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Taxonomy

Taxonomy. Defined as the science of classification of organisms Taxonomic categories are arranged to show degree of similarities among organisms Relatedness through evolution. Three Domain System. System of classification above the five kingdoms

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Taxonomy

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  1. Taxonomy • Defined as the science of classification of organisms • Taxonomic categories are arranged to show degree of similarities among organisms • Relatedness through evolution

  2. Three Domain System • System of classification above the five kingdoms • Based on molecular techniques of ribosomal RNA analysis • Domains consists of the: • Eukarya • Bacteria • Archaea

  3. Taxonomic Hierarchy

  4. Bacteria Peptidoglycan in cell wall All pathogenic and non-pathogenic bacteria Archaea No peptidoglycan in cell wall Extreme environments Methanogens Extreme halophiles Hyperthermophiles Prokaryote Classification

  5. How could you classify bacteria? • Gram reaction • Shape • Nutritional requirements • Oxygen requirements • Aerobic - requires oxygen • Anaerobic - killed by oxygen • Facultative anaerobe - lives with or without oxygen • DNA profiles – G+C ratios • Combination of all of the above

  6. Prokaryotes • Grouped into two Domains • Domain Archaea • Domain Bacteria – two major divisions • Proteobacteria – 5 classes • Gram positive bacteria – two groups • High G+C ratios – phylum Firmicutes • Low G+C ratios – phylum Actinobacteria

  7. Proteobacteria • Five classes • Very diverse group • Most of the gram negative bacteria • Alpha, beta, gamma, delta, and epsilon – proteobacteria • General survey of some the better known and medically important members of this group

  8. Alphaproteobacteria • Genus Rickettsia • Obligate intracellular parasites • Transmission to human by bites of ticks and insects • Spotted fever diseases • Epidemic typhus • Rocky Mountain Spotted Fever

  9. Betaproteobacteria Medically important genus: • Genus Neisseria – aerobic G- cocci • mucous membranes of mammals • Neisseria gonorrhoeae – gonorrhoea • Neisseria meningitidis - meningococcal meningitis

  10. Figure 11.6

  11. Gammaproteobacteria • Largest sub-group of the Proteobacteria • Many pathogenic orders and genera in this group • Important groups: • Genus - Pseudomonas • Order Enternbacteriales (enteric bacteria)

  12. Pseudomonas • Pseudomonas aeruginosa is the important bacteria of this genus • Motile, G- rod, aerobe – produces a blue-green pigment • Highly antibiotic resistant • Important bacteria in urinary tract infections and wound/burn infection

  13. Figure 11.7

  14. Order Enterobacteriales • All members of this order are straight G- rods, facultative anaerobes • Commonly found in the gut of humans and other animals – ENTERICS • Fimbriae for surface attachment • Sex pili for exchange of genetic information

  15. Important genera of order Enterobacteriales • Escherichia • Salmonella • Shigella • Klebsiella • Serratia • Proteus • Enterobacter

  16. Escherichia • E. coli • Common gut bacteria, usually non-pathogenic • Used as indicator for fecal contamination of water • Common cause of traveler’s diarrhea • Most toxic strain is called 0157:H7 - foodborne disease

  17. Salmonella • Intestinal tracts of poultry and cattle • Food contaminate • Typhoid fever and gastrointestinal illness • Almost all members of this genus are pathogenic

  18. Shigella • Found only in humans • Causes bacillary dysentery

  19. Klebsiella • Common in soil and water • Klebsiella pneumoniae can cause a serious pneumonia in humans

  20. Serratia • Serratia marcescens produces a red pigment when grown at room temperature • Cause of urinary and respiratory infections in hospitals

  21. Proteus • Highly motile bacteria • Shows swarming growth on agar plates • Important in urinary tract and wound infections

  22. Figure 11.9b

  23. Enterobacter • Widely found in humans and other animals, also found in sewage, water, and soil • Two important pathogens are: • Enterobacter aerogenes • Enterobacter cloacae • Urinary tract infections and nosocomial infections

  24. Epsilonproteobacteria • Slender G- rods that are helical or vibroid • Two important genera: • Helicobacter • Helicobacter pylori – common cause of peptic ulcers in humans and stomach cancer • Campylobacter • Leading cause of food-borne intestinal disease especially from chicken

  25. Figure 11.12

  26. FirmicutesLow G+C Gram + bacteria • This group includes the following important groups of bacteria: • Clostridium • Bacillus • Staphylococcus • Streptococcus • Lactobacillus • Enterococcus

  27. Clostridium • Rod shaped, obligate anaerobes • SPORE FORMERS • Many medically important members of this genus • Clostridium tetani - tetanus • Clostridium botulinum - botulism • Clostridium perfringenes – gas gangrene • Clostridium difficile - diarrhea

  28. Bacillus • Rod shaped, facultative anaerobes • SPORE FORMERS • Common in the soil, few important pathogens • Bacillus anthracis - anthrax • Bacillus cereus – food poisoning

  29. Staphylococcus • Cocci usually occur in grape-like clusters • Facultative anaerobe • Grow well in high salt • Found on human skin • CATALASE POSITIVE - reaction with hydrogen peroxide • Important pathogen: • Staphylococcus aureus

  30. Figure 11.18

  31. Lactobacillus • Rod shaped, non-spore forming • Aerotolerant, grow in the presence of oxygen, but poorly • Important in production of lactic acid and also sauerkraut, pickles, buttermilk, and yogurt • Commonly found in the vagina, intestinal tract, and oral cavity

  32. Streptococcus • Cocci, growing in chains • CATALASE NEGATIVE • Cause more illness than any other group of bacteria • Two typical reactions on a media called blood agar: • β- hemolytic streptococci • Streptococcus pyogenes • α- hemolytic streptococci • Streptococcus pneumoniae

  33. Figure 11.19

  34. Enterococcus • Common hospital pathogen • Low oxygen requirement, catalase negative • Found in the GI tract, vagina, and oral cavity. Also fecal matter. • Two important members of this genera: • Enterococcus faecalis • Enterococcus faecium • Both are highly antibiotic resistant • Nosocomial infections

  35. ActinobacteriaHigh G+C bacteria • Genus Mycobacterium • Acid-fast bacteria; mycolic acid • Mycobacterium tuberculosis • Mycobacterium leprae • Genus Mycoplasma • NO CELL WALL • Mycoplasam pneumoniae • Genus Corynebacterium • Highly pleomorphic • Genus Propionibacterium • Propionibacterium acne • Genus Streptomyces • Filamentous bacteria; common in soil; antibiotics

  36. Phylum Chlamydiae • No peptidoglycan in the cell wall • Intracellular parasites • Spread through direct personal contact or air borne transmission • Chlamydia trachomatis • Best known pathogen in this group • Common cause of blindness - trachoma • Most common STD in the US.

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