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DNA Cytosine Methyltransferase Promotes Stationary Phase Fitness in Escherichia coli
Author(s) -
Kambhampati Ooha,
FinnertyHaggerty Lara,
Huss Rebecca,
Knapp Rachel,
Militello Kevin
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.595.7
Subject(s) - gene knockout , cytosine , biology , microbiology and biotechnology , escherichia coli , gene , wild type , dna methylation , operon , dna methyltransferase , dnmt1 , knockout mouse , genetics , gene expression , mutant
In Escherichia coli , DNA cytosine methyltransferase (Dcm) methylates the second cytosine in the sequence 5′CCWGG3, where W is A or T. Dcm is in an operon with the very short patch repair ( vsr ) gene, an endonuclease that repairs T‐G mismatches caused by the deamination of 5‐methylcytosine. The role of cytosine DNA methylation and the dcm operon in E. coli is unknown and remains an enigma. Growth curve analyses of wild‐type, dcm knockout and vsr knockout strains at both 37°C and 20°C indicated no effect of the dcm or vsr genes on growth rate. Our laboratory's microarray data comparing expression patterns between a wild‐type and dcm knockout strain indicated numerous gene expression changes occur at stationary phase. Similar results were obtained from microarray experiments comparing gene expression differences between untreated cells and cells treated with the cytosine DNA methylation inhibitor 5‐azacytidine. In summary, the microarray experiments suggest a role for Dcm in stationary phase but not logarithmic phase. Then, we tested whether there was an advantage of either the dcm or vsr genes during stationary phase. We performed competition experiments between the wild‐type strain and the dcm knockout strain or vsr knockout strain to determine which strain would persist during long term stationary phase. In the wild‐type/ dcm knockout strain competition at 20°C, the wild‐type strain outcompeted the dcm knockout strain; thus the cells lacking the dcm gene have a disadvantage over wild‐type cells. The addition of a plasmid containing a functional copy of the dcm gene to the dcm knockout strain reversed the loss of fitness in the dcm knockout strain. In the wild‐type/ vsr knockout strain competition experiment at 20°C, loss of the vsr gene resulted in a modest loss of fitness. Overall, our data indicate that dcm and the dcm operon promote stationary phase fitness. We aim to determine the mechanism for Dcm‐dependent increases in stationary phase fitness which may include changes in the composition of the transcriptome and/or mutation rate. Support or Funding Information Geneseo Foundation