Microbe Mission B/C

[Nano1llus10n]

Here's a topic that we haven't brought up yet: What are 8 limitations to fluorescence microscopy?

[fffurious]

Don't know all 8 but here's my answer:
1. The dye loses its ability to fluoresce after a period of time because the fluorophores are damaged by excitation light
2. Live cells will die after a period of time because they're damaged by excitation light/the fluorescent dye(?)
3. Only the part of the specimen that was dyed can be observed
4. Uh, not sure about the other 5...

[whythelongface]

Don't know all 8 but here's my answer:
1. The dye loses its ability to fluoresce after a period of time because the fluorophores are damaged by excitation light
2. Live cells will die after a period of time because they're damaged by excitation light/the fluorescent dye(?)
3. Only the part of the specimen that was dyed can be observed
4. Uh, not sure about the other 5...

Compounding on the limitations, I'd say a few practical ones: 1. Cost - Lots of sensitive and hard-to-get hardware
2. Complexity - lots of breakable things
3. Power, unlimited power! (firing a laser continuously requires a lot more power than your friendly neighborhood compound microscope)
4. Fluorescent dyes are more toxic? (idk but from my observations of EtBr it seems that those kinds of dyes seem more dangerous than your average cresyl violet/methyl blue/bismark brown)

[Nano1llus10n]

Don't know all 8 but here's my answer:
1. The dye loses its ability to fluoresce after a period of time because the fluorophores are damaged by excitation light
2. Live cells will die after a period of time because they're damaged by excitation light/the fluorescent dye(?)
3. Only the part of the specimen that was dyed can be observed
4. Uh, not sure about the other 5...

The answers you listed (1,2, & 3) are correct! The rest of them (including yours) are below...

Answer (Click to Show Hidden Text)

1. photobleaching (#1 also called fading), 2. phototoxicity (#2), 3. generating reactive chemical species, 4. allows observation only of labeled structure (#3), 5. easy blurring, 6. bleedthrough/nonspecific fluorescence, 7. Autofluorescence, 8. fluorescence is not permanent

[whythelongface]

Don't know all 8 but here's my answer:
1. The dye loses its ability to fluoresce after a period of time because the fluorophores are damaged by excitation light
2. Live cells will die after a period of time because they're damaged by excitation light/the fluorescent dye(?)
3. Only the part of the specimen that was dyed can be observed
4. Uh, not sure about the other 5...

The answers you listed (1,2, & 3) are correct! The rest of them (including yours) are below...

Answer (Click to Show Hidden Text)

1. photobleaching (#1 also called fading), 2. phototoxicity (#2), 3. generating reactive chemical species, 4. allows observation only of labeled structure (#3), 5. easy blurring, 6. bleedthrough/nonspecific fluorescence, 7. Autofluorescence, 8. fluorescence is not permanent

Doesn't number 4 (originally #3) apply to a lot of stains, though? Many stains are very specific in their binding properties.

[fffurious]

I guess its my turn now:

1) What is the difference between positive and negative sense in viruses?
2) What do negative sense viruses need to carry that positive sense do not?
3) Name an example of a negative sense virus.

[Alex-RCHS]

I guess its my turn now:

1) What is the difference between positive and negative sense in viruses?
2) What do negative sense viruses need to carry that positive sense do not?
3) Name an example of a negative sense virus.

Answer (Click to Show Hidden Text)

1. For RNA viruses, positive sense means the RNA can already be translated into the correct peptide and negative sense means the RNA must be copied with each nucleotide "reversed" (cytidine monophosphate to guanosine monophosphate, etc.) before it can be translated into the correct peptide.
2. RNA polymerase, so that it can create positive sense RNA.
3. Ebola (had to use my cheat sheet for this but I think that's usually ok)

[fffurious]

Correct! Your turn.

[Alex-RCHS]

Here are a few questions that I considered adding to the test I'm writing, but decided not to include.

1. In a catalase test, if a bacteria tests positive what will be observed?

2. When a bacterial colony displays beta hemolysis, what color does the medium under the colony turn?

3. Where in a bacterial cell is the DNA found?

[Nano1llus10n]

Here are a few questions that I considered adding to the test I'm writing, but decided not to include.

1. In a catalase test, if a bacteria tests positive what will be observed?

2. When a bacterial colony displays beta hemolysis, what color does the medium under the colony turn?

3. Where in a bacterial cell is the DNA found?

Answer (Click to Show Hidden Text)

1. bubbles of oxygen 2. yellow and transparent due to lysis of RBCs 3. nucleoid (chromosomal DNA) & Plasmids