Help with some more questions

November 8, 2009 at 2:45 am #12230

Participant

I have some more problems with a few questions if u guys dont mind helping me out on

Q Part a) Explain how a nucleic acid probe could be used to detect the presence of the bacterium Salmonella in a cample of powdered milk.
Part b) compare this process to the detection of salmonella using conventional microbiology techniques (i.e. culturing and biochemical tests). Consider the need for a pure culture, the specificity of the tests and the sensitivity of the tests (i.e. how many cells can be detected)?

Ok i dont know what a nucleic acid probe is nor have i had a chance to use one. I found a definition at this website http://www.websters-online-dictionary.o … probe.html . I’ll admit i dont quite understand what they are saying at this website.

Q) When tracing the source of an outbreak of a communicable disease, it is necessary to
a) distinguish between the terms strain and species
b) name 4 test methods that can distinguish between strains within a species.

According to my 1st yr biology textbook (i didnt buy a textbook for microbiology as im the typical poor student), It said there was no real definition for species, as it is often debated. All it said was it is a taxonomix categoy of lowest rank. And for strain the closest thing to a definition i found was this: A varient or a mutation of a species. For part B my guesses would be some test such as gram stain, spore stain, acid fast stain – thats all i could really think of.

Q) Based on studies of ribosomal RNA living organisms are currently classified into three domains. Identify and compare the three domains and discuss how rRNA studies have contributed to our understanding of the phylogenetic relationships between them

I know the three domains are eukaryotes, prokaryotes and archaea. analysis of these depends on the gene sequence and cladistics. Genes encoding rRNA are ancient and distributed over all lineages of life with little or no horizontal gene transfer – and thats about all the relevant info i have found so far.

Any extra info on any of these questions is largely appreciated. Thanks

November 8, 2009 at 5:21 am #94632

JackBean

Participant

1) basically, you will extract all DNA from some milk a do some qPCR or chip, when will you detect DNA specific for your patogen. If is it present, you know, it was infected, if it’s not, it was under your detection limit (including absence).
b) it’s definitelly simplier, faster, more specific…

2) by what you listed you can distinguish like species, maybe only genus, definitelly not strain.
Strains often differ in some mutations, they can be auto/heterotrophs (so, plate them on media with(out) of nutrient), they can grow at some special conditions etc.

3) compare the possible trees of live (archea more related to bacteria vs. to eukaryotes), I have seen an article about that, but I don’t know, where, sorry 🙁
(do you have access to PubMed or something?)

November 8, 2009 at 6:18 am #94633

djiang87

Participant

No i dont have access to PubMed nor do i even have a microbiology textbook. I was trying to save money and didnt end up buying a textbook for this subject (which is really regret now). For the 3rd question are you talking about a Phylogenetic tree? If so ive seen one, ill post the link here http://www.dnabaser.com/articles/phylog … ee-big.jpg

November 8, 2009 at 6:59 am #94634

JackBean

Participant

Yeah, that’s exactly, what I mean.
Try these two articles
http://www.ncbi.nlm.nih.gov/pubmed/1977 … dinalpos=3
http://www.ncbi.nlm.nih.gov/pubmed/1963 … dinalpos=6
Unfortunatelly, they are from Springer, so you probably won’t have access (Springer sucks :twisted:)

So, what did you post is one possibility, another one is, that archea will be more related to bacteria (why are they archeaBACTERIA?)

November 11, 2009 at 2:40 am #94737

MrMistery

Participant

jackbean, archea are actually more closely related to eukaryotes than they are to eubacteria. they are called arhebacteria only because they are both prokaryotes, which all used to be clumped together in a single kingdom called Monera.

Now we know different

November 11, 2009 at 9:22 am #94748

JackBean

Participant

quote JackBean:

another (possibility) is, that archea will be more related to bacteria (why are they archeaBACTERIA?)

😉

November 12, 2009 at 2:42 pm #94786

djiang87

Participant

Just letting u guys know i had my exam the other day. Thx for the help guys. A question about a nucleic acid probe was in there as well as a question about drawing a phylogenetic tree. However with the phylogenetic question i couldnt answer the part about the relationship between archaea and eukaryotes. Unfortunately i couldnt answer this part =[

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