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Malaria-bug of the week

Malaria-bug of the week. Protozoan disease Plasmodium vivax, P. malariae, P. ovale and P. falciparum Requires the female mosquito (Anopheles)as an insect vector . Most important of human parasites . Epidemiology. • 300 million people infected each year • 1 million die in Africa alone

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Malaria-bug of the week

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  1. Malaria-bug of the week • Protozoan disease • Plasmodium vivax, P. malariae, P. ovale and P. falciparum • Requires the female mosquito (Anopheles)as an insect vector . • Most important of human parasites

  2. Epidemiology • 300 million people infected each year • 1 million die in Africa alone •Mainly a disease of the tropics where there are lots of mosquito vectors

  3. Life Cycle

  4. Malarial erythrocyte cycle-trophozoites in RBC

  5. Pathological changes • Symptoms are from synchronized release of merzoites from RBC • RBC lyse and release toxins etc causing fever, chills and sweating. Occurs at 48-72 hour intervals • Remission after a few weeks then repetition

  6. Treatment • Usually a quinine such as chloroquine, amodiaquine or mefloquine which eradicate erythrocite stage • Drug resistant strains cropping up so there are new treatments • Prophylactic treatment effective

  7. Asides • Sickle Cell associated with resistance-individuals have modified Hb • Recently finished genome project of Anopheles and Plasmodium falciparum and combined with Human Genome project new molecular cures likely

  8. BACTERIAL NUTRITION • Major (Macro) elements. Carbon (C), Nitrogen (N), Oxygen (O), Phosphorous (P) and Sulfur (S). Makes up over 95% of cell dry weight. • These 5 macroelements are the elemental components of the 4 macromolecules of life: nucleic acids, proteins, lipids and carbohydrates.

  9. Bacterial Nutrition • Other Macro Elements: Potassium (K), Iron (Fe), Calcium (Ca),and Magnesium (Mg) all required in the ionic form are used in a variety of critical functions of the cell and are in mg quantities • Functions: heat resistance, enzyme activity, respiration, maintainance of ionic strength.

  10. Bacterial Nutrition Trace Elements: Manganese (Mn), Zinc (Zn), Cobalt (Co),Molybdenum(Mo)and Copper (Cu). Required in ug quantities per liter. Required for enzyme function.

  11. Classification of Microbes Based on Nutrition

  12. Classification of Microbes Based on Nutrition

  13. Nutritional Forms of Nitrogen Used by Microorganisms • Preformed organic nitrogen compounds such as amino acids or purines and pyrimidines. Deamination reactions convert the nitrogen groups to ammonia which is then assimilated into biomass

  14. Nutritional Forms of Nitrogen Used by Microorganisms • Ammonia is the most commonly used for of nitrogen by microorganisms • NH4+ is incorporated into glutamate by glutamate dehydrogenase when in high concentrations. • Glutamate synthase-glutamine synthetase system is used when NH4 is in low conc.

  15. Nutritional Forms of Nitrogen Used by Microorganisms • Many bacteria can use nitrate as a sole nitrogen source • Nitrate is reduced to ammonia by the assimilatory nitrate reduction process • ammonia is incorporated as previously described

  16. Nutritional Forms of Phosphorous Used by Microorganisms • Most use a form of Phosphate (PO4=) • In growth medium it is usually incorporated as phosphate buffer system

  17. Nutritional Forms of Sulfur Used by Microorganisms • Most organisms incorporate sulfur as sulfate (SO4-) • In growth medium it is often incorporated as a salt of ammonia (ammonium sulfate) or magnesium (Magnesium sulfate) • Used mainly to make the sulfur amino acids methionine and cystiene

  18. Terms relating to nutritional requirements of a microorganism • Prototroph-An organism that requires the same nutrients for growth as the majority of naturally occuring members of its species. • Auxotroph-A mutated prototroph that lacks the ability to synthesize an essential nutrient therefore must obtain it or a precursor from its surrounding environment.

  19. Culture Media • Defined Medium- All components of the medium are known and in a specific concentration. • Minimal Salts media are composed of the minimum growth requirements for a given organism

  20. Defined, minimal medium for a photolithotrophic autotroph • NaNO3 (sodium nitrate) • K2HPO4 (potassium dibasic phosphate • MgSO4 (magnesium sulfate) • CaCl2 (calcium chloride) • EDTA (ethylene diamine tetraacetic acid, chelator) • NaCO3 (sodium carbonate) • pH 7.4 • Note no organic carbon or energy source

  21. Defined Minimal Salts Medium for E. coli • glucose • NaHPO4(sodium monobasic phosphate) • KH2PO4(potassium monobasic phosphate • (NH4)2SO4 (ammonium sulfate) • Mg2SO4 (magnesium sulfate) • CaCl2 (calcium chloride) • FeSO4 (ferrous sulfate) • final pH 6.8-7.4 • Note glucose is both carbon and energy.

  22. Complex media • Generally an organic rich medium of unknown composition • routinely used because allows fast growth and supports growth of many different organnisms

  23. Selective Media • This type of media favors growth of a particular kind of organism and selects against others: eosin methylene blue, endoagar, MaConkey’s all used to detect enterics

  24. Differential Media • Distinguishes between certain groups of bacteria by a color reaction with a dye or some other characteristics • Blood agar for hemolytic streptococcus

  25. Cardinal Growth Temperatures For any given organism there is a minimum growth temperature, optimum growth temperature and maximum growth temperatures. These are known as the cardinal temperatures.

  26. Categorization of Bacteria Based on Growth Temp Fig. 6.15 p. 128

  27. Temperature and Growth Psychrophiles- Most belong to genera Psuedomonas,Flavobacterium,Achromobacter and Alcaligenes. • Proteins function best at low temperatures • membranes contain high levels of unsaturated fatty acids

  28. Temperature and Growth Thermophiles grow at temperatures of 55C or higher • Obligate thermophiles can only grow above temperatures of 45C. Bacillus stearothermophilus. • Facultative thermophiles can grow at temperatures lower than 45C but optimal is at 55C. Bacillus coagulans • Hyperthermophiles grow optimally between 80C and 110 C and usually do not grow below 55C. Pyrococcus abyssi.

  29. Oxygen and Growth • Facultative anaerobes prefer growing in the presence of oxygen but can grow anaerobically. E. coli • Obligate aerobes - require atmospheric oxygen (20%).Azotobacter vinelandi. • Strict or Obligateanaerobes can only grow in the absence of oxygen and are killed by oxygen. Clostridium botulinum. • Microaerophilic bacteria are damaged by 20% oxygen but require 2%-10% oxygen.

  30. Oxygen and Growth Fig.6.16 p.129

  31. Oxygen and Growth Oxygen sensitivity • Oxygen is toxic to all organisms at some concentration • Toxicity is due to the formation of reactive oxygen molecules or compounds:1) superoxide (O2-); and 2)hydrogen peroxide (H2O2). These are both powerful oxidizing agents and damage proteins, nucleic acids and lipids.

  32. Oxygen Toxicity Superoxide • Superoxide is formed during respiration by the univalent reduction of oxygen which occurs primarily via the reduced flavins of the respiratory chain O2 + (e-)-----------------> O2- SUPEROXIDE • Detoxification occurs through the action of the enzyme superoxide dismutase. 2 O2- + 2H+ ------superoxide dismutase--------> H2O2 SUPEROXIDE HYDROGEN PEROXIDE

  33. Oxygen Toxicity Hydrogen Peroxide H2O2 • Hydrogen peroxide is formed primarily through the action of superoxide dismutase • Detoxification occurs through the action of catalase 2 H2O2-------------catalase---------------->2 H2O + O2

  34. Oxygen Toxicity Strict or obligate anaerobes lack or have very low levels of superoxide dismutase (SOD) and catalase and thus are killed by the presence of oxygen.

  35. MICROBE OF THE WEEK • Clostridium difficile. Obligate anaerobic spore forming rod gram positive bacteria. • Significance. Cause of 3 million cases of hospital diarrhea and colitis (7% of admitted hospital patients per year).

  36. MICROBE OF THE WEEK • Infection usually results because of antibiotic therapy which disturbs normal bacterial flora of colon. • Cause- C. difficile releases 2 toxins, A and B. A is an enterotoxin and B is a cytotoxin. Both bind to receptors on the intestinal mucal cells compromising fluid absorption + retention

  37. MICROBE OF THE WEEKClostridium difficile • Disposition to: Hospitalization, antibiotic therapy, Age (elderly). Most common antibiotics implicated are chephalosorins, ampicillin/amoxicillin and clindamycin • Mechanism: Spores of bacteria prevalent in hospitals. Ingestion or surgical contamination of patient. Spores germinate in colon and colonize producing toxins.

  38. MICROBE OF THE WEEK • Symptoms. Mild to moderate watery diarrhea(rarely bloody) cramping, anorexia, fever, dehydration, abdominal tenderness. Diagnosis. Conclusive diagnosis depends on detection of toxin in stool. Fibroblast tissue culture-24-48h(94-100%). Commercial enzyme immunoassay kits (69-87%). Less sensitive but very quick (hours)

  39. MICROBE OF THE WEEK • Treatment. Usually Vancomycin or Metronidazole. Organism is very susceptible to vancomycin. It is resistant to cephalosporins, ampicillin/amoxicillin, and clindamycin and aminoglycosides. • Support therapy. Hydration.

  40. Solute Concentration and Microbes

  41. Solute Concentration and Growth Halophiles • Require levels of NaCl between 2.8 and 6.2 M to grow. • Extreme halophiles like Halobacterium require 6.2M which approaches saturation. Many are Archeabacteria • Structure of proteins and membranes have been significantly altered. • Generally they accumulate huge concentrations of potassium in order to remain hypertonic to environment. • Enzymes, ribosomes protein structure requires high concentrations of sodium.

  42. pH and growth • Neutrophiles (Most bacteria) can grow between pH 5.5-8 E.coli • Acidophiles prefer pH between 0 and 5.5.Thiobacillus thiooxidans • Alkalophiles prefer pH above 10.Bacillus alcalophilus • Fungi prefer pH 4-6

  43. pH and Microbes

  44. Bacterial Growth in Batch Cultures: The Growth Curve Fig. 6.1 p 114

  45. Bacterial Growth Curve in Batch Culture The Lag Phase • No cell division occurs • Cells adjusting to medium and new environment (temp, nutrients, etc) • Synthesis of some new cell components • Varies in length depending on media shift, temperature shift and age of inoculum

  46. Bacterial Growth Curve in Batch Culture Exponential or Log Phase • Bacteria are actively dividing at the maximum rate given their genetic potential, nature of medium and environmental conditions • Cells are most uniform in terms of chemical and phsyiological properties. Log phase cells are commonly used experimentally

  47. Bacterial Growth Curve in Batch Culture Stationary Phase • No net increase in cell numbers thus growth curve levels off • Total number of viable cells is constant • Cell death may =cell division or the populations ceases to divide but remains metabolically active

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