1. Mechanisms of Bacterial Resistance Against Mercury Toxicity By Monique Smit Supervisor: Prof Erick Strauss http://www.ramehart.com/newsletters/mercury_drops.jpg

2. Introduction Why is Mercury so TOXIC? Mercury Mercury Poisoning Different Enzymatic Mechanisms of Mercury Detoxification General Mechanism Adaptationsof Different Bacteria Conclusions

3. Mercury ‘Hydrargyrum’ ‘hydr’: watery ‘argyros’: silver ‘Mad as a Hatter !’ Roman god, Mercury http://www.ecorazzi.com/wp-content/uploads/2009/06/depp_madhatter.jpg

4. Why is Mercury so TOXIC?

5. Mercury: Properties

6. Mercury: Occurrence Earth’s crust: Lower crust: 21 ppb Upper crust : 56 ppb Forms: Elemental Deposits; Cinnabar (HgS, Binary Minerals) Transformation available (three redox states) http://www.google.co.za/imgres?imgurl=http://www.kidsgeo.com/images/earths-crust.jpg&imgrefurl=http://www.kidsgeo.com/geology-for-kids/0021-earths-crust.php&usg=__dZYwJ_hngjFJrDMaXCWykpchXp8=&h=338&w=338&sz=29&hl=en&start=0&zoom=1&tbnid=ygnWpZE4hwsLnM:&tbnh=123&tbnw=121&prev=/images%3Fq%3DEarth%2Bcrust%26hl%3Den%26biw%3D1366%26bih%3D552%26gbv%3D2%26tbs%3Disch:1&itbs=1&iact=hc&vpx=117&vpy=92&dur=2547&hovh=225&hovw=225&tx=140&ty=84&ei=lKOUTNCpMcKblgeRpdGnCg&oei=lKOUTNCpMcKblgeRpdGnCg&esq=1&page=1&ndsp=24&ved=1t:429,r:0,s:0

7. Mercury: General Uses Thermometers Barometers Manometers http://www.home-weather-stations-guide.com/images/Howardmiller-presqueisle-fromAmazon.jpg http://www.greenlight300.com/pictures/02_why_mercury.jpg http://themoderatevoice.com/wordpress-engine/files/2008-june/mercury_thermometer.jpg http://www.oncallmedicalsupplies.com/acatalog/0125large.jpg

8. Mercury: Applications to Different Sectors Google Images Growing CONCERN?

13. Hearing, speech, vision impairment

14. Involuntarymuscle movements

15. Skin & mucous membrane corrosionGoogle Images

16. Mercury Poisoning Exposures to differentforms Inorganic & Organic Mercury

17. Mechanism of Action Hg binds to Sulfhydryl groups INCAPACITATION of key enzymes Severely DamagedNervous System NO: - Involvement in Cellular Stress Response - Protein Repair - Oxidative Damage Prevention

18. Different Enzymatic Methods Of Mercury Detoxification

19. Bacteria to the rescue? DEFENCE Mechanisms  Reductionof Hg Natural& Engineered role in bioremediation??? http://ianjuby.org/newsletters/superbacteria.jpg

20. General Mechanism CommonMechanism ‘mer’ Operon, respective Mer proteins Mercury Resistance Genes: *Gram NEG. bacteria

21. Mercury Resistance Genes

22. General Mechanism Detoxification Process: Transport of Hg(II) into the cell Delivery of Hg(II) to Reductase Reduction Export of reduced Hg(II) 1 2 3 4

23. 1 CELL MEMBRANE 4 CYTOPLASM 2 3 N.L Brown et al. (2002)

24. Adaptationsof Different Bacteria Diversity of Hg Resistance Loci Variationin mer operon structure Mer as part of mobile genetic elements

25. Diversity of Hg Resistance Loci Variationin operon structure Difference between Gram+ and Gram- Bacteria: An additional enzyme, MerB seldom found in Gram- bacteria but dominantlyfound in Gram+ bacteria

26. Diversity of Hg Resistance Loci Mer operon as part of mobile genetic elements Mer resistance operon  transposons Transposons carry integronswith 1/more antibiotic resistance genes HOW? Horizontal Gene Transfer & Recombination Events

27. Bacteria used in bioremediation?