1. Response and tolerance/avoidance strategies of microorganisms to oxidative stress Karthikeyan Nanjappan Roll No: 10007 Division of Microbiology

7. ROS Molecule Main sources Defense systems Hypochlorous acid (HOCl) By myeloperoxidase from H 2 O 2 Peroxynitrite anion (ONOO-) Formed during the reaction between O 2 •− and NO• Organic hydroperoxide (ROOH) Formed by radical reactions with cellular components such as lipids and nucleobases Alkylhydroperoxide Reductases (Ahp)

12. Mechanism of oxidative damage in cells: Endocellular (Storz and Imlay, 1999)

13. Mechanism of Oxidative damage: Exocellular (Storz and Imlay, 1999)

14. Response mechanisms in microorganisms

17. (Penninckx, 2000) Oxidative stress tolerance mechanism present in different groups of organisms Oxidative stress tolerance mechanism Organisms Glutathione (GSH) (L- γ -glutamyl-L- cysteinyl- glycine) Most microorganisms to humans More frequently in aerobic gram negative & less frequently in anaerobes and gram positive bacteria Mycothiol (an alternative thiol) Gram positive bacteria of the actinomycetes lineage L- γ -glutamyl-L- cysteine Halobacteria

18. Antioxidant activities in E. coli Gene Activity Regulators sod A Manganese superoxide dismutase SoxRS, ArcAB, FNR, Fur, IHF fum C Fumarase C SoxRS, ArcAB, σ s acn A Aconitase A SoxRS, ArcAB, FNR, Fur, σ s zwf Glucose 6 phosphate dehydrogenase SoxRS fur Ferric uptake repressor SoxRS, OxyR mic F RNA regulator of omp F SoxRS, OmpR, LRP acr AB Multidrug efflux pump SoxRS tol C Outer membrane protein SoxRS fpr Ferridoxin reductase SoxRS fld A Flavodoxin SoxRS nfo Endonuclease IV SoxRS sod B Iron superoxide dismutase FNR, σ s sod C Cu-Zn superoxide dismutase kat G Hydroperoxidase I OxyR, σ s

19. Antioxidant activities in E. coli (Storz and Imlay, 1999) Gene Activity Regulators ahp CF Alkyl hydroperoxide reductase OxyR gor A Glutathione reductase OxyR, σ s grx A Glutaredoxin 1 OxyR dps Non specific DNA binding protein OxyR, IHF, σ s oxy S Regulatory RNA OxyR kat E Hydroperoxidase II σ s xth A Exonuclease III Σ s pol A DNA polymerase I RecA, LexA rec A RecA msr A Methionine sulfoxide reductase hsl O Molecular chaperone

20. Operation of SoxRS system in E. coli Luschak, 2011

21. Operation of OxyR system in E. coli (Luschak, 2011)

29. Regulatory mechanism in S. cerevisiae to oxidative stress Gpx3- Glutathione peroxidase NES-Nuclear export sequence Yap 1- yeast activator protein Crm- cysteine rich motif (Lushchak, 2011)

30. Cyanobacteria Cyanobacterium Synechocystis sp PCC 6803 has the similar sequences of gene coding for Glutaredoxin (Grx). The gene expression study conducted on E.coli confirmed that the amino acid sequence homology with glutaredoxin of other organisms. (Li et al., 2005)

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