Cookies and coffee will be available at 3:45pm…


When Gram-negative bacteria acquire iron, the metal crosses both the outer membrane (OM) and the inner membrane (IM). But, existing radioisotopic uptake assays only measure iron passage into the cell as the accumulation of the radionuclide in the cytoplasm. We devised a novel methodology that exclusively observes the OM transport reaction of ferric enterobactin (FeEnt) by Escherichia coli FepA. This technique, called postuptake binding, revealed previously unknown aspects of TonB-dependent ferric siderophore transport reactions. The experiments showed, for the first time, that despite the discrepancy in cell envelope concentrations of FepA and TonB (approximately 35:1), all FepA proteins were active and equivalent in FeEnt uptake, with a maximum turnover number of approximately 5/min.   The accumulation of FeEnt in the periplasm required the binding protein and inner membrane permease components of its overall transport system; postuptake binding assays on strains devoid of FepB, FepD, or FepG did not show uptake of FeEnt through the OM. However, fluorescence labeling data implied that FepA was active in the fepB-minus strain, suggesting that FeEnt entered the periplasm but then leaked out. Further experiments confirmed this futile cycle; cells without FepB transported FeEnt across the OM, but it immediately escaped through TolC.  These ferric siderophore acquisition systems are crucial to the pathogenesis of Gram-negative bacteria, and our results show that cathecolate siderophores, which are transported by OM receptors such as FepA, CirA, FecA and Fiu, play a defining role in colonization of the gut by E.coli.

Anyone who falls asleep will hurt my feelings!   😉

25 thoughts on “YOU ARE ALL INVITED!

    • Wouldn’t that be amazing? Hey, it only sounds complicated, it’s the lingo. The substance is a piece of cake. Did I say cake? I must be going nuts. Nuts? Well, this IS a food blog after all….


  1. I have no plans at 3:45, but unfortunately it’s a bit long of a drive. 😉 Best of luck to you! Looks like it will be a very informative seminar. I should tell Mike to make cookies for his sometime. 🙂


  2. It’s been a long time since my bio classes on active and passive transport systems, I might need to have it ‘dumbed down’ just a little. But it would be fun to get together for a post seminar booze up at the student center/pub. 🙂 Too bad they won’t let me drive for a while longer so I’ll have to be there in spirit.


    • Too bad you could not be here “for real”. INdeed, a lot has changed in the passive and active transport system over the years, but I am sure glad I work on the active transport side, as it’s a lot more exciting and complex (well, don’t tell anyone in the “other team” 😉

      I will sleep very well tonight, good to have this over!


  3. Dh and I find your work interesting-we’re both in the medical field.Sometime in the last year or so there was a report on gut flora in Scientific American. Researching cell mechanisms can lead to breakthroughs that can benefit disease control. My hat is off to you and Phil…


    • Thank you! We both feel there’s so much to do, and not enough time, not enough hands, not enough resources. But, I would not change my work for anything… and I know Phil feels exactly the same way.

      We are lucky to be able to do something we love for a living.


    • Yeah, right…. But OF COURSE they were store bought! You think I wuold bake the cookies and then give a talk? 🙂

      (come to think of it, I just baked a cake and brought to the department yesterday… )


    • Wish I was as brilliant as you think! 😉 But I am a lot more stubborn and persistent than clever, and that often works well for research. You simply cannot give up and let the frustrations of puzzling results bring you down.


  4. I actually considered coming. So as not to add to your stress by having a guest to entertain I would have shown up just in time for the talk then helped you celebrate afterwards. Maybe next time.


    • Oh, you crazy woman! You would have killed me right on the spot! 😉
      I already almost got into hyperventilation when I saw the director of the Cancer Research Center entering the room. First time I saw him in the Biochem seminar series, my knees got a bit weak. He sat on the FIRST ROW, right in the center, can you imagine the pressure?

      seriously, thanking for considering the loooong drive, but you must come when I am not at risk of a cardiac arrest 😉 December is sounding pretty good!


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