Hk. Dressman et Jw. Drake, Lysis and lysis inhibition in bacteriophage T4: rV mutations reside in theholin t gene, J BACT, 181(14), 1999, pp. 4391-4396
Upon infecting populations of susceptible host cells, T-even bacteriophages
maximize their yield by switching from lysis at about 25 to 35 min at 37 d
egrees C after infection by a single phage particle to long-delayed lysis (
lysis inhibition) under conditions of sequential infection occurring when f
ree phages outnumber host cells. The timing of lysis depends upon gene t an
d upon one or more rapid-lysis (r) genes whose inactivation prevents lysis
inhibition. t encodes a holin that mediates the movement of the T4 endolysi
n though the inner cell membrane to its target, the cell wall. The rI prote
in has been proposed to sense superinfection, Of the five reasonably well c
haracterized r genes, only two, rI and rV, are clearly obligatory for lysis
inhibition. We show here that rV mutations are alleles oft that probably r
ender the t protein unable to respond to the lysis inhibition signal. The t
r alleles cluster in the 5' third of t and produce a strong r phenotype, wh
ereas conditional-lethal t alleles produce the classical t phenotype (inabi
lity to lyse) and other t alleles produce additional, still poorly understo
od phenotypes. tr mutations are dominant to t(+), a result that suggests sp
ecific ways to probe T4 holin function.