Abiotic adaptation of bacterial populations
Growth performance of bacterial populations from the end of the
evolution experiment was measured in the absence of phages, without
immigration (Figure 3). The bacteria evolution lines (B) showed the most
pronounced increase in growth performance compared with the ancestral
strain (one-tailed t -test: t 5 = 17.831,P < 0.001), followed by bacterial lines with
immigration (B+IB) (one-tailed t -test: t 5= 8.120, P < 0.001). Growth performance of bacteria
from bacteria/phage lines (BP) was not different from the ancestral
strain (one-tailed t -test: t 5 = 0.681,P = 0.737). Bacteria from bacteria/phage lines with phage
immigration (BP+IP) showed the poorest growth performance, significantly
lower than that of the ancestral strain (one-tailed Wilcoxon test:V = 2, P = 0.047); and those from bacteria/phage lines
with bacteria/phage immigration (BP+IBP) did not significantly differ
from the ancestral strain (one-tailed t -test:t 4 = -0.605, P = 0.290).
Comparisons between evolution lines were also carried out (Figure 3).
Immigration of bacteria from 28°C habitats reduced the extent of abiotic
adaptation (B versus B+IB treatment, one-tailed Welch two-samplet -test: t 9.682 = 5.169, P< 0.001). The presence of phages limited bacterial abiotic
adaptation (B versus BP, one-tailed Welch two-sample t -test:t 5.500 = 3.230, P = 0.010); and
immigration of phages only further reduced bacterial abiotic adaptation
(BP versus BP+IP, one-tailed Welch two-sample t -test:t 9.599 = 1.924, P = 0.042), though joint
bacteria and phage immigration did not significantly alter bacterial
abiotic adaptation (BP versus BP+IBP, one-tailed Welch two-samplet -test: t 7.732 = 0.891, P = 0.200).