Microbiology - Bacteria Flashcards
When were microscopes discovered?
1600’s, until then scientists did not know about cells
Gram positive appear…
Purple (stain with crystal violet dye)
Gram negative appear…
Pink (stain with safranin dye)
What is taxonomy?
Study of naming and classifying organisms. Five kingdom system developed by Robert Whittaker
Eukaryotes vs Prokaryotes
Eukaryotes: -have a nucleus -no cell wall Prokaryotes: -no nucleus -cell wall
How is taxonomy divided?
- Domain
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
Bacteria cell morphology
- Cocci (round and spherical)
- Bacilla (rod-shaped)
- Spirilla (curved or spiral)
Bacteria cell structures
- Capsule
- Cell wall
- Outer membrane (gram -)
- Cytoplasmic membrane
- Cytoplasm
- Flagella
- Pilli/fimbriae
- Nucleoid
- Ribosomes
Why do antibiotics not attack our regular cells?
Detect the cell wall made of peptidoglycan and penetrate (create holes) in it. Results in killing of some good bacteria as well :(
Why are gram negative bacteria so much harder to kill?
They have an outer membrane as well
What is the gram staining procedure?
Stain the bacteria first with crystal violet, it will turn purple immediately. Then, rinse it with water and apply iodine solution, which will decrease solubility of violet stain. If it retains the purple, it is gram positive, if discolouration happens, stain it with safranin as it is likely gram negative, and this will cause it to turn pink
How do antimicrobial agents work?
Interfere with nutrient intake and metabolism of cell by acting on cytoplasmic membrane
How do bacteria grow and reproduce?
Growth: increase in cell number or multiplication
Reproduce through binary fission (each cell divides into 2 daughter cells)
What are the 5 major conditions/growth requirements for bacteria?
- Temperature
- pH
- Nutrients
- Oxygen
- Water
What is a thermophile?
Bacterias that love heat (above 56 Celsius)
What are mesophiles?
Bacteria that grow best at body temperature (37 celsius)
What are psychophiles?
Bacteria that love the cold (0-15 celsius, grow best at 7)
What are obligate aerobes?
Bacteria that require high oxygen (20%)
What are microaerophiles?
Bacteria that can only tolerate a little oxygen (2-10%)
What are obligate anaerobes?
Bacteria that can only grow in the absence of oxygen
What are facultative anaerobes?
Bacteria that can grow with or without oxygen but prefer without
Which type of bacteria are most commonly found in the oral cavity?
99% of oral bacteria are oligtate anaerobes or facultative anaerobes
What do all bacteria require in order to grow?
Water
How do we control growth of bacteria?
-preventing multiplication of microbe
or
-killing/destruction of microbe
