Mechanisms of Bacterial Resistance Against Mercury Toxicity<br />By Monique Smit<br />Supervisor: Prof Erick Strauss<br />...
Introduction<br />Why is Mercury so TOXIC?<br />Mercury<br />Mercury Poisoning<br />Different Enzymatic Mechanisms of Merc...
Mercury ‘Hydrargyrum’<br />‘hydr’: watery<br />‘argyros’: silver<br />‘Mad as a <br />Hatter !’ <br />Roman god, Mercury<...
Why is Mercury so TOXIC?<br />
Mercury: Properties<br />
Mercury: Occurrence<br />Earth’s crust:<br />Lower crust:  21 ppb<br />Upper crust : 56 ppb<br />Forms: <br />Elemental<br...
Mercury: General Uses<br />Thermometers<br />Barometers<br />Manometers<br />http://www.home-weather-stations-guide.com/im...
Mercury: Applications to Different Sectors<br />Google Images<br />Growing CONCERN?<br />
Mercury Poisoning<br />Exposure : High toxicity: mercurialism<br />Minamata Disease<br /><ul><li>Ataxia
Impairment of speech & hearing</li></ul>Acrodynia(‘Pink Disease’)<br /><ul><li>Pain
Pink discolouration</li></li></ul><li>Different Methods to Exposure<br />Ingestion		Inhalation		 Skin Contact & 							 Ab...
Effects on Health<br /><ul><li> Nervous system deterioration
 Hearing, speech, vision impairment
 Involuntarymuscle movements
 Skin & mucous membrane corrosion</li></ul>Google Images<br />
Mercury Poisoning<br />Exposures to differentforms<br />Inorganic & Organic Mercury <br />
   Mechanism of Action<br />Hg binds to Sulfhydryl groups<br />INCAPACITATION of key enzymes<br />Severely DamagedNervous ...
Different Enzymatic<br />Methods Of Mercury Detoxification<br />
Bacteria to the rescue?<br />DEFENCE Mechanisms  Reductionof Hg<br />Natural& Engineered role in bioremediation???<br />h...
General Mechanism<br />CommonMechanism<br />‘mer’ Operon, respective Mer proteins<br />Mercury Resistance Genes:<br />*Gra...
Mercury Resistance Genes<br />
General Mechanism<br />	  Detoxification Process:<br />		Transport of Hg(II) into the cell<br />Delivery of Hg(II) to Redu...
1<br />CELL MEMBRANE<br />4<br />CYTOPLASM<br />2<br />3<br />N.L Brown et al. (2002)<br />
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Mechanisms Of Bacterial Resistance Against Mercury Toxicity

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Mechanisms Of Bacterial Resistance Against Mercury Toxicity

  1. 1. Mechanisms of Bacterial Resistance Against Mercury Toxicity<br />By Monique Smit<br />Supervisor: Prof Erick Strauss<br />http://www.ramehart.com/newsletters/mercury_drops.jpg<br />
  2. 2. Introduction<br />Why is Mercury so TOXIC?<br />Mercury<br />Mercury Poisoning<br />Different Enzymatic Mechanisms of Mercury Detoxification<br />General Mechanism<br />Adaptationsof Different Bacteria<br />Conclusions<br />
  3. 3. Mercury ‘Hydrargyrum’<br />‘hydr’: watery<br />‘argyros’: silver<br />‘Mad as a <br />Hatter !’ <br />Roman god, Mercury<br />http://www.ecorazzi.com/wp-content/uploads/2009/06/depp_madhatter.jpg<br />
  4. 4. Why is Mercury so TOXIC?<br />
  5. 5. Mercury: Properties<br />
  6. 6. Mercury: Occurrence<br />Earth’s crust:<br />Lower crust: 21 ppb<br />Upper crust : 56 ppb<br />Forms: <br />Elemental<br />Deposits; Cinnabar (HgS, Binary Minerals)<br />Transformation available (three redox states)<br />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<br />
  7. 7. Mercury: General Uses<br />Thermometers<br />Barometers<br />Manometers<br />http://www.home-weather-stations-guide.com/images/Howardmiller-presqueisle-fromAmazon.jpg<br />http://www.greenlight300.com/pictures/02_why_mercury.jpg<br />http://themoderatevoice.com/wordpress-engine/files/2008-june/mercury_thermometer.jpg<br />http://www.oncallmedicalsupplies.com/acatalog/0125large.jpg<br />
  8. 8. Mercury: Applications to Different Sectors<br />Google Images<br />Growing CONCERN?<br />
  9. 9. Mercury Poisoning<br />Exposure : High toxicity: mercurialism<br />Minamata Disease<br /><ul><li>Ataxia
  10. 10. Impairment of speech & hearing</li></ul>Acrodynia(‘Pink Disease’)<br /><ul><li>Pain
  11. 11. Pink discolouration</li></li></ul><li>Different Methods to Exposure<br />Ingestion Inhalation Skin Contact & Absorption<br />
  12. 12. Effects on Health<br /><ul><li> Nervous system deterioration
  13. 13. Hearing, speech, vision impairment
  14. 14. Involuntarymuscle movements
  15. 15. Skin & mucous membrane corrosion</li></ul>Google Images<br />
  16. 16. Mercury Poisoning<br />Exposures to differentforms<br />Inorganic & Organic Mercury <br />
  17. 17. Mechanism of Action<br />Hg binds to Sulfhydryl groups<br />INCAPACITATION of key enzymes<br />Severely DamagedNervous System<br />NO:<br />- Involvement in Cellular Stress Response<br />- Protein Repair<br />- Oxidative Damage Prevention<br />
  18. 18. Different Enzymatic<br />Methods Of Mercury Detoxification<br />
  19. 19. Bacteria to the rescue?<br />DEFENCE Mechanisms  Reductionof Hg<br />Natural& Engineered role in bioremediation???<br />http://ianjuby.org/newsletters/superbacteria.jpg<br />
  20. 20. General Mechanism<br />CommonMechanism<br />‘mer’ Operon, respective Mer proteins<br />Mercury Resistance Genes:<br />*Gram NEG. bacteria<br />
  21. 21. Mercury Resistance Genes<br />
  22. 22. General Mechanism<br /> Detoxification Process:<br /> Transport of Hg(II) into the cell<br />Delivery of Hg(II) to Reductase<br /> Reduction<br />Export of reduced Hg(II)<br />1<br />2<br />3<br />4<br />
  23. 23. 1<br />CELL MEMBRANE<br />4<br />CYTOPLASM<br />2<br />3<br />N.L Brown et al. (2002)<br />
  24. 24. Adaptationsof Different Bacteria<br />Diversity of Hg Resistance Loci<br />Variationin mer operon <br />structure<br />Mer as part of mobile <br />genetic elements<br />
  25. 25. Diversity of Hg Resistance Loci<br />Variationin operon structure<br />Difference between Gram+ and Gram- Bacteria:<br />An additional enzyme, MerB<br />seldom found in Gram- bacteria<br />but dominantlyfound in Gram+ <br />bacteria<br />
  26. 26. Diversity of Hg Resistance Loci<br />Mer operon as part of mobile <br />genetic elements<br />Mer resistance operon  transposons<br />Transposons carry integronswith <br />1/more antibiotic resistance genes<br />HOW? <br />Horizontal Gene Transfer & Recombination<br />Events<br />
  27. 27. Bacteria used in bioremediation?<br />

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