E. coli Converted into Novel Antibiotic Generating Factories

The white filter disks holding antibiotics sit on petri dishes housing erythromycin-resistant Bacillus subtilis. The filter disks circled in red hold new forms of erythromycin created by University at Buffalo researchers, and the dark halo around them indicates that the drug has seeped out of the disk to kill the surrounding bacteria. [Guojian Zhang]

The monumental hurdles needed to be overcome for the use of complex bacterial hosts in the generation of intricate biosynthetic molecules is daunting, at the very least. Often entire metabolic pathways must be genetically introduced, coordinately expressed, and successfully translated to achieve an active final product.

However, researchers at the University of Buffalo, after many years of engineering the appropriate strain, have now been able to coax E. coli to produce new forms of antibiotics—including three that show promising potential to combat drug-resistant bacteria.  

“We're focused on trying to come up with new antibiotics that can overcome antibiotic resistance, and we see this as an important step forward,” explained Blaine Pfeifer, Ph.D., associate professor of chemical and biological engineering at the University at Buffalo School of Engineering and Applied Sciences. “We have not only created new analogs of erythromycin, but also developed a platform for using E. coli to produce the drug. This opens the door for additional engineering possibilities in the future; it could lead to even more new forms of the drug.”

The findings from this study were published recently in Science Advances through an article entitled “Tailoring pathway modularity in the biosynthesis of erythromycin analogs heterologously engineered in E. coli.”

Over the past decade, Dr. Pfeifer’s research has been centered on manipulating E. coli so that the organism produces all of the materials necessary for creating erythromycin. Once that portion of the biological factory was built the investigators went about tweaking the engineered microbes to produce multiple biological variations of erythromycin slightly different than currently utilized compounds.

Dr. Pfeifer’s team began the antibiotic production process by supplying the requisite metabolic precursors—chemical compounds that are combined and fed through a biologic assembly line in order to form the final product, erythromycin.

To generate erythromycin compounds with discreet chemical differences, the scientists could theoretically manipulate any part of the assembly line process to affix the molecule with chemical groups, leading to an end product that deviates slightly from all the others.

“Our results suggest a similar modularity associated with the downstream tailoring reactions that offer as much or more opportunity for compound variation and altered bioactivity given the necessity of these steps in endowing therapeutic properties,” stated the scientists.  

Interestingly, Dr. Pfeifer’s team homed in on a part of the antibiotic construction process that had been overlooked by many scientists in the past. The researchers focused on enzymes that attached a carbohydrate moiety called 6-deoxyerythronolide B at the end of the metabolic assembly line process—leading to the generation of more than 40 new active analogs of erythromycin, a few of which were able to kill drug-resistant microbes.  

“The system we've created is surprisingly flexible, and that's one of the great things about it,” said Dr. Pfeifer. “We have established a platform for using E. coli to produce erythromycin, and now that we've got it, we can start altering it in new ways.”