title: MazEF toxin-antitoxin proteins alter Escherichia coli cell morphology and infrastructure during persister formation and regrowth.
abstract: When exposed to antibiotics, many bacteria respond by activating intracellular 'toxin' proteins, which arrest cell growth and induce formation of persister cells that survive antibiotics. After antibiotics are removed, persisters can regrow by synthesizing 'antitoxin' proteins that sequester toxin proteins. In Escherichia coli, MazE antitoxin sequesters the activity of MazF toxin, which extensively cleaves cellular RNAs. Although the functions of MazEF proteins are well characterized, there is surprisingly little known about their effects on cell structure. Here, using a combination of microscopy techniques, we visualized the effects of MazEF and three bactericidal antibiotics on E. coli cell morphology and infrastructure. When ectopically expressed in E. coli, MazF temporarily stalled cell growth and induced persister formation, but only mildly elevated DNA mutagenesis. Viewed by electron microscopy, MazF-expressing persister cells were arrested in cell growth and division. Their chromosomal DNAs were compacted into thread-like structures. Their ribosomes were excluded from their nucleoids. After exposure to ciprofloxacin, persister regrowth was activated by MazE. Cell division remained inhibited while cells became extraordinarily elongated, then divided multiple times during stationary growth phase. This extreme filamentation during persister regrowth was unique to ciprofloxacin-treated persisters, likely caused by inhibition of cell division during regrowth, and was not observed with kanamycin-treated persisters.
authors.affiliation: Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078, USA.
authors.forename: Junho
authors.initials: J
authors.lastname: Cho
authors.affiliation: Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078, USA.
authors.forename: Anita Nicole
authors.initials: AN
authors.lastname: Carr
authors.affiliation: Microscopy Laboratory, Oklahoma State University, Stillwater, OK 74078, USA.
authors.forename: Lisa
authors.initials: L
authors.lastname: Whitworth
authors.affiliation: Microscopy Laboratory, Oklahoma State University, Stillwater, OK 74078, USA.
authors.forename: Brent
authors.initials: B
authors.lastname: Johnson
authors.affiliation: Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078, USA.
authors.forename: Kevin Scott
authors.initials: KS
authors.lastname: Wilson
mesh_terms: D000667:Ampicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects*; D002701:Chloramphenicol / Q000494:pharmacology; D002939:Ciprofloxacin / Q000494:pharmacology; D004261:DNA Replication / Q000187:drug effects; D004269:DNA, Bacterial / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004722:Endoribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D007612:Kanamycin / Q000494:pharmacology; D008854:Microscopy, Electron
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C422954:MazE protein, E coli; C422955:MazF protein, E coli; D007612:Kanamycin; D002939:Ciprofloxacin; D002701:Chloramphenicol; D000667:Ampicillin; D004722:Endoribonucleases