Chapter 6 Flashcards
– Thrive in moderate environments:
– Temperature: Around 37°C (human body temperature).
– pH: Neutral to slightly alkaline (around pH 7.4).
– Oxygen: Aerobic, anaerobic, or facultative anaerobic.
Normophiles (Mesophiles):
o Escherichia coli (E. coli)
o Staphylococcus aureus
o Salmonella species
o Streptococcus species
are what type of pathogens
Normophiles (Mesophiles):
pathogen that need oxygen
aerobic
pathogen that lives in the presence of no oxygen
anaerobic
pathogen that lives in the presence of both oxygen and no oxygen
facultative anaerobic
These bacterias thrive in extreme environments:
▪ Extremophiles
pathogen that thrives in high temperatures (e.g., hot springs).
Thermophiles
Pathogen that thrives in high salt concentrations
Halophiles
pathogen that thrives in very acidic conditions
Acidophiles
This type of pathogen is rarely pathogenic!
Extremophiles, as the human body does not provide environment conditions needed for survival
Psychrophile
Thrive in cold temperatures
Growth in which populatiion size doubles at a fixed rate is called what?
For example: two cells divide to become four cells, then four
cells divide to become eight.
exponential growth.
In an environment with few bacteria but plenty of resources, bacteria will divide at a constant interval called?
the generation time (also called doubling time).
Bacteria are preparing their call machinery for growth
lag phase
growth approximates an exponential curve
log phase
cells stop growing and shut down their growth machinery while turning on stress responses to help retain viability
stationary phase
cells begin to die at an exponential rate
death phase
for detailed laboratory studies, microbes must be grown separately in?
Pure cultures (single species)
bacterial culture media can be?
liquid or solid
a) … media is useful to separate
mixtures of different organisms.
solid
a)… media allows bacteria to move
freely.
liquid
allows for separation
of colonies into pure
cultures.
isolation streaking
Bacterial cells form a) …. on solid media with agar added to make a firm surface.
colonies
Compounds in the media prevent some types of bacteria from growing, favoring the growth of one specific type.
selective media
Species grow equally well but compounds in the media are metabolized differently, often distinguished by a color indicator.
Differential media
A medium that does both selective and differential agents
MacConkey medium
MacConkey medium
bile salts and crystal violet, which prevent the growth of
bacteria other than Gram-negative enteric bacteria.
Selective agents
MacConkey medium
is lactose, which
some bacteria ferment (pink) and others
do not.
differential agent
compounds a microbe cannot make itself but must gather
from its immediate environment if the cell is to grow and divide.
Essential nutrients
In the gut, dietary proteins are broken down into a…, which are further deaminated to release b)…
a) amino acids
b) ammonia.
is needed by cells to make proteins and nucleic acids.
nitrogen
converts nitrogen to various forms.
nitrogen cycle
happening in bacteria outside of the body
Some bacteria perform a) … to convert nitrogen
gas (N2) to ammonium ions (NH4+), which is a form that can be used for biosynthesis.
a) nitrogen fixation
bacteria transform ammonia to nitrate NO3
nitrification
bacteria transform ammonia to nitrate NO3 and then convert nitrate to N2, which is called?
denitrification
if nitrite is found in the urine we can say what?
That there is a presence of a bacteria because normal human body mechanisms will not reduce nitrate to nitrite
look for the metabolites of nitrite reductase, an enzyme generated by a variety of microorganisms.
Nitrite tests
nitrite tests have a
* sensitivity of:
* specificity of:
- sensitivity of: 25% and a
- specificity of: 94-100%
catch everything (find the disease or true
positives).
sensitive test
are exclusive (confirm only the healthy or true negatives)
Specific test
- Require oxygen for energy metabolism
- Successfully detoxify reactive oxygen species (ROS)
- Survive only in environments with oxygen
strict aerobes
- Do not require oxygen for energy metabolism
- Generally unable to detoxify ROS, making oxygen toxic
- Survive only in environments without oxygen
Strict anaerobes
- Aerobic, but ROS can be toxic
- Survive in environments with lower oxygen concentration
Microaerophiles
- Anaerobic but less susceptible to ROS, and usually lack catalase
- Prefer anaerobic conditions
- Cannot use oxygen but tolerates it’s presence
Aerotolerant anaerobes
- Aerobic AND anaerobic
- Can use oxygen if it is present but can grow without it
Facultative anaerobes
an enzyme produced by bacteria that catalyzes the decomposition of hydrogen peroxide into oxygen and water.
Catalase
▪ In the catalase test, bacteria are
exposed to?
hydrogen peroxide
Bacteria capable of synthesizing catalase will contain a)… as a result of the reaction
bubbles
If no bubbles are present in a catalase test =
bacteria is anaerobic
if bubbles are present in a catalase test =
bacteria is aerobic
