Ch.6 Part 2 Flashcards by Meklit Bonse

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

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what is an obligate halophile

high osmotic pressure (30% salt)
needs salt

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what is a facultative halophile

halotolerant- S. aureus can survive 20% salt
can survive in salt but doesn’t need it

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what is hydrostatic pressure?

pressure from water

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what is a Barophile

stand extreme pressure

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what is microbial interactions

organisms behave differently in a lab environment than in nature

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what is antagonistic

kill or harm another microbe (virus)

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what is synergistic

cooperate and receive benefits by association, but could live alone

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what is symbiotic

interdependent on each other for nutrients or physical contact

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what is biofilms

community of microbes living on a surface

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How can quorum sensing lead to biofilm formation?

communication via signaling molecules that help microbes coordinate behaviors like biofilm formation

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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

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What is Koch’s postulate

-isolate and culture the suspected causative agent
-important to diagnose a disease

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what is a streak plate

gradually dilute the sample until individual colonies are isolated

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what is CFU

colony forming coming from a single progenitor cell

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Pour plate

CFU is separated through serial dilution; comes from in & on the agar

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fastidious

some microbes are picky growth factors whereas others are not
-specialized growth requirements or high levels of growth factors needed

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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)

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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