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Understanding Bacteria: Structure, Function, and Diseases

Explore the basic structure of bacteria, their different modes of nutrition, Gram staining reactions, and bacterial diseases such as anthrax, tuberculosis, and tetanus. Learn about E. coli in the GI tract and how pathogens are transmitted.

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Understanding Bacteria: Structure, Function, and Diseases

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  1. Bacteria • Kingdom: Prokaryotae (原核生物界) 1.Cells have no distinct nucleus / no nuclear envelope 2.Single circular DNA molecule in cytoplasm 3.Membranous organelles absent 4.Infolding of the cell membrane forms mesosomes for respiration

  2. Basic structure of bacteria

  3. Binary fission

  4. Mode of nutrition •   Photosynthetic – cyanobacteria • Chemosynthetic – nitrogen-fixing bacteria • Saprophytic – putrefying bacteria • Parasitic – pathogenic bacteria • Oxygen demand •   Aerobes – bacteria require oxygen for respiration • Anaerobic – bacteria unable to tolerate oxygen • Facultative anaerobes – can grow with or without • oxygen) • Gram stain reaction •   Bacteria can be categorized based on the cell wall • structures which in turn influences the Gram stain • reaction. •   Gram –ve : appears pink after staining •   Gram +ve : appears purple after staining

  5. Bacterial diseases • 1.Anthrax炭疽病 • 2.Tuberculosis (TB) 肺結核/肺癆 • 3.Cholera 霍亂 • 4.Diphtheria 白喉 • 5.Syphilis 梅毒 (STD) • 6. Gonorrhea 淋病 (STD) • 7. Leprosy 痲瘋 • 8.Plague 瘟疫/黑死病/鼠疫 • 9.Tetanus 破傷風 • 10.Typhoid 傷寒 • 11.Typhus 斑疹傷寒

  6. Escherichia coli (E. coli) -- in gastrointestinal (GI) tract and colon S synthesis of vitamin K In immunosuppressed host, even non-pathogenic strains can cause infection Diarrhoea

  7. Anthrax 炭疽病 – caused by spore-formingBacillus anthracis • - occur in humans when they are exposed to infected animals or to tissue from infected animals or when anthrax spores are used as a bioterrorist weapon. • -  will not transmit from person to person • -  the spores can be used as a bioterroist weapon, • as was the case in 2001, when the spores had been intentionally distributed through the postal system, causing 22 cases of anthrax, including 5 deaths

  8. Bacillus anthracis, Gram stain Anthrax skin lesion

  9. Tuberculosis (TB) 肺結核/ 肺癆- caused by rod-shaped Mycobacterium tuberculosis Tuberculosis creates cavities visible in x-rays like this one in the patient's right upper lobe. -  chronic or acute bacterial infection that primarily attacks the lungs -  transmitted by inhaling bacteria-carrying droplets drug resistant strains developed

  10. Tetanus 破傷風 - caused by bacillus Clostridium tetani, • - bacteria on rusty nails • - release exotoxin • - serious infections disease to the nervous system • - lockjaw, stiffness of abdominal and back muscles , facial muscle spasms, fast pulse, slight fever, severe sweating ,headache

  11. Fungi 真菌界 - eukaryotic, heterotrophic organisms that have rigid cellulose- or chitin-based cell walls -  unicellular e.g. yeast or multicellular -  saprophytic fungi – decomposer parasitic fungi – pathogenic - may be opportunistic

  12. Ringworm Athlete’s foot Yeast invade internal tissues: Fungi that are external parasites of humans: Ringworm, athlete’s foot

  13. Protozoa 原生動物Kingdom – protoctista　原生生物界 • Ｍalaria瘧疾 －　by Plasmodium - transmitted by bite of female mosquitoes Trypanosomiasis 昏睡病 by Trypanosoma

  14. Life cycle of Plasmodium

  15. Other pathogens (not microorganisms) Wuchereria bancrofti絲蟲 -> Elephantiasis 象皮腫 • Parasitic worms

  16. Mad cow disease – caused by prion

  17. Prion – protein

  18. Transmission of infectious diseases 1. Through air or air-borne particles 2.  Through contaminated food and water 3.  Direct contact (including sexual) 4.  Blood transfusion 5.  Through body fluid 6. Though sharing infected tools (needles) 7. Through sexual contact  8. Through vector

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