Selection of Acinetobacter calcoaceticus mutants deficient in the p-hydroxybenzoate hydroxylase gene (pobA), a member of a supraoperonic cluster

Hartnett, Gail B.; Averhoff, Beate; Ornston, L N

doi:10.1128/jb.172.10.6160-6161.1990

Cited by 37 publications

(36 citation statements)

References 15 publications

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“…4), in agreement with the notion that coordinated expression of genes is an economical strategy for maintaining the fluidity of sequential enzymatic steps. This coordination may be particularly relevant for the gene encoding PcaB, because its substrate, ␤-carboxymuconate, is known to be a toxic intermediary metabolite (22). Examination of the regulatory strategies invoked by members of the Roseobacter lineage may reveal unique mechanisms to ensure stringent coordination of genes involved in the formation and degradation of ␤-carboxymuconate.…”

Section: Discussionmentioning

confidence: 99%

Diverse Organization of Genes of the β-Ketoadipate Pathway in Members of the Marine Roseobacter Lineage

Buchan¹,

Neidle

Moran³

2004

Appl Environ Microbiol

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Members of the Roseobacter lineage, an ecologically important marine clade within the class ␣-Proteobacteria, harbor genes for the protocatechuate branch of the ␤-ketoadipate pathway, a major catabolic route for lignin-related aromatic compounds. The genes of this pathway are typically clustered, although gene order varies among organisms. Here we characterize genes linked to pcaH and -G, which encode protocatechuate 3,4-dioxygenase, in eight closely related members of the Roseobacter lineage (pairwise 16S rRNA gene sequence identities, 92 to 99%). Sequence analysis of genomic fragments revealed five unique pca gene arrangements. Identical gene organization was found for isolates demonstrating species-level identity (i.e., >99% 16S rRNA gene similarity). In one isolate, six functionally related genes were clustered: pcaQ, pobA, pcaD, pcaC, pcaH, and pcaG. The remaining seven isolates lacked at least one of these genes in their clusters, although the relative order of the remaining genes was preserved. Three genes (pcaC, -H, and -G) were physically linked in all isolates. A highly conserved open reading frame (ORF) was found immediately downstream of pcaG in all eight isolates. Reverse transcription-PCR analysis of RNA from one isolate, Silicibacter pomeroyi DSS-3, provides evidence that this ORF is coexpressed with upstream pca genes. The absence of this ORF in similar bacterial pca gene clusters from diverse microbes suggests a niche-specific role for its protein product in Roseobacter group members. Collectively, these comparisons of bacterial pca gene organization illuminate a complex evolutionary history and underscore the widespread ecological importance of the encoded ␤-ketoadipate pathway.

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Section: Discussionmentioning

confidence: 99%

Diverse Organization of Genes of the β-Ketoadipate Pathway in Members of the Marine Roseobacter Lineage

Buchan¹,

Neidle

Moran³

2004

Appl Environ Microbiol

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“…Earlier investigations of the ␤-ketoadipate pathway suggested that short nucleotide sequence elements had been transferred within and among genes during their evolution (21,23,24,38,43,57). A model emerging from such findings proposed that a transposition might trigger secondary genetic events in which nucleotide sequence copies were acquired in DNA segments flanking junction points created by the transposition (42).…”

Section: Downloaded Frommentioning

confidence: 99%

“…It therefore is surprising that the biosynthetic AroD function in the gram-negative bacterium Acinetobacter calcoaceticus is served by a constitutively expressed enzyme that appears to be type II as judged by its thermostability (53). Catabolism of dehydroquinate in these bacteria is initiated by an inducible QuiB enzyme that, as indicated by its thermolability, appears to be type I (28,53,54).Further exploration of relationships among the A. calcoaceticus dehydratases was made possible by localization of the qui genes in a supraoperonic cluster between pca genes (associated with the catabolism of protocatechuate) and pob genes (associated with conversion of p-hydroxybenzoate to protocatechuate) (2,20,23). Engineered deletion mutations were introduced into A. calcoaceticus by natural transformation, and the properties of the resulting mutant strains allowed identification of quiA, the gene for the dehydrogenase that catalyzes the conversion of quinate and shikimate to dehydroquinate and dehydroshikimate, respectively ( Fig.…”

mentioning

confidence: 99%

“…Further exploration of relationships among the A. calcoaceticus dehydratases was made possible by localization of the qui genes in a supraoperonic cluster between pca genes (associated with the catabolism of protocatechuate) and pob genes (associated with conversion of p-hydroxybenzoate to protocatechuate) (2,20,23). Engineered deletion mutations were introduced into A. calcoaceticus by natural transformation, and the properties of the resulting mutant strains allowed identification of quiA, the gene for the dehydrogenase that catalyzes the conversion of quinate and shikimate to dehydroquinate and dehydroshikimate, respectively ( Fig.…”

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confidence: 99%

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Unusual ancestry of dehydratases associated with quinate catabolism in Acinetobacter calcoaceticus

Elsemore

Ornston

1995

J Bacteriol

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Catabolism of quinate to protocatechuate requires the consecutive action of quinate dehydrogenase (QuiA), dehydroquinate dehydratase (QuiB), and dehydroshikimate dehydratase (QuiC). Genes for catabolism of protocatechuate are encoded by the pca operon in the Acinetobacter calcoaceticus chromosome. Observations reported here demonstrate that A. calcoaceticus qui genes are clustered in the order quiBCXA directly downstream from the pca operon. Sequence comparisons indicate that quiX encodes a porin, but the specific function of this protein has not been clearly established. Properties of mutants created by insertion of ⍀ elements show that quiBC is expressed as part of a single transcript, but there is also an independent transcriptional initiation site directly upstream of quiA. The deduced amino acid sequence of QuiC does not resemble any other known sequence. A. calcoaceticus QuiB is most directly related to a family of enzymes with identical catalytic activity and biosynthetic AroD function in coliform bacteria. Evolution of A. calcoaceticus quiB appears to have been accompanied by fusion of a leader sequence for transport of the encoded protein into the inner membrane, and the location of reactions catalyzed by the mature enzyme may account for the failure of A. calcoaceticus aroD to achieve effective complementation of null mutations in quiB. Analysis of a genetic site where a DNA segment encoding a leader sequence was transposed adds to evidence suggesting horizontal transfer of nucleotide sequences within genes during evolution.Dehydroquinate dehydratase (QuiB) and dehydroshikimate dehydratase (QuiC) catalyze consecutive reactions allowing growth of microorganisms with quinate by its conversion to protocatechuate ( Fig. 1) and subsequent metabolism by the ␤-ketoadipate pathway (41, 52). The enzymatic activity of QuiB is identical to that of AroD, an enzyme that catalyzes biosynthetic formation of dehydroshikimate (Fig. 1). Enzymes with similar catalytic activities often can be traced to a common ancestor (32), and the similarity of dehydratases associated with dehydroshikimate metabolism raised the possibility that a single ancestral protein was the evolutionary precursor of two or more of these enzymes.In contrast to this prediction, biosynthetic dehydroquinate dehydratases differ substantially from catabolic enzymes with this activity (18,30). With the exception of the dehydroquinate dehydratases of gram-positive bacteria (13, 15), enzymes with the biosynthetic function indicated as AroD in Fig. 1 are classified as type I and are thermolabile, a property that distinguishes them from the isofunctional type II enzymes which are heat stable and mediate the activity indicated as QuiB in Fig. 1 Some gram-negative bacteria elaborate a single dehydroquinate dehydratase associated solely with the biosynthetic function indicated as AroD in Fig. 1. Genes for this enzyme from Enterococcus faecalis (3), Salmonella typhi (51), and Escherichia coli (10) have been sequenced and shown to encode type I enzymes. These fi...

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“…Additional benefits are provided by quirks of aromatic catabolism that allow for positive selection of mutants that have lost specific metabolic functions (12,42). Ruben Kok and David D'Argenio first put these technical advantages together by applying random PCR mutagenesis to determine amino acid residues that were essential for the function of a repressor, PobR (20).…”

Section: Acinetobacter Re-entersmentioning

confidence: 99%

Conversations with a Psychiatrist

Ornston

2010

Annu. Rev. Microbiol.

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This reminiscence is a celebration of my good fortune in family, biological and scientific. The biological family into which I was born gave me a strong start, although not entirely in the direction I took. I swerved from an anticipated career in medical practice into continuing delight in those who became my scientific family in microbiology. The families changed, yet they continued to give me strength and inspiration. In my youth, I was gently guided by mentors who gave me freedom to explore where curiosity beckoned. I hope I repaid this gift to my laboratory colleagues who enlightened me over the years. I learned much from my students, and my horizons were extended by industrial scientists. It has been my particular good fortune to learn the workings of microorganisms and microbiologists as editor of Journal of Bacteriology for a decade, as editor-in-chief of Applied and Environmental Microbiology for a decade, and as editor of Annual Review of Microbiology for a quarter of a century.

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Selection of Acinetobacter calcoaceticus mutants deficient in the p-hydroxybenzoate hydroxylase gene (pobA), a member of a supraoperonic cluster

Cited by 37 publications

References 15 publications

Diverse Organization of Genes of the β-Ketoadipate Pathway in Members of the Marine Roseobacter Lineage

Diverse Organization of Genes of the β-Ketoadipate Pathway in Members of the Marine Roseobacter Lineage

Unusual ancestry of dehydratases associated with quinate catabolism in Acinetobacter calcoaceticus

Conversations with a Psychiatrist

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