title: Vitamin C targets (p)ppGpp synthesis leading to stalling of long-term survival and biofilm formation in Mycobacterium smegmatis.
abstract: Earlier, vitamin C was demonstrated to sterilize Mycobacterium tuberculosis culture via Fenton's reaction at high concentration. It alters the regulatory pathways associated with stress response and dormancy. Since (p)ppGpp is considered to be the master regulator of stress response and is responsible for bacterial survival under stress, we tested the effect of vitamin C on the formation of (p)ppGpp. In vivo estimation of (p)ppGpp showed a decrease in (p)ppGpp levels in vitamin C-treated M. smegmatis cells in comparison to the untreated cells. Furthermore, in vitro (p)ppGpp synthesis using RelMSMenzyme was conducted in order to confirm the specificity of the inhibition in the presence of variable concentrations of vitamin C. We observed that vitamin C at high concentration can inhibit the synthesis of (p)ppGpp. We illustrated binding of vitamin C to RelMSMby isothermal titration calorimetry. Enzyme kinetics was followed where K0.5was found to be increased with the concomitant reduction of Vmaxvalue suggesting mixed inhibition. Both long-term survival and biofilm formation were inhibited by vitamin C. The experiments suggest that vitamin C has the potential to be developed as the inhibitor of (p)ppGpp synthesis and stress response, at least in the concentration range used here.
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India.
authors.forename: Kirtimaan
authors.initials: K
authors.lastname: Syal
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India.
authors.forename: Neerupma
authors.initials: N
authors.lastname: Bhardwaj
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India dipankar@mbu.iisc.ernet.in.
authors.forename: Dipankar
authors.initials: D
authors.lastname: Chatterji
mesh_terms: D001205:Ascorbic Acid / Q000378:metabolism / Q000494:pharmacology*; D018441:Biofilms / Q000254:growth & development*; D002151:Calorimetry; D006158:Guanosine Pentaphosphate / Q000096:biosynthesis*; D007700:Kinetics; D008025:Ligases / Q000378:metabolism; D050296:Microbial Viability / Q000187:drug effects; D020102:Mycobacterium smegmatis / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D013312:Stress, Physiological / Q000187:drug effects
chemical_list: D006158:Guanosine Pentaphosphate; D008025:Ligases; C028812:guanosine 3',5'-polyphosphate synthetases; D001205:Ascorbic Acid
keywords: (p)ppGpp; Mycobacteria; biofilm; long-term survival; stress response; vitamin C