Approximately 340 independent wells were
infected with an average of two pfu each and
incubated overnight (2). Lysates were plated onto the selective strain E. coli gro89, a defective mutant of the
rep gene, which encodes a DNA helicase required for particle maturation, to score for
phages with the ability to infect this strain.
From 12 wells, it was determined that f = 1.7 ´ 10-5. The
average final number of pfu per well was 6.6 ´ 107, and B = 180 as estimated in another study (1). Thus, using Equation 1, c = log (6.6 ´ 107 / 2) / log 180 = 3.3. Sequencing of 156 independent mutants showed
that T = Ts = 12. Since Ts was determined, there is
no selection bias due to lethals. Some
bias could exist due to non-lethal effect.
However, since c was small,
this should not produce a large deviation in the estimate (probably less than
twofold, not shown). Neglecting this
effect, ms/n/c =
3 ´ 1.7 ´ 10-5 / 3.3 / 12 = 1.3 ´ 10-6.
1. De Paepe,
M. and F. Taddei. 2006. Viruses' life
history: towards a mechanistic basis of a trade-off between survival and
reproduction among phages. PLoS Biol. 4:e193.
2. Raney, J. L., R. R. Delongchamp, and C. R. Valentine. 2004. Spontaneous
mutant frequency and mutation spectrum for gene A of phiX174 grown in E. coli. Environ. Mol. Mutagen. 44:119-127.