Biology Reference
In-Depth Information
CHAPTER 3
CO-TRANSDUCTION AND LOCATION OF
Escherichia coli
GENETIC MARKERS
INTRODUCTION
Escherichia coli
has been one of the central tools to study the basic
principles of biochemistry, molecular biology and cell biology. Non-
pathogenic strains were used in many laboratories. Metabolic pathways
have been delineated carefully. Mutants were isolated with certain selected
defective enzymes involved in these pathways. Various methods of genetic
manipulation using these mutants have been developed. The collection of
these experimental findings verified the circular chromosomal structure.
Then, a detailed
E. coli
genetic map was constructed, followed by complete
sequencing of its genomic DNA.
In this chapter, one of the genetic methods developed for
E. coli
,
transduction (Lederberg
et al.
, 1951; Zinder and Lederberg, 1952; Lennox,
1955), will be discussed in detail. Experimentally, two genetic markers can
be co-transduced if they are sufficiently close to each other. The frequency
of co-transduction will be related to the distance between these two markers.
This relationship can be derived theoretically by considering all aspects of
the biological process of transduction. Many experiments were also carried
out with three nearby genetic markers, known as three-point analysis.
Some
researchers even studied four closely linked markers.
In order for an experimental study of transduction to be successful, it is
essential to determine the approximate locations of the involved genetic
markers. Such estimations can be achieved by another genetic manipulation
also developed for
E. coli
known as conjugation (Lederberg and Tatum,
1946). This process involves the transfer of the entire
E. coli
chromosome
from the donor to the recipient in 100 minutes at 37
0
C in a rich medium, and
will thus be reviewed first.
