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MICROBIOLOGY 2420 > Lab 4 > Flashcards

Lab 4 Flashcards

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Biology 101 flashcards
1
Q

Which bacteria are able to emit visible light by a process called biolumiscence

A 
Allivibrio,
 Vibrio, 
Photobacterium, 
Shewanella, 
Photohabdus
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2
Q

What enzyme allows the bio-luminescence

A

luciferase

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3
Q

what does luciferase do?

A

The luciferase catalyzes the oxidation of reduced flavin mononucleotide (FMH2) and a long chain of aliphatic aldehyde (RCHO) by using molecular oxygen to produce blue-green light

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4
Q

The luminous bactera live

A

Free living in the oceans or symbiotic with marine animals

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5
Q

By living in animals they can reach what?

A

High cell densities

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6
Q

What symbiotic relationship are we studying in the lab?

A

Between the Aliivibrio fischeri and Hawaiian bobtail squid

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7
Q

The microbial host mutualism

A

-The squid hunts at dusk and it modulates the intensity of the light produced by the bacterium to match the moonlight or to counterilluminate

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8
Q

How does the bacterua Aliivibrio fischeri benefit from this?

A
  • It benefits since it consumes a lot of cells total energy to produce light
  • It is also able to attain a high cell density which is not possible in free living
  • At dawn the squid expels most of the bacteria to bury itself and with that the squid seeds the seawater with the bacteria allowing it to colonize the next generation and also to disseminate
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9
Q

No light is emmitted until the Aliivibrio fischeri has reached

A
  • A certain threshold cell density called the phenomen quorum sensing.
  • This system is controlled by a certain genetically modulated, diffusable signal molecule HOMOSERINE LACTONE-AUTOINDUCER
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10
Q

When the autoinducer exceeds the threshold

A

It will trigger synchronous and continuous light production.

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11
Q

Bioluminescent genes

A

LUX genes has an application in reserach to image bacteria in live animals, and to monitor contaminats in the environment and in foods.

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12
Q

How do we culture the Aliivibrio fischeri?

A

-We culture it on a LUMINESCENT AGAR WITH 3% SODiUM CHLORIDE AND OBSERVE BIOLUMINESCENCE

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13
Q

How do bacteria move?

A
  • In liquids they move by swimming
  • on wet surface by swarming, twitching, gliding or sliding.
  • swimming is for unicellular and swarming is for multicellular movement of bacteria across a SOLID surface
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14
Q

What is a flagellum and its structure?

A

-The flagellum is long, thin, tail like appendage
-Use to propel like a propeller to generate a force for movement.
-motor, hook and a long extracellular filament
-

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15
Q

How many flagella are in the species we study?

A
  1. PSEUDOMONAS AERUGINOSA-1 POLAR FLAGELLUM
  2. ALIIVIBRIO FISCHERI-3-12
  3. Proteus mirabilis-many flagella arranged around the cell
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16
Q

How do we see such a small flagella?

A

-It can be seen after being stained with special dyes to increase the diameter

17
Q

We observe the motility in what medium (SWIMMING MOTILITY)

A

in a semi solid medium and with microscopic observation of live cells
-we must observe that is it true movement, if they move great distances and now Brownian motion or currents

18
Q

Swimming motility procedure

A
  • Uses a semi-soli medium

- 0.4% is used instead of the usual 1.5% because it is used to facilitate movement

19
Q

The semi-solid medium (0.4% agar) is (SWIMMING MOTILITY)

A
  • STAB INOCULATED
  • to allow the motile bacteria to swim away to form colonies whereas the non-motile bacteria grow along the stab line
  • The TTC dye helps to detect the colonial growth as it turns red
  • The intensity of the colour formed is proportional to the amount of colonial growth
20
Q

SWARMMING MOTILITY

A
  • We use the TRYPTIC SOY AGAR 0.5% instead of the usual 1.5%

- The medium remains solid to allow for streaking and spreading and also inhibit swimming motility through the medium

21
Q

It is placed in a laminar hood why?

A
  • To remove excess surface moisture
  • This will minimize the swimming motility on the surface and permit more swarming motility to take place on the agar surface
22
Q

Swarming bacteria secrete what

A

-they secrete SURFACANT (surface active agents) molecular to redue the surface tension of the water between the substrate and teh cells thus permiting the cells to spread over the surface.

23
Q

Cells can move by

A

Physical stimuli from the environment-swim to positive(to) or negative (away) to stimuli by a process called TAXIS
-Chemical-chemotaxis
Light-phototaxis

24
Q

In our lab we will

A
  1. Examine motile and non-motile strain of Aliivibrio fischeri using the wet mount and the motility agar test
  2. We will look for swimming and swarming motility in Proteus mirabilis, E.coli, Pseduomonas aeruginosa

MICROBIOLOGY 2420 (6 decks)

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