What is fitness in expanding populations?
Bacteria, as well as other organisms, must reproduce and spread in order to survive. While a great deal of research has focused on the evolution of reproduction. But much less has been devoted to the evolution of spread.
“Spreading of species is of immense practical interest because it underlies the spread of diseases, invasive species, and pests as well as the invasion of host tissue by pathogens and cancer cells,” note researchers Kirill Korolev, Boston University, and Minsu Kim, Emory University.
“Previous studies have shown that organisms do not grow and disperse simultaneously; instead, they alternate between two life stages that exclusively focus on either growth or dispersal,” the researchers observe. “Why dispersal and growth are temporally separated and how this separation is regulated has not been systematically explored.”
Korolev and Kim recently began a collaboration to better understand how reproduction (growth) and spreading (dispersal) are integrated to promote an organism’s survival. They are focusing on the bacterium Proteus mirabilis, which, under certain circumstances, strongly regulates its dispersal and growth properties, leading to a pattern of periodic rings. “Our central hypothesis is that this division in labor, i.e., growth and migration, is crucial for maximizing fitness,” the researchers theorize.
By combining analytical theory with quantitative experiments, they hope to extend the concept of fitness to realistic environments and understand the general principles behind the division of labor in spreading populations. Specifically they aim to:
Clearly describe the growth and dispersal stages in P. mirabilis; develop a theory for the evolution of the bacterium’s growth-dispersal strategy; and then test the theory using experimental evolution that selects for different properties, such as fast growth vs. fast colonization.
“The general theory that we develop will have implications for processes outside the Petri dish,” the researchers predict. “For example, one day we may be able to quantitatively reason about the best combination of drugs that inhibit growth or migration of cancer cells to prevent metastasis.”
The scientists formed their collaboration at the most recent Scialog: Molecules Come to Life meeting organized by the private foundation Research Corporation for Science Advancement (RCSA).
The $112,500 in funding for Korolev and Kim’s collaboration is provided by the Gordon and Betty Moore Foundation, which is cosponsoring Scialog: Molecules Come to Life.