title: The effect of extrinsic mortality on genome size evolution in prokaryotes.
abstract: Mortality has a significant role in prokaryotic ecology and evolution, yet the impact of variations in extrinsic mortality on prokaryotic genome evolution has received little attention. We used both mathematical and agent-based models to reveal how variations in extrinsic mortality affect prokaryotic genome evolution. Our results suggest that the genome size of bacteria increases with increased mortality. A high extrinsic mortality increases the pool of free resources and shortens life expectancy, which selects for faster reproduction, a phenotype we called 'scramblers'. This phenotype is realised by the expansion of gene families involved in nutrient acquisition and metabolism. In contrast, a low mortality rate increases an individual's life expectancy, which results in natural selection favouring tolerance to starvation when conditions are unfavourable. This leads to the evolution of small, streamlined genomes ('stayers'). Our models predict that large genomes, gene family expansion and horizontal gene transfer should be observed in prokaryotes occupying ecosystems exposed to high abiotic stress, as well as those under strong predator- and/or pathogen-mediated selection. A comparison of genome size of cyanobacteria in relatively stable marine versus more turbulent freshwater environments corroborates our predictions, although other factors between these environments could also be responsible.
authors.affiliation: School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK.|Institute of Environmental Biology, Faculty of Biology, Adam Mickiewicz University, Poznań, Poland.
authors.forename: Piotr
authors.identifier: 0000-0002-1220-1075
authors.initials: P
authors.lastname: Bentkowski
authors.affiliation: School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK.
authors.forename: Cock
authors.initials: C
authors.lastname: van Oosterhout
authors.affiliation: Department of Mathematical Sciences, University of Bath, Bath, UK.|Department of Integrative Biology, University of California, Berkeley, CA, USA.
authors.forename: Ben
authors.initials: B
authors.lastname: Ashby
authors.affiliation: School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK.
authors.forename: Thomas
authors.identifier: 0000-0001-9604-0362
authors.initials: T
authors.lastname: Mock
mesh_terms: D001419:Bacteria / Q000235:genetics* / Q000378:metabolism; D005075:Biological Evolution; D019143:Evolution, Molecular; D015964:Gene Expression Regulation, Bacterial; D022761:Gene Transfer, Horizontal; D059646:Genome Size; D016680:Genome, Bacterial / Q000235:genetics*; D012641:Selection, Genetic