How does resource presentation change adaptive trajectories?
by Neetika Ahlawat | Pavithra Venkatraman | R. G. Brajesh | Supreet Saini | Indian Institute of Technology Bombay | Indian Institute of Technology Bombay | Indian Institute of Technology Bombay | Indian Institute of Technology Bombay
Abstract ID: 25
Event: The 3rd AsiaEvo Conference
Topic: Open category
Presenter Name: Neetika Ahlawat

Adaptive trajectories of populations are dictated by the make-up of the environment in which they evolve. For instance, the adaptive trajectory in a glucose-limiting environment is distinct from when adaptation takes place in presence of glycerol. However, how do adaptive trajectories of a population change when the same resource is presented to the population in different packaging? To answer this question, we evolve E. coli in three similar but non-identical environments where glucose and galactose were presented in the form of lactose, or melibiose, or as a mixture of glucose and galactose. Six lines of E. coli were evolved in each of the three environments for 300 generations. Phenotypic characterization of the evolved lines shows that melibiose evolved lines behave qualitatively differently than the lactose- and glucose-galactose evolved lines. Specifically, melibiose-evolved lines have a higher fitness in not only melibiose, but also in non-native environments (lactose and glucose-galactose). Thus, from the context of phenotypic adaptive response, resource packaging and presentation dictates adaptive trajectories. Genome sequencing of evolved lines shows that adaptation in glucose-galactose, in each of the six lines, happens via mutation in either RpoB or RpoC, thus exhibiting convergent adaptation. On the other hand, all melibiose-evolved lines exhibit mutations in distinct genes, leading to adaptation.  This genetic diversity provides insights into challenges associated with predictability of evolutionary processes. More importantly, we report a novel phenomenon, that the nature of resource packaging might alter the evolutionary trajectories of evolving populations.