Chirality provides a direct fitness advantage and facilitates intermixing in cellular aggregates
Fig 4
Effects of chirality persist despite growth rate differences.
We competed strains with different growth rates and chirality starting from well-mixed initial conditions. The abundances of the strains were equal at the beginning of the simulations, but changed over time leading either to stable coexistence or to the exclusion of one of the strains. The outcome of the competition depends on the relative growth rates of the strains quantified by Δg. The competition between a left-handed strain and a faster growing non-chiral strain is shown in (A). The non-chiral strain is outcompeted even if it has a growth advantage as high as to 2%. The chiral strain becomes extinct only when its growth penalty exceeds 7%. For intermediate Δg, the two strains stably coexist. Similar dynamics occur during the competition between the strains with equal, but opposite chirality shown in panel (B). The stable coexistence between the strains is destroyed only by growth rate differences higher than about 7%. Here, m0 = ms = mb = md = 0 for both strains and N = 200. In (A), ,
,
,
on a lattice of 1000x3600 sites. We fixed g = 0.01 for the left handed-strain and varied the growth rate of the non-chiral strain according to g(1 + Δg/100%). In (B),
,
,
,
on a lattice of 500x3000 sites. We set g = 0.1 for the left-handed strain, and varied the growth rate of the right-handed strain according to g(1 + Δg/100%). The distances on the x-axis were measured in 100 units where Δx = Δy = 1 unit. We verified stable coexistence by starting the simulation above and below the observed steady-state relative abundances and checking that they return to the same steady-state values.