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Hi everyone!

For those of you who don’t know me already, my name is Stewart (@Stewart_Barker on Twitter), and i am a final year Biology BSc student at Sheffield Hallam University. I have been active with #microtwjc for a few months now, and it is my turn to lead a discussion session!

This week’s paper –

Correlation between virulence gene expression and proton pump inhibitors and ambient pH in C. difficile: Results of an in vitro study 

The paper has very kindly been made open access by the Society for General Microbiology from 27th September to 2nd October here: http://jmm.sgmjournals.org/content/early/2013/06/25/jmm.0.059709-0.full.pdf+html

Proton pump inhibitors (PPIs), such as Omeprazole and Lansoprazole are frequently prescribed as outpatient medication and are even prescribed over the counter. They produce an antacid effect in the stomach, used to treat diseases caused by excess acid, like Peptic ulcers. As gut microorganisms are highly adapted to survive in the low pH, a change in the environment will alter their physiology and virulence. This has long been thought to be a secondary cause of Clostridium difficile infections, after the use of broad spectrum antibiotics.

The authors look beyond just the manipulation of stomach pH – at the direct effect of PPIs on the expression of toxins and their regulators. Considering the growing issue with antibiotic resistance, and the continuous use of orally administered broad-spectrum antibiotics, it is crucial to investigate other options to inhibit C. difficile infections.

Questions:

  1. Is the paper well written, easy to understand and thoroughly explained?
  2. Are the methods appropriate?
  3. What do the results tell us – how significant is the impact of this research?
  4. What research can and should this follow on to?
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Hey everyone,

I am not sure If we have had this area before…Thought it was interesting as it is on bacterial metabolism and how engineer it…

The discussion will be as usual on a Tuesday night at 8 pm BST on twitter. It will be on the 17th of September.

The paper title is:

Electrochemical Gating of Tricarboxylic Acid Cycle in Electricity-Producing Bacterial Cells of Shewanella

and it can be found here:

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0072901

Abstract

Energy-conversion systems mediated by bacterial metabolism have recently attracted much attention, and therefore, demands for tuning of bacterial metabolism are increasing. It is widely recognized that intracellular redox atmosphere which is generally tuned by dissolved oxygen concentration or by appropriate selection of an electron acceptor for respiration is one of the important factors determining the bacterial metabolism. In general, electrochemical approaches are valuable for regulation of redox-active objects. However, the intracellular redox conditions are extremely difficult to control electrochemically because of the presence of insulative phospholipid bilayer membranes. In the present work, the limitation can be overcome by use of the bacterial genus Shewanella, which consists of species that are able to respire via cytochromes abundantly expressed in their outer-membrane with solid-state electron acceptors, including anodes. The electrochemical characterization and the gene expression analysis revealed that the activity of tricarboxylic acid (TCA) cycle in Shewanella cells can be reversibly gated simply by changing the anode potential. Importantly, our present results forShewanella cells cultured in an electrochemical system under poised potential conditions showed the opposite relationship between the current and electron acceptor energy level, and indicate that this unique behavior originates from deactivation of the TCA cycle in the (over-)oxidative region. Our result obtained in this study is the first demonstration of the electrochemical gating of TCA cycle of living cells. And we believe that our findings will contribute to a deeper understanding of redox-dependent regulation systems in living cells, in which the intracellular redox atmosphere is a critical factor determining the regulation of various metabolic and genetic processes.

Discussion points:

  1. What did you think of the paper? Nicely written? Easy to understand? Aims of the study?
  2. Did you miss any experiment/controls etc that would have been nice to see?
  3. How could this research be used in future?
  4. Could the outer-membrane cytochromes (OMC) of Shewanella be expressed in other genus of bacteria and which effect would it have?