Figure 2.

Isolation of explorers and builders.A. A scheme describing explorers’ isolation. P. vortex culture was pre-exposed to 10, 20 and 40 μg ml⁻¹ kanamycin (represented by light pink, pink and red colours, respectively) for 18 h 37°C, and spread over LB plates without kanamycin (to measure spreading abilities). Cells were picked from microcolonies and inoculated in liquid LB without kanamycin (to evaluate growth rate and yield).B. Explorers have an increased colony diameter in comparison to the mixed culture upon growth on 1.5% (w/v agar) LB plates without antibiotics. Colony expansion diameter has increased with correspondence to kanamycin concentration. C –mixed culture, 10, 20 and 40 are μg ml⁻¹ kanamycin respectively. Pictures were taken 24 h post-inoculation.C. Reduction in the growth rate of explorers isolated from different concentrations of kanamycin. All pre-exposed cultures show a reduction in the growth rate at the early (1–5 h) (P < 0.001) and mid (10–15 h) (P < 0.05) log phases, and growth yield after 20 h (P < 0.05) in liquid which is correlated to increase in kanamycin concentrations. The growth curves were made in kanamycin-free liquid LB medium. 10, 20 and 40 μg ml⁻¹ kanamycin represented by light pink, pink and red colours respectively; cream colour, mixed culture.D. A scheme describing builders’ isolation. LB liquid culture was diluted at the early log phase (4 h) ×4 times to reduce the slow-growing explorers morphotype, then spread on LB agar. Blue colour, builders; white colour, non-treated culture.E. Builders picked from microcolonies were immediately diluted in liquid LB then inoculated on LB agar. I – The mixed culture shows normal expansion on solid medium. II – isolated builders show no expansion on solid medium. Pictures were taken 48 h post-inoculation.F. Growth curve was measured by inoculation of bacteria picked from microcolonies into a fresh LB medium for 20 h. Builders have shown increase in growth rate (compared with mixed cultures) at the early (1–4 h) (P < 1 × 10⁻⁴) and mid (9–13 h) (P < 0.01) log phases, and growth yield after 20 h (P < 1 × 10⁻⁴) in liquid.