Microbiology - Introduction

Question 1

3 types of morphology term

Answer 1

-Coccus (Spherical) 0
-Bacillus (Rod shape) []
-Spirillum (Spiral) \/\/\

Shape maintained by cell way made of murein

Question 2

What is Gram staining technique trying to find

Answer 2

-Gram positive bacteria (purple colour)
-Gram negative bacteria (pink colour)

Question 3

Gram staining technique 1-3

Answer 3

1)Heat fixing - hover slide with bacteria over Bunsen fire = bacteria fixed (not movable)

2)Crystal violet stain - put on slide as primary stain

3) Put Gram’s iodine on slide (fix the stain) = increase crystal violet absorption with cell wall

Question 4

Gram staining technique 4 -5

Answer 4

4)Pour alcohol on slide to remove excess crystal violet on slide + Gram negative bacteria. Until no colour coming off slide.

5)Pour safarin (counter stain - pink) on slide - allow bacteria cell to be visible + stain Gram negative bacteria

Between stage 2-5 after every stage slide is rinsed with water

Question 5

Gram positive bacteria

Answer 5

-Under microscope appear purple, since absorbed by cell wall + colour more intense than safarin

-Shows penicillin works - disrupt bond between cell wall + cell membrane. Die of dedication.

-Thicker cell wall than gram negative, over a layer of cell membrane

Question 6

Gram negative bacteria

Answer 6

-Under microscope appear pink, since not absorbed by cell wall, pink shows the bacteria since not rinsed or decolourised

-Shows penicillin not works - Outer membrane made of lipopolysaccharide + protein block crystal violet + penicillin. Other stuff (lysozyme) work

-Thinner cell wall than gram posrive, outer membrane over a layer of cell wall over memebrane

Question 7

How bacteria replicate

Answer 7

Binary fission asexually
-less complex, faster (less gene+organelle) than of mitosis (divide in 2)

-Happens every 20 minutes in optimal condition (exponential growth)

-Transfers plasmid (genes), eg antibiotics resistant gene

Question 8

How to grow bacteria in lab

Answer 8

-Petri dish with agar (nutrient containing glucose, N, Minerals, vitamin, water)

-Temperature (37 degrees for human pathogens, 25 for normal school, higher or lower for extremophiles)

-pH (7.4 bacteria most prefer slightly alkaline, stomach acid bacteria like low pH)

-Anti-biotic can be added to make super bug

Question 9

O2 requirement by bacteria

Answer 9

Obligate aerobes - must have o2 for metabolism + reproduction

Obligate anaerobes - must have no o2 environment for metabolism + reproduction

Facultative anaerobes - can do it without o2 but better with o2

Question 10

Life of bacteria in Petri dish

Answer 10

1)Lag - Not much cell division, climatising to environment and not yet active.

2)Exponential growth - Rapid growth vs low death rate. Lot of nutrient + space. Low toxin level

3)Stationary - Equal rate of death vs reproduce. Resources start to deplete. Toxin level increases. Bacteria produce fungi (eg penicillin) to kill other bacteria colony

4)Death - bacteria die quickly than reproduce, no resources left. Very high toxin level.