3.4 - Micro Biology

Question 1

Classification of bacteria

Question 2

Bacillus?

Answer 2

Rod-shaped

Question 3

Examples?

Answer 3

E.Coli
Bacillus

Question 4

Coccus?

Answer 4

spherical
not circular

Question 5

2 examples?

Answer 5

staphylococcus
streptococcus

Question 6

Spirillium?

Answer 6

Spiral

Question 7

how can they be classified?

Answer 7

arrangement

Question 8

Single?

Answer 8

Heliobacter

Question 9

How can they also be arranged in?

Answer 9

pairs
Diplococcus pneumonia

Question 10

Chains?

Answer 10

Streptococcus

Question 11

Clusters?

Answer 11

Staphlococcus

Question 12

What does Gram Staining do?

Answer 12

distinguishes between Gram-positive and Gram-negative bacteria

Question 13

What colour does Gram positive stain?

Answer 13

violet

Question 14

What colour does Gram negative stain?

Answer 14

red

Question 15

Bacterial cell wall?

Answer 15

3D network of polysaccharide and polypeptide
which together is murein or peptidoglycen
this network is cross-linked to provide strength and shape
this wall protects against lysis of water = taken up

Question 16

Gram-positive examples?

Answer 16

Bacillus
Stapholococcus
Streptococcus
All stain purple because they lack a lipopolysaccharide layer so stain binds effectively

Question 17

What are they susceptible to?

Answer 17

Antibiotic pencillin
will kill it

Question 18

What is the bacteria destroyed by?

Answer 18

enzyme lysosyme
found in lysosyme
in tears + saliva
hydrolyses the bonds of peptido glycen

Question 19

Gram negative?

Answer 19

a chemically complex cell wall
has 3 components
lipopolysaccharide layer
peptidoglycen layer
cell membrane

Question 20

Lipopolysaccharide layer?

Answer 20

most important as it protects the cell from the water soluble dyes such as crystal violet so Gram negative will counterstain pink

Question 21

Examples?

Answer 21

Salmonella
E.coli

Question 22

Lipolysaccharide layer?

Answer 22

protects bacteria from attack by pencillin and lysozyme

Question 23

Staining technique?

Answer 23

before staining, all bacteria = colourless
all bacteria = then stained with the dye ( crystal violet)
all bacteria = stained violet
add mordant which is lydols iodine to all the bacteria to fix the stain
add decolouriser ( propanone / alcholo)
add a counter stain of safranin to gram negative and tuen red
gram negative go colourless + gram positive go violet

Question 24

Growing a culture?

Answer 24

Conditions for growth
1) nutrients ( source of C) - glucose
Source of N such as amino acids (organic) or nitrate ions (inorganic)
2)Vitamis and ions Na+, Mg2+,Cl-,SO42-,PO43-
3)Temps of 25 degres - 45degrees
4)pH FOR BACTERIA = 7.4
fungi = 6.8
5) Obligate aerobe - must have oxygen
faculitiative anaerobe
grows best in oxygen but can survive in the absence
obligate anaerobe - best in no oxygen

Question 25

Types of medium?

Answer 25

Defined - al the ingredients = known
Undefined - not all of the components = known
selective - only allows specific bacteria to grow

Question 26

Aseptic techniques?

Answer 26

Method - protecting the culture - bacteria in the bottom
1) sterilise all apparatus + flame the neck of the culture vessel/bottle
2) place the sterile loop in a bunsen flame until it glows red
Protecting the environment
3) sterilise the surface with 3% lysol - disinfectant
4) hold the culture bottle in one hand, remove cap with little finger, dont place the cap on worl surface
when the ennoculating loop glows red, allow to cool and place in a culture bottle to remove the sample
6) lift petri desh by 45 degrees and use a swipe action to distibute the culture.
7) close the lid and attatch the 2 pieces of tape but dont seal completely as this will create anaerobic condition
8) Incubate at 25 degrees never 37 as that would grow pathogenic species as well
9) dont open petri dish after incubation

Question 27

Disposal?

Answer 27

place the petri dish in an auto clavable bag
place in an autoclave at a temp of 121 degrees under high pressure steam for 15 mins
place the bags in a biohazard bin

Question 28

measuring growth of bacteria?

Answer 28

the size of the population of bacteria can be measured in 2 ways

Question 29

Number 1?

Answer 29

directly ( coutning the cells)
viable count ( only living cells)
total count ( living anddead)
If use a light microscope - only look at living
Electron - kills and can only look at dead cells through it

Question 30

Indirect?

Answer 30

by measuring the turbidity using acolorimeter
usually used for taking river samples to count the water of bacteria

Question 31

Measuring growth directly?

Answer 31

Colony - a cluster of cells or a clone which arises from a single bacterim or fungal spore by a sexual reproduction
not possible to count the whole population so a small sample is counted and multiplied
The count is still too high and must be dilluted

Question 32

Haemocyter?

Answer 32

an accurate method for colony coutning
cannot be distinguished between living and dead cells so only gives a total count