[7] Uses of transposons with emphasis on Tn10

Kleckner, Nancy; Bender, Judith; Gottesman, Susan

doi:10.1016/0076-6879(91)04009-d

Cited by 412 publications

(367 citation statements)

References 45 publications

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“…The cld pHS-2 insertion plasmid pMA9 was constructed by inserting a 1.6 kb Hin dIII fragment carrying a chloramphenicol-resistance gene (cam) from pNK2884 (Kleckner et al, 1991) into the Hin dIII site within cld pHS-2 (Fig. 2).…”

Section: Construction Of Recombinant Plasmids and Strainsmentioning

confidence: 99%

Effect of mutations in Shigella flexneri chromosomal and plasmid‐encoded lipopolysaccharide genes on invasion and serum resistance

Hong

Payne

1997

Molecular Microbiology

118

120

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SummaryThis study shows that both length and distribution of lipopolysaccharide (LPS) are important for Shigella flexneri invasion and virulence. Mutants were generated in the chromosomal LPS synthesis genes rfa, rfb, and rol, and in a plasmid-encoded O-antigen chain-length regulator, cld pHS-2 . LPS analysis showed that mutations in rfb genes and in a candidate rfaL gene either eliminated the entire O-antigen side chains or produced chains of greatly reduced length. Mutation in a previously unidentified gene, rfaX, affected the LPS core region and resulted in reduced amounts of O-antigen. Mutants defective in cld pHS-2 or rol had different distributions of O-antigen chain lengths. The results of tissue-culture cell invasion and plaque assays, the Seré ny test, and serum-sensitivity assay suggested roles for the different LPS synthesis genes in bacterial survival and virulence; rfaL, rfaX and rfb loci are required for serum resistance and intercellular spread, but not for invasion; cld pHS-2 is required for resistance to serum killing and for full inflammation in the Seré ny test, but not for invasion or intercellular spread, while rol is required for normal invasiveness and plaque formation, but not for serum resistance. Thus, O-antigen synthesis and chain-length regulation genes encoded on both the chromosome and the small plasmid pHS-2 play important roles in S. flexneri invasion and virulence.

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Section: Construction Of Recombinant Plasmids and Strainsmentioning

confidence: 99%

Effect of mutations in Shigella flexneri chromosomal and plasmid‐encoded lipopolysaccharide genes on invasion and serum resistance

Hong

Payne

1997

Molecular Microbiology

118

120

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“…Two control TA2 transposons, conferring Gm r or chloramphenicol (Cm r ) resistance, were also used. The mini-Tn10 transposons contain a mutation that reduces insertion site bias (Kleckner et al 1991). Our method therefore reflects the situation where a mobile element encoding a TA system initially infects a population, creating a heterogeneous population of cells.…”

Section: Methodsmentioning

confidence: 99%

Within-host competition selects for plasmid-encoded toxin–antitoxin systems

2010

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Toxin-antitoxin (TA) systems are commonly found on bacterial plasmids. The antitoxin inhibits toxin activity unless the system is lost from the cell. Then the shorter lived antitoxin degrades and the cell becomes susceptible to the toxin. Selection for plasmid-encoded TA systems was initially thought to result from their reducing the number of plasmid-free cells arising during growth in monoculture. However, modelling and experiments have shown that this mechanism can only explain the success of plasmid TA systems under a restricted set of conditions. Previously, we have proposed and tested an alternative model explaining the success of plasmid TA systems as a consequence of competition occurring between plasmids during co-infection of bacterial hosts. Here, we test a further prediction of this model, that competition between plasmids will lead to the biased accumulation of TA systems on plasmids relative to chromosomes. Transposon-encoded TA systems were added to populations of plasmid-containing cells, such that TA systems could insert into either plasmids or chromosomes. These populations were enriched for transposon-containing cells and then incubated in environments that did, or did not, allow effective within-host plasmid competition to occur. Changes in the ratio of plasmid-to chromosome-encoded TA systems were monitored. In agreement with our model, we found that plasmid-encoded TA systems had a competitive advantage, but only when host cells were sensitive to the effect of TA systems. This result demonstrates that within-host competition between plasmids can select for TA systems.

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“…Mini-Tn10 insertions are usually very stable, i.e. they can neither precisely excise nor undergo secondary transposition owing to the features engineered into the mini-Tn10 system (Kleckner et al 1991).…”

Section: (A) Bacterial Genotypes and Culture Conditionsmentioning

confidence: 99%

Pervasive compensatory adaptation inEscherichia coli

Moore

Rozen

Lenski

2000

Proc. R. Soc. Lond. B

127

115

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To investigate compensatory adaptation (CA), we used genotypes of Escherichia coli which were identical except for one or two deleterious mutations. We compared CA for (i) deleterious mutations with large versus small e¡ects, (ii) genotypes carrying one versus two mutations, and (iii) pairs of deleterious mutations which interact in a multiplicative versus synergistic fashion. In all, we studied 14 di¡erent genotypes, plus a control strain which was not mutated. Most genotypes showed CA during 200 generations of experimental evolution, where we de¢ne CA as a ¢tness increase which is disproportionately large relative to that in evolving control lines, coupled with retention of the original deleterious mutation(s). We observed greater CA for mutations of large e¡ect than for those of small e¡ect, which can be explained by the greater bene¢t to recovery in severely handicapped genotypes given the dynamics of selection. The rates of CA were similar for double and single mutants whose initial ¢tnesses were approximately equal. CA was faster for synergistic than for multiplicative pairs, presumably because the marginal gain which results from CA for one of the component mutations is greater in that case. The most surprising result in our view, is that compensation should be so readily achieved in an organism which is haploid and has little genetic redundancy. This ¢nding suggests a degree of versatility in the E. coli genome which demands further study from both genetic and physiological perspectives.

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[7] Uses of transposons with emphasis on Tn10

Cited by 412 publications

References 45 publications

Effect of mutations in Shigella flexneri chromosomal and plasmid‐encoded lipopolysaccharide genes on invasion and serum resistance

Effect of mutations in Shigella flexneri chromosomal and plasmid‐encoded lipopolysaccharide genes on invasion and serum resistance

Within-host competition selects for plasmid-encoded toxin–antitoxin systems

Pervasive compensatory adaptation inEscherichia coli

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