title: Roles of Lon protease and its substrate MarA during sodium salicylate-mediated growth reduction and antibiotic resistance in Escherichia coli.
abstract: The cellular proteolytic machinery orchestrates protein turnover and regulates several key biological processes. This study addresses the roles of Lon, a major ATP-dependent protease, in modulating the responses of Escherichia coli strain MG1655 to low and high amounts of sodium salicyclate (NaSal), a widely used clinically relevant analgesic. NaSal affects several bacterial responses, including growth and resistance to multiple antibiotics. The loss of lon reduces growth in response to high, but not low, amounts of NaSal. From amongst a panel of Lon substrates, MarA was identified to be the downstream target of Lon. Thus, stabilization of MarA in the absence of lon lowers growth of the strain in the presence of higher amounts of NaSal. The steady-state transcript levels of marA and its target genes, acrA, acrB and tolC, are higher in the Δlon strain compared with the WT strain. Consequently, the resistance to antibiotics, e.g. tetracycline and nalidixic acid, is enhanced in Δlon in a marA-dependent manner. Furthermore, the target genes of MarA, i.e. acrB and tolC, are responsible for NaSal-mediated antibiotic resistance. Studies using atomic force microscopy demonstrated that ciprofloxacin led to greater cell filamentation, which is lower in the Δlon strain due to higher levels of MarA. Overall, this study delineates the roles of Lon protease, its substrate MarA and downstream targets of MarA, e.g. acrB and tolC, during NaSal-mediated growth reduction and antibiotic resistance. The implications of these observations in the adaptation of E. coli under different environmental conditions are discussed.
authors.affiliation: Department of Biochemistry, Indian Institute of Science,Bangalore,India.
authors.forename: Chetana
authors.initials: C
authors.lastname: Bhaskarla
authors.affiliation: Department of Biochemistry, Indian Institute of Science,Bangalore,India.
authors.forename: Mrinmoy
authors.initials: M
authors.lastname: Das
authors.affiliation: Centre for Biosystems Science and Engineering, Indian Institute of Science,Bangalore,India.
authors.forename: Taru
authors.initials: T
authors.lastname: Verma
authors.affiliation: Department of Biochemistry, Indian Institute of Science,Bangalore,India.
authors.forename: Anujith
authors.initials: A
authors.lastname: Kumar
authors.affiliation: Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science,Bangalore,India.
authors.forename: S
authors.initials: S
authors.lastname: Mahadevan
authors.affiliation: Department of Biochemistry, Indian Institute of Science,Bangalore,India.
authors.forename: Dipankar
authors.initials: D
authors.lastname: Nandi
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D002939:Ciprofloxacin / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D008074:Lipoproteins / Q000235:genetics; D026901:Membrane Transport Proteins / Q000235:genetics; D008826:Microbial Sensitivity Tests; D018625:Microscopy, Atomic Force; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics; D009268:Nalidixic Acid / Q000494:pharmacology; D049070:Protease La / Q000235:genetics / Q000378:metabolism*; D012980:Sodium Salicylate / Q000378:metabolism / Q000494:pharmacology*; D013752:Tetracycline / Q000494:pharmacology; D013753:Tetracycline Resistance / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D002939:Ciprofloxacin; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D008074:Lipoproteins; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009268:Nalidixic Acid; D049070:Protease La; D012980:Sodium Salicylate; D013752:Tetracycline; C083497:AcrA protein, E coli; C083496:AcrB protein, E coli; C080002:MarA protein, E coli; C073126:tolC protein, E coli; C483567:Lon protein, E coli