The Haemophilus influenzae sxy-1 mutation is in a newly identified gene essential for competence

Williams, Paul; Bannister, Laura A.; Redfield, Rosemary J.

doi:10.1128/jb.176.22.6789-6794.1994

Cited by 36 publications

(40 citation statements)

References 16 publications

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“…Competence genes in strain RR554 are constitutively expressed due to overproduction of the positive regulator Sxy from the plasmid (Williams et al 1994). Cells were cultured in brain-heart infusion supplemented with hemin and NAD (sBHI) as described (Poje and Redfield 2003a).…”

Section: Methodsmentioning

confidence: 99%

Bacterial DNA Uptake Sequences Can Accumulate by Molecular Drive Alone

Maughan¹,

Wilson²,

Redfield

2010

Genetics

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Uptake signal sequences are DNA motifs that promote DNA uptake by competent bacteria in the family Pasteurellaceae and the genus Neisseria. The genomes of these bacteria contain many copies of their canonical uptake sequence (often .100-fold overrepresentation), so the bias of the uptake machinery causes cells to prefer DNA derived from close relatives over DNA from other sources. However, the molecular and evolutionary forces responsible for the abundance of uptake sequences in these genomes are not well understood, and their presence is not easily explained by any of the current models of the evolution of competence. Here we describe use of a computer simulation model to thoroughly evaluate the simplest explanation for uptake sequences, that they accumulate in genomes by a form of molecular drive generated by biased DNA uptake and evolutionarily neutral (i.e., unselected) recombination. In parallel we used an unbiased search algorithm to characterize genomic uptake sequences and DNA uptake assays to refine the Haemophilus influenzae uptake specificity. These analyses showed that biased uptake and neutral recombination are sufficient to drive uptake sequences to high densities, with the spacings, stabilities, and strong consensuses typical of uptake sequences in real genomes. This result greatly simplifies testing of hypotheses about the benefits of DNA uptake, because it explains how genomes could have passively accumulated sequences matching the bias of their uptake machineries.

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Section: Methodsmentioning

confidence: 99%

Bacterial DNA Uptake Sequences Can Accumulate by Molecular Drive Alone

Maughan¹,

Wilson²,

Redfield

2010

Genetics

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“…The product of HI0601 tfoX (sxy) is required for transcription of operons containing the CRE, and insertions into tfoX completely abolish transformation development (32,61,63). Adenylate cyclase, encoded by the cya gene, is also required for competence development but the transformation-defective phenotype expressed by the cya mutant can be suppressed by addition of exogenous cAMP (15).…”

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confidence: 99%

Characterization of Three New Competence-Regulated Operons in Haemophilus influenzae

VanWagoner

Whitby²,

Morton³

et al. 2004

J Bacteriol

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Haemophilus influenzae is one of a growing number of bacteria in which the natural ability to uptake exogenous DNA for potential genomic transformation has been recognized. To date, several operons involved in transformation in this organism have been described. These operons are characterized by a conserved 22-bp regulatory element upstream of the first gene and are induced coincident with transfer from rich to nutrientdepleted media. The previously identified operons comprised genes encoding proteins that include members of the type II secretion system and type IV pili, shown to be essential for transformation in other bacteria, and other proteins previously identified as required for transformation in H. influenzae. In the present study, three novel competence operons were identified by comparative genomics and transcriptional analysis. These operons have been further characterized by construction of null mutants and examination of the resulting transformation phenotypes. The putative protein encoded by the HI0366 gene was shown to be essential for DNA uptake, but not binding, and is homologous to a protein shown to be required for pilus biogenesis and twitching motility in Pseudomonas aeruginosa. An insertion in HI0939 abolished both DNA binding and uptake. The predicted product of this gene shares characteristics with PulJ, a pseudopilin involved in pullulanase export in Klebsiella oxytoca.

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“…The cAMP-CRP (cyclic-AMP receptor protein) complex helps to promote their expression and induce competence (the ability to take up and incorporate DNA) (Chandler, 1992;Redfield et al, 2005;Cameron and Redfield, 2006). Induction of competence in H. influenzae also requires the product of the tfoX (sxy) gene (Redfield, 1991;Williams et al, 1994;Zulty and Barcak, 1995;Redfield et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

“…The TfoX protein of H. influenzae itself does not seem to bind DNA, but to interact with CRP (Macfadyen, 2000;Redfield et al, 2005). Plasmids containing the tfoX gene make H. influenzae cells constitutively competent (Williams et al, 1994;Zulty and Barcak, 1995).…”

Section: Introductionmentioning

confidence: 99%

tfoX (sxy)-dependent transformation of Aggregatibacter (Actinobacillus) actinomycetemcomitans

Bhattacharjee

Fine

Figurski

2007

Gene

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AbstracttfoX (sxy) is a regulatory gene needed to turn on competence genes. Aggregatibacter (Actinobacillus) actinomycetemcomitans has a tfoX gene that is important for transformation. We cloned this gene on an IncQ plasmid downstream of the inducible tac promoter. When this plasmid was resident in cells of A. actinomycetemcomitans and tfoX was induced, the cells became competent for transformation. Several strains of A. actinomycetemcomitans, including different serotypes, as well as rough (adherent) and isogenic smooth (nonadherent) forms were tested. Only our two serotype f strains failed to be transformed. With the other strains, we could easily get transformants with extrachromosomal plasmid DNA when closed circular, replicative plasmid carrying an uptake signal sequence (USS) was used. When a replicative plasmid carrying a USS and cloned DNA from the chromosome of A. actinomycetemcomitans was linearized by digestion with a restriction endonuclease or when genomic DNA was used directly, the outcome was allelic exchange. To facilitate allelic exchange, we constructed a suicide plasmid (pMB78) that does not replicate in A. actinomycetemcomitans and carries a region with two inverted copies of a USS. This vector gave allelic exchange in the presence of cloned and induced tfoX easily and without digestion. Using transposon insertions in cloned katA DNA, we found that as little as 78 bp of homology at one of the ends was sufficient for that end to participate in allelic exchange. The cloning and induction of tfoX makes it possible to transform nearly any strain of A. actinomycetemcomitans, and allelic exchange has proven to be important for site-directed mutagenesis.

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The Haemophilus influenzae sxy-1 mutation is in a newly identified gene essential for competence

Cited by 36 publications

References 16 publications

Bacterial DNA Uptake Sequences Can Accumulate by Molecular Drive Alone

Bacterial DNA Uptake Sequences Can Accumulate by Molecular Drive Alone

Characterization of Three New Competence-Regulated Operons in Haemophilus influenzae

tfoX (sxy)-dependent transformation of Aggregatibacter (Actinobacillus) actinomycetemcomitans

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