5 research outputs found
Cooperation in Microbial Populations: Theory and Experimental Model Systems
Cooperative behavior, the costly provision of benefits to others, is common
across all domains of life. This review article discusses cooperative behavior
in the microbial world, mediated by the exchange of extracellular products
called public goods. We focus on model species for which the production of a
public good and the related growth disadvantage for the producing cells are
well described. To unveil the biological and ecological factors promoting the
emergence and stability of cooperative traits we take an interdisciplinary
perspective and review insights gained from both mathematical models and
well-controlled experimental model systems. Ecologically, we include crucial
aspects of the microbial life cycle into our analysis and particularly consider
population structures where an ensemble of local communities (sub populations)
continuously emerge, grow, and disappear again. Biologically, we explicitly
consider the synthesis and regulation of public good production. The discussion
of the theoretical approaches includes general evolutionary concepts,
population dynamics, and evolutionary game theory. As a specific but generic
biological example we consider populations of Pseudomonas putida and its
regulation and utilization of pyoverdines, iron scavenging molecules. The
review closes with an overview on cooperation in spatially extended systems and
also provides a critical assessment of the insights gained from the
experimental and theoretical studies discussed. Current challenges and
important new research opportunities are discussed, including the biochemical
regulation of public goods, more realistic ecological scenarios resembling
native environments, cell to cell signalling, and multi-species communities.Comment: Review article, 88 pages, 14 figure
Evolutionary game theory in growing populations
Existing theoretical models of evolution focus on the relative fitness
advantages of different mutants in a population while the dynamic behavior of
the population size is mostly left unconsidered. We here present a generic
stochastic model which combines the growth dynamics of the population and its
internal evolution. Our model thereby accounts for the fact that both
evolutionary and growth dynamics are based on individual reproduction events
and hence are highly coupled and stochastic in nature. We exemplify our
approach by studying the dilemma of cooperation in growing populations and show
that genuinely stochastic events can ease the dilemma by leading to a transient
but robust increase in cooperationComment: 4 pages, 2 figures and 2 pages supplementary informatio
Range expansion with mutation and selection: dynamical phase transition in a two-species Eden model
The colonization of unoccupied territory by invading species, known as range expansion, is a spatially heterogeneous non-equilibrium growth process. We introduce a two-species Eden growth model to analyze the interplay between uni-directional (irreversible) mutations and selection at the expanding front. While the evolutionary dynamics leads to coalescence of both wild-type and mutant clusters, the non-homogeneous advance of the colony results in a rough front. We show that roughening and domain dynamics are strongly coupled, resulting in qualitatively altered bulk and front properties. For beneficial mutations the front is quickly taken over by mutants and growth proceeds Eden-like. In contrast, if mutants grow slower than wild-types, there is an antagonism between selection pressure against mutants and growth by the merging of mutant domains with an ensuing absorbing state phase transition to an all-mutant front. We find that surface roughening has a marked effect on the critical properties of the absorbing state phase transition. While reference models, which keep the expanding front flat, exhibit directed percolation critical behavior, the exponents of the two-species Eden model strongly deviate from it. In turn, the mutation-selection process induces an increased surface roughness with exponents distinct from that of the classical Eden model