| 1. |
Hagen RM,
Gauthier YP,
Sprague LD,
Vidal DR,
Zysk G,
Finke EJ,
Neubauer H,
( 2002 ) Strategies for PCR based detection of Burkholderia pseudomallei DNA in paraffin wax embedded tissues. PMID : 12456780 : DOI : 10.1136/mp.55.6.398 PMC : PMC1187279 Abstract >>
Recently, several cases of melioidosis imported to Europe have been reported. The diagnosis of the acute or chronic infection remains challenging. This report describes an optimised protocol for fast and reliable DNA preparation for use in two different polymerase chain reaction (PCR) assays, namely: (1) a seminested PCR assay targeting a genus specific sequence of the ribosomal protein subunit 21 (rpsU) gene and (2) a nested PCR assay targeting the gene encoding the filament forming flagellin (fliC). Various strains of Burkholderia spp, strains of closely related genera, and spleen tissue samples of experimentally infected mice were investigated. The combination of PCR and sequencing of the amplicons resulted in high sensitivity and specificity. These procedures may allow rapid, sensitive, and reliable detection of B pseudomallei DNA in routinely formalin fixed and paraffin wax embedded samples, thus providing a safe diagnostic tool and avoiding the cultivation of a risk group 3 agent. In addition, this method could be useful for retrospective histopathological investigations.
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2. |
Park W,
Padmanabhan P,
Padmanabhan S,
Zylstra GJ,
Madsen EL,
( 2002 ) nahR, encoding a LysR-type transcriptional regulator, is highly conserved among naphthalene-degrading bacteria isolated from a coal tar waste-contaminated site and in extracted community DNA. PMID : 12177326 : DOI : 10.1099/00221287-148-8-2319 Abstract >>
In Pseudomonas putida strain G7, a LysR-type positive transcriptional activator protein encoded by nahR is necessary for activation of two operons involved in naphthalene catabolism [Schell, M. A. & Poser, E. F. (1989). J Bacteriol 171, 837-846]. The role of an nahR homologue, NCIB-nahR, in another naphthalene-metabolizing bacterium, P. putida NCIB 9816-4 was verified. Targeted disruption of NCIB-nahR by homologous recombination resulted in a growth defect in the presence of naphthalene or salicylate as sole carbon and energy source. The nahR homologues and intergenic regions between nahR-like and nahG-like genes from P. putida NCIB 9816-4 and seven bacteria native to a naphthalene-rich coal tar contaminated site were amplified by PCR using degenerate primers. The amplified nahR homologues and the intergenic regions were cloned and sequenced. Alignment of the deduced amino acid sequences from NahR homologues revealed that NahR-like proteins showed only minor variations in all investigated naphthalene-degrading isolates. The intergenic regions, together with known NahR-binding sites showed the consensus NahR-protein-binding sites (5'-ATTCACGCTN(2)TGAT-3'). Surprisingly, amplified intergenic regions from naphthalene-degrading micro-organisms native to this study site were 100% identical to that of the pDTG1 plasmid (an archetypal naphthalene-catabolic plasmid from Pseudomonas putida NCIB 9816-4), but the nahR coding regions were not. DNA representing the uncultured microbial community was extracted from six sediment samples with varying coal tar exposure histories. PCR amplification of nahR from sediment DNA was observed in contaminated samples, but in uncontaminated samples only following laboratory incubation with naphthalene. The sediment-derived PCR products were sequenced and also found to be almost identical to known nahR genes. Thus, the structure and function of nahR-nahG regulatory genes appear to be highly conserved.
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3. |
Wagner UG,
Petersen EI,
Schwab H,
Kratky C,
( 2002 ) EstB from Burkholderia gladioli: a novel esterase with a beta-lactamase fold reveals steric factors to discriminate between esterolytic and beta-lactam cleaving activity. PMID : 11847270 : DOI : 10.1110/ps.33002 PMC : PMC2373480 Abstract >>
Esterases form a diverse class of enzymes of largely unknown physiological role. Because many drugs and pesticides carry ester functions, the hydrolysis of such compounds forms at least one potential biological function. Carboxylesterases catalyze the hydrolysis of short chain aliphatic and aromatic carboxylic ester compounds. Esterases, D-alanyl-D-alanine-peptidases (DD-peptidases) and beta-lactamases can be grouped into two distinct classes of hydrolases with different folds and topologically unrelated catalytic residues, the one class comprising of esterases, the other one of beta-lactamases and DD-peptidases. The chemical reactivities of esters and beta-lactams towards hydrolysis are quite similar, which raises the question of which factors prevent esterases from displaying beta-lactamase activity and vice versa. Here we describe the crystal structure of EstB, an esterase isolated from Burkholderia gladioli. It shows the protein to belong to a novel class of esterases with homology to Penicillin binding proteins, notably DD-peptidase and class C beta-lactamases. Site-directed mutagenesis and the crystal structure of the complex with diisopropyl-fluorophosphate suggest Ser75 within the "beta-lactamase" Ser-x-x-Lys motif to act as catalytic nucleophile. Despite its structural homology to beta-lactamases, EstB shows no beta-lactamase activity. Although the nature and arrangement of active-site residues is very similar between EstB and homologous beta-lactamases, there are considerable differences in the shape of the active site tunnel. Modeling studies suggest steric factors to account for the enzyme's selectivity for ester hydrolysis versus beta-lactam cleavage.
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4. |
Petersen EI,
Valinger G,
Sölkner B,
Stubenrauch G,
Schwab H,
( 2001 ) A novel esterase from Burkholderia gladioli which shows high deacetylation activity on cephalosporins is related to beta-lactamases and DD-peptidases. PMID : 11472796 : Abstract >>
The gene (estB) encoding for a novel esterase (EstB) from Burkholderia gladioli (formerly Pseudomonas marginata) NCPPB 1891 was cloned in Escherichia coli. Sequence analysis showed an open reading frame encoding a polypeptide of 392 amino acid residues, with a molecular mass of about 42 kDa. Comparison of the amino acid sequence with those of other homologous enzymes indicated homologies to beta-lactamases, penicillin binding proteins and DD-peptidases. The serine residue (Ser(75)) which is located within a present class A beta-lactamase motif ([F,Y]-X-[L,I,V,M,F,Y]-X-S-[T,V]-X-K-X-X-X-X-[A,G,L]-X-X-[L,C]) was identified by site-directed mutagenesis to represent the active nucleophile. A second serine residue (Ser(149)) which is located within a G-x-S-x-G motif which is typically found in esterases and lipases was demonstrated not to play a significant role in enzyme function. The estB gene was overexpressed in E. coli using a tac promoter-based expression system. Investigation of EstB protein with respect to the ability to hydrolyse beta-lactam substrates clearly demonstrated that this protein has no beta-lactamase activity. The recombinant enzyme is active on triglycerides and on nitrophenyl esters with acyl chain lengths up to C6. The preference for short chain length substrates indicated that EstB is a typical carboxylesterase. As a special feature EstB esterase was found to have high deacetylation activity on cephalosporin derivatives.
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5. |
Reiter B,
Glieder A,
Talker D,
Schwab H,
( 2000 ) Cloning and characterization of EstC from Burkholderia gladioli, a novel-type esterase related to plant enzymes. PMID : 11152069 : Abstract >>
By screening a genomic library of Burkholderia gladioli (formerly Pseudomonas marginata) for clones exhibiting esterolytic activity, the gene for a novel-type esterase (EstC) showing significant homology to plant enzymes could be isolated. High homology was found to two hydroxynitrile lyases originating from Hevea brasiliensis (tropical rubber tree) and Manihot esculenta (cassava), and to two proteins from Oryza sativa (rice) that are specifically induced upon infection by Pseudomonas syringae pv. syringae. The sequenced ORF encodes for a protein of 298 amino acids. The enzyme was efficiently overexpressed in Escherichia coli, purified and characterized with respect to enzymatic capabilities. The enzyme was able to hydrolyze a variety of esterase substrates of low to medium carbonic acid chain length, but no triglycerides were hydrolyzed. Despite the high sequence homology, no hydroxynitrile lyase activity could be recognized.
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6. |
Shimosaka M,
Fukumori Y,
Zhang XY,
He NJ,
Kodaira R,
Okazaki M,
( 2000 ) Molecular cloning and characterization of a chitosanase from the chitosanolytic bacterium Burkholderia gladioli strain CHB101. PMID : 11030572 : Abstract >>
A chitosanase was purified from the culture fluid of the chitino- and chitosanolytic bacterium Burkholderia gladioli strain CHB101. The purified enzyme (chitosanase A) had a molecular mass of 28 kDa, and catalyzed the endo-type cleavage of chitosans having a low degree of acetylation (0-30%). The enzyme hydrolyzed glucosamine oligomers larger than a pentamer, but did not exhibit any activity toward N-acetylglucosamine oligomers and colloidal chitin. The gene coding for chitosanase A (csnA) was isolated and its nucleotide sequence determined. B. gladioli csnA has an ORF encoding a polypeptide of 355 amino acid residues. Analysis of the N-terminal amino acid sequence of the purified chitosanase A and comparison with that deduced from the csnA ORF suggests post-translational processing of a putative signal peptide and a possible substrate-binding domain. The deduced amino acid sequence corresponding to the mature protein showed 80% similarity to the sequences reported from Bacillus circulans strain MH-K1 and Bacillus ehimensis strain EAG1, which belong to family 46 glycosyl hydrolases.
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7. |
Ivancic M,
Valinger G,
Gruber K,
Schwab H,
( 2007 ) Inverting enantioselectivity of Burkholderia gladioli esterase EstB by directed and designed evolution. PMID : 17147964 : DOI : 10.1016/j.jbiotec.2006.10.007 Abstract >>
Esterase EstB from Burkholderia gladioli, showing moderate S-enantioselectivity (E(S)=6.1) in the hydrolytic kinetic resolution of methyl-beta-hydroxyisobutyrate, was subjected to directed evolution in order to reverse its enantioselectivity. After one round of ep-PCR, saturation mutagenesis and high-throughput screening, it was found that different mutations at position 152 (in the vicinity of the active site) increase, decrease and even reverse the natural enantioselectivity of this enzyme. The newly created R-enantioselectivity of the esterase mutein (E(Rapp)=1.5) has been further enhanced by a designed evolution strategy involving random mutations close to the active site. Based on the three-dimensional structure nineteen amino acid residues have been selected as mutation sites for saturation mutagenesis. Mutations at three sites (135, 253 and 351) were found to increase R-enantioselectivity. Successive rounds of saturation mutagenesis at these "hot spots" resulted in an increase in R-enantioselectivity from E(Rapp)=1.5 for the parent mutant to E(Rapp)=28.9 for the best variant which carried four amino acid substitutions. Our results prove designed evolution followed by high-throughput screening to be an efficient strategy for engineering enzyme enantioselectivity.
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8. |
Valinger G,
Hermann M,
Wagner UG,
Schwab H,
( 2007 ) Stability and activity improvement of cephalosporin esterase EstB from Burkholderia gladioli by directed evolution and structural interpretation of muteins. PMID : 17137667 : DOI : 10.1016/j.jbiotec.2006.10.008 Abstract >>
Esterase EstB from Burkholderia gladioli, which belongs to a family of esterases related to beta-lactamases and DD-peptidases was evolved for increased stability and simultaneously maintaining high cephalosporin C deacetylation activity. Random mutagenesis PCR was used to generate up to 5 aa substitutions per gene. A newly designed colony filter-screening assay, which was based on pH change after deacetylation of cephalosporin C in presence of DMF was established. In a first evolution round employing random mutagenesis, which included about 10(6) mutants, a set of interesting mutants was isolated. Distinct mutations identified as significant for stability were combined by a rational recombination step and the resulting recombinant was further evolved by an additional random mutagenesis round. After screening an additional 10(5) clones, it was possible to isolate a variant of EstB having more than 100-fold better activity in reactions containing 35% DMF. This mutant also showed a high increase in temperature stability (T(m) was raised by 13 degrees C) and retained high activity towards cephalosporin C under standard assay conditions. The molecular effects of mutations found in random mutants are discussed in view of the three-dimensional structure of wild-type EstB.
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9. |
Maeda Y,
Shinohara H,
Kiba A,
Ohnishi K,
Furuya N,
Kawamura Y,
Ezaki T,
Vandamme P,
Tsushima S,
Hikichi Y,
( 2006 ) Phylogenetic study and multiplex PCR-based detection of Burkholderia plantarii, Burkholderia glumae and Burkholderia gladioli using gyrB and rpoD sequences. PMID : 16627650 : DOI : 10.1099/ijs.0.64184-0 DOI : 10.1099/ijs.0.64184-0 Abstract >>
In order to develop a detection method for the rice pathogens Burkholderia plantarii, Burkholderia glumae and Burkholderia gladioli, the phylogeny of six plant-pathogenic Burkholderia species was analysed using the combined nucleotide sequences of gyrB and rpoD. B. plantarii, B. glumae and B. gladioli formed tight monophyletic branches supported by high bootstrap probabilities. The high sequence similarity revealed a close phylogenetic relationship between B. glumae and B. plantarii. B. plantarii strains were divided into three subclusters comprising rice strains, whereas the single Vanda strain occupied a unique position in the phylogenetic tree. The gyrB and rpoD sequences of all B. glumae strains examined were highly conserved. In contrast, B. gladioli strains demonstrated a far greater sequence diversity, but this diversity did not correlate with pathovar, host plant or geographical origin of the strains. A multiplex-PCR protocol using specific primers from the gyrB sequences was designed that allowed the specific detection and identification of B. plantarii, B. glumae and B. gladioli in rice seeds infected with these pathogenic species.
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10. |
Kodaira R,
Nogawa M,
Okazaki M,
Shimosaka M,
Fukumori Y,
Narita T,
Zhang X,
( 2001 ) The bacterium Burkholderia gladioli strain CHB101 produces two different kinds of chitinases belonging to families 18 and 19 of the glycosyl hydrolases. PMID : 16232958 : Abstract >>
Two genes (chiA and chiB) coding for chitanases A and B (ChiA and ChiB) were isolated from the chitinolytic bacterium, Burkholderia gladioli strain CHB101. chiA contains an open reading frame that encodes a protein of 343 amino acids, whereas chiB encodes a protein of 307 amino acids. The deduced amino acid sequence of ChiA showed a high similarity to those of microbial chitinases belonging to family 18 of the glycosyl hydrolases, while ChiB showed significant sequence similarity to plant chitinases and Streptomyces spp. chitinases belonging to family 19.
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11. |
Payne GW,
Vandamme P,
Morgan SH,
Lipuma JJ,
Coenye T,
Weightman AJ,
Jones TH,
Mahenthiralingam E,
( 2005 ) Development of a recA gene-based identification approach for the entire Burkholderia genus. PMID : 16000805 : DOI : 10.1128/AEM.71.7.3917-3927.2005 PMC : PMC1169057 Abstract >>
Burkholderia is an important bacterial genus containing species of ecological, biotechnological, and pathogenic interest. With their taxonomy undergoing constant revision and the phenotypic similarity of several species, correct identification of Burkholderia is difficult. A genetic scheme based on the recA gene has greatly enhanced the identification of Burkholderia cepacia complex species. However, the PCR developed for the latter approach was limited by its specificity for the complex. By alignment of existing and novel Burkholderia recA sequences, we designed new PCR primers and evaluated their specificity by testing a representative panel of Burkholderia strains. PCR followed by restriction fragment length polymorphism analysis of an 869-bp portion of the Burkholderia recA gene was not sufficiently discriminatory. Nucleotide sequencing followed by phylogenetic analysis of this recA fragment differentiated both putative and known Burkholderia species and all members of the B. cepacia complex. In addition, it enabled the design of a Burkholderia genus-specific recA PCR that produced a 385-bp amplicon, the sequence of which was also able to discriminate all species examined. Phylogenetic analysis of 188 novel recA genes enabled clarification of the taxonomic position of several important Burkholderia strains and revealed the presence of four novel B. cepacia complex recA lineages. Although the recA phylogeny could not be used as a means to differentiate B. cepacia complex strains recovered from clinical infection versus the natural environment, it did facilitate the identification of clonal strain types of B. cepacia, B. stabilis, and B. ambifaria capable of residing in both niches.
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12. |
Lemaire B,
Van Oevelen S,
De Block P,
Verstraete B,
Smets E,
Prinsen E,
Dessein S,
( 2012 ) Identification of the bacterial endosymbionts in leaf nodules of Pavetta (Rubiaceae). PMID : 21378132 : DOI : 10.1099/ijs.0.028019-0 Abstract >>
Three genera in the Rubiaceae (Pavetta, Psychotria and Sericanthe) harbour bacterial endosymbionts within leaf nodules or galls. The present paper identifies the bacterial endophytes in three leaf-nodulating Pavetta species. In order to reveal their identity and assess their phylogenetic position, 16S rRNA, recA and gyrB genes were sequenced from an extensive sampling of Burkholderia strains. This multigene approach results in a robust phylogeny, which places the bacterial endosymbionts of Pavetta at two distinct positions within the genus Burkholderia (class Betaproteobacteria), suggesting that leaf-nodulating endosymbionts within Pavetta have different origins. The endophytes of nodulated Psychotria species were recognized as the closest relatives to the Pavetta endosymbionts. Our results suggest that the endosymbionts of Pavetta represent novel species, which can be classified as 'Candidatus Burkholderia hispidae', 'Candidatus Burkholderia rigidae' and 'Candidatus Burkholderia schumannianae'.
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13. |
Tayeb LA,
Lefevre M,
Passet V,
Diancourt L,
Brisse S,
Grimont PA,
( 2008 ) Comparative phylogenies of Burkholderia, Ralstonia, Comamonas, Brevundimonas and related organisms derived from rpoB, gyrB and rrs gene sequences. PMID : 18280706 : DOI : 10.1016/j.resmic.2007.12.005 Abstract >>
Phylogenetic analysis of strains from Burkholderia, Ralstonia, Cupriavidus, Comamonas, Delftia, Acidovorax, Brevundimonas, Herbaspirillum huttiense and "Pseudomonas butanovora" was performed based on the protein-coding genes rpoB and gyrB and on the 16S rRNA-coding gene rrs. Overall, the phylogenies deduced from the three genes were concordant among themselves and with current taxonomy. However, a few differences among individual gene phylogenies were noted. For example, the separation of Cupriavidus from Ralstonia was not supported in the rpoB tree, as Ralstonia was nested within Cupriavidus. Similarly, the separation of Delftia from Comamonas was not supported in the gyrB tree. Based on rrs and rpoB, the genus Burkholderia contained four groups: (i) the B. cepacia complex, (ii) the B. pseudomallei-B. thailandensis group, (iii) a 6-species group including B. caledonica and B. glathei and (iv) the B. plantarii-B. glumae-B. gladioli group. However, B. caribensis and B. glathei stood as a fifth group based on gyrB. It appears that a phylogeny cannot be reliably based on a single gene. Using rpoB and gyrB, better separation of closely related species was obtained compared to rrs, indicating the potential of these two genes for identification and species definition. Nevertheless, intraspecific sequence diversity will need to be determined to fully establish the value of these genes for strain identification.
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14. |
Lynch KH,
Dennis JJ,
( 2008 ) Development of a species-specific fur gene-based method for identification of the Burkholderia cepacia complex. PMID : 18057135 : DOI : 10.1128/JCM.01460-07 PMC : PMC2238088 Abstract >>
Burkholderia is an important bacterial genus with a complex taxonomy that contains species of both ecological and pathogenic importance, including nine closely related species collectively termed the Burkholderia cepacia complex (BCC). Unfortunately, 16S rRNA gene analysis has proven to be not sensitive enough to discriminate between species of the BCC. Alternative species identification strategies such as recA-based PCR followed by restriction fragment length polymorphism analysis, although initially useful, have proven to be inaccurate with the increasing species diversity of the BCC. recA gene sequence analysis is more discriminatory and corroborates other biochemical and polyphasic means of taxonomic differentiation. However, it is limited by the fact that certain BCC species are subdivided into discrete recA sequence subgroups that may confuse clinical diagnoses. In this study, an effective approach is described for the rapid differentiation of BCC species from both environmental and clinical sources by means of a single-locus sequencing and PCR assay using fur as a target gene that provides sequence phylogenies that are species specific and, with few exceptions, not divided into subspecies clusters. This assay is specific and can be used to correctly determine the species status of BCC strains tested following sequencing and amplification of the fur gene by both general and species-specific primers. Based on our results, this typing strategy is simpler than and as sensitive as established tests currently in use clinically. This assay is useful for the rapid, definitive identification of all nine current BCC species and potentially novel species groups.
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15. |
( 1996 ) Molecular cloning and homology modeling of protocatechuate 3,4-dioxygenase from Pseudomonas marginata. PMID : 9022300 : Abstract >>
The genes that encode the alpha and beta subunits of protocatechuate 3,4-dioxygenase (3,4-PCD [EC 1.13.11.3]) were cloned from a Pseudomonas marginata genomic library. These genes pcaG and pcaH, were found when screening the library for hydrolase genes. The two open reading frames of the PCD genes could be identified adjacent to an esterase gene by sequence homology. A 1.7-kb KpnI/ApaI fragment, carrying pcaG and pcaH, was subcloned and the genes were functionally expressed in Escherichia coli. The deduced amino acid sequence shows high homology to previously determined amino acid sequences of bacterial protocatechuate 3,4-dioxygenases. A homology model based on the available crystal structure of the protocatechuate 3,4-dioxygenase from Pseudomonas aeruginosa shows high similarity with the binding and catalytic sites.
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16. |
Becka SA,
Zeiser ET,
Marshall SH,
Gatta JA,
Nguyen K,
Singh I,
Greco C,
Sutton GG,
Fouts DE,
LiPuma JJ,
Papp-Wallace KM,
( 2018 ) Sequence heterogeneity of the PenA carbapenemase in clinical isolates of Burkholderia multivorans. PMID : 29983287 : DOI : 10.1016/j.diagmicrobio.2018.06.005 PMC : PMC6173980 Abstract >>
Multidrug-resistant gram-negative pathogens are a significant health threat. Burkholderia spp. encompass a complex subset of gram-negative bacteria with a wide range of biological functions that include human, animal, and plant pathogens. The treatment of infections caused by Burkholderia spp. is problematic due to their inherent resistance to multiple antibiotics. The major �]-lactam resistance determinant expressed in Burkholderia spp. is a class A �]-lactamase of the PenA family. In this study, significant amino acid sequence heterogeneity was discovered in PenA (37 novel variants) within a panel of 48 different strains of Burkholderia multivorans isolated from individuals with cystic fibrosis. Phylogenetic analysis distributed the 37 variants into 5 groups based on their primary amino acid sequences. Amino acid substitutions were present throughout the entire �]-lactamase and did not congregate to specific regions of the protein. The PenA variants possessed 5 to 17 single amino acid changes. The N189S and S286I substitutions were most prevalent and found in all variants. Due to the sequence heterogeneity in PenA, a highly conserved peptide (18 amino acids) within PenA was chosen as the antigen for polyclonal antibody production in order to measure expression of PenA within the 48 clinical isolates of B. multivorans. Characterization of the anti-PenA peptide antibody, using immunoblotting approaches, exposed several unique features of this antibody (i.e., detected <500 pg of purified PenA, all 37 PenA variants in B. multivorans, and Pen-like �]-lactamases from other species within the Burkholderia cepacia complex). The significant sequence heterogeneity found in PenA may have occurred due to selective pressure (e.g., exposure to antimicrobial therapy) within the host. The contribution of these changes warrants further investigation.
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17. |
Lopes EF,
Da Costa JG,
Wolf IR,
Lima JPA,
Astolfi-Filho S,
( 2018 ) Draft Genome Sequence of Burkholderia gladioli Coa14, a Bacterium with Petroleum Bioremediation Potential Isolated from Coari Lake, Amazonas, Brazil. PMID : 29674552 : DOI : 10.1128/genomeA.00301-18 PMC : PMC5908936 Abstract >>
Burkholderia gladioli Coa14 is a bacterium isolated from water collected from Coari Lake (Amazonas, Brazil) that shows a capacity for survival in a medium containing only oil as a carbon source. Here, we report its draft genome sequence, highlighting some genes involved with petroleum derivative degradation.
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18. |
Flórez LV,
Scherlach K,
Miller IJ,
Rodrigues A,
Kwan JC,
Hertweck C,
Kaltenpoth M,
( 2018 ) An antifungal polyketide associated with horizontally acquired genes supports symbiont-mediated defense in Lagria villosa beetles. PMID : 29946103 : DOI : 10.1038/s41467-018-04955-6 PMC : PMC6018673 Abstract >>
Microbial symbionts are often a source of chemical novelty and can contribute to host defense against antagonists. However, the ecological relevance of chemical mediators remains unclear for most systems. Lagria beetles live in symbiosis with multiple strains of Burkholderia bacteria that protect their offspring against pathogens. Here, we describe the antifungal polyketide lagriamide, and provide evidence supporting that it is produced by an uncultured symbiont, Burkholderia gladioli Lv-StB, which is dominant in field-collected Lagria villosa. Interestingly, lagriamide is structurally similar to bistramides, defensive compounds found in marine tunicates. We identify a gene cluster that is probably involved in lagriamide biosynthesis, provide evidence for horizontal acquisition of these genes, and show that the naturally occurring symbiont strains on the egg are protective in the soil environment. Our findings highlight the potential of microbial symbionts and horizontal gene transfer as influential sources of ecological innovation.
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19. |
Dose B,
Niehs SP,
Scherlach K,
Flórez LV,
Kaltenpoth M,
Hertweck C,
( 2018 ) Unexpected Bacterial Origin of the Antibiotic Icosalide: Two-Tailed Depsipeptide Assembly in Multifarious Burkholderia Symbionts. PMID : 30160099 : DOI : 10.1021/acschembio.8b00600 Abstract >>
Icosalide is an unusual two-tailed lipocyclopeptide antibiotic that was originally isolated from a fungal culture. Yet, its biosynthesis and ecological function have remained enigmatic. By genome mining and metabolic profiling of a bacterial endosymbiont (Burkholderia gladioli) of the pest beetle Lagria villosa, we unveiled a bacterial origin of icosalide. Functional analysis of the biosynthetic gene locus revealed an unprecedented nonribosomal peptide synthetase (NRPS) that incorporates two �]-hydroxy acids by means of two starter condensation domains in different modules. This unusual assembly line, which may inspire new synthetic biology approaches, is widespread among many symbiotic Burkholderia species from diverse habitats. Biological assays showed that icosalide is active against entomopathogenic bacteria, thus adding to the chemical armory protecting beetle offspring. By creating a null mutant, we found that icosalide is a swarming inhibitor, which may play a role in symbiotic interactions and bears the potential for therapeutic applications.
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