Why Sequence Zymomonas mobilis strains?

Z. mobilis industrial strain CP4, originating from Brazil, vigorously fermenting glucose to ethanol and CO₂ (gas bubbles in the culture tube). Photo courtesy Katherine M. Pappas.

A primary goal for the U.S., the E.U., and other nations is to find cleaner, safer and renewable alternatives to fossil fuels, and to that end 4 billion gallons of corn-derived ethanol was used as fuel additive in 2006, in the U.S. alone. The bacterium Zymomonas mobilis is a highly potent ethanol producer already used in industrial-scale fermentations. Zymomonas converts sugars to ethanol and carbon dioxide, exhibiting up to 98% yields, minimal by-products, simple fermentation requirements, and several-fold the production rates of yeast. Beside its robust capability for biofuel production, this organism has been additionally proposed as a desirable candidate for sorbitol, levan, and other fine-chemical production, and it has attracted interest for its high content of membrane steroids, called hopanoids.

Taxonomically, Z. mobilis is an α-proteobacterium of the Sphingomonadaceae family, believed to dwell in the natural environment of plants. Different strains have been isolated from various geographic places as naturally fermenting (or spoiling) organisms in alcoholic beverages, and this renders the organism also important for food technology. More than merely safe, Z. mobilis has also been proven effective against parasitic microorganisms and used as a therapeutic agent in animal and human infections. The sequence of the industrial Z. mobilis strain ZM4 (ATCC 31821) circular chromosome was published in 2005 (Macrogen Inc.), however, most of this strain's high-molecular-weight plasmids remain to be sequenced. DOE-JGI plans to sequence the ZM4 plasmids so that this important strain’s genome is completed. In addition, since strain ZM4 is the only representative of this organism sequenced thus far, we will also sequence several of the most characteristic Z. mobilis strains, varying in their properties and stemming from various locations throughout the globe, in their entirety (both chromosomal and extrachromosomal material). Given that comparative analysis is the key to understanding the biology of sequenced organisms, we believe that this endeavor will offer fundamental insights into Zymomonas and prove essential to future exploitation of its full biotechnological potential.

Principal Investigator: Katherine M. Pappas (Univ. of Athens)