Ch.6 Part 2 Flashcards
what is osmotic pressure
-the pressure required to stop the flow of water across a semipermeable membrane due to osmosis.
-restrict organisms to an environment
what is an obligate halophile
high osmotic pressure (30% salt)
needs salt
what is a facultative halophile
halotolerant- S. aureus can survive 20% salt
can survive in salt but doesn’t need it
what is hydrostatic pressure?
pressure from water
what is a Barophile
stand extreme pressure
what is microbial interactions
organisms behave differently in a lab environment than in nature
what is antagonistic
kill or harm another microbe (virus)
what is synergistic
cooperate and receive benefits by association, but could live alone
what is symbiotic
interdependent on each other for nutrients or physical contact
what is biofilms
community of microbes living on a surface
How can quorum sensing lead to biofilm formation?
communication via signaling molecules that help microbes coordinate behaviors like biofilm formation
Quorum sensing
bacteria communicate with each other using chemical signals to coordinate behavior based on their population density; protection from UV, drugs, desiccation, pH, temperature
What is Koch’s postulate
-isolate and culture the suspected causative agent
-important to diagnose a disease
what is a streak plate
gradually dilute the sample until individual colonies are isolated
what is CFU
colony forming coming from a single progenitor cell
Pour plate
CFU is separated through serial dilution; comes from in & on the agar
fastidious
some microbes are picky growth factors whereas others are not
-specialized growth requirements or high levels of growth factors needed
The majority of microbes have
NEVER been cultured
-the focus has been on commercially important or pathogenic
-treponema pallidum has never been cultured (fastidious, causes syphilis)
what is broth
liquid media for fast, luxuriant growth
what is agar
“solid” surface for growth
-complex polysaccharide that cannot be digested
-high liquifying temp
-low solidifying temp
what is culture media
nutrient-rich substances used to grow and support the development of microorganisms, cells, or tissues in a laboratory setting.
what are the 6 types of culture media
defined media
complex media
selective media
differential media
anaerobic media
transport media
what is fastidious
-microorganisms, that have complex nutritional requirements and are difficult to grow because they need specific environmental conditions or nutrients.
-require a large number of growth factors
what is a defined synthetic medium
very specific & you know what’s exactly in there
complex media
-culture media containing nutrients released from partially digested yeast, beef, soy, etc.
-Exact composition is unknown
-Good for most chemoheterotrophs
what are examples of complex media
Nutrient broth
TSB- Tryptic soy broth
McConkey agar
what is selective media
substances that favor one or inhibit another microbe
ex: add NaCl to select for halophiles
S. aureus can stand up to 20% salt- allows to live on skin
Bacterial colonies- pH 7.3
Fungal colonies- pH 5.6
Differential media
-Visible change in media or appearance of the colony
-Takes advantage of the different ways bacteria utilize media
Ex: blood agar
Alpha hemolysis
Partially digested blood-green
Beta-hemolysis
fully digested blood- clear
Gamma-hemolysis
no digestion
If it ferments lactose what color is it?
red
does NOT ferment lactose
yellow
what is a stab culture
oxygen cannot penetrate into the agar near the bottom
what is reducing media
sodium thioglycolate removes oxygen from the broth
what is a thioglycolate broth
creates a gradient of oxygen top=high O2, bottom= No O2
what is a GasPak
sache that has chemicals to convert to O2, as long as it’s closed it is anaerobic
what is transport media
its important, used by hospital personnel to ensure clinical specimens are not contaminated and to protect people from infection
How do we grow microaerophiles
need low oxygen, high CO2 content, Candle Jar
what is a candle jar
Uses a lit candle to consume the O2 within the jar and replace it with CO2
* When the candle no longer has enough oxygen to burn, it goes out
* Good for microbes that need a higher CO2 concentration (3-10%) and lower O2 concentration (2-10%)
* Example: Neisseria sp., Streptococcus sp.
explain binary fission
Bacterial reproduction
1.)Replicate chromosome
2.)Elongate
3.)Form a septum
New membrane wall
5.)Cells remain attached or separate
How you get arrangements
6.) Repeat
what is generation time
Time required for a bacterial cell to grow
and divide
* Dependent on chemical and physical conditions
* Variable length:
* 20 minutes – E. coli
* 1-3 hours – standard
* 10 days – M. tuberculosis
what is Log Phase
rapid, exponential growth of microorganisms in a culture.
Most susceptible to drugs that
interfere with metabolism or cell structure
Best for Gram stain
what is Lag Phase
-The lag phase is the initial period where microorganisms adjust to their environment before starting to grow.
-No immediate
reproduction
-Make enzymes/
molecules, etc
what are Direct methods of messing bacterial populations
No incubation required
* Microscope count
* Uses a cell counter
* Difficult to distinguish live vs dead
Incubation
* Serial dilution – Viable plate
count
* Membrane filtration
* Small population
* Most probable number (MPN)
* Statistical estimation
* Useful if does not grow well on agar
what are Indirect methods of messing bacterial populations
Turbidity
Increase in population = increase in
cloudiness of broth
* Use spectrophotometer
what is a spectrophotometer
Measures the amount of light transmitted through the culture under standard conditions
