by limited...
Burkholderia pseudomallei, the etiological agent of melioidosis in humans and animals, often occupies environmental niches and infection sites characterized by limited concentrations of oxygen. Versatile genomic features enable this pathogen to maintain its physiology and virulence under hypoxia, but the crucial regulatory networks employed to switch from oxygen dependent respiration to alternative terminal electron acceptors (TEA) like nitrate, remains poorly understood. Here, we combined a Tn5 transposon mutagenesis screen and an anaerobic growth screen to identify a two-component signal transduction system with homology to RegAB. We show that RegAB is not only essential for anaerobic growth, but also for full virulence in cell lines and a mouse infection model. Further investigations of the RegAB regulon, using a global transcriptomic approach, identified 20 additional regulators under transcriptional control of RegAB, indicating a superordinate role of RegAB in the B. pseudomallei anaerobiosis regulatory network. Of the 20 identified regulators, NarX/L and a FNR homolog were selected for further analyses and a role in adaptation to anaerobic conditions was demonstrated. Growth experiments identified nitrate and intermediates of the denitrification process as the likely signal activateing RegAB, NarX/L, and probably of the downstream regulators Dnr or NsrR homologs. While deletions of individual genes involved in the denitrification process demonstrated their important role in anaerobic fitness, they showed no effect on virulence. This further highlights the central role of RegAB as the master regulator of anaerobic metabolism in B. pseudomallei and that the complete RegAB-mediated response is required to achieve full virulence. In summary, our analysis of the RegAB-dependent modulon and its interconnected regulons revealed a key role for RegAB of B. pseudomallei in the coordination of the response to hypoxic conditions and virulence, in the environment and the host.
Topics: Adaptation, Physiological; Anaerobiosis; Animals; Bacterial Proteins; Burkholderia pseudomallei; Female; Gene Expression Regulation, Bacterial; Hypoxia; Melioidosis; Mice; Mice, Inbred BALB C; Mutation; Nitrates; Oxidation-Reduction; Transcriptome; Virulence
PubMed: 34048488
DOI: 10.1371/journal.ppat.1009604 -
PloS One 2018Burkholderia pseudomallei is the environmental bacillus that causes melioidosis; a disease clinically significant in Australia and Southeast Asia but emerging in...
Burkholderia pseudomallei is the environmental bacillus that causes melioidosis; a disease clinically significant in Australia and Southeast Asia but emerging in tropical and sub-tropical regions around the globe. Previous studies have placed the ancestral population of the organism in Australia with a single lineage disseminated to Southeast Asia. We have previously characterized B. pseudomallei isolates from New Guinea and the Torres Strait archipelago; remote regions that share paleogeographic ties with Australia. These studies identified regional biogeographical boundaries. In this study, we utilize whole-genome sequencing to reconstruct ancient evolutionary relationships and ascertain correlations between paleogeography and present-day distribution of this bacterium in Australasia. Our results indicate that B. pseudomallei from New Guinea fall into a single clade within the Australian population. Furthermore, clades from New Guinea are region-specific; an observation possibly linked to limited recent anthropogenic influence in comparison to mainland Australia and Southeast Asia. Isolates from the Torres Strait archipelago were distinct yet scattered among those from mainland Australia. These results provide evidence that the New Guinean and Torres Strait lineages may be remnants of an ancient portion of the Australian population. Rising sea levels isolated New Guinea and the Torres Strait Islands from each other and the Australian mainland, and may have allowed long-term isolated evolution of these lineages, providing support for a theory of microbial biogeography congruent with that of macro flora and fauna. Moreover, these findings indicate that contemporary microbial biogeography theories should consider recent and ongoing impacts of globalisation and human activity.
Topics: Anthropology, Medical; Australasia; Australia; Burkholderia pseudomallei; DNA, Bacterial; Genetic Variation; History, Ancient; Humans; Melioidosis; New Guinea; Phylogeny; Whole Genome Sequencing
PubMed: 30395628
DOI: 10.1371/journal.pone.0206845 -
BMC Microbiology Mar 2015Burkholderia pseudomallei is a Gram-negative bacterium that causes melioidosis, an often fatal disease in tropical countries. Burkholderia thailandensis is a...
BACKGROUND
Burkholderia pseudomallei is a Gram-negative bacterium that causes melioidosis, an often fatal disease in tropical countries. Burkholderia thailandensis is a non-virulent but closely related species. Both species are soil saprophytes but are almost never isolated together.
RESULTS
We identified two mechanisms by which B. pseudomallei affects the growth of B. thailandensis. First, we found that six different isolates of B. pseudomallei inhibited the growth of B. thailandensis on LB agar plates. Second, our results indicated that 55% of isolated strains of B. pseudomallei produced a secreted compound that inhibited the motility but not the viability of B. thailandensis. Analysis showed that the active compound was a pH-sensitive and heat-labile compound, likely a protein, which may affect flagella processing or facilitate their degradation. Analysis of bacterial sequence types (STs) demonstrated an association between this and motility inhibition. The active compound was produced from B. pseudomallei during the stationary growth phase.
CONCLUSION
Taken together, our results indicate that B. pseudomallei inhibits both the growth and motility of its close relative B. thailandensis. The latter phenomenon appears to occur via a previously unreported mechanism involving flagellar processing or degradation.
Topics: Agar; Antibiosis; Bacterial Proteins; Biological Factors; Burkholderia; Burkholderia pseudomallei; Culture Media; Culture Media, Conditioned; Flagella; Hydrogen-Ion Concentration; Movement; Protein Stability; Proteolysis; Soil Microbiology; Thailand
PubMed: 25879538
DOI: 10.1186/s12866-015-0395-7 -
Journal of Bacteriology Jul 2018, the causative agent of melioidosis, encodes almost a dozen predicted polyketide (PK) biosynthetic gene clusters. Many of these are regulated by LuxR-I-type...
, the causative agent of melioidosis, encodes almost a dozen predicted polyketide (PK) biosynthetic gene clusters. Many of these are regulated by LuxR-I-type acyl-homoserine (AHL) quorum-sensing systems. One of the PK gene clusters, the gene cluster, is conserved in the close relative The genes code for the cytotoxin malleilactone and are regulated by a genetically linked LuxR-type transcription factor, MalR. Although AHLs typically interact with LuxR-type proteins to modulate gene transcription, the MalR does not appear to be an AHL receptor. Here, we characterize the genes and MalR in We use chemical analyses to demonstrate that the genes code for malleilactone. Our results show that MalR and the genes contribute to the ability of to kill In , antibiotics like trimethoprim can activate MalR by driving transcription of the genes, and we demonstrate that some of the same antibiotics induce expression of We also demonstrate that MalR does not respond directly to AHLs. Our results suggest that MalR is indirectly repressed by AHLs, possibly through a repressor, ScmR. We further show that malleilactone is a virulence factor and provide the foundation for understanding how malleilactone contributes to the pathology of melioidosis infections. Many bacterially produced polyketides are cytotoxic to mammalian cells and are potentially important contributors to pathogenesis during infection. We are interested in the polyketide gene clusters present in , which causes the often-fatal human disease melioidosis. Using knowledge gained by studies in the close relative , we show that one of the polyketide biosynthetic clusters produces a cytotoxic polyketide, malleilactone. Malleilactone contributes to virulence in a infection model and is regulated by an orphan LuxR family quorum-sensing transcription factor, MalR. Our studies demonstrate that malleilactone biosynthesis or MalR could be new targets for developing therapeutics to treat melioidosis.
Topics: A549 Cells; Animals; Anti-Bacterial Agents; Bacterial Proteins; Burkholderia pseudomallei; Caenorhabditis elegans; Gene Expression Regulation, Bacterial; Humans; Jurkat Cells; Lactones; Quorum Sensing; Virulence; Virulence Factors
PubMed: 29735757
DOI: 10.1128/JB.00008-18