Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

PMP 101 - Health, Disease And The Patient > Bacterial Population Growth (w19) > Flashcards

Bacterial Population Growth (w19) Flashcards

1
Q

How do most prokaryotes reproduce ?

A

By binary fission

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe the steps to bacterial cell division …

A

1) cell elongates, enlarging it volume and DNA is replicated.
2) cell wall and plasma membrane begins to constrict.
3) cross-wall forms, completely separating the two DNA copies.
4) the cells separate.

  • this is also known as binary fission in bacteria
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the phases of bacterial population growth ?

A

1) LAG phase (no increase in population but intense activity preparing for population growth)
2) LOG phase - or exponential (exponential increase on population)
3) stationary phase (period of equilibrium, microbial deaths balance production of new cells)
4) DEATH phase (population is decreasing at a logarithmic rate)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is LAG phase of bacterial population growth ?

A
  • little or no cell division occurs.
  • intense metabolic activity, individual cells increase in size.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the LOG or exponential phase of bacterial population growth ?

A
  • rapid and constant population growth (exponential manner)
  • number of cells produced > number of cells dying
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What occurs during the stationary phase of bacterial population growth ?

A
  • population size begins to stabilize
  • number of cells produced = number of cells dying
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What occurs during the death phase of bacterial population growth ?

A
  • population size begins to decrease
  • number of cells produced < number of cells dying
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What happens to the number of cells in each generation during binary fission ?

A

It doubles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the physical requirements for bacterial growth ?

A
  • temperature
  • pH
  • osmotic pressure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the chemical requirements for bacterial growth ?

A
  • carbon source
  • ions, trace elements
  • oxygen
  • nitrogen, sulphur, and phosphate
  • organic growth factors
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What type of bacteria grow between pH 6.5 and 7.5 ?

A

Neutrophiles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What bacteria grow in acidic environments (pH 0-5) ?

A

Acidophiles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What bacteria prefer the pH range of 8.0-11.5 ?

A

Alkalphiles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does hypertonic environments (higher in solutes than inside the cell) cause the bacterial cell to do ?

A

Causes plasmolysis, due to high osmotic pressure, the water will move from the inside of the cell to outside of cell potentially causing it to burst.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is inoculum ?

A

The introduction of microbes into a medium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is agar ?

A

Agar is a complex polysaccharide, used as a solidifying agent for culture media in Petri plates (liquefies at 100C and Solidifies at ~40C)
- Generally not metabolized by microbes

17
Q

What does selective culture media do ?

A

Suppress unwanted microbes and encourage desired microbes
E.g. Saboraud’s Agar: 5.6pH discourages bacterial growth. Used to isolate fungi.

18
Q

What does differential culture media do ?

A

Allow distinguishing of colonies of different microbes on the same plate
E.g. Blood Agar: to distinguish bacteria that destroy red blood cells (hemolysis).

19
Q

What does enrichment culture do ?

A

Encourages the growth of a desired microbe by increasing very small numbers of a desired organisms to detectable levels (without suppressing other microbes).

20
Q

What does obligate aerobes require and what is it ?

A

Obligate Aerobes - require oxygen to live. E.g. Pseudomonas, causing infections in humans, mostly in hospital patients

21
Q

What are the three classifications of microorganisms based on their oxygen requirements ?

A
  • obligate aerobes
  • facultative anaerobes
  • obligate anaerobes
22
Q

What are facultative anaerobes ?

A

Facultative anaerobes – can grow via fermentation or anaerobic respiration when oxygen is not available. Grow best in aerobic conditions. E.g. E.coli

23
Q

What are obligate anaerobes ?

A

Obligate anaerobes – do not tolerate oxygen and are harmed by it. E.g. Clostridium bacteria that cause tetanus and botulism

24
Q

What is a culture medium ?

A

Culture medium: Nutrients prepared for microbial growth in a laboratory (chemical requirements)

25
Q

What is a culture ?

A

Culture: Microbes growing in/on culture medium at appropriate conditions (physical requirements)

26
Q

How is a pure culture obtained ?

A

To obtain a pure culture, individual organisms must be isolated
Streak-plate method is commonly used

27
Q

What are aseptic techniques ?

A

Procedures under suitably controlled conditions to maintain the sterility, free from external sources of contamination

28
Q

How are microorganisms isolated in pure culture (list the two steps) ?

A

(a) streaking techinque, in which a sterile loop is inserted into a sample and streaked onto a plate in a pattern (e.g. 3 sectors), to obtain individual colonies.

Next

(b) Colony formation: A population of cells arising from a single cell (also referred to as CFU, colony forming unit).

29
Q

Why is measuring microbial growth crucial for a variety of applications ?

A

Measuring the microbial growth is crucial for a variety of applications:

  • Diagnose bacterial infections from patient specimens (blood, urine, etc)
  • Food safety and process hygiene assessment against relevant criteria
  • Microbiologic sampling of environmental sources
  • Assessing microbial contamination of sterile pharmaceutical products - test for sterility for Quality Assurance (YEAR 3)
  • Microbiological assessment of non-sterile pharmaceutical products (e.g. topical use preparation, herbal remedies) comply with the specifications / acceptance criteria outlined in the British Pharmacopoeia (YEAR 3)
30
Q

What is direct measurements for measuring microbial growth ?
List the three methods …

A

Direct measurements–count microbial cells
1) Plate count
2) Filtration
3) Direct microscopic count

31
Q

What is indirect measurements for measuring microbial growth ?
List the three methods …

A

Indirect measurements–count microbial cells
1) Turbidity (mass)
2) Metabolic activity
3) Cell mass - Dry weight

32
Q

What is serial dilution ?

A

Sequential dilutions in a stepwise manner

33
Q

What is membrane filtration ?

A

A method used for low counts, where a filter is applied to a Petri dish and bacteria can grow as colonies on the surface. Before this a solution is passed through a cellulose filter (0.45 μM) that collects and retains bacteria (bacteria size > pore size)

34
Q

What does direct microscopic count rely on ?

A

Direct microscopic count = Rely on light microscopy and a cell counter and involves placing a small amount of samples on a microscope slide with a special grid

35
Q

How do you calculate the number of bacteria per ml ?

A

= number of cells counted / volume of area counted

36
Q

What are some barriers to direct microscopic count ?

A
  • Difficult to distinguish live/dead bacteria
  • Often laborious
  • Only suitable with high counts
37
Q

Define metabolic activity …

A

Metabolic activity - amount of metabolic product is proportional to the population size

38
Q

What is turbidity/ cell mass ?

A

Turbidity/Cell mass - measurement of cloudiness/optical density (linked to the cell mass) of liquid media by a spectrophotometer

PMP 101 - Health, Disease And The Patient (35 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions