BI 234 MIDTERM 2 EXAM QUESTIONS AND ANSWERS
WITH COMPLETE SOLUTIONS GRADED A++
1%
What % of microbes can be grown in pure culture?
There is so much that we don't know about because it is impossible to grow and
observe the majority of these organisms.
Why is it significant for microbiologists to recognize the % above?
Melts at 95℃ and solidifies at 45 ℃
What is the melting temperature and solidifying temperature of agar?
It provides nutrients for them.
Why is agar especially suitable to grow microbes?
Sterile
Completely free of microbes
Aseptic technique
Procedures to minimize unintentional introduction of microorganisms
-10 ℃ - 20 ℃, optimum 15 ℃
What are the minimum/optimum/maximum temperature ranges for Psychrophiles?
0 ℃ - 30 ℃, optimum 25 ℃
What are the minimum/optimum/maximum temperature ranges for Psychrotrophs?
10 ℃ -50 ℃, optimum 37 ℃
What are the minimum/optimum/maximum temperature ranges for Mesophiles?
,40 ℃ - 70 ℃, optimum 60 ℃
What are the minimum/optimum/maximum temperature ranges for Thermophiles?
65 ℃ - 110 ℃, optimum 95 ℃
What are the minimum/optimum/maximum temperature ranges for Hyperthermophiles?
Minimum survivable temperatures are due to enzyme & membrane fluidity
problems
Maximum survivable temperatures are due to enzyme denaturation
Why does microbial growth stop below and above the temperature ranges?
Hypertonic environments cause plasmolysis
(high sugar or salt concentrations)
What is osmotic pressure in your own words?
Disrupts osmosis.
How does osmotic pressure affect microbes?
Energy
Why do microbes require carbon?
Amino acids and proteins
Why do microbes require sulfur?
Amino acids, proteins
Why do microbes require nitrogen?
Inorganic elements required in small amounts.
What is a cofactor?
Obligate aerobes
Only aerobic growth; oxygen required
, Facultative anaerobes
Both aerobic and anaerobic growth; best growth in oxygen
Obligate anaerobes
Only anaerobic growth, NO growth in presence of oxygen
Aerotolerant anaerobes
Only anaerobic growth, but survives in presence of oxygen
Microaerophiles
Only aerobic growth, oxygen required in low concentration
Sepsis
Refers to microbial contamination
Asepsis
The absence of significant contamination
Sterilization
Removal of all microbes
Commercial sterilization
Killing C. botulinum endospores
Disinfection
Removal of pathogens
Antisepsis
Removal of pathogens from living tissue
Degerming
Removal of microbes from a limited area
Sanitization
WITH COMPLETE SOLUTIONS GRADED A++
1%
What % of microbes can be grown in pure culture?
There is so much that we don't know about because it is impossible to grow and
observe the majority of these organisms.
Why is it significant for microbiologists to recognize the % above?
Melts at 95℃ and solidifies at 45 ℃
What is the melting temperature and solidifying temperature of agar?
It provides nutrients for them.
Why is agar especially suitable to grow microbes?
Sterile
Completely free of microbes
Aseptic technique
Procedures to minimize unintentional introduction of microorganisms
-10 ℃ - 20 ℃, optimum 15 ℃
What are the minimum/optimum/maximum temperature ranges for Psychrophiles?
0 ℃ - 30 ℃, optimum 25 ℃
What are the minimum/optimum/maximum temperature ranges for Psychrotrophs?
10 ℃ -50 ℃, optimum 37 ℃
What are the minimum/optimum/maximum temperature ranges for Mesophiles?
,40 ℃ - 70 ℃, optimum 60 ℃
What are the minimum/optimum/maximum temperature ranges for Thermophiles?
65 ℃ - 110 ℃, optimum 95 ℃
What are the minimum/optimum/maximum temperature ranges for Hyperthermophiles?
Minimum survivable temperatures are due to enzyme & membrane fluidity
problems
Maximum survivable temperatures are due to enzyme denaturation
Why does microbial growth stop below and above the temperature ranges?
Hypertonic environments cause plasmolysis
(high sugar or salt concentrations)
What is osmotic pressure in your own words?
Disrupts osmosis.
How does osmotic pressure affect microbes?
Energy
Why do microbes require carbon?
Amino acids and proteins
Why do microbes require sulfur?
Amino acids, proteins
Why do microbes require nitrogen?
Inorganic elements required in small amounts.
What is a cofactor?
Obligate aerobes
Only aerobic growth; oxygen required
, Facultative anaerobes
Both aerobic and anaerobic growth; best growth in oxygen
Obligate anaerobes
Only anaerobic growth, NO growth in presence of oxygen
Aerotolerant anaerobes
Only anaerobic growth, but survives in presence of oxygen
Microaerophiles
Only aerobic growth, oxygen required in low concentration
Sepsis
Refers to microbial contamination
Asepsis
The absence of significant contamination
Sterilization
Removal of all microbes
Commercial sterilization
Killing C. botulinum endospores
Disinfection
Removal of pathogens
Antisepsis
Removal of pathogens from living tissue
Degerming
Removal of microbes from a limited area
Sanitization
