Papers by Paulina Estrada
Burkholderia is a diverse and dynamic genus, containing pathogenic species as well as species tha... more Burkholderia is a diverse and dynamic genus, containing pathogenic species as well as species that form complex interactions with plants. Pathogenic strains, such as B. pseudomallei and B. mallei, can cause serious disease in mammals, while other Burkholderia strains are opportunistic pathogens, infecting humans or animals with a compromised immune system. Although some of the opportunistic Burkholderia pathogens are known to promote plant growth and even fix nitrogen, the risk of infection to infants, the elderly, and people who are immunocompromised has not only resulted in a restriction on their use, but has also limited the application of non-pathogenic, symbiotic species, several of which nodulate legume roots or have positive effects on plant growth. However, recent phylogenetic analyses have demonstrated that Burkholderia species separate into distinct lineages, suggesting the possibility for safe use of certain symbiotic species in agricultural contexts. A number of environm...
Genes, 2018
sensu lato is a large and complex group, containing pathogenic, phytopathogenic, symbiotic and no... more sensu lato is a large and complex group, containing pathogenic, phytopathogenic, symbiotic and non-symbiotic strains from a very wide range of environmental (soil, water, plants, fungi) and clinical (animal, human) habitats. Its taxonomy has been evaluated several times through the analysis of 16S rRNA sequences, concantenated 4⁻7 housekeeping gene sequences, and lately by genome sequences. Currently, the division of this group into , , and is strongly supported by genome analysis. These new genera broadly correspond to the various habitats/lifestyles of s.l., e.g., all the plant beneficial and environmental (PBE) strains are included in (which also includes all the N₂-fixing legume symbionts) and , while most of the human and animal pathogens are retained in sensu stricto. However, none of these genera can accommodate two important groups of species. One of these includes the closely related and , which are both symbionts of the fungal phytopathogen . The second group comprises the...
Annals of Microbiology, 2015
The genus Burkholderia is a large group of species of bacteria that inhabit a wide range of envir... more The genus Burkholderia is a large group of species of bacteria that inhabit a wide range of environments. We previously recommended, based on multilocus sequence analysis, that the genus be separated into two distinct groups-one that consists predominantly of human, plant, and animal pathogens, including several opportunistic pathogens, and a second, much larger group of species comprising plant-associated beneficial and environmental species that are primarily known not to be pathogenic. This second group of species is found mainly in soils, frequently in association with plants as plant growth-promoting bacteria. They also possess genetic traits that bestow them with an added potential for agriculture and soil restoration, such as nitrogen fixation, phosphate solubilization, iron sequestration, and xenobiotic degradation, and they are not pathogenic. In this review, we present an update of current information on this second group of Burkholderia species, with the goal of focusing attention on their use in agriculture and environmental remediation. We describe their distribution in the environment, their taxonomy and genetic features, and their relationship with plants as either associative nitrogen-fixers or legume-nodulating/nitrogen-fixing bacteria. We also propose that a concerted and coordinated effort be made by researchers on Burkholderia to determine if a definitive taxonomic split of this very large genus is justified, especially now as we describe here for the first time intermediate groups based upon their 16S rRNA sequences. We need to learn more about the plant-associated Burkholderia strains regarding their potential for pathogenicity, especially in those strains intermediate between the two groups, and to discover whether gene exchange occurs between the symbiotic and pathogenic Burkholderia species. The latter studies will require both field and laboratory analyses of gene loss and gain.
Archives of Microbiology, 2014
During a survey of plant-associated bacteria in northeast Mexico, a group of 13 bacteria was isol... more During a survey of plant-associated bacteria in northeast Mexico, a group of 13 bacteria was isolated from agave, maize and sorghum plants rhizosphere. This group of strains was related to Cupriavidus respiraculi (99.4 %), but a polyphasic investigation based on DnA-DnA hybridization analysis, other genotypic studies and phenotypic features showed that this group of strains actually belongs to a new Cupriavidus species. Consequently, taking all the results together, the description of Cupriavidus plantarum sp. nov. is proposed.
The Journal of Microbiology, 2011
The presence of Burkholderia, Cupriavidus, and Ralstonia species in northeastern Mexico was inves... more The presence of Burkholderia, Cupriavidus, and Ralstonia species in northeastern Mexico was investigated. An analysis of the root surrounding soil from different agricultural plants led to the isolation of Burkholderia and Cupriavidus species but no Ralstonia strains. Most Cupriavidus species were unknown and grouped into two clusters according to ARDRA profiles. The 16S rRNA sequence analysis showed that the Cupriavidus isolates were highly related among them and with different Cupriavidus species with validated names. However, SDS-PAGE profiles were distinct among the different ARDRA profiles and to other Cupriavidus species examined, suggesting new species in the genus. This shows that Cupriavidus is more widely associated with plants than previously appreciated. The BCC isolate was 99% similar to B. cenocepacia by recA sequence analysis. Additionally, most Cupriavidus strains from the two largest groups grew on media containing up to 0.1 mg/ml of copper, 10.0 mg/ml arsenic and 1.0 mg/ml zinc. Burkholderia strains grew on media containing up to 10.0 mg/ml zinc, 5.0 mg/ml arsenic and 0.1 mg/ml copper.
Systematic and Applied Microbiology, 2012
A group of 20 bacterial strains was isolated from the rhizosphere of different agricultural plant... more A group of 20 bacterial strains was isolated from the rhizosphere of different agricultural plants growing in alkaline soils in the northeast of Mexico. The phylogenetic analysis of the 16S rRNA gene sequence from four strains showed that this novel group belonged to the Cupriavidus genus, with C. taiwanensis (∼98.9%) and C. necator (∼98.8%) as the closest species. However, DNA-DNA reassociation values were less than 20%. The novel group did not fix nitrogen and lacked nifH and nodA genes, unlike C. taiwanensis. Wholecell protein patterns were highly similar among the 20 strains but different from the closest Cupriavidus species. BOX-PCR patterns were distinct among the 20 strains but also differed from other Cupriavidus type species. The major cellular fatty acids from strains ASC-732 T and SLV-2362 were C 16:0 , C 18:1 7c/12t/9t and C 16:1 7c and/or C 15:0 iso 2OH. The major polar lipids consisted of phosphatidylglycerol, cardiolipin, phosphatidylethanolamine, 2-hydroxylated-phosphatidylethanolamine and an unknown aminolipid. The DNA G+C content of strain ASC-732 T was 66.8 mol%. All 20 strains grew in the presence of 5-10 mg mL -1 arsenic, 1 mg mL -1 zinc, and 0.1 mg mL -1 copper. Consequently, the group of strains was considered to represent a novel species for which the name Cupriavidus alkaliphilus sp. nov. is proposed.
Molecular Plant-Microbe Interactions, 2011
Rhizobia form specialized nodules on the roots of legumes (family Fabaceae) and fix nitrogen in e... more Rhizobia form specialized nodules on the roots of legumes (family Fabaceae) and fix nitrogen in exchange for carbon from the host plant. Although the majority of legumes form symbioses with members of genus Rhizobium and its relatives in class Alphaproteobacteria, some legumes, such as those in the large genus Mimosa, are nodulated predominantly by betaproteobacteria in the genera Burkholderia and Cupriavidus. The principal centers of diversity of these bacteria are in central Brazil and South Africa. Molecular phylogenetic studies have shown that betaproteobacteria have existed as legume symbionts for approximately 50 million years, and that, although they have a common origin, the symbiosis genes in both subclasses have evolved separately since then. Additionally, some species of genus Burkholderia, such as B. phymatum, are highly promiscuous, effectively nodulating several important legumes, including common bean (Phaseolus vulgaris). In contrast to genus Burkholderia, only one s...
INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY, 2004
In an ecological survey of nitrogen-fixing bacteria isolated from the rhizosphere and as endophyt... more In an ecological survey of nitrogen-fixing bacteria isolated from the rhizosphere and as endophytes of sugarcane, maize and teosinte plants in Brazil, Mexico and South Africa, a new phylogenetically homogeneous group of N2-fixing bacteria was identified within the genus Burkholderia. This polyphasic taxonomic study included microscopic and colony morphology, API 20NE tests and growth on different culture media at different pH and temperatures, as well as carbon source assimilation tests and whole-cell protein pattern analysis. Analysis of 16S rRNA gene sequences showed 99·2–99·9 % similarity within the novel species and 97·2 % similarity to the closest related species, Burkholderia sacchari. The novel species was composed of four distinct amplified 16S rDNA restriction analysis groups. The DNA–DNA reassociation values within the novel species were greater than 70 % and less than 42 % for the closest related species, B. sacchari. Based on these results and on many phenotypic characte...
INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY, 2012
Phylogenetic analysis of the 16S rRNA gene sequences of strains TE26T and K6 belonging to Wauters... more Phylogenetic analysis of the 16S rRNA gene sequences of strains TE26T and K6 belonging to Wautersia numazuensis Kageyama et al. 2005 showed the strains to be deeply intermingled among the species of the genus Cupriavidus . The comparison showed that strain TE26T was closely related to the type strains of Cupriavidus pinatubonensis (99.1 % 16S rRNA gene sequence similarity), C. basilensis (98.7 %), C. necator (98.7 %) and C. gilardii (98.0 %). However, DNA–DNA hybridization experiments (less than 20 % relatedness) demonstrated that strain TE26T is different from these Cupriavidus species. A comparative phenotypic and chemotaxonomic analysis (based on fatty acid profiles) in combination with the 16S rRNA gene sequence phylogenetic analysis and the DNA–DNA hybridization results supported the incorporation of Wautersia numazuensis into the genus Cupriavidus as Cupriavidus numazuensis comb. nov.; the type strain is TE26T ( = LMG 26411T = DSM 15562T = CIP 108892T).
Chemistry & Biology, 2011
Under control of the Gac regulatory system, Pseudomonas putida RW10S1 produces promysalin to prom... more Under control of the Gac regulatory system, Pseudomonas putida RW10S1 produces promysalin to promote its own swarming and biofilm formation, and to selectively inhibit many other pseudomonads, including the opportunistic pathogen Pseudomonas aeruginosa. This amphipathic antibiotic is composed of salicylic acid and 2,8-dihydroxymyristamide bridged by a unique 2-pyrroline-5-carboxyl moiety. In addition to enzymes for salicylic acid synthesis and activation, the biosynthetic gene cluster encodes divergent type II fatty acid biosynthesis components, unusual fatty acid-tailoring enzymes (two Rieske-type oxygenases and an amidotransferase), an enzyme resembling a proline-loading module of nonribosomal peptide synthetases, and the first prokaryotic member of the BAHD family of plant acyltransferases. Identification of biosynthetic intermediates enabled to propose a pathway for synthesis of this bacterial colonization factor.
Antonie van Leeuwenhoek, 2013
Burkholderia comprises more than 60 species of environmental, clinical, and agro-biotechnological... more Burkholderia comprises more than 60 species of environmental, clinical, and agro-biotechnological relevance. Previous phylogenetic analyses of 16S rRNA, recA, gyrB, rpoB, and acdS gene sequences as well as genome sequence comparisons of different Burkholderia species have revealed two major species clusters. In this study, we undertook a multilocus sequence analysis of 77 type and reference strains of Burkholderia using atpD, gltB, lepA, and recA genes in combination with the 16S rRNA gene sequence and employed maximum likelihood and neighbor-joining criteria to test this further. The phylogenetic analysis revealed, with high supporting values, distinct lineages within the genus Burkholderia. The two large groups were named A and B, whereas the B. rhizoxinica/B. endofungorum, and B. andropogonis groups consisted of two and one species, respectively. The group A encompasses several plant-associated and saprophytic bacterial species. The group B comprises the B. cepacia complex (opportunistic human pathogens), the B. pseudomallei subgroup, which includes both human and animal pathogens, and an assemblage of plant pathogenic species. The distinct lineages present in Burkholderia suggest that each group might represent a different genus. However, it will be necessary to analyze the full set of Burkholderia species and explore whether enough phenotypic features exist among the different clusters to propose that these groups should be considered separate genera. Burkholderia cepacia complex ML Maximum likelihood NJ Neighbor-joining
Current Microbiology, 2013
Burkholderia comprises more than 60 species of environmental, clinical, and agro-biotechnological... more Burkholderia comprises more than 60 species of environmental, clinical, and agro-biotechnological relevance. Previous phylogenetic analyses of 16S rRNA, recA, gyrB, rpoB, and acdS gene sequences as well as genome sequence comparisons of different Burkholderia species have revealed two major species clusters. In this study, we undertook a multilocus sequence analysis of 77 type and reference strains of Burkholderia using atpD, gltB, lepA, and recA genes in combination with the 16S rRNA gene sequence and employed maximum likelihood and neighbor-joining criteria to test this further. The phylogenetic analysis revealed, with high supporting values, distinct lineages within the genus Burkholderia. The two large groups were named A and B, whereas the B. rhizoxinica/B. endofungorum, and B. andropogonis groups consisted of two and one species, respectively. The group A encompasses several plant-associated and saprophytic bacterial species. The group B comprises the B. cepacia complex (opportunistic human pathogens), the B. pseudomallei subgroup, which includes both human and animal pathogens, and an assemblage of plant pathogenic species. The distinct lineages present in Burkholderia suggest that each group might represent a different genus. However, it will be necessary to analyze the full set of Burkholderia species and explore whether enough phenotypic features exist among the different clusters to propose that these groups should be considered separate genera. Abbreviations MLSA Multilocus sequence analysis BCC Burkholderia cepacia complex ML Maximum likelihood NJ Neighbor-joining Electronic supplementary material The online version of this article (
Burkholderia sensu lato is a large and complex group, containing pathogenic, phytopathogenic, sym... more Burkholderia sensu lato is a large and complex group, containing pathogenic, phytopathogenic, symbiotic and non-symbiotic strains from a very wide range of environmental (soil, water, plants, fungi) and clinical (animal, human) habitats. Its taxonomy has been evaluated several times through the analysis of 16S rRNA sequences, concantenated 4–7 housekeeping gene sequences, and lately by genome sequences. Currently, the division of this group into Burkholderia, Caballeronia, Paraburkholderia, and Robbsia is strongly supported by genome analysis. These new genera broadly correspond to the various habitats/lifestyles of Burkholderia s.l., e.g., all the plant beneficial and environmental (PBE) strains are included in Paraburkholderia (which also includes all the N 2-fixing legume symbionts) and Caballeronia, while most of the human and animal pathogens are retained in Burkholderia sensu stricto. However, none of these genera can accommodate two important groups of species. One of these includes the closely related Paraburkholderia rhizoxinica and Paraburkholderia endofungorum, which are both symbionts of the
Paraburkholderia caballeronis is a plant-associated bacterium. Strain TNe-841 T was isolated from... more Paraburkholderia caballeronis is a plant-associated bacterium. Strain TNe-841 T was isolated from the rhizosphere of tomato (Solanum lycopersicum L. var. lycopersicum) growing in Nepantla Mexico State. Initially this bacterium was found to effectively nodulate Phaseolus vulgaris L. However, from an analysis of the genome of strain TNe-841 T and from repeat inoculation experiments, we found that this strain did not nodulate bean and also lacked nodulation genes, suggesting that the genes were lost. The genome consists of 7,115,141 bp with a G + C content of 67.01%. The sequence includes 6251 protein-coding genes and 87 RNA genes.
Current Microbiology, 2013
Burkholderia comprises more than 60 species of environmental, clinical, and agro-biotechnological... more Burkholderia comprises more than 60 species of environmental, clinical, and agro-biotechnological relevance. Previous phylogenetic analyses of 16S rRNA, recA, gyrB, rpoB, and acdS gene sequences as well as genome sequence comparisons of different Burkholderia species have revealed two major species clusters. In this study, we undertook a multilocus sequence analysis of 77 type and reference strains of Burkholderia using atpD, gltB, lepA, and recA genes in combination with the 16S rRNA gene sequence and employed maximum likelihood and neighbor-joining criteria to test this further. The phylogenetic analysis revealed, with high supporting values, distinct lineages within the genus Burkholderia. The two large groups were named A and B, whereas the B. rhizoxinica/B. endofungorum, and B. andropogonis groups consisted of two and one species, respectively. The group A encompasses several plant-associated and saprophytic bacterial species. The group B comprises the B. cepacia complex (opportunistic human pathogens), the B. pseudomallei subgroup, which includes both human and animal pathogens, and an assemblage of plant pathogenic species. The distinct lineages present in Burkholderia suggest that each group might represent a different genus. However, it will be necessary to analyze the full set of Burkholderia species and explore whether enough phenotypic features exist among the different clusters to propose that these groups should be considered separate genera.
Molecular plant-microbe interactions : MPMI, 2011
Rhizobia form specialized nodules on the roots of legumes (family Fabaceae) and fix nitrogen in e... more Rhizobia form specialized nodules on the roots of legumes (family Fabaceae) and fix nitrogen in exchange for carbon from the host plant. Although the majority of legumes form symbioses with members of genus Rhizobium and its relatives in class Alphaproteobacteria, some legumes, such as those in the large genus Mimosa, are nodulated predominantly by betaproteobacteria in the genera Burkholderia and Cupriavidus. The principal centers of diversity of these bacteria are in central Brazil and South Africa. Molecular phylogenetic studies have shown that betaproteobacteria have existed as legume symbionts for approximately 50 million years, and that, although they have a common origin, the symbiosis genes in both subclasses have evolved separately since then. Additionally, some species of genus Burkholderia, such as B. phymatum, are highly promiscuous, effectively nodulating several important legumes, including common bean (Phaseolus vulgaris). In contrast to genus Burkholderia, only one species of genus Cupriavidus (C. taiwanensis) has so far been shown to nodulate legumes. The recent availability of the genome sequences of C. taiwanensis, B. phymatum, and B. tuberum has paved the way for a more detailed analysis of the evolutionary and mechanistic differences between nodulating strains of alpha-and betaproteobacteria.
The genus Burkholderia is a large group of species of bacteria that inhabit a wide range of envir... more The genus Burkholderia is a large group of species of bacteria that inhabit a wide range of environments. We previously recommended, based on multilocus sequence anal- ysis, that the genus be separated into two distinct groups—one that consists predominantly of human, plant, and animal path- ogens, including several opportunistic pathogens, and a sec- ond, much larger group of species comprising plant-associated beneficial and environmental species that are primarily known not to be pathogenic. This second group of species is found mainly in soils, frequently in association with plants as plant growth-promoting bacteria. They also possess genetic traits that bestow them with an added potential for agriculture and soil restoration, such as nitrogen fixation, phosphate solubili- zation, iron sequestration, and xenobiotic degradation, and they are not pathogenic. In this review, we present an update of current information on this second group of Burkholderia species, with the goal of focusing attention on their use in agriculture and environmental remediation. We describe their distribution in the environment, their taxonomy and genetic eatures, and their relationship with plants as either associative nitrogen-fixers or legume-nodulating/nitrogen-fixing bacteria. We also propose that a concerted and coordinated effort be made by researchers on Burkholderia to determine if a defin- itive taxonomic split of this very large genus is justified, es- pecially now as we describe here for the first time intermediate groups based upon their 16S rRNA sequences. We need to learn more about the plant-associated Burkholderia strains regarding their potential for pathogenicity, especially in those strains intermediate between the two groups, and to discover whether gene exchange occurs between the symbiotic and pathogenic Burkholderia species. The latter studies will re- quire both field and laboratory analyses of gene loss and gain.
Chemistry & Biology, 2011
Under control of the Gac regulatory system, Pseudomonas putida RW10S1 produces promysalin to prom... more Under control of the Gac regulatory system, Pseudomonas putida RW10S1 produces promysalin to promote its own swarming and biofilm formation, and to selectively inhibit many other pseudomonads, including the opportunistic pathogen Pseudomonas aeruginosa. This amphipathic antibiotic is composed of salicylic acid and 2,8-dihydroxymyristamide bridged by a unique 2-pyrroline-5-carboxyl moiety. In addition to enzymes for salicylic acid synthesis and activation, the biosynthetic gene cluster encodes divergent type II fatty acid biosynthesis components, unusual fatty acid-tailoring enzymes (two Rieske-type oxygenases and an amidotransferase), an enzyme resembling a proline-loading module of nonribosomal peptide synthetases, and the first prokaryotic member of the BAHD family of plant acyltransferases. Identification of biosynthetic intermediates enabled to propose a pathway for synthesis of this bacterial colonization factor.
Rhizobia form specialized nodules on the roots of legumes
(family Fabaceae) and fix nitrogen in e... more Rhizobia form specialized nodules on the roots of legumes
(family Fabaceae) and fix nitrogen in exchange for carbon
from the host plant. Although the majority of legumes
form symbioses with members of genus Rhizobium and its
relatives in class Alphaproteobacteria, some legumes, such
as those in the large genus Mimosa, are nodulated predominantly
by betaproteobacteria in the genera Burkholderia
and Cupriavidus. The principal centers of diversity of
these bacteria are in central Brazil and South Africa. Molecular
phylogenetic studies have shown that betaproteobacteria
have existed as legume symbionts for approximately
50 million years, and that, although they have a
common origin, the symbiosis genes in both subclasses
have evolved separately since then. Additionally, some species
of genus Burkholderia, such as B. phymatum, are
highly promiscuous, effectively nodulating several important
legumes, including common bean (Phaseolus vulgaris).
In contrast to genus Burkholderia, only one species of genus
Cupriavidus (C. taiwanensis) has so far been shown to
nodulate legumes. The recent availability of the genome
sequences of C. taiwanensis, B. phymatum, and B. tuberum
has paved the way for a more detailed analysis of the evolutionary
and mechanistic differences between nodulating
strains of alpha- and betaproteobacteria. Initial analyses of
genome sequences have suggested that plant-associated
Burkholderia spp. have lower G+C contents than
Burkholderia spp. that are opportunistic human pathogens,
thus supporting previous suggestions that the plant- and
human-associated groups of Burkholderia actually belong
in separate genera.
Under control of the Gac regulatory system, Pseudomonas
putida RW10S1 produces promysalin to
prom... more Under control of the Gac regulatory system, Pseudomonas
putida RW10S1 produces promysalin to
promote its own swarming and biofilm formation,
and to selectively inhibitmany other pseudomonads,
including the opportunistic pathogen Pseudomonas
aeruginosa. This amphipathic antibiotic is composed
of salicylic acid and 2,8-dihydroxymyristamide
bridged by a unique 2-pyrroline-5-carboxyl moiety.
In addition to enzymes for salicylic acid synthesis
and activation, the biosynthetic gene cluster
encodes divergent type II fatty acid biosynthesis
components, unusual fatty acid-tailoring enzymes
(two Rieske-type oxygenases and an amidotransferase),
an enzyme resembling a proline-loading
module of nonribosomal peptide synthetases, and
the first prokaryotic member of the BAHD family of
plant acyltransferases. Identification of biosynthetic
intermediates enabled to propose a pathway for
synthesis of this bacterial colonization factor.
Uploads
Papers by Paulina Estrada
(family Fabaceae) and fix nitrogen in exchange for carbon
from the host plant. Although the majority of legumes
form symbioses with members of genus Rhizobium and its
relatives in class Alphaproteobacteria, some legumes, such
as those in the large genus Mimosa, are nodulated predominantly
by betaproteobacteria in the genera Burkholderia
and Cupriavidus. The principal centers of diversity of
these bacteria are in central Brazil and South Africa. Molecular
phylogenetic studies have shown that betaproteobacteria
have existed as legume symbionts for approximately
50 million years, and that, although they have a
common origin, the symbiosis genes in both subclasses
have evolved separately since then. Additionally, some species
of genus Burkholderia, such as B. phymatum, are
highly promiscuous, effectively nodulating several important
legumes, including common bean (Phaseolus vulgaris).
In contrast to genus Burkholderia, only one species of genus
Cupriavidus (C. taiwanensis) has so far been shown to
nodulate legumes. The recent availability of the genome
sequences of C. taiwanensis, B. phymatum, and B. tuberum
has paved the way for a more detailed analysis of the evolutionary
and mechanistic differences between nodulating
strains of alpha- and betaproteobacteria. Initial analyses of
genome sequences have suggested that plant-associated
Burkholderia spp. have lower G+C contents than
Burkholderia spp. that are opportunistic human pathogens,
thus supporting previous suggestions that the plant- and
human-associated groups of Burkholderia actually belong
in separate genera.
putida RW10S1 produces promysalin to
promote its own swarming and biofilm formation,
and to selectively inhibitmany other pseudomonads,
including the opportunistic pathogen Pseudomonas
aeruginosa. This amphipathic antibiotic is composed
of salicylic acid and 2,8-dihydroxymyristamide
bridged by a unique 2-pyrroline-5-carboxyl moiety.
In addition to enzymes for salicylic acid synthesis
and activation, the biosynthetic gene cluster
encodes divergent type II fatty acid biosynthesis
components, unusual fatty acid-tailoring enzymes
(two Rieske-type oxygenases and an amidotransferase),
an enzyme resembling a proline-loading
module of nonribosomal peptide synthetases, and
the first prokaryotic member of the BAHD family of
plant acyltransferases. Identification of biosynthetic
intermediates enabled to propose a pathway for
synthesis of this bacterial colonization factor.
(family Fabaceae) and fix nitrogen in exchange for carbon
from the host plant. Although the majority of legumes
form symbioses with members of genus Rhizobium and its
relatives in class Alphaproteobacteria, some legumes, such
as those in the large genus Mimosa, are nodulated predominantly
by betaproteobacteria in the genera Burkholderia
and Cupriavidus. The principal centers of diversity of
these bacteria are in central Brazil and South Africa. Molecular
phylogenetic studies have shown that betaproteobacteria
have existed as legume symbionts for approximately
50 million years, and that, although they have a
common origin, the symbiosis genes in both subclasses
have evolved separately since then. Additionally, some species
of genus Burkholderia, such as B. phymatum, are
highly promiscuous, effectively nodulating several important
legumes, including common bean (Phaseolus vulgaris).
In contrast to genus Burkholderia, only one species of genus
Cupriavidus (C. taiwanensis) has so far been shown to
nodulate legumes. The recent availability of the genome
sequences of C. taiwanensis, B. phymatum, and B. tuberum
has paved the way for a more detailed analysis of the evolutionary
and mechanistic differences between nodulating
strains of alpha- and betaproteobacteria. Initial analyses of
genome sequences have suggested that plant-associated
Burkholderia spp. have lower G+C contents than
Burkholderia spp. that are opportunistic human pathogens,
thus supporting previous suggestions that the plant- and
human-associated groups of Burkholderia actually belong
in separate genera.
putida RW10S1 produces promysalin to
promote its own swarming and biofilm formation,
and to selectively inhibitmany other pseudomonads,
including the opportunistic pathogen Pseudomonas
aeruginosa. This amphipathic antibiotic is composed
of salicylic acid and 2,8-dihydroxymyristamide
bridged by a unique 2-pyrroline-5-carboxyl moiety.
In addition to enzymes for salicylic acid synthesis
and activation, the biosynthetic gene cluster
encodes divergent type II fatty acid biosynthesis
components, unusual fatty acid-tailoring enzymes
(two Rieske-type oxygenases and an amidotransferase),
an enzyme resembling a proline-loading
module of nonribosomal peptide synthetases, and
the first prokaryotic member of the BAHD family of
plant acyltransferases. Identification of biosynthetic
intermediates enabled to propose a pathway for
synthesis of this bacterial colonization factor.