Micro 302 Online
Homework #5 Primary Paper (whole paper)
15 pts
Gut inflammation provides a respiratory electron acceptor for Salmonella
Winter SE, Thiennimitr P, Winter MG, Butler BP, Huseby DL, Crawford RW, Russell JM, Bevins CL, Adams LG, Tsolis RM,
Roth JR, & Bäumler AJ (2010). Gut inflammation provides a respiratory electron acceptor for Salmonella. Nature, 467
(7314), 426-9 PMID: 20864996
This Paper has response (blog) post and a podcast associated with it (in other words, this discovery caused some
scientists to reconsider how Salmonella bacteria infect the gut). Blog: http://schaechter.asmblog.org/schaechter/2012/03/salmonellas-exclusive-intestinal-restaurant.html Podcast: http://www.microbeworld.org/podcasts/this-week-in-microbiology/archives/1133-twim-27-aninflamed-gut-is-good-for-salmonella Some definitions:
Neutrophil: A type immune cell that can engulf invading pathogens and produce reactive oxygen species by expressing
NADPH oxidase.
Reactive oxygen molecules: Highly reactive molecules containing oxygen that are highly antimicrobial.
Caecum: a specialized compartment where the small intestine meets the large intestine; high bacterial load. Mice have a
large caecum, while our appendix is really all that is left of the human caecum.
NADPH oxidase: An enzyme complex expressed in some immune cells. When immune cells become activated (perhaps
due to presence of a pathogen), NADPH oxidase produces the reactive oxygen species superoxide, in immunology terms
this is called an oxidative burst because it oxidizes many different molecules
Nos2: The gene Nos2 encodes for the enzyme nitric oxide synthase. Nitric oxide synthase produces nitric oxide, a reactive
nitrogen species which causes inflammation.
Cybb (-/-): The innate immune cells of mice lacking the Cybb gene are unable to produce reactive oxygen species like
superoxide.
ttr gene cluster -Salmonella genes that are required to use tetrathionate as an electron acceptor
Please look the techniques used in this paper. There is NO WAY you can understand a figure if you don’t understand how
the experiment was run.
Questions (this is what you will respond to and submit). Please type your responses and use complete sentences to
answer each question. If you use other sources besides the paper, please reference them (APA style). Please save page
2 as a pdf with your responses to the questions (not the questions themselves) and submit on Blackboard before the due
date (June 19, 2017) Doing:
1. From the introduction: How is tetrathionate broth made and why is this relevant? (please look at the paper, not
Google as the paper describes it much more simply than Google would)
2. From the introduction and figure 1a.
a. Which sulfur-containing compound (thiosulphate or tetrathionate) accepts electrons and what does it
become after it is reduced?
b. Based on this, which compound would you expect to have a higher standard reduction potential (Eo) thiosulphate or tetrathionate? Why?
3. Figure 1c : Comparing mock-infected to Salmonella typhimurium infected lanes in Figure 1c –
a. What does Salmonella do to NADPH oxidase expression (increase or decrease it)?
b. Why is tubulin included in this figure?
c. What is the main conclusion of this figure (in context of the intro and paper’s theme)?
4. Figure 1e: Fill out the following table (where highlighted) The first row is an example...
Variable
Observation
Explanation (one sentence)
Wt mice + mock infected
These mice were not exposed to The thiosulfate remained
Salmonella, and produced no
thiosulfate because no oxidative
detectable tetrathionate.
burst oxidized it to
tetrathionate..
Wild type mice + Salmonella
Exposed to wild type
Why?
infection
Salmonella, but no
tetrathionate detected.
Wild type mice + invA/spiB
No tetrathionate detected.
Why?
(Salmonella that can’t attach to
gut lining)
Wild type mice + ttr (Salmonella Tetrathionate detected
Why?
that cannot reduce
tetrathionate)
Cybb mice + ttr (Salmonella that No tetrathionate detected.
Why?
cannot reduce tetrathionate)
5. Figure 4c.
a. What was being measured in figure 4c and how was it measured?
b. How do wild type Salmonella differ from ttrA Salmonella? (How the strains are different, not how the
results differ).
c. Why did the authors include both wild type and ttrA restored Salmonella in this figure?
6. Looking at the title of figure 4, which sub-figure a, b, c, or d most clearly demonstrates that Tetrathionate
respiration gives a competitive advantage to S. typhimurium? Explain your answer.
Summary “Take Home Message”:
7. Explain (3-4 sentences) why inflammation gives Salmonella a competitive advantage?
8. Would you expect to see this competitive advantage more in an aerobic or anaerobic environment? Why?
Reflecting:
9. How did your thinking about electron transport chains change with this exercise?
10.How confident are you in your answers to this exercise? Explain.

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