Cell structure

Question 1

What growth considered in microbial growth?

Answer 1

increase in the number of bacteria, not their size

Question 2

How does microbial growth happen?

Answer 2

by cell division ; on parent cell grows, then splits into 2 - process known as binary fission

Question 3

What is binary fission?

Answer 3

the cells gets bigger -> copies its DNA -> a wall called septum starts forming in the middle -> the cell splits into 2 identical ‘daughter’ cells

Question 4

How are microbes studied in the lab?

Answer 4

• grow bacteria under controlled conditions
• use aseptic techniques to avoid contamination
• grow pure cultures (only one kind of microbe)
• use n autoclave to sterilise tools

Question 5

How is the bacterial growth measured?

Answer 5

1. direct microscopic count
2. plate count

Question 6

What is the bacterial growth curve? - has 4 phases

Answer 6

1. Lag phase - bacteria adjusting, making enzymes + energy + copying DNA ; no increase in number yet
2. Exponential (Log) phase - rapid cell division , nutrients and conditions are perfect
3. Stationary Phase - growth slows, balance between new cells and dying ones ; caused by lack of nutrients,O2 and toxic waste buildup
4. Death Phase : cells start dying, total number stays high, but live cells decrease

Question 7

What factors affect growth?

Answer 7

2 types of factors
1. Physical
2. Nutritional

Question 8

What physical factors affect growth?

Answer 8

pH : needs to be in the right range
temperature : most like 37C (body temp)
O2 : some need it, some are killed by it
moisture

Question 9

What nutritional factors affect growth?

Answer 9

carbon : main energy source
nitrogen, sulphur, phosphorus : needed for DNA, proteins
trace elements and vitamins : required in small amounts

Question 10

What types of culture media are out there?

Answer 10

1. Complex media : made from extracts such as yeast and cheap/flexible
2. Synthetic (Defined) media : exact ingredients are known, expensive but precise
3. Natural media : mimics the natural environment such as blood and plant juice

Question 12

What is special media?

Answer 12

• selective media : allows only certain microbes to grow
• differential media : shows differences between microbes

Question 13

What is an example of special media?

Answer 13

MacConkey agar (both selective and differential)