title: Ciprofloxacin triggered glutamate production by Corynebacterium glutamicum.
abstract: BACKGROUND
  Corynebacterium glutamicum is a well-studied bacterium which naturally overproduces glutamate when induced by an elicitor. Glutamate production is accompanied by decreased 2-oxoglutatate dehydrogenase activity. Elicitors of glutamate production by C. glutamicum analyzed to molecular detail target the cell envelope.
  
  
  RESULTS
  Ciprofloxacin, an inhibitor of bacterial DNA gyrase and topoisomerase IV, was shown to inhibit growth of C. glutamicum wild type with concomitant excretion of glutamate. Enzyme assays showed that 2-oxoglutarate dehydrogenase activity was decreased due to ciprofloxacin addition. Transcriptome analysis revealed that this inhibitor of DNA gyrase increased RNA levels of genes involved in DNA synthesis, repair and modification. Glutamate production triggered by ciprofloxacin led to glutamate titers of up to 37 ± 1 mM and a substrate specific glutamate yield of 0.13 g/g. Even in the absence of the putative glutamate exporter gene yggB, ciprofloxacin effectively triggered glutamate production. When C. glutamicum wild type was cultivated under nitrogen-limiting conditions, 2-oxoglutarate rather than glutamate was produced as consequence of exposure to ciprofloxacin. Recombinant C. glutamicum strains overproducing lysine, arginine, ornithine, and putrescine, respectively, secreted glutamate instead of the desired amino acid when exposed to ciprofloxacin.
  
  
  CONCLUSIONS
  Ciprofloxacin induced DNA synthesis and repair genes, reduced 2-oxoglutarate dehydrogenase activity and elicited glutamate production by C. glutamicum. Production of 2-oxoglutarate could be triggered by ciprofloxacin under nitrogen-limiting conditions.
authors.affiliation: Genetics of Prokaryotes, Faculty of Biology and Center for Biotechnology, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany.
authors.forename: Dorit
authors.initials: D
authors.lastname: Lubitz
authors.affiliation: Genetics of Prokaryotes, Faculty of Biology and Center for Biotechnology, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany. volker.wendisch@uni-bielefeld.de.
authors.forename: Volker F
authors.initials: VF
authors.lastname: Wendisch
mesh_terms: D000596:Amino Acids / Q000096:biosynthesis / Q000187:drug effects; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001710:Biotin / Q000378:metabolism; D002939:Ciprofloxacin / Q000494:pharmacology*; D048230:Corynebacterium glutamicum / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D027081:DNA Gyrase / Q000378:metabolism; D018698:Glutamic Acid / Q000096:biosynthesis*; D007218:Industrial Microbiology / Q000379:methods; D007655:Ketoglutarate Dehydrogenase Complex / Q000378:metabolism; D007656:Ketoglutaric Acids / Q000378:metabolism; D053858:Metabolic Networks and Pathways / Q000187:drug effects; D009584:Nitrogen / Q000378:metabolism; D012313:RNA / Q000096:biosynthesis; D059005:Topoisomerase II Inhibitors / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D007656:Ketoglutaric Acids; D059005:Topoisomerase II Inhibitors; D018698:Glutamic Acid; D002939:Ciprofloxacin; D012313:RNA; D001710:Biotin; D007655:Ketoglutarate Dehydrogenase Complex; D027081:DNA Gyrase; D009584:Nitrogen
keywords: 2-oxoglutarate; Arginine; Ciprofloxacin; Corynebacterium glutamicum; DNA gyrase; Glutamate; Lysine; Ornithine; Overflow metabolism; Putrescine