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BIO 220 [Exam #1] > Ch. 6 - Microbial Growth > Flashcards

Ch. 6 - Microbial Growth Flashcards

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1
Q

How is microbial (bacterial) growth determined in the lab?

Provide examples

A

observation of a culture medium
ex: nutrient agar, nutrient broth

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2
Q

When determining microbial (bacterial) growth in a (solid) nutrient agar, what do you see/look for?

What “thing(s)” are nutrient agar usually placed in?

A

colonies: large population of bacterial cells

plate or slant

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3
Q

When determining microbial (bacterial) growth in a (liquid) nutrient broth, what do you see/look for?

What “thing(s)” is nutrient broth usually placed in?

A

color change to cloudiness; turbid

test tube

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4
Q

How do bacteria (prokaryotes) divide?

A

binary fission
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(euk. divide via mitosis)

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5
Q

Name the physical and chemical requirements for microbial (bacterial) growth

A

physical:
- temperature
- pH of enviornment
- osmotic pressure

chemical:
- macronutrients
- micronutrients
- oxygen requirements

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6
Q

Describe temperature (ex: different growth temps)

Name some examples of microbes (bacteria) that you can find in various temperatures

A

minimum growth temperature (min. temp req for growth)
maximum growth temperature (highest temp tolerated for growth)
optimal growth temeprature (best temp to grow at)

psychrophiles (“cold loving”: mountain, deep ocean)
mesophiles (“middle loving”: live on human body)
thermophiles (“heat loving”: hot spring, volcano)

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7
Q

What does pH measure?
Whats the scale for pH?

Name microbes and what pH they prefer

A

measure of [H+]
1 = acidic
7 = neutral
14 = alkaline

bacteria = pH 7
mold and yeast = pH 5-6 (slightly acidic)
acidophiles = pH 1-2 (ex: H. pylori in stomach, acidic)

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8
Q

Describe how osmotic pressure may lead to cell death.

What type of solution is optimal for survival?

A

If the osmotic pressure is not equal inside and outside the cell, the cell will either shrink or swell = cell will die!

cell in isotonic solution is ideal for survival

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9
Q

High osmotic pressure outside the cell is produce by ________ salt environment. The cell will _______

A

high
shrink

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10
Q

How are Halophiles able to live in extremly salty environments, like the ocean?

Normally, high salt concentration (hypertonic solution) will cause the cell the shrink.

A

halophile cells are capable of producing solutes inside the cell, which balances the osmotic pressure = CELL SURVIVES :)

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11
Q

Macronutrients are chemicals ______ by microbes in ________ quantities

A

required
large

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12
Q

Microbes can use and ________ different chemimcal elements.

Which macronutrients are needed for microbes to grow?

A

metabolize

Phosphorus
Carbon
Nitrogen
Sulfur

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13
Q

Why do microbes need carbon?

A

to produce energy

(ex: organic compounds like carbohyrates and lipids have high energy in the bonds between carbons, thus making them rich in energy)

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14
Q

Know the difference between an autotroph and heterotroph. Where does their source of carbon come from?

A

autotroph: organism that can produce its own food
heterotroph: organism that relys on consuming others for food

Both need carbon for energy. Autotrophs get carbon from CO2 for energy, while heterotrophs get carbon from organic compounds for energy.

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15
Q

Understand where nitrogen, sulfure, and phosphorus can be found in organic compounds.

Are these macronutrients or micronutrients?

A

Macronutrients

Organic compounds with nitrogen:
- proteins and nucleic acids
-> (N is needed to make AA (amino group), which is why N is found in proteins; N is needed to make nucleotides (nitrogenous base; purine and pyrimidine family, which is why N is found in nucleic acids)

Organic compounds with sulfur:
- proteins
-> (S is needed to make 2 sulfur containing AA (out of 20), which is why S is found in proteins)

Organic compounds with phosphorus:
- nucleic acids (nucleotides)
- cell membrane formation
-> (P is needed to make nucleotides, which is why P is found in nucleic acids. P is also needed to make up the cell membrane (head of phospholipid bilayer)

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16
Q

Micronutrients are AKA “_________ ___________.” These are chemicals _______ by microbes in ________ quantities.

A

“trace elements”
required
small

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17
Q

What are the functions of micronutrients to microbes?

Include examples of micronutrients

A

Function as:
- inorganic enzyme cofactors to help enzyme work better (ex: ions)
- organic growth factors (ex: vitamins, animal extract in lab media)

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18
Q

Name the four oxygen-level requirements for bacteria.

Compare and contrast the four-oxygen level requirement for bacteria.

Include the type of growth (aerobic/anaerobic), conditions needed for growth, and what area of the test tube the microbes will grow

A

PREFACE:
High [O2] at top of test tube, while low [O2] at bottom of test tube

Obligate Aerobes:
- only aerobic growth; growth occurs in high [O2] area
- growth only at surface

Obligate Anaerobes:
- only anaerobic growth; growth occurs in ABSENSE of O2
- growth only at bottom

Facultative Anaerobes:
- both aerobic and anaerobic growth, but best/more growth where most [O2] present
- growth throughout, but mainly at top

Microaerophiles:
- only aerobic growth; O2 required but in low concentration
- growth in middle

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19
Q

What is culture media?

A

a solid or liquid preparation for microbial growth (ex: solid agar media, liquid broth media)

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20
Q

Define inoculum

A

introduction of microbes into a medium

21
Q

Define culture

A

microbes growing in or on a culture medium (ex: colonies)

22
Q

Define pure culture

A

contains only ONE species seen on a solid agar plate; no contamination, all colonies look similar

23
Q

Define colony

A colony is AKA…

A

population of cells from a single cell or from a group of attached cells

A colony is often called a colony-forming unit (CFU)

24
Q

Define the streak plate method

A

method used to isolate PURE BACTERIAL CULTURES

(spread, separate, and isolate the colony/CFU)

25
Q

TRUE or FALSE: A virus requires a host cell (ex: bacterial cell) to grow

A

True (remember: obligate intracellular parasite)

26
Q

Describe the culture media for viral growth

A

viruses req. host cell (ex: bacterial cell)

form a viral plaque

plaque-forming unit (PFU)

27
Q

Name the (6) different types of culture media.

A

CCRSDE

  • chemically defined media
  • complex media
  • reducing media
  • selective media
  • differential media
  • enrichment media
28
Q

Describe: Chemically Defined Media

Include its characteristics

A

Characteristics:
- The exact chemical composition is known

Function:
N/A

Examples:
N/A

How it works:
N/A

29
Q

Describe: Complex Media

Include its characteristics

A

Characteristics:
- Varying chemical composition from batch to batch; vague

Function:
N/A

Examples:
N/A

How it works:
N/A

30
Q

Describe: Reducing Media

Include: Characteristics, Function, Examples, and How it works

A

Characteristics:
- All available O2 removed
- Contains chemicals that combine with O2 to deplete it

Function:
- For growth of anaerobic bacteria (obligate anaerobes)

Examples:
- Ex: anaerobic jar

How it works:
- Jar contains chemicals that will draw out the O2 from the petri dish and deplete it, thus creating a reducing media

31
Q

Describe: Selective Media

Include: Characteristics, Function, Examples, and How it works

A

Characteristics:
- Only 1 type of bacteria will grow

Function:
- Suppresses/inhibits unwanted microbes and encourages growth of desired microbe

Examples:
- Ex: EMB agar

How it works:
- EMB agar will select FOR gram-negative bacteria (ex: E. coli) and will INHIBIT/select against gram-positive bacteria

EMB AGAR ONLY GROWS GRAM NEGATIVE BACTERIA!!!!

32
Q

TRUE or FALSE: EMB agar will select for gram + bacteria and select against/inhibit gram - bacteria.

A

False, it selects for gram negative bacteria (ex: E. coli) and selects against/inhibits gram positive bacteria.

33
Q

Name a bacteria that can grow on EMB agar. Why?

A

E. coli because it is gram negative, and EMB agar selects for gram negative bacteria.

34
Q

Describe: Differential Media

Include: Characteristics, Function, Examples, and How it works

A

Characteristics:
- Some media have both selective and differential characteristics

Function:
- Allows differentiation between bacteria within the same group (ex: differentiating between various gram-negative bacteria)

Examples:
- Allows differentiation between bacteria in same group: ex - blood agar
- Media that has both selective and differential characteristics: ex - EMB agar

How it works:
- EMB agar (dual function):
1. Selective; selects gram-negative only
2. Differential: determine the difference between various gram-negative bacteria

35
Q

TRUE or FALSE: EMB agar can first act as a differential media, then a selective media.

A

False, it always acts first as a selective media by selecting for gram-negative bacteria. Then it can act a differential media to distinguish amount different bacteria in the same group (gram-negative bacteria)

EMB agar contains a dual function :)

36
Q

A selective media, EMB agar, is shown with streaks that are dull, and brown in color. Joshua claims that E. coli is growing on the EMB agar. Abby claims that E. coli is not growing on the EMB agar.

Who is correct and why?

A

Abby is correct (as always) because E. coli that is grown on EMB agar will appear shiny, green, and metallic. The thing being observed is none of those things, so Joshua is incorrect (womp womp).

37
Q

Describe: Enrichment Media

Include: Characteristics, Function

A

Characteristics:

  • Considered non-selective media; everything will grow
  • Rich in growth factors
  • Usually exists as liquid (nutrient broth)

Function:

  • Stimulates growth of different types of bacterial species
  • Grows some fastidious bacteria (picky/difficult eaters; require many growth factors)

Examples:
N/A

How it works:
N/A

38
Q

What is bacterial growth represented by?

A

growth curves

(x axis: time; y axis: log of number of bacteria)

39
Q

Define Bacterial Division

A

increase in number of cells, NOT cell size

by process called: binary fission (asexual reproduction)

40
Q

Define Generation Time

A

time required for a cell to divide (double)

ranges: minutes to hours

41
Q

Name the four phases of the bacterial growth curve and describe key events

Draw it out and label the axis.

A

1. Lag phase: No growth, but cell is actively preparing for population growth via DNA replication

2. Log phase: Logarithmic/exponential increase in population due to reproduction via binary fission (bacteria) or mitosis (yeast)

3. Stationary phase: bacteria have run out of nutrient; no more bacterial growth

4. Death phase: population decreasing at logarithmic rate due to increases in metabolic waste, which is toxic -> cell death

42
Q

Name the different direct measurements and indirect measurement methods.

How does direct and indirect measurement methods generally differ?

A

Direct measurements = DIRECTLY counting
- plate count
- filtration method
- direct microscopic count

Indirect measurements = NOT directly counting
- turbitity
- metabolic activity
- dry weight

43
Q

Describe the Plate Count method.
Include how it works (ex: understand the examples) and include the steps

Is this method Direct or Indirect?

A

Direct: count how many colonies on plate after sufficient dilution

Plate Count:
inoculum is placed into sterile test tube, and mixed with dilutions; however, when poured onto the plate, it is far too concentrated

you must dilute by pouring sample into new sterile test tubes, until it becomes dilute enough to when you pour it on a plate it is easy to count colonies

STEPS:
- perform serial dilutions of sample
- plate out serial dilutions
- colony count

44
Q

Describe the Filtration method.
Include how it works (ex: understand the examples)

Is this method Direct or Indirect?

A

Direct: able to count # of colonies on petri dish

Filtration method:
Liquid solution is passed through a filter, and bacteria gets caught in tiny holes in the paper

Take the filter paper, turn it upside down, and touch it on a petri dish

Colonies will grow on the surface

45
Q

Describe the Direct Micorscopic Count method
Include how it works (ex: understand the examples)

Is this method Direct or Indirect?

A

Direct: count numer of cells in each box

Direct Microscopic Count:
use a dropper to place a volume of bacteria onto a slide, containing a cell counter with a grid

count amount of cells in x # of boxes

average number of bacteria per viewing field is then calculated

46
Q

Describe the Turbidity method
Include how it works (ex: understand the example)

Is this method direct or indirect?

A

Indirect: because you are only assuming how much bacteria is in here based on how much light passes through

Turbitity:
observe liquid broth (in test tube)

uses a light source and a spectrophotometer to observe how much light passes through the tube

If theres no growth, more light will pass through. If theres growth, less like will pass through (turbitiy)

47
Q

Tubitity measures the cloudiness with a ______________

A

spectrophotometer

48
Q

Describe the Metabolic Activity method
Include how it works (ex: understand the example)

Is this method direct or indirect?

A

Indirect

You observe how much metabolic waste is produced. Amount is proportional to # of bacteria

more metabolic waste = assume more bacteria
less metabolic waste = assume less bacteria

49
Q

Describe the Dry Weight method
Include how it works (ex: understand the example)

Is this method direct or indirect?

A

Indirect

you assume based on weight

if higher weight = assume more bacteria
if less weight = assume less bacteria

BIO 220 [Exam #1] (6 decks)

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