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Lesson 6 Prokaryotes: Part II

Lesson 6 Prokaryotes: Part II. October 2, 2014. Gram-Positive Bacteria. Divided into two groups based on G + C content (%of GC in the DNA) Firmicutes (low G + C ratio) Staphylococcus, Enterococcus , Streptococcus Endospore -forming bacteria Clostridium and Bacillus

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Lesson 6 Prokaryotes: Part II

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  1. Lesson 6 Prokaryotes: Part II October 2, 2014

  2. Gram-Positive Bacteria • Divided into two groups based on G + C content (%of GC in the DNA) • Firmicutes (low G + C ratio) • Staphylococcus, Enterococcus, Streptococcus • Endospore-forming bacteria • Clostridium and Bacillus • Mycoplasma lacks a cell-wall • Actinobacteria (high G + C ratio) • Highly pleomorphic • Mycobacterium, Corynebacterium, Propionibacterium • Streptomycesis the source of several antibiotics

  3. Firmicutes

  4. Order Clostridiales • Clostridium • Endospore-producing • Obligate anaerobes • Causative agent of tetanus (tetani), botulism (botulinum), foodborne diarrhea (perfringens) • C. difficile normal part of intestinal microbiota • Produces toxins

  5. Figure 11.13 Clostridium difficile. Endospore

  6. Order Bacillales • Bacillus • Endospore-producing rods • B. cereus and B. anthracis are human pathogens • B. thurigenesis infects insects. Used as insecticide • Staphylococcus • Clusters of cocci • Halophilic and survive in low moisture environments • Produces enterotoxins. Targets intestines. • Causes food poisoning and Toxic Shock Syndrome

  7. Figure 11.15 Bacillus. Endospore case This Bacillus cereus cell is shown emerging from the endospore.

  8. Figure 11.16 Staphylococcus aureus. Aureus = golden Color may provide protection from Antimicrobial properties of the sun

  9. Order Lactobacillales • Generally aerotolerant anaerobes; lack an electron transport chain • Produce lactic acid that restricts growth of other bacteria • Lactobacillus located in vagina, intestines, oral cavity • Streptococcus produce exotoxins that destroy phagocytic cells, connective tissue, fibrin • Enterococcuslive in areas rich in nutrients but low in oxygen. Important in nosocomial infections • Listeriacontaminates dairy products. Survives within phagocytes and can grow in refrig. temps. Can cause stillbirth in pregnant women

  10. Order Mycoplasmatales • Lacks a cell wall; highly pleomorphic • Difficult to treat • Very small size range (0.1–0.24 µm) • Primary source of laboratory contamination • M. pneumoniaeis the causative agent of pneumonia and M. ureaplasmaare associated with urinary tract infections

  11. Actinobacteria

  12. Actinobacteria • Actinomyces • Corynebacterium • Frankia • Gardnerella • Mycobacterium • Nocardia • Propionibacterium • Streptomyces

  13. Mycobacterium • Aerobic, non-endospore forming rods • Cell wall is similar to gram negative but the LPS is replaced with mycolic acids (forms wax layer) • Resists drying • Disallows many antimicrobial drugs from entering • Multi-drug Resistant Tuberculosis (efflux pumps) • Nutrients also enter slowly (slow growth of bacteria) • Causative agents of tuberculosis (tuberculosis) and leprosy (leprae)

  14. Propionibacteria • Slow growing aerotolerant anaerobe rods • Located within pores of the skin and uses sebum and fatty acids as food source • More sebum causes more growth • Destroys cells in pores allowing other bacteria to colonize the pores • Produces propionic acid • Used to ferment swiss cheese

  15. Streptomyces • Largest group of the Actinobacteria • Commonly found in soil • Produces geosmin (gaseous compound that gives soil its “musty” odor) • Produce over two-thirds of the clinically used antibiotics • Neomycin, chloramphenicol, Amphotericin B • Streptomycin takes its name from this bacteria

  16. NonproteobacteriaGram-Negative Bacteria

  17. Chlamydia and Chlamydophila • Obligate intracellular pathogens • Gram negative • Chlamydia trachomatis • Trachoma • STI, urethritis. Most common STD in U.S. • Chlamydophilapneumoniae • Prevalent in young adults • Chlamydophilapsittaci (zoonosis) • Psittacosis • Very distinct developmental cycle

  18. Developmental Cycle Beatty et. al., 1994

  19. Nonproteobacteria Gram-Negatives • Bacteroidetes • Anaerobic • Bacteroides are found in the mouth and large intestine • Most common bacteria in the intestine (1 billion per gram of fecal matter) • Cytophaga: degrade cellulose in soil • Fusobacterium • Resides in the mouth • May be involved in dental diseases

  20. Spirochaetes • Move via axial filaments (corkscrew) • Many are located in the oral cavity • Treponemapallidium causes syphilis. • Spread by sexual contact or mother to fetus (congenitalsyphilis) • Borrelliacauses Lyme disease. Carried by ticks/lice

  21. Microbial Diversity • Microbiologists have described ~5000 bacterial species • PCR indicates up to 10,000 bacterial species per gram of soil • Many bacteria have not been identified because they • Have not/can not be cultured • Need special nutrients • Are a part of complex food chains requiring the products of other bacteria

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