Microbe Mission B/C

[SciBomb97]

What are the most difficult questions you guys have seen at competitions so far?

[FullMetalMaple]

I have a whole test worth of slightly harder questions here (that I need to upload onto the Test Exchange soon...) from an invitational.

There's a section on matching characteristics to the three domains. One characteristic is about membrane lipids - if they have unbranched or branched hydrocarbons. There's another about if the domains have histones or introns. (Some of them are easier, though, such as if they have peptidoglycan in their cell walls or not.)

Beyond a weird form of serial dilutions that tripped up even my event coach, I'd say those are some of the hardest questions I've had. Most of my tests have been really easy.

[syo_astro]

Most questions I have seen aren't bad. It came down to whether my partner and I are focused and make sure to check our work. At most, the questions that are the worst are the questions that are slightly opinionated in answer (title this graph, bad questions). The only thing would be using tools, setups, working with pictures.

[TheWiseGirl]

Hi Everyone!

So recently at my regional tournament there was a question on the test asking why you could not view flagellum using UV microscopy. I figured it was because the flagellum is too small to effectively pick up the fluorescent dye, and thus cannot be viewed. However, I'm not sure if this is correct. Can somebody give me a more "scientific" answer?

Also, what is the chemical basis for negative staining? The chemical basis for staining in general? (I know for general staining you use a class-specific dye, and the dye particles will bond with the specific compound to qualify/quantify its presence...)

[SciBomb97]

Hi Everyone!

So recently at my regional tournament there was a question on the test asking why you could not view flagellum using UV microscopy. I figured it was because the flagellum is too small to effectively pick up the fluorescent dye, and thus cannot be viewed. However, I'm not sure if this is correct. Can somebody give me a more "scientific" answer?

Also, what is the chemical basis for negative staining? The chemical basis for staining in general? (I know for general staining you use a class-specific dye, and the dye particles will bond with the specific compound to qualify/quantify its presence...)

I don't know about the first thing, but I do know the Gram-staining. During the colorization step, the crystal violet solution is absorbed by both Gram-positive and Gram-negative bacteria. But the difference is that since Gram-positive bacteria have a thicker peptidoglycan layer than Gram-negative, they retain the crystal violet even through the decolorization step (where acetone is applied). In the decolorization step, the acetone not only removes the crystal violet from the Gram-negative bacteria (due to their thinner peptidoglycan layer) but it also dissolves the lipopolysaccharide layer. So, when safranin is applied, the LPS-devoid Gram-negative bacteria absorb the safranin while the Gram-positive bacteria don't, hence the Gram-negative bacteria appear red while the Gram-positive bacteria appear blue.

[syo_astro]

Hi Everyone!

So recently at my regional tournament there was a question on the test asking why you could not view flagellum using UV microscopy. I figured it was because the flagellum is too small to effectively pick up the fluorescent dye, and thus cannot be viewed. However, I'm not sure if this is correct. Can somebody give me a more "scientific" answer?

Also, what is the chemical basis for negative staining? The chemical basis for staining in general? (I know for general staining you use a class-specific dye, and the dye particles will bond with the specific compound to qualify/quantify its presence...)

That first question confuses me, I thought that you could use most microscopes to view flagella. Also, flagella can pick up dyes (maybe it doesn't work with fluorescent or the UV radiation destroys it). But that doesn't make much sense and it seems like you could use it. Scrolling down this website you can even find a pic, you can probably find more on google:
http://www.tcd.ie/Biology_Teaching_Cent ... la%202.pdf

For the second question. I think negative staining uses some chemical (wikipedia says nigrosin, need to check that) to act as a darker background for better contrast in light microscopy, making it much easier to view a sample (as stains do). It is used for electron microscopy (transmission specifically) to act as a better way for electrons to pass through and become scattered, making better images. What do you mean by the chemical basis for staining? Gram stains act as a nice example but was that what you were looking for?
Hope that helps.

[TheWiseGirl]

Chemical basis meaning like "the dye particles bond with this/react with this". I guess the molecular basis would be a more apt way to describe it...

And thanks SciBomb and themachine!

[syo_astro]

Chemical basis meaning like "the dye particles bond with this/react with this". I guess the molecular basis would be a more apt way to describe it...

And thanks SciBomb and themachine!

I think it involves how stains form ions in water, and these ions bond to cell parts (class specific aspect) since the ions will be differently charged and attract to oppositely charged particles if it comes out of solution. They are also able to get into cells since they are small particles that can be diffused, and the cell membrane is porous. The reason it changes color is because as you change chemical composition the type of light that can be absorbed/reflected by atoms change (hopefully that answers your question/is comprehensible). Though, that may be slightly generalized and not explain all stains. Oxidation numbers, atomic structure, bonding, all that determines the color. May have overcomplicated that a bit to the point where I may have confused myself...I guess it would be good to check me on the last two posts I made.

[syo_astro]

Sorry to double post, and sorry that this was noted earlier. If on a test they asked for the microbial cause of potato blight, would protist be the answer or fungus since that's what it says on the nats website? The cause is not fungal (it is caused by the fungal-like oomycete, but that doesn't make it fungal). Has someone already asked for confirmation on this/knows the answer? Have they even asked about plant diseases?
Also, would how deep would they go on parasitic worm questions? Would they start asking about their anatomy, cell processes, and different types or are more basic questions more likely?
Does anyone know any sources for hands-on/real world problems with microbiology (so far I think there is one on test tubes, staining, microscopes, growth, probably some other ones).
Last question, does anyone have tips on IDing an archae? They pretty much look like bacteria to me (I can see why we were confused at first, ah worrying since states is in about a week).

[deezee]

Sorry to double post, and sorry that this was noted earlier. If on a test they asked for the microbial cause of potato blight, would protist be the answer or fungus since that's what it says on the nats website? The cause is not fungal (it is caused by the fungal-like oomycete, but that doesn't make it fungal). Has someone already asked for confirmation on this/knows the answer? Have they even asked about plant diseases?
Also, would how deep would they go on parasitic worm questions? Would they start asking about their anatomy, cell processes, and different types or are more basic questions more likely?
Does anyone know any sources for hands-on/real world problems with microbiology (so far I think there is one on test tubes, staining, microscopes, growth, probably some other ones).
Last question, does anyone have tips on IDing an archae? They pretty much look like bacteria to me (I can see why we were confused at first, ah worrying since states is in about a week).

On the Microbe mission disease list for 2012, potato blight is classified under fungal diseases. the tests are way more likely to ask about what you said (anatomy, cell processes, basic questions etc.) but since this event is pretty broad, some questions about plant diseases and worms are mixed in there. I recommend finding some sample tests (I think that some are one this website) to see what types of questions are on there.