Regulation of the Integration-Excision Reaction by Bacteriophage

Miller, Heather G.; Abraham, Judith A.; Benedik, Michael J.; Campbell, Allan; Court, Donald L.; Echols, Harrison; Fischer, R.; Galindo, José Luis Ortíz; Guarneros, Gabriel; Hernández, T Araceli; Mascarenhas, Desmond; Montañéz, Cecilia; Schindler, Daniel; Schmeissner, Ursula; Sosa, L

doi:10.1101/sqb.1981.045.01.058

Cited by 17 publications

(8 citation statements)

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“…Neither nor Mu produces significant single-cell bursts in stationary phase, and gyrase modulates the lytic/lysogeny outcome in both viruses. excision is reduced from some locations in the bacterial chro- on May 12, 2018 by guest http://jb.asm.org/ mosome in himB (gyrB) mutants (57,58). In E. coli, Mu burst size and plaque size are reduced in gyrB mutants (94) and the lysis/lysogeny fate is directly linked to negative supercoiling (33,48).…”

Section: Discussionmentioning

confidence: 99%

Growth Rate Toxicity Phenotypes and Homeostatic Supercoil Control Differentiate Escherichia coli from Salmonella enterica Serovar Typhimurium

Champion

Higgins

2007

J Bacteriol

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Escherichia coli and Salmonella enterica serovar Typhimurium share high degrees of DNA and amino acid identity for 65% of the homologous genes shared by the two genomes. Yet, there are different phenotypes for null mutants in several genes that contribute to DNA condensation and nucleoid formation. The mutant R436-S form of the GyrB protein has a temperature-sensitive phenotype in Salmonella, showing disruption of supercoiling near the terminus and replicon failure at 42°C. But this mutation in E. coli is lethal at the permissive temperature. A unifying hypothesis for why the same mutation in highly conserved homologous genes of different species leads to different physiologies focuses on homeotic supercoil control. During rapid growth in mid-log phase, E. coli generates 15% more negative supercoils in pBR322 DNA than Salmonella. Differences in compaction and torsional strain on chromosomal DNA explain a complex set of single-gene phenotypes and provide insight into how supercoiling may modulate epigenetic effects on chromosome structure and function and on prophage behavior in vivo.Dichotomous growth is an adaptation that allows certain bacteria to divide rapidly under nutrient-rich conditions. During dichotomous growth, wild-type (WT) Escherichia coli can divide every 20 min, even though it takes Ͼ50 min to replicate the genome. Cells can divide rapidly only as long as initiation of bidirectional DNA synthesis with the DnaA "initiator" complex at the oriC "replicator" (42) is well coordinated with the formation of nucleoids and the distribution of replicated copies of the chromosome to each daughter cell at the time of partition. Recent studies with live cells show that a highly organized traffic pattern deposits each replisome arm at opposing edges of growing nucleoids (2, 90). At high growth rates, the average cell has a complex chromosome structure, with nucleoids containing two or four partially replicated arcs spanning the oriC initiator region. To distribute nucleoids, the cell division machinery needs to find the cell midpoint, decatenate all cross-links between chromosomal replicas at the dif site (19, 49), and move the nucleoids into each new daughter cell.The initiation frequency at oriC is critical for cell division. Hyperinitiation is toxic or lethal (77), with one problem being fork overrun. If a fork from a recent initiation cycle overtakes a previously initiated fork, large chromosome fragments with double-strand ends can be generated (4). We previously showed that the Salmonella gyrB652 mutation causes "growth rate toxicity" that includes topological chaos near the dif site (68). Gyrase hypomorphs in Salmonella lose supercoiling near the terminus of replication, even though plasmids in the same cell maintain near-normal superhelical densities (68). Recent experiments suggest that a similar fate may occur in gyrase mutants of E. coli (29,45).The GyrB protein is highly conserved in E. coli and Salmonella. Of its 804 amino acids, 97% are identical in the two species, with most substitutions being ...

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Section: Discussionmentioning

confidence: 99%

Growth Rate Toxicity Phenotypes and Homeostatic Supercoil Control Differentiate Escherichia coli from Salmonella enterica Serovar Typhimurium

Champion

Higgins

2007

J Bacteriol

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“…Although Int is needed for phage DNA integration after infection, Int along with Xis is required for prophage DNA excision after induction (42). After integration of the phage DNA into the bacterial chromosome via attP, the sib site is physically separated from int and is located on the opposite side of the prophage (Fig.…”

Section: Fig 2 Looping Of the Operators Ol And Or During CI Bindingmentioning

confidence: 99%

A New Look at Bacteriophage λ Genetic Networks

2007

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“…HimA protein also has both a catalytic and a regulatory role: It is a subunit of the integration host factor (IHF) required for integrative recombination by A DNA (18), and it is also needed for efficient expression of the int and cI genes specific for the lysogenic response by A (19,20). Because of the multiple roles ofHimA in prophage insertion, we expected that the himA gene might be subject to a variety of cellular control signals.…”

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confidence: 99%