Wednesday, May 25, 2011

Matt Gets Published! I

As you will recall [1], I am doing original research on symbiotic nitrogen fixation as a major component of my Ph.D. studies. Specifically, in my lab we are investigating how the bacterium Sinorhizobium meliloti and the plant Medicago sativa (alfalfa) recognize each other. We know that the plants and the bacteria secrete specific chemicals that allow them to identify themselves to each other, but not all of those chemicals have been elucidated, yet.

One of the chemicals that has already been identified as playing a role is called cyclic glucan. The exact role of cyclic glucans in the establishment of symbiosis is not yet completely understood. But it is known that if they are not secreted by the bacteria while they are invading the root nodule, that the plant will mount an immune response and kill the bacteria. Since invasion of the root nodule is one of the early events in the establishment of symbiosis, it is unknown whether cyclic glucans are required during later stages.

One of the questions my lab would like to answer is what role is played by bacterial genes at different stages of the symbiosis. To address this question, we've developed a genetic tool which allows you to delete a gene at a time of your choosing [2], simply by adding a specific chemical called an inducer. We tested this genetic tool by deleting a gene called feuN [3], which plays a role in turning on or off the genes which produce cyclic glucans. When we did this in a test tube, we successfully deleted feuN from all the bacteria within 9 hours after adding the inducer chemical. This is the gist of the paper that we published last month.[4] Experiments are ongoing to see what happens when we add the inducer chemical to bacteria which are already on plant roots.


[1] See my post What Is It That Matt Does, Anyway?

[2] Since this is a biological process, the deletion of the gene from all of the treated bacteria actually takes a few hours.

[3] In most cases, when saying the name of a gene, you just read the letters. So feuN would be pronounced EFF-EEE-YOU-EHN (mouse over for IPA).

[4] We published in a journal called Applied Environmental Microbiology. You can see the abstract here (to read the full paper you have to have a subscription to Applied and Environmental Microbiology Online). As you can see, I am the second author listed. That means that I made some significant contributions (to be specific, I generated figure 5A), but that the majority of the work was done by someone else (the first author listed). Since my contributions were limited, rather than central, this does not count towards the two publications I need for my Ph.D.

Image attributions:

Cyclic glucan of Sinorhizobium meliloti is by Ninjatacoshell, available at

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