Environmental Factors Influencing the Growth Flashcards
What are the 3 factors inffluencing the growth of bacteria?
-pH
-Temperature
- Gaseous composition of atmosphere
T or F
Most bacteria grow best in neutral pH. (7.0-7.35)
True
Types of bacteria grow best in cold temp (10-20°C) are called
Psychrophiles
Bacteria that grow best in moderate temp. (20-40°C)
Mesophiles
Bacteria grow best at high temperatures. (50-60°C)
Thermophiles
T or F most bacteria grow in the human body are mesophiles
True- near the body temp (37°C)
Diagnostic laboratories routinely incubate cultures for bacterial growth at what degree celsius?
A. 37
B. 36
C. 35
D. 38
C
Fungal culture are incubated at what temp?
30°C
Example of Thermophiles bacteria
Pseudomonas sp.
Type of bacteria that require oxygen to grow.
Obligate aerobes
Example of obligate aerobes bacteria.
M. tuberculosis
It can survive in the presence of O but not used O in metabolism.
Aerotolerant anaerobes/ facultative aerobes
Cannot grows in the presence of Oxygen. Common in body.
Obligate anaerobes
Common spp. of aerotolerant anaerobes.
Clostridium spp.
Can grow either with or w/o the presence of oxygen. Majoritiy in the body.
Facultative anaerobes
Organisms grow best in increase of CO2
Capnophilic
Examples of capnophilic
- Helicobacter
- campylobacter
Type of bacteria that require a decrease in O2.
Microaerophilic
Examplen of facultative anaerobes.
E. coli
Bacteria replicates through what?
Binary fission
The time required for one cell to divide into two cells is called
Generation time or doubling time
T or F
The fast growing bacteria usually grow for about 20 mins.
True
T or F
For slow-growing bacteria, it usually takes 12 hours to grow.
False- 24 hrs.
Example of fast and slow growing bacteria.
Fast (E. coli)
Slow (M. tuberculosis)
T or F
If bacteria are in a balanced growth state, the increase in bacterial numbers is proportional to the increase of mass, protein content, nucleic acid content.
True
What are the 4 phases of bacterial growth phase?
- lag phase
- log phase
- stationary phase
- death phase
In this phase, there is no multiplication of bacteria because they’re only preparing to divide.
Lag phase
Which is true about the log phase?
A. High multiplication, low no. of bacteria, short period of time
B. No multiplication, long period of time, low no. of bacteria
C. High multiplication, high no. Of bacteria, short period of time
D. No multiplication, low no. Of bacteria, short perdiod of time
C
It is a phase in which nutrients are limited. The no. of bacteria is constant. (Equal no. of dead and living cells.)
Stationary phase
Phase in which the no. of nonviable bacterial cells exceeds the no. of viable cells.
Death phase
Adjustments phase: lag phase
Plate phase:
Stationary phase
It is a procedure done to maintain the living bacteria alive.
Subculture
3 ways in determination of cell numbers.
- Direct microscope count
- Direct plate count
- Density measurement
Which is/are true about Direct microscopic count?
A. It distinguishes between live and dead cells
B. All bacteria are already dead
C. Estimate the no. of bacteria present in specimen
D. Common in urine sample
B,C,D
Which is/are not true about direct plate count?
A. Can be done by growing dillution of broth cultures on agar plates.
B. Can determine the no. of colony-forming units per milliliters (CFU/mL)
C. Limit is 500 colonies
D. Provides a count of viable cells only
C. Limit is only 300 colonies
A measurement based on the density of bacterial broth culture in log phase.
Density measurement.
The desity refers to what?
Turbidity/cloudliness
This method is used to prepare a standard inoculum for antimicrobial susceptibility testing
Density measurement.
method usually used in water analysis
Direct plate count
What equipment is used in density measurement?
Spectrophotometer
