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Microbiology > Lecture 6 > Flashcards

Lecture 6 Flashcards

1
Q

Define colonization.

A

When there is a sufficiently high concentration of organisms at a site that they can be detected.

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2
Q

Define contamination.

A

Organism not present initially, but was introduced (modes of transmission-pervious lectures, arthropods, sexual, etc.)

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3
Q

Define carrier.

A

Person colonized with an organism and is able to transmit the organism to other people.

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4
Q

Define infectious disease.

A

Disorders caused by organisms such as bacteria, viruses, fungi or parasites.

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5
Q

How long can colonization persist?

A

For days to years

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6
Q

What is colonization influenced by?

A

Factors such as immune response to the organism, competition at the site from other organisms, use of antimicrobials, etc.

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7
Q

What is the typical size of bacteria? What size does 10^12 of bacteria occupy and weigh?

A
  • typical size is 1 to 2 um
  • 10^12 bacteria occupies 1 cubic meter
  • weighs 1 gram
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8
Q

How many bacteria on on a human?

A

10 to 100 trillion bacteria

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9
Q

How quickly does metabolic efficiency replicate?

A

*every 20 minutes (average)

Note: mycobacteria is slower

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10
Q

The amazing speed of nutrient conversion and biosynthesis is necessary for what?

A
  • to anticipate bacterial weaknesses

* suggest how to intervene therapeutically against pathogenic bacteria

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11
Q

What is growth in bacterial culture also known as?

A

population dynamics

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12
Q

Describe population dynamics in a chart.

A
  • lag: at 2 and slowly rises
  • exponential rises quickly
  • stationary starts to die off

Total count is the highest point of the chart and viable count is the amount in the stationary section.

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13
Q

How long is exponential growth?

A

5 to 10 hours of growth

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14
Q

What are some examples of mechanisms of action of drugs that treat bacteria?

A
  • inhibition of protein synthesis
  • inhibition of metabolic pathways
  • decrease cell wall integrity
  • inactivation of cell wall synthesis
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15
Q

Bacteria grow in a large variety of habitats. What are the most abundantly populated by microbes?

A
  • humans

* anatomic sites: colon, large bowel, urethra, vagina, and nasopharynx are highly colonized

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16
Q

Other than humans, where can bacteria grow?

A

Basically anywhere including deep sea vents, in ponds, oceans, air conditioners, in food, etc.

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17
Q

What are the 3 requirements for bacterial growth?

A
  • energy
  • nutrients (environment must contain all nutrients needed)
  • environment
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18
Q

What kind of energy is required for bacterial growth?

A

Chemical energy is required for the synthesis of new cellular components.

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19
Q

What type of environment is needed for bacterial growth?

A
  • aeration
  • pH
  • temperature
20
Q

What are auxotrophs?

A

Bacteria that derive energy from inorganic substrates plus minimal carbon source. They need water, inorganic salts, glucose, and carbon dioxide. (Pseudomonas)

21
Q

What are heterotrophs?

A

Includes all bacteria of medical importance. Need organic carbon source (various), inorganic salts, and carbon dioxide. (Staphylococcus, Streptococcus)

22
Q

What are some examples of nutrients needed for bacterial growth?

A
  • Nitrogen: must be fixed from environment by certain bacteria and converted to a useable form such as NH3.
  • Phosphorus: found in nature as free inorganic phosphorus
  • Sulfur: can’t be used in its elemental form. Some auxotrophs oxidize it to SO4 -2 which can be used by most bacteria.
  • Others: pathogenic bacteria can’t make or get one or more essential metabolites (amino acids, vitamins, iron, growth factors)
23
Q

Where is free iron scarce? Why?

A

In the blood and tissues because it is bound by proteins like transferrin, lactoferrin, or ceruloplasmin.

24
Q

Is free iron essential for bacterial growth?

A

Yes

25
Q

What do pathogenic bacteria excrete?

A

Chelating compounds, siderophores, which bind iron with great avidity.

26
Q

What kind of bacteria are more dependent on free iron? Why?

A
  • pathogenic bacteria

* most have multiple siderophores, thus trying to gain an edge on the other organisms in the same environment

27
Q

Bacteria have a wide range of responses to oxygen. What are they?

A
  1. Strict or obligate aerobes: must have oxygen to grown.
  2. Obligate anaerobes: can’t grow in the presence of oxygen.
  3. Facultative anaerobes: can grow whether or not oxygen is present.
28
Q

The largest of pathogenic bacteria belong to what type of oxygen requirement group?

A

Facultative anaerobes

29
Q

Describe the reaction of superoxide dismutase (SOD).

A

2 oxygen + 2 hydrogen –> H2O2 (peroxide) + oxygen

SOD breaks down into peroxides and oxygen which is further down into water and oxygen.

30
Q

What does 2 H2O2 break down to?

A

2 H2O2 –> 2 water + oxygen

31
Q

What is the relationship between aerobes and oxygen?

A

They require oxygen. (mycobacterium, pseudomonas)

SOD +
Catalase +

32
Q

What is the relationship between anaerobes and oxygen?

A

Oxygen is toxic. (ABC organisms)

SOD -
Catalase +

33
Q

What is the relationship between facultative anaerobes and oxygen?

A

Can survive with or without oxygen. (E. coli, Staphylococcus)

SOD +
Catalase +

34
Q

Why can’t strict anaerobes (ABC organisms) live in an oxygen atmosphere? (examples: actinomyces, bactericides, and clostridium)

A

Because they lack SOD and catalase that protect from oxygen free radicals. They have a primitive mechanism that transfers electrons (reducing equivalents) to ‘oxidants’ like nitrates instead of to molecular oxygen.

Note: selected antibiotics are used to exploit this metabolic characteristic of anaerobes.

35
Q

What is SOD?

A

Superoxide Dismutase

36
Q

What does liquid media contain?

A

All essential nutrients and factors, usually in the form of complex extracts (yeast, beef heart).

37
Q

What happens when liquid media is inoculated?

A

When it is inoculated with a small number of bacteria results in growth of a clonal population over time.

38
Q

How is solid media made?

A

It is produced by adding agar to liquid media. An inoculum is placed on to the plate medium and then spread by streaking out.

39
Q

The technique to make solid media is used for what?

A
  • to isolate colonies of bacteria of medical importance

* determine the number of living or viable counts

40
Q

What is a colony?

A

A clonal population of bacteria derived from a single bacterium.

41
Q

When is a bacterium called viable?

A

When it is able to produce a colony on plates

42
Q

What type of technique needs to be used to prevent contamination on plates?

A

aseptic technique

43
Q

In response to the competition for iron, most pathogenic bacteria use which of the following?

a. Hemoglobins
b. Lactoferrins
c. Myoglobins
d. Siderophores
e. Transferrins

A

Siderophores

44
Q

Bacteria have a wide range of responses to oxygen. Most pathogenic bacteria belong to which of the groups for efficient parasitism?

A

Facultative anaerobes

45
Q

What do you need to make a plate streak of bacteria?

A
  • source of bacteria
  • liquid culture/bacteria on previous plate
  • new plate
  • inoculating loop
  • lighters
  • bunsen burner
  • safety glasses
46
Q

When removing bacteria from a plate, how much should you take? How should you handle the cover?

A
  • take only one colony
  • never completely remove the cover to prevent contamination and store with the cover on the bottom to prevent condensation from contaminating the sample

Microbiology (10 decks)

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