Download 7 Lysogeny and Transduction

7 Lysogeny and Transduction
John H Paul' and Sunny C Jiang2
~Department of Marine Science, University of South Florida, St. Petersburg, FL 33 70 I, USA
2School of Social Ecology, University of California, Irvine, Irvine, CA 92697, USA
CONTENTS
Introduction and background
Screening marine bacteria for lysogeny
Transduction assay
Future directions
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INTRODUCTION
AND BACKGROUND
Lysogeny and transduction describe a type of phage/host interaction and
a method of bacterial gene transfer (procaryotic sex), respectively.
Although they are often reviewed together, these topics are linked only in
that one type of transduction (specialized) has an obligate requirement for
a lysogenic interaction. In this chapter we describe the background for
understanding both of these processes, and give methods that we have
found useful in studying lysogeny and transduction in the marine
environment.
Lysogeny and pseudolysogeny
Lysogeny occurs when a phage enters into a stable symbiosis with its host
(Ackermann and DuBow, 1987). The host (bacterium or algal cell) and
phage capable of entering into such a relationship are termed a lysogen
and temperate phage, respectively. The temperate phage genome
becomes integrated into one of the replicons of the cell (chromosome,
plasmid, or another temperate phage genome) and is termed a prophage
(Figure 7.1). The lysogenic state is a highly evolved state (Levin and
Lenski, 1983) requiring coordinated expression (and repression) of both
host and viral genes. There is a selective pressure to favor lysogeny, particularly at times of low host density, because a temperate phage is less likely
to drive its host to extinction (Levin and Lenski, 1983). Other advantages
of lysogeny include the expression of prophage encoded genes, termed
conversion. This is in contrast to transduction (see below), whereby the
genes imparted into an infected host were the result of a phage packaging
error during a prior infection cycle. That is, in transduction the genes
METHODS IN MICROBIOLOGY, VO1,UME 30
ISBN 0-12-521530 4
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