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Open Access Highly Accessed Research article

On the viability of Escherichia coli cells lacking DNA topoisomerase I

Anna Stockum12, Robert G Lloyd1 and Christian J Rudolph13*

Author Affiliations

1 Centre for Genetics and Genomics, University of Nottingham, Queen's Medical Centre, Nottingham, NG7 2UH, UK

2 Division of Medicine, Imperial College London, St Mary's Campus, Norfolk Place, London, W2 1PG, UK

3 Division of Biosciences, School of Health Sciences and Social Care, Brunel University London, Uxbridge, UB8 3PH, UK

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BMC Microbiology 2012, 12:26  doi:10.1186/1471-2180-12-26

Published: 28 February 2012

Additional files

Additional file 1:

Figure S1. Viability of cells lacking DNA topoisomerase I at various temperatures and salt concentrations. (A) Effect of an increased temperature on ΔtopA cells. The plate photographs shown are of synthetic lethality assays as described in detail in Materials and Methods. The relevant genotype of the construct used is shown above each photograph, with the strain number in parentheses. The growth conditions are shown to the left. The fraction of white colonies is shown below with the number of white colonies/total colonies analyzed in parentheses. (B) Effect of various salt concentrations on the viability of cells lacking topoisomerase I.

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Additional file 2:

Figure S2. The viability of cells increased levels of RNase HI is reduced. Wild type cells carrying a ParaBAD rnhA expression plasmid (pECR15) show a growth defect that depends on the concentration of arabinose present in the growth medium. Even growth on glucose, which suppresses expression from the ParaBAD promoter, leads to a mild growth defect, presumably due to a combination of the high plasmid copy number and the leakiness of the ParaBAD promoter. Cells carrying a control plasmid (ParaBAD eCFP, pAST110) show no growth restriction.

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