GCSU (Bachoon) Microbiology Test 2 || Errorless Answers 100%.
Why do we study microbial growth? correct answers 1) to prove what causes disease
2) for antibiotic susceptibility (how to kill)
3) for research
what are the physical aspects of microbial growth? correct answers - temperature
- pH
- osmotic pressure
what are the 3 main groups microbes are classified into based on their optimum temperature?
correct answers 1) psychrophiles
2) mesophiles
3) thermophiles
psychrophiles correct answers - cold loving microbes
- don't cause disease
- (-10 deg. C to 20 deg. C)
what is a psychrotroph? correct answers - organism that is capable of growth between 0 deg. C
and 30 deg. C
mesophiles correct answers - moderate temperature loving microbes, most common type
- (25 deg. C - 40 deg. C)
- these are human pathogens also include most of the common spoilage and disease organisms.
- ex: 37 deg. C (the optimum temp. for many pathogenic bacteria)
thermophiles correct answers - heat loving microbes
- (40 deg. C - 70 deg. C)
,- many can't grow at temps below 45 deg. C
- hyperthermophiles = (70 deg. C - 110 deg. C)
what temperature do pathogens grow at? correct answers - human body temp. (37 degrees
celsius)
what pH range do most bacteria grow best in? correct answers - a narrow pH range
- neutral (6.5 - 7.5)
- very few grow below pH 4
- foods with low pH (cheese, pickles..) don't spoil easily)
What are some examples of bacteria that grow below pH 4? correct answers - sulfur oxidizers
- H. pylori
____ have more H+ than ______ correct answers acids, bases
what is the osmotic pressure inside bacterial cells in an isotonic solution? correct answers -
0.85% NaCl
What type of solution inhibits bacterial growth? correct answers - hypertonic solutions (solutes
are higher outside the cell)
- water leaves the cell
what is plasmolysis? correct answers - the osmotic loss of water from the cell in a hypertonic
environment
- shrinkage of the cell plasma membrane - die
, What causes high osmotic pressure and can be used to preserve food? correct answers - salt or
sugar
- causes plasmolysis
ex: salted meat, jams, jelly
What percentage of salt and sugar are solutions that restrict growth? correct answers solutions
that restrict growth are:
> 5% salt
> 10% sugar
- How do salts and sugars preserve foods?
- Why are these considered physical rather than chemical methods of microbial control? correct
answers - they create a hypertonic environment.
- As preservatives they don't directly affect cell structures or metabolism; instead they alter the
osmotic pressure
What microorganisms can actually grow in salts and sugar preservatives? correct answers -
staphylococcus aureus grow in up to 7% salt and spoils salted foods
- some fungi can grow in jelly and jams
(MOLDS are more capable of growth in high osmotic pressure than bacteria is)
What are the chemical requirements of microbial growth? correct answers - carbon
- nitrogen
- sulfur
- phosphorus
- trace elements
- oxygen
Why do we study microbial growth? correct answers 1) to prove what causes disease
2) for antibiotic susceptibility (how to kill)
3) for research
what are the physical aspects of microbial growth? correct answers - temperature
- pH
- osmotic pressure
what are the 3 main groups microbes are classified into based on their optimum temperature?
correct answers 1) psychrophiles
2) mesophiles
3) thermophiles
psychrophiles correct answers - cold loving microbes
- don't cause disease
- (-10 deg. C to 20 deg. C)
what is a psychrotroph? correct answers - organism that is capable of growth between 0 deg. C
and 30 deg. C
mesophiles correct answers - moderate temperature loving microbes, most common type
- (25 deg. C - 40 deg. C)
- these are human pathogens also include most of the common spoilage and disease organisms.
- ex: 37 deg. C (the optimum temp. for many pathogenic bacteria)
thermophiles correct answers - heat loving microbes
- (40 deg. C - 70 deg. C)
,- many can't grow at temps below 45 deg. C
- hyperthermophiles = (70 deg. C - 110 deg. C)
what temperature do pathogens grow at? correct answers - human body temp. (37 degrees
celsius)
what pH range do most bacteria grow best in? correct answers - a narrow pH range
- neutral (6.5 - 7.5)
- very few grow below pH 4
- foods with low pH (cheese, pickles..) don't spoil easily)
What are some examples of bacteria that grow below pH 4? correct answers - sulfur oxidizers
- H. pylori
____ have more H+ than ______ correct answers acids, bases
what is the osmotic pressure inside bacterial cells in an isotonic solution? correct answers -
0.85% NaCl
What type of solution inhibits bacterial growth? correct answers - hypertonic solutions (solutes
are higher outside the cell)
- water leaves the cell
what is plasmolysis? correct answers - the osmotic loss of water from the cell in a hypertonic
environment
- shrinkage of the cell plasma membrane - die
, What causes high osmotic pressure and can be used to preserve food? correct answers - salt or
sugar
- causes plasmolysis
ex: salted meat, jams, jelly
What percentage of salt and sugar are solutions that restrict growth? correct answers solutions
that restrict growth are:
> 5% salt
> 10% sugar
- How do salts and sugars preserve foods?
- Why are these considered physical rather than chemical methods of microbial control? correct
answers - they create a hypertonic environment.
- As preservatives they don't directly affect cell structures or metabolism; instead they alter the
osmotic pressure
What microorganisms can actually grow in salts and sugar preservatives? correct answers -
staphylococcus aureus grow in up to 7% salt and spoils salted foods
- some fungi can grow in jelly and jams
(MOLDS are more capable of growth in high osmotic pressure than bacteria is)
What are the chemical requirements of microbial growth? correct answers - carbon
- nitrogen
- sulfur
- phosphorus
- trace elements
- oxygen
