|E. coli Genome Map
By Sean Henahan, Access Excellence
WI (9/4/97)- The completion of a genome map of the E.coli bacteria
is an important milestone in fields of medical and biological research,
A team of researchers in the Laboratory of Genetics at the University
of Wisconsin-Madison determined the complete genome sequence of the E.
coli. The the 4,639,221 base pairs of the genome contain 4,403 genes. The
function of on third of the genes has yet to be determined.
The bacterium Escherichia coli is truly the workhorse of biology. Originally
isolated in 1922 from a diphtheria patient, the strain of E. coli sequenced
was used in 1945 in the discovery of spontaneous gene transfer. The
strain, known as K-12, was universally adopted for fundamental work in
biochemistry, genetics and physiology. In recent years, it has become the
'heavy lifter' of biotechnology where it is used to produce human insulin
and other medicines.
"Determination of the complete inventory of the genes of organisms is
one of the holy grails of biology, analogous to development of the periodic
table of the elements in chemistry," said lead investigator Frederick R.
Blattner. "Once they are all known and relationships between them become
evident, a classification system for understanding the basic functions
of life can be erected."
E.coli is not the first bacterial genome to be sequenced, but with more
than 4.6 million bases, it is the largest and possibly most important.
More than 250 people, including undergraduates new to genomic research,
participated in the project. The raw data was made available on the
at the beginning of the year. It took another nine months to analyze and
describe the findings.
The most important aspect of the research is that it represents a record
of the genes that make up the genome of the organism, and the establishment,
where possible, of their functions. A surprising
number of the genes are new, Blattner said.
The researchers also compared every gene of E. coli and every gene of
every other completely sequenced organism. This comparison indicates that
many genes appear commonly throughout nature while others are unique to
E. coli. This information is essential to any understanding of how E. coli
and other bacteria have evolved, and what genes are required at a minimum
to create life, he explained.
To find E. coli, one need look no further than one's lower intestine.
The K-12 strain of E. coli is not pathogenic, but closely-related strains
are toxic and have been implicated in an increasing number of human food
poisonings from products ranging from ground beef to unpasteurized apple
juice. The data from the K-12 E. coli genome will make it possible to make
a gene by gene comparison with its pathogenic relatives and isolate genes
that govern the toxic nature of the bacteria.
The sequencing of the E. coli genome is also a critical milestone towards
the ultimate goal of sequencing the human genome. Data from bacterial genomes
will help identify common genes found in many organisms, which int run
will help elucidate their function, said Blattner.
The research is reported in the Sept. 5, 1997 issue of the journal