Microbiology

Question 1

What are bacteria and fungi important in

Answer 1

Decaying dead organisms and recycling nutrients

Question 2

What are the three different shapes of bacteria

Answer 2

BACILLUS (rod shaped)
COCCI (spherical)
SPIRILLUM (cork screw shaped)

Question 3

How else can you differentiate bacteria

Answer 3

How they are grouped e.g. Clusters 
Size
Shape 
Antigenic properties 
Staining characteristics 
Metabolism 
DNA sequences

Question 4

What is a gram stain

Answer 4

Enables microbiologists to distinguish between two types of bacteria 
Gram negative( purple) and gram positive (red) 
Different staining properties are due to composition of cell walls

Question 5

Explain how and why gram negative bacteria reacts how it does

Answer 5

More chemically complex
Walls do not retain dyes like crystal violet
E.g. Salmonella
(They have an extra layer of lipopolysaccharides) with porins)

Question 6

How do gram positive bacteria react to the gram stain

Answer 6

Do retain crystal violet e.g. Bacillus and staphylococcus

They have a thicker layer of peptidogcylcan

Question 7

Explain how penicillin works with bacteria

Answer 7

GRAM POSITIVE - thick peptidoglycan walls which is highly cross linked. These bonds are constantly being reformed. Penicillin is an antibiotic which interferes with this process weakening the wall and leaving it susceptible to osmotic Lysis
GRAM NEGATIVE - more complex wall with a thin layer of peptidoglycan and an outer layer of lipopolysaccharide the outer membrane makes the bacteria resistant to the entry of penicillin which does not affect them

Question 8

Explain the pattern in bacterial growth

Answer 8

1- lag phase
2- log phase
3- stationary
4- death

Question 9

Explain the procedure of GRAM staining

Answer 9

Begin with heat fixed cells 
Flood slide with crystal violet dye for one minute 
Add iodine solution for one minute 
Wash slide with Alcohol for 20 seconds
Counter stain with safranin

Question 10

what are the conditions necessary for growth

Answer 10

NUTRIENTS carbon and nitrogen
pH most bacteria favour slightly alkaline conditions
TEMP optimum (37)
OXYGEN obligate aerobes - require oxygen to respire
obligate anaerobes - cannot grow in the presence of oxygen e.g. clostridium bacteria produce toxins in a wound and destroy body tissue
facultative anaerobes - can grow in oxygen but also in the absence of them