scholarly journals Defence versus growth in a hostile world: lessons from phage and bacteria

2020 ◽  
Vol 7 (9) ◽  
pp. 201118
Author(s):  
Rasmus Skytte Eriksen ◽  
Sandeep Krishna
Keyword(s):  
Growth Rate ◽  
Competitive Exclusion ◽  
Burst Size ◽  
Exclusion Principle ◽  
Bacterial Strains ◽  
Closely Related Species ◽  
Competitive Exclusion Principle ◽  
Trade Off ◽  
Bacterial Growth Rates ◽  
Restriction Modification

Bacterial communities are often highly diverse with several closely related species (or strains) coexisting together. These bacteria compete for resources and the competitive exclusion principle predicts that all but the fastest-growing bacteria will go extinct. When exposed to phage, it is predicted that bacterial strains with restriction–modification (RM) systems can circumvent the competitive exclusion principle and reach diversity of the order of the phage burst size. We show that with a trade-off between bacterial growth rates and the strength of their RM systems, the diversity of such an ecosystem can further increase several fold beyond the burst size limit. Moreover, we find that the ratio of the growth rate of a bacterial strain to the imperfection of its RM system is an excellent predictor of (i) whether the strain will go extinct or not, and (ii) the biomass of the strain if it survives. In contrast, the growth rate alone is not a determinant of either of these properties. Our work provides a quantitative example of a model ecosystem where the fitness of a species is determined not by growth rate, but by a trade-off between growth and defence against predators.

scholarly journals Defense versus growth in a hostile world – Lessons from phage and bacteria

2020 ◽  
Author(s):  
Rasmus Skytte Eriksen ◽  
Sandeep Krishna
Keyword(s):  
Growth Rate ◽  
Competitive Exclusion ◽  
Burst Size ◽  
Exclusion Principle ◽  
Bacterial Strains ◽  
Closely Related Species ◽  
Competitive Exclusion Principle ◽  
Trade Off ◽  
Bacterial Growth Rates ◽  
Restriction Modification

AbstractBacterial communities are often highly diverse with several closely related species (or strains) coexisting together. These bacteria compete for resources and the competitive exclusion principle predicts that all but the fastest-growing bacteria will go extinct. When exposed to phage, it is predicted that bacterial strains with restriction-modification (RM) systems can circumvent the competitive exclusion principle and reach diversity on the order of the phage burst size. We show that with a trade-off between bacterial growth rates and the strength of their RM systems, the diversity of such an ecosystem can further increase several fold beyond the burst size limit. Moreover, we find that the ratio of the growth rate of a bacterial strain to the imperfection of its RM system is an excellent predictor of (i) whether the strain will go extinct or not, and (ii) the biomass of the strain if it survives. In contrast, the growth rate alone is not a determinant of either of these properties. Our work provides a quantitative example of a model ecosystem where the fitness of a species is determined not by growth rate, but by a trade-off between growth and defence against predators.

scholarly journals Cancer Community Ecology

2020 ◽  
Vol 27 (1) ◽  
pp. 107327482095177
Author(s):  
Burt P. Kotler ◽  
Joel S. Brown
Keyword(s):  
Community Ecology ◽  
Cancer Cells ◽  
Cancer Biology ◽  
Competitive Exclusion ◽  
Variance Partitioning ◽  
Exclusion Principle ◽  
Ecological Communities ◽  
Closely Related Species ◽  
Local Conditions ◽  
Competitive Exclusion Principle

Here we advocate Cancer Community Ecology as a valuable focus of study in Cancer Biology. We hypothesize that the heterogeneity and characteristics of cancer cells within tumors should vary systematically in space and time and that cancer cells form local ecological communities within tumors. These communities possess limited numbers of species determined by local conditions, with each species in a community possessing predictable traits that enable them to cope with their particular environment and coexist with each other. We start with a discussion of concepts and assumptions that ecologists use to study closely related species. We then discuss the competitive exclusion principle as a means for knowing when two species should not coexist, and as an opening towards understanding how they can. We present the five major categories of mechanisms of coexistence that operate in nature and suggest that the same mechanisms apply towards understanding the diversification and coexistence of cancer cell species. They are: Food-Safety Tradeoffs, Diet Choice, Habitat Selection, Variance Partitioning, and Competition-Colonization Tradeoffs. For each mechanism, we discuss how it works in nature, how it might work in cancers, and its implications for therapy.

Ecological Theory and the Superfluous Niche

2019 ◽  
Vol 47 (1) ◽  
pp. 105-123
Author(s):  
James Justus ◽  
Keyword(s):  
Competitive Exclusion ◽  
Ecological Theory ◽  
Character Displacement ◽  
Exclusion Principle ◽  
Limiting Similarity ◽  
Competitive Exclusion Principle ◽  
Ecological Equivalence

Perhaps no concept has been thought more important to ecological theorizing than the niche. Without it, technically sophisticated and well-regarded accounts of character displacement, ecological equivalence, limiting similarity, and others would seemingly never have been developed. The niche is also widely considered the centerpiece of the best candidate for a distinctively ecological law, the competitive exclusion principle. But the incongruous array and imprecise character of proposed definitions of the concept square poorly with its apparent scientific centrality. I argue this definitional diversity and imprecision reflects a problematic conceptual indeterminacy that challenges its putative indispensability in ecology.

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