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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
Basic structure of bacteria
Binary fission
Mode of nutrition
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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
Bacterial diseases
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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
Escherichia coli (E. coli)
- - in gastrointestinal (GI)
tract and colon
S synthesis of vitamin K
In immunosuppressed
host, even nonpathogenic strains can
cause infection
Diarrhoea
Anthrax 炭疽病 – caused by spore-forming
Bacillus 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
Bacillus anthracis,
Gram stain
Anthrax skin lesion
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
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
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
Yeast invade internal tissues:
Fungi that are external parasites of humans:
Ringworm, athlete’s foot
Ringworm
Athlete’s foot
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
Life cycle of Plasmodium
Other pathogens
 Parasitic worms
(not microorganisms)
Wuchereria bancrofti
絲蟲 -> Elephantiasis 象皮腫
Mad cow disease – caused by prion
Prion – protein
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