Microbiology 2 Flashcards
1
Q
why should we control Bacterial cell cycle
A
- Infectious disease caused by bacteria
- Food spoilage
- Pharmaceutical spoilage
- Environmental microbial contamination
2
Q
Bacterial cell cycle (binary fission)
A
- Cells elongate and enlarge its volume and DNA replicates
- Cell wall and plasma membrane begin to constrict
- Cross-wall forms,completelyseparating the two DNA copies
- Cells seperate
3
Q
Stages of bacterial cell growth
Lag phase
A
- Intense activity preperation of population growth but no increase in population
- Little or no cell division occurs
- Intense metabolic activity. Individual cells increase in size
4
Q
Stages of bacterial cell growth
Log phase
A
- Logarithmic or exponential increase in population
- Rapid and constant population growth (exponential manner)
- Number of cells produced > Number of cells dying
5
Q
Stages of bacterial cell growth
Stationary phase
A
- Period of equalibrium microbial deaths balance production of new cells
- Population size begins to stabilize
- Number of cells produced = Number of cells dying
6
Q
Stages of bacterial cell growth
Death phase
A
- Population is decreasing at a logarithmic rate
- Number of cells produced < Number of cells dying
7
Q
Generation time
A
- Time required for a bacteria to complete the cell cycle
- Binary fission doubles the number of cells each
generation
8
Q
Biofilms
A
- Microbial communities
- Form slime or hydrogels that adhere to surfaces
- Bacteria communicate cell-to-cell
- Share nutrients
- Shelter bacteria from harmful environmental
factors or microbicides
9
Q
physical requirements for bacterial growth
A
- Temperature
- pH
- Osmotic pressure
10
Q
Chemical requirement for bacteria growth
A
- Carbon source
- Ions and trace elements
- Oxygen nitrogen sulpher and phosphates
- Organic growth factors
11
Q
Temperature for optimum growth of Psychrophiles
A
Cold loving at the temperature < 15 degrees
12
Q
Temperature for optimum growth for Psychrotrophs
A
- 20 to 30 degrees is the optimum temperature
13
Q
Mesophiles optimum temperature
A
- between 25-30 degrees division of bacteria
14
Q
Thermophiles
A
Heat loving at like 50-60 degrees
15
Q
Temperatures effect on storing medicines
A
- 60 - 130 degrees Temperatures in this range destroy most microbes, although lower temperatures take more time
- 50-60 degrees very slow bacterial growth
- 15-50 danger zone rapid replication
- 5-15 many bacteria survive some may grow
- 0-5 refridgerator temp may slow growth and cause spoilage but few pathogen
- No significant growth below freezing
16
Q
pH and inhibiting microbial growth
A
- Low pH cause a decrease in microbial growth
- Alkali not usually used for preservation
17
Q
Osmotic requirements for bacteria
A
- Simlar requires isotonic and hypertonic could cause plasmolysis due to high osmotic pressure
- Halophiles tolerate high osmotic pressure
