culturing microorganisms

Question 1

why are aseptic techniques important ?

Answer 1

they help to prevent other microorganisms from the air and surfaces from contaminating the microorganisms being prepared

Question 2

list the basic aseptic techniques

Answer 2

Wipe surfaces with antibacterial cleaner
Set up Bunsen burners
Flame inoculation loop and neck of bottles before use
Minimise time vessels containing bacteria are open
Sterilise all equipment
Wear protective clothing

Question 3

outline how to culture microorganisms

Answer 3

1. Transfer bacteria to agar plate using sterile inoculation loop or pipette
2. Tape lid on two ends and invert the dish, and incubate. Ensure the dish is not airtight and do not incubate above 25°C

Question 4

what is the spread plate methods ?

Answer 4

Distribute microorganisms evenly with a sterile spreader

Question 5

what is the streak plate method ?

Answer 5

Inoculating loop is used to draw the inoculum back and forth across the agar plate to separate individual cells of microbial population

Question 6

what are the types of culture ?

Answer 6

agar plate
selective media

Question 7

what is an agar plate ?

Answer 7

• contains nutrient agar, a solid mixed with nutrient broth poured into a petri dish and allowed to set
• agar acts like a sponge to hold the nutrients in a solid block

Question 8

why is selective media used ?

Answer 8

to gown specific types of organisms by using a recipe that discourages the growth of unwanted organisms

Question 9

what are the problems with culturing microorganisms ?

Answer 9

• pathogens may enter the culture and grow, risking the spread of the culture
• safe organisms may mutate to dangerous forms in the culture
• contamination with unwanted organisms can spoil in an investigation

Question 10

what are the precautions to take when culturing microorganisms ?

Answer 10

• adequate 02 supply, as anaerobic conditions encourages the growth of pathogens
• culture temperature 30 degrees or below, as human body temperature encourages growth of human pathogens

Question 11

what are the conditions of growth for microorganisms ?

Answer 11

nutrients
suitable temperature and pH
access to O2

Question 12

investigate the rate of growth of bacteria in liquid culture

Answer 12

1. known volume of nutrient broth
2. add bacteria
3. shake to distribute bacteria evenly
4. take inital value and count bacteria
5. keep temperature contast and take count sample at regular intervals