Phylogenetic distribution of branched RNA-linked multicopy single-stranded DNA among natural isolates of Escherichia coli.
Multicopy single-stranded DNA (msDNA), a branched DNA-RNA molecule, has been shown in Escherichia coli B and clinical strain Cl-1 to be synthesized by reverse transcriptase. We report that 13% of the strains of the ECOR collection, a sample of 72 E. coli isolates representing the breadth of genetic variation of the species, produce msDNA. Three of the four major subspecific groups include msDNA-producing strains. Screening of 25 isolates that are genetically related to msDNA-producing clinical strains uncovered 22 additional msDNA-producing strains. A phylogenetic tree based on allelic variation detected electrophoretically at 20 enzyme-encoding loci revealed two major clusters and several deep branches composed of strains that synthesize msDNA. Although E. coli K-12 does not harbor msDNA, other closely related strains of the K-12 family do. The results support the hypothesis that msDNA-synthesizing systems, including reverse transcriptase genes, were acquired recently and independently in different lineages of E. coli.
Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway 08854.
P J
PJ
Herzer
S
S
Inouye
M
M
Inouye
T S
TS
Whittam
D000818:Animals; D004277:DNA, Single-Stranded / Q000235:genetics* / Q000302:isolation & purification; D004926:Escherichia coli / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D010802:Phylogeny; D012329:RNA, Bacterial / Q000235:genetics* / Q000302:isolation & purification
D004277:DNA, Single-Stranded; D012329:RNA, Bacterial; C058681:msDNA