title: Nonoptimal microbial response to antibiotics underlies suppressive drug interactions.
abstract: Suppressive drug interactions, in which one antibiotic can actually help bacterial cells to grow faster in the presence of another, occur between protein and DNA synthesis inhibitors. Here, we show that this suppression results from nonoptimal regulation of ribosomal genes in the presence of DNA stress. Using GFP-tagged transcription reporters in Escherichia coli, we find that ribosomal genes are not directly regulated by DNA stress, leading to an imbalance between cellular DNA and protein content. To test whether ribosomal gene expression under DNA stress is nonoptimal for growth rate, we sequentially deleted up to six of the seven ribosomal RNA operons. These synthetic manipulations of ribosomal gene expression correct the protein-DNA imbalance, lead to improved survival and growth, and completely remove the suppressive drug interaction. A simple mathematical model explains the nonoptimal regulation in different nutrient environments. These results reveal the genetic mechanism underlying an important class of suppressive drug interactions.
authors.affiliation: Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.
authors.forename: Tobias
authors.initials: T
authors.lastname: Bollenbach
authors.forename: Selwyn
authors.initials: S
authors.lastname: Quan
authors.forename: Remy
authors.initials: R
authors.lastname: Chait
authors.forename: Roy
authors.initials: R
authors.lastname: Kishony
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D004247:DNA / Q000096:biosynthesis; D004347:Drug Interactions; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology*; D014176:Protein Biosynthesis / Q000187:drug effects; D012270:Ribosomes / Q000378:metabolism
chemical_list: D000890:Anti-Infective Agents; D019384:Nucleic Acid Synthesis Inhibitors; D004247:DNA