This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Iqbal, S.
Right arrow Articles by Robson, R. L.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Iqbal, S.
Right arrow Articles by Robson, R. L.

 Previous Article  |  Next Article 

Journal of Bacteriology, September 2004, p. 6118-6123, Vol. 186, No. 18
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.18.6118-6123.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Reversible Phase Variation in the phnE Gene, Which Is Required for Phosphonate Metabolism in Escherichia coli K-12

Samina Iqbal, George Parker, Helen Davidson, Elham Moslehi-Rahmani, and Robert L. Robson*

Microbiology Division, School of Animal and Microbial Sciences, University of Reading, Reading, United Kingdom

Received 23 April 2004/ Accepted 22 June 2004

It is known that Escherichia coli K-12 is cryptic (Phn–) for utilization of methyl phosphonate (MePn) and that Phn+ variants can be selected for growth on MePn as the sole P source. Variants arise from deletion via a possible slip strand mechanism of one of three direct 8-bp repeat sequences in phnE, which restores function to a component of a putative ABC type transporter. Here we show that Phn+ variants are present at the surprisingly high frequency of >10–2 in K-12 strains. Amplified-fragment length polymorphism analysis was used to monitor instability in phnE in various strains growing under different conditions. This revealed that, once selection for growth on MePn is removed, Phn+ revertants reappear and accumulate at high levels through reinsertion of the 8-bp repeat element sequence. It appears that, in K-12, phnE contains a high-frequency reversible gene switch, producing phase variation which either allows ("on" form) or blocks ("off" form) MePn utilization. The switch can also block usage of other metabolizable alkyl phosphonates, including the naturally occurring 2-aminoethylphosphonate. All K-12 strains, obtained from collections, appear in the "off" form even when bearing mutations in mutS, mutD, or dnaQ which are known to enhance slip strand events between repetitive sequences. The ability to inactivate the phnE gene appears to be unique to K-12 strains since the B strain is naturally Phn+ and lacks the inactivating 8-bp insertion in phnE, as do important pathogenic strains for which genome sequences are known and also strains isolated recently from environmental sources.

* Corresponding author. Mailing address: Microbiology Division, School of Animal and Microbial Sciences, University of Reading, Reading RG6 6AJ, United Kingdom. Phone: 44-118-9316639. Fax: 44-118-9316562. E-mail: r.l.robson{at}rdg.ac.uk.

Journal of Bacteriology, September 2004, p. 6118-6123, Vol. 186, No. 18
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.18.6118-6123.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Adams, M. M., Gomez-Garcia, M. R., Grossman, A. R., Bhaya, D. (2008). Phosphorus Deprivation Responses and Phosphonate Utilization in a Thermophilic Synechococcus sp. from Microbial Mats. J. Bacteriol. 190: 8171-8184 [Abstract] [Full Text]  


Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»