High-Carb Diets Can Be Tough on Bacteria, Too

Sugars are toxic in excess because they are highly reactive. But we don’t normally think of them as toxic to bacteria. Bacteria thrive by eating sugars.

I was reading “TB or Not TB?” at The Scientist and was amused at this anecdote, about efforts to find new ways to kill drug-resistant TB:

Rainer Kalscheuer, now at Heinrich-Heine University in Germany, was searching for genes and proteins that made some TB cells more treatment tolerant than others. After doing a microarray analysis, Kalscheuer wanted to investigate a metabolic intermediate enzyme called GlgE, but Jacobs balked. “I told him a group at Harvard had already shown that glgE was an essential gene that can’t be manipulated,” Jacobs remembers. But Kalscheuer persevered and found out that glgE could be knocked out and studied if grown in the right culture medium.

Note for grammarians: glgE is the gene, GlgE is the protein.

The key to creating viable glgE knockout strains turned out to be trehalose, a cell wall carbohydrate. TB bacteria that lacked glgE died instantly when trehalose was present, but survived if it was removed. The Harvard group had used medium that contained trehalose without realizing it because the carbohydrate, used as a preservative, was an unlisted ingredient.

This is the kind of thing that drives impatient biologists crazy. Experiments are so sensitive to subtle variations, such as an unlisted preservative in the culture medium, that Biology smiles only on those who are exceedingly careful, thoughtful, and patient with tedious troubleshooting. Also, those who don’t put too much faith in the results of their peers!

The next step for Kalscheuer and Jacobs was figuring out the functional relationship between the two proteins. GlgE had been implicated in glycogen metabolism, but the connection with trehalose was unclear. Finally, after a painstaking series of suppressor genetics experiments, they elucidated the biochemical pathway: Glycogen and glucose produce trehalose; an enzyme known as trehalose synthase converts the trehalose into maltose; then, the maltose becomes maltose-1-phosphate, the protein that GlgE converts into glucan. When glgE is knocked out, maltose-1-phosphate accumulates, which kills the tuberculosis bacterium.

Turnabout is fair play. It seems only fitting that bacteria should die from high-carb diet toxicity. Why should humans be the only ones?

Leave a comment ?


  1. Honey is an old-fashioned wound treatment – keeps the area sterile. Only problem would be stickiness. And ants, I suppose!

  2. And if maggot therapy is good for us, why not for casu marzu casu marzu? Mmmmmm.

    Great post as always. Speaking of honey, yesterday I didn’t get the amount of carbs I needed (I’m fighting a fungal infection), so I had a tablespoonful of honey right after a fatty meal (lamb chops). Would it have been better to have forgone the honey or was the ingestion of carbs more important? Thanks as always.

  3. Better and less sticky than honey would be propolis! It have antifungal, antiviral and antibacterial properties. Also, it was used by the egyptians for mummification!



  4. Poisonguy,

    I’m afraid if I ate those jumping larvae I might go down the unfortunate road of this lady.

    On low carb diets some fructose can be converted to liver glycogen and then released as glucose to the immune system, so it may be helpful that way. And I see that honey may even have antifungal properties: http://www.ncbi.nlm.nih.gov/pubmed/19888803.

    Maybe my next book should be the “All Honey Diet”!

    Mario – Thanks, one more item for the pharmacopeia! The mummification only happens to dead folks, right?

  5. By the way, Shou-Ching tells me that high concentrations of sugar will kill bacteria, it diffuses in by osmotic pressure. This is why putting lots of sugar in jams acts as a preservative.

    So maybe it’s not necessary to knock out glgE for the All Honey Diet to be effective!

  6. Yes, it isn’t a good idea to exert the osmotic pressure from honey in a diffuse manner throughout the human body – that would be a gruesome death, I would think! But it can do the trick on a bad surface wound. It may interfere with the fibroblasts trying to close the wound… not sure, I’m not exactly at the forefront of wound research. But it is preferable to a horrible antibiotic resistant infection.

  7. So, load up with VitC and Magnesium Citrate AND honey results in a gut bacteria make-over?

  8. Paul,

    Do you have any thoughts on autism doctor Amy Yasko’s recommendation to supplement trehalose to dampen excitotoxicity?

  9. Hi MM,

    I’m not really familiar with trehalose’s effects and would like to see it tested better before I would endorse it. There’s a very healthy and natural fix for glutamate excitotoxicity — intermittent ketogenic dieting — so I wouldn’t be quick to turn to an unproven supplement for this purpose.

  10. #04 – Mézet sem eszel? | AllyToGood! NightmareToYou? - pingback on September 22, 2014 at 4:57 pm

Leave a Comment

NOTE - You can use these HTML tags and attributes:
<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>

This site uses Akismet to reduce spam. Learn how your comment data is processed.