Table 2.
Experimental evolution of lysis time in phages.
| Phage | Results |
|---|---|
| RB691 | Basic Result supported, optimality model not tested. An early lysing holin mutation (with reduced burst size) introduced against wild-type prevailed at high cell density but not at low cell density |
| λ2 | Basic Result and optimality model not tested. Eleven known holin mutations were separately introduced into a constant genomic background and characterized for lysis time and burst size. Fitnesses were measured in parallel under constant conditions. A mutant with intermediate lysis time had highest fitness, demonstrating existence of an intermediate optimum but not whether that optimum was quantitatively as predicted |
| λ3 | Basic Result supported, optimality result not tested. Six known holin mutations were separately introduced into a common genomic background with side tail fibres (high adsorption rates) and tested in pairwise competitions with each other; the holin mutation lysing at 46 min had highest fitness. When the same holin mutations were tested in a genomic background without side tail fibres (low adsorption rates), the mutation lysing at 64 min was superior. The presence/absence of side tail fibres thus had the same qualitative effect as that predicted from high/low cell density |
| T74 | Basic Result supported, optimality result largely supported at high cell density, failed at low cell density. A T7 pre-adapted to growth at high cell density was further evolved at high density. The initial lysis time was 1.9 min too slow but evolved to within 1.3 min of the optimum; the final difference was statistically significant but too small to be considered biologically meaningful. The evolution was accompanied by a large deletion of nonessential genes and seven substitutions, one in the holin gene. The low cell density evolution was initiated with the phage evolved at high density, otherwise using the same environmental conditions. The low-density evolution exhibited a slight increase in lysis time (and larger burst size) but remained over 6 min too early. Eclipse time (E) also increased in violation of the model. Seven substitutions evolved, none in the holin, but one was just upstream of holin and could have been regulatory. Any role of other mutations in lysis time is unknown |