Posted: November 26th, 2015

Lipopolysaccharide: Biosynthetic pathway and structure modification

So to the actual assignment: Collect the paper in electronic format from Science Direct (already uploaded). (you are need to be able to select the figures and put them into an electronic format that you can manipulate; copy and paste into a power point file) print you off a hard copy and read through it with a writing instrument and take notes. Bloom’s version of comprehension and a little synthesis and analysis. You will find some glaring contradictions such as the structure of lipid A is more widely conserved than are core oligosaccharides and then the authors go in to differences in Lipid A structure and biological activity seems a little contradictory but depends on what you mean by conserved. I am going to be picky on one little point: At the top of page 99 the authors state “Lipid A is known to be responsible for the toxic effects of infections with Gram-negative bacteria [4].” Wrong choice of words, resulting in an erroneous statement. Yes everyone makes mistakes (if there is not at least one typo in my products, I probably did not create it) but we try not to make them in published articles. Thus,
for question #1 and six points explain why that statement is wrong and give two examples to support your contention. You may have to do a little research or it may be a case of recall. This is a question that should contribute to better writing style.

Question 2. Paste Figure 1 into a Power point document (or different format if you have something that works for you, just have to save the final product as a PDF.) Put it in your own words and describe LPS biosynthesis with the role of those nine enzymes from table 1. Do not just stick the information from the Table1onto the diagram!!! Use information from the text and put it into your own words. If you have to figure out what acylation is, look it up. You have two goals make that figure self-explanatory and demonstrate an understanding of the biosynthesis.

3. Do the same thing with Figure 2 and table 2 for the Export of LPS to the outer membrane

4. For modification of LPS, three general areas, change in membrane stability, change in membrane charge, and change in interaction with TLR-4 (don’t get into O antigen, yes fourth area). A little help; page 99 second paragraph describes the events in that PowerPoint slide of the septic shock from the LPS interaction with the macrophage (think monocytes, neutrophile in bloodstream) to the point of TNF and IL-1 production, the cytokines listed. Describe from the text two ways modification of LPS results in increased virulence with examples. Also define: polymixin B and give the mechanism of action, CAMPs, PhoP-PhoQ and why are they important?