Microbial techniques; Types of micro-organism, their morphology, culture and media preparation, SPC, TPC
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Question No. 1
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At what temperature and pressure is culture media typically sterilized in an autoclave?
A.
121°C at 15 lbs pressure for 15 minutes
B.
100°C at 10 lbs pressure for 20 minutes
C.
150°C at 20 lbs pressure for 10 minutes
D.
80°C at 5 lbs pressure for 30 minutes
Question No. 2
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Which of the following is the
primary source
of both carbon and nitrogen in culture media?
A.
Distilled water
B.
Agar
C.
Beef extract
D.
Peptone
Question No. 3
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What does SPC stand for in microbiology?
A.
Special Pathogen Culture
B.
Standard Plate Count
C.
Selective Plate Culture
D.
Sterilized Petri Count
Question No. 4
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Which bacterial shape is described as spherical or elliptical?
A.
Spirilla
B.
Bacilli
C.
Vibrio
D.
Cocci
Question No. 5
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What is the typical size range of bacteria?
A.
100 to 200 micrometers
B.
20 to 50 micrometers
C.
0.2 to 2.0 micrometers
D.
5 to 10 micrometers
Question No. 6
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Which arrangement describes bacteria dividing in one plane to form a chain of cells?
A.
Sarcina
B.
Staphylococcus
C.
Streptococcus
D.
Diplococcus
Question No. 7
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What does TPC measure in food microbiology?
A.
Toxic Pathogen Content
B.
Total Plate Count - total viable bacterial count
C.
Temperature Pressure Control
D.
Time Period for Culture
Question No. 8
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Beef extract in culture media primarily provides:
A.
pH indicators
B.
Only carbohydrates
C.
Solidifying agents
D.
Amino acids, vitamins, and minerals
Question No. 9
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Which bacterial shape is comma-shaped?
A.
Spirilla
B.
Vibrio
C.
Cocci
D.
Bacilli
Question No. 10
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What is the purpose of using 70% alcohol in laminar air flow during media preparation?
A.
Sterilization of the work area
B.
Adjusting pH
C.
Dissolving agar
D.
Solidifying media
Question No. 11
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Rod-shaped bacteria are classified as:
A.
Spirilla
B.
Bacilli
C.
Cocci
D.
Vibrio
Question No. 12
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In SPC/TPC testing, results are typically expressed as:
A.
Percentage
B.
CFU/g or CFU/mL
C.
pH units
D.
mg/L
Question No. 13
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Which type of culture media contains additional substances like blood, serum, or egg yolk?
A.
Differential media
B.
Selective media
C.
Basal media
D.
Enriched media
Question No. 14
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Yeast extract in culture media serves as a source of:
A.
Vitamins, carbon, and nitrogen
B.
Only water
C.
Solidifying agents
D.
Antibiotics
Question No. 15
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What is the typical incubation temperature for most bacterial cultures?
A.
60°C
B.
0°C
C.
37°C
D.
100°C
Question No. 16
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Bacteria that divide in three planes to form cube-like configurations are called:
A.
Streptococcus
B.
Sarcina
C.
Diplococcus
D.
Staphylococcus
Question No. 17
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The pour plate technique used in TPC allows growth of:
A.
Only fungi
B.
Only viruses
C.
Aerobic and facultative anaerobic bacteria
D.
Only strict anaerobes
Question No. 18
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What is the typical incubation period for Standard Plate Count?
A.
30 days
B.
2 to 4 hours
C.
48 to 72 hours
D.
1 week
Question No. 19
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Which bacterial arrangement results from division in three planes to form grape-like clusters?
A.
Diplococcus
B.
Sarcina
C.
Staphylococcus
D.
Streptococcus
Question No. 20
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What concentration of agar is typically used to solidify liquid broth into solid medium?
A.
1-7%
B.
0.1-0.5%
C.
20-30%
D.
15-20%
Question No. 21
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Bacteria that lack a cell wall are called:
A.
Mycoplasmas
B.
Spirilla
C.
Bacilli
D.
Cocci
Question No. 22
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Which of the following is NOT a common ingredient in culture media?
A.
Yeast extract
B.
Plastic polymer
C.
Beef extract
D.
Peptone
Question No. 23
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Selective media contain substances that:
A.
Decrease pH only
B.
Support growth of all organisms equally
C.
Encourage specific microorganisms while inhibiting others
D.
Only solidify the medium
Question No. 24
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Spiral-shaped bacteria are classified as:
A.
Spirilla
B.
Vibrio
C.
Bacilli
D.
Cocci
Question No. 25
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What is the purpose of adjusting pH in culture media preparation?
A.
To solidify the medium
B.
To create optimal growth conditions for specific microorganisms
C.
To change the color of media
D.
To prevent agar from dissolving
Question No. 26
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Which bacterial arrangement consists of four round cells formed by division in two planes?
A.
Monococcus
B.
Streptococcus
C.
Tetracoccus
D.
Diplococcus
Question No. 27
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Differential media are used to:
A.
Distinguish between different microorganisms based on their characteristics
B.
Solidify liquid media
C.
Kill all bacteria
D.
Measure pH only
Question No. 28
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Liquid culture media is characterized by:
A.
Presence of 10% gelatin
B.
Absence of solidifying agents
C.
Solid consistency
D.
High agar concentration
Question No. 29
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Which technique is used for TPC determination?
A.
Microscopy only
B.
PCR only
C.
Pour plate technique
D.
Gram staining only
Question No. 30
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After autoclaving, culture media flasks are placed in:
A.
Laminar air flow
B.
Direct sunlight
C.
Refrigerator
D.
Open air
Question No. 31
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Bacteria arranged as two cells after division are called:
A.
Staphylococcus
B.
Diplococcus
C.
Tetracoccus
D.
Streptococcus
Question No. 32
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What is the purpose of serial dilution in TPC testing?
A.
To change media color
B.
To add nutrients
C.
To reduce bacterial concentration to countable levels
D.
To increase bacterial growth
Question No. 33
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Which of the following bacteria have branching, filamentous forms?
A.
Spirilla
B.
Cocci
C.
Actinomycetes
D.
Vibrio
Question No. 34
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Why are petri plates kept inverted during incubation?
A.
To increase oxygen supply
B.
To save space
C.
To prevent condensation from dripping onto colonies
D.
To reduce temperature
Question No. 35
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A single, discrete round bacterial cell is called:
A.
Diplococcus
B.
Staphylococcus
C.
Streptococcus
D.
Monococcus or Micrococcus
Question No. 36
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What is the main difference between SPC and TPC?
A.
They are essentially the same, both measure total viable bacteria
B.
SPC measures only pathogens
C.
SPC measures viruses
D.
TPC measures only spores
Question No. 37
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Which component provides structure without interfering with microbial growth?
A.
Peptone
B.
Yeast extract
C.
Agar
D.
Beef extract
Question No. 38
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Facultative anaerobic bacteria can grow:
A.
Only without oxygen
B.
Only with oxygen
C.
Only at high temperatures
D.
In presence or absence of oxygen
Question No. 39
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What is the purpose of sealing petri plates with paraffin after inoculation?
A.
To change pH
B.
To increase oxygen supply
C.
To accelerate growth
D.
To prevent contamination and moisture loss
Question No. 40
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Which bacterial morphology is described as comma-shaped with a single curve?
A.
Cocci
B.
Spirilla
C.
Bacilli
D.
Vibrio
Question No. 41
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Ready-to-use culture media is:
A.
Supplied in ready-to-use form or ready after remelting
B.
Requires complete sterilization
C.
Cannot be stored
D.
Must be prepared from individual components
Question No. 42
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What does CFU stand for in microbiology?
A.
Culture Fluid Units
B.
Colony Forming Units
C.
Cell Formation Units
D.
Contamination Free Units
Question No. 43
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Which statement is TRUE about obligate parasites?
A.
They grow on all types of media
B.
They grow faster than other bacteria
C.
They only require liquid media
D.
They cannot grow on culture media in any condition
Question No. 44
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The process of transferring microorganisms onto culture media is called:
A.
Sterilization
B.
Inoculation
C.
Autoclaving
D.
pH adjustment
Question No. 45
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Which concentration of gelatin is used as an alternative solidifying agent?
A.
0.5-1%
B.
1-7%
C.
30-40%
D.
10-20%
Question No. 46
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What is the main purpose of using pH indicators in culture media?
A.
To monitor and maintain optimal pH levels
B.
To kill bacteria
C.
To provide nutrients
D.
To solidify the medium
Question No. 47
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Microaerophilic bacteria require:
A.
Less than atmospheric oxygen levels
B.
No specific oxygen requirement
C.
Complete absence of oxygen
D.
High oxygen levels
Question No. 48
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Which bacterial property allows identification using culture media?
A.
Only shape
B.
Only color
C.
Only size
D.
Growth characteristics and metabolic reactions
Question No. 49
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What is the purpose of boiling agar during media preparation?
A.
To adjust pH
B.
To kill all bacteria
C.
To completely dissolve agar in the solution
D.
To add nutrients
Question No. 50
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TPC in food samples is done to determine:
A.
pH level
B.
Vitamin content
C.
Only pathogenic bacteria
D.
Total bacterial load indicating food quality
Question No. 51
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Which tool is used for streaking bacteria on solid media?
A.
pH meter
B.
Inoculation loop
C.
Centrifuge
D.
Spectrophotometer
Question No. 52
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What is the advantage of using separate autoclaving for phosphate and agar?
A.
Increases agar concentration
B.
Reduces sterilization time
C.
Prevents hydrogen peroxide formation that inhibits growth
D.
Changes media color
Question No. 53
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Which type of bacteria can survive in the complete absence of oxygen?
A.
Microaerophiles
B.
Obligate anaerobes
C.
Facultative anaerobes
D.
Obligate aerobes
Question No. 54
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The streaking technique on solid media is primarily used for:
A.
Isolation of pure cultures
B.
Sterilization
C.
Measuring pH
D.
Counting total cells
Question No. 55
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Which media preparation method involves rehydration of dry formulations?
A.
On-demand medium
B.
Commercially dehydrated formulations
C.
Fresh media only
D.
Ready-to-use medium
Question No. 56
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What is the primary purpose of culturing microorganisms?
A.
Only for food preparation
B.
Only for industrial production
C.
Only for teaching
D.
For research, diagnostics, and identification
Question No. 57
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Which bacterial characteristic is used for Gram classification?
A.
Cell wall structure and composition
B.
Motility only
C.
Shape only
D.
Size only
Question No. 58
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Semi-solid media contains approximately what concentration of agar?
A.
25-30%
B.
15-20%
C.
0.5% or less
D.
5-7%
Question No. 59
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What indicates successful bacterial growth in liquid broth culture?
A.
Clear transparent appearance
B.
No visible change
C.
Red color only
D.
Turbidity or cloudiness of the broth
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