Culinary microbes add tang to
salami, cheese and pickles and de-acidify wine. Now, their decoded DNA provides
a blueprint for new bio-based industrial uses. Image courtesy Roy
Kaltschmidt, Lawrence Berkeley National
"Domesticated" Microbes Flex Industrial
Muscle By Rosalie Marion Bliss
November 16, 2006
A range of tangy and tart flavor compounds in hundreds of popular food
and beverage products worldwide are the result of friendly fermentative
microorganisms that carry out a variety of key biosynthetic processes.
Now, a consortium of public, private and academic
researchersincluding three with the Agricultural Research Service (ARS)has decoded the DNA of nine
representative strains of lactic acid-producing bacteria, or LAB.
While yeasts are responsible for putting the bubbles in beer and
bread, LAB impart sharpness or mildness to cheeses and lively flavors to yogurt
The study, published recently in the Proceedings of the National Academy of
Sciences, was done by a multi-institute group of academic researchers
under the Lactic Acid Bacteria Genome Consortium, headed by microbiologist
David Mills at the University of
California-Davis. Among the researchers were ARS microbiologists
Diaz-Muniz, and plant pathologist
Wechter. The multi-year study also involved scientists with the Walnut
Creek, Calif.-based Department of Energy
Joint Genome Institute, which coordinates
with the U.S. Department of Agriculture on
targeted DNA sequencing projects.
The versatile LAB produce lactic acid as an end product of
enzymatically fermenting lactose, or milk sugar, without the assistance of
exposure to air. The metabolism of this functional clan of bacteria has been
exploited for thousands of years to preserve nonrefrigerated foods.
One finding based on comparative genomic analysis uncovered coding
regions that allow LAB to produce antimicrobials. Bacteriocin, for example, is
produced by certain LAB strains and has been found to inhibit the human
pathogenic bacterium Listeria monocytogenes.
The data allow researchers to better understand how the LABs
fermentative gymnastics can be exploited for new biobased and other industrial
applications. The polymer dextran, for example, can be biologically produced
when one of the newly sequenced LABLeuconostoc
mesenteroidesacts on cane or beet sugars. Dextran can be used as a
biobased chemical ingredient in commercial products such as cosmetics and
ARS is USDA's chief scientific research agency.