Monday 10 November 2008

E-coli & Ascorbic Acid Electron Micrographs

Back in my university days I found employment at University Hospital in London at which I studied the effects of the antibiotic Metronidazole (Flagyl) against various bacteria (1). Metronidazole has long been established as one of the premier antibiotics with activity directed against most gram negative as well as many gram positive anaerobic bacteria. More interestingly, our research unexepectantly found that Metronidazole was able to exhibit remarkable activity against the facultative organism Gardnerella vaginalis (2). This was found to be a result of the metronidazole molecule being metabolized in the liver to both an ‘acid’ and a ‘hydroxy’ metabolite. Further experimentation showed that the hydroxy metabolite exhibited significant activity against this organism.

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In the experiments using various anaerobic (oxygen hating) organisms, liquid tubed media was used to grow the bacteria and in which to dilute the antibiotic. In order to “reduce” the media, so that it was oxygen free, a variety of chemical ingredients could be added. We chose ascorbic acid and used the facultative anaerobic organism E-coli as a control. The test anaerobic organisms reacted as expected however significant changes were visible on the control E-coli bacteria as well, against which metronidazole should have no appreciable effect. The E-coli cells were visibly stressed and damaged, often showing uncharacteristic morphology such as incomplete cellular division, elongated cell forms and bifurcated ends. In a rather unexciting explanation, it was determined that this was due to the ascorbic acid content itself stressing the E-coli cells.

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Regardless of this outcome, the entire process served as a learning experience and afforded me a chance to work with the university’s electron microscope. I’ve included some of those electron micrographs here. In particular I never tire of marveling at the physical and molecular structure of these fascinating bacteria. Included here is an electron micrograph of an E-coli bacterium demonstrating the cell wall structure which is responsible for it’s gram staining properties. Other smaller photos show the stressed nature of the bacteria which should have appeared as rather uniform bacilli. Various magnifications were taken and if I recall, the electrondense negative stain was phosphotunstic acid (PTA).

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*all electron micrographs were taken by Yuri.

So, perhaps this is evidence that you should get your daily dose of ascorbic acid (vitamin C) as it may itself have a direct effect on bacteria in your system. You know what they say, “an apple a day keeps the doctor away” - perhaps with some truth to it.

(1) Edward D. Ralph & Yuri E. Amatnieks
Antimicrob Agents Chemother. 1980 March; 17(3): 379-382

(2) E.D. Ralph & Y.E. Amatnieks
Antimicrob Agents Chemother. 1980 July; 18(1): 101-104