Dataset Information

Xer site-specific recombination, an efficient tool to introduce unmarked deletions into mycobacteria.

ABSTRACT: Genetic manipulation of mycobacteria still represents a serious challenge due to the lack of tools and selection markers. In this report, we describe the development of an intrinsically unstable excisable cassette for introduction of unmarked mutations in both Mycobacterium smegmatis and Mycobacterium tuberculosis.

SUBMITTER: Cascioferro A

PROVIDER: S-EPMC2916470 | biostudies-literature | 2010 Aug

REPOSITORIES: biostudies-literature

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Xer site-specific recombination, an efficient tool to introduce unmarked deletions into mycobacteria.

Cascioferro Alessandro A Boldrin Francesca F Serafini Agnese A Provvedi Roberta R Palù Giorgio G Manganelli Riccardo R

Applied and environmental microbiology 20100611 15

Genetic manipulation of mycobacteria still represents a serious challenge due to the lack of tools and selection markers. In this report, we describe the development of an intrinsically unstable excisable cassette for introduction of unmarked mutations in both Mycobacterium smegmatis and Mycobacterium tuberculosis. ...[more]

PMID: 20543044

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Project description:In E. coli, 10 to 15% of growing bacteria produce dimeric chromosomes during DNA replication. These dimers are resolved by XerC and XerD, two tyrosine recombinases that target the 28-nucleotide motif (dif) associated with the chromosome's replication terminus. In streptococci and lactococci, an alternative system is composed of a unique, Xer-like recombinase (XerS) genetically linked to a dif-like motif (dif(SL)) located at the replication terminus. Preliminary observations have suggested that the dif/Xer system is commonly found in bacteria with circular chromosomes but that assumption has not been confirmed in an exhaustive analysis. The aim of the present study was to extensively characterize the dif/Xer system in the proteobacteria, since this taxon accounts for the majority of genomes sequenced to date. To that end, we analyzed 234 chromosomes from 156 proteobacterial species and showed that most species (87.8%) harbor XerC and XerD-like recombinases and a dif-related sequence which (i) is located in non-coding sequences, (ii) is close to the replication terminus (as defined by the cumulative GC skew) (iii) has a palindromic structure, (iv) is encoded by a low G+C content and (v) contains a highly conserved XerD binding site. However, not all proteobacteria display this dif/XerCD system. Indeed, a sub-group of pathogenic epsilon-proteobacteria (including Helicobacter sp and Campylobacter sp) harbors a different recombination system, composed of a single recombinase (XerH) which is phylogenetically distinct from the other Xer recombinases and a motif (dif(H)) sharing homologies with dif(SL). Furthermore, no homologs to dif or Xer recombinases could be detected in small endosymbiont genomes or in certain bacteria with larger chromosomes like the Legionellales. This raises the question of the presence of other chromosomal deconcatenation systems in these species. Our study highlights the complexity of dif/Xer recombinase systems in proteobacteria and paves the way for systematic detection of these components in prokaryotes.

Dataset Information

Xer site-specific recombination, an efficient tool to introduce unmarked deletions into mycobacteria.

Publications

Xer site-specific recombination, an efficient tool to introduce unmarked deletions into mycobacteria.

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