scholarly journals Cross-feeding shapes both competition and cooperation in microbial ecosystems

2021 ◽  
Author(s):  
Pankaj Mehta ◽  
Robert Marsland
Keyword(s):  
Ecological Model ◽  
Mean Field ◽  
Cavity Method ◽  
Complex Interplay ◽  
Competition And Cooperation ◽  
Microbial Ecosystems ◽  
Species Packing ◽  
Ecosystem Level ◽  
Competition For Resources ◽  
Metabolic Exchange

Recent work suggests that cross-feeding -- the secretion and consumption of metabolic biproducts by microbes -- is essential for understanding microbial ecology. Yet how cross-feeding and competition combine to give rise to ecosystem-level properties remains poorly understood. To address this question, we analytically analyze the Microbial Consumer Resource Model (MiCRM), a prominent ecological model commonly used to study microbial communities. Our mean-field solution exploits the fact that unlike replicas, the cavity method does not require the existence of a Lyapunov function. We use our solution to derive new species-packing bounds for diverse ecosystems in the presence of cross-feeding, as well as simple expressions for species richness and the abundance of secreted resources as a function of cross-feeding (metabolic leakage) and competition. Our results show how a complex interplay between competition for resources and cooperation resulting from metabolic exchange combine to shape the properties of microbial ecosystems.

scholarly journals Information Technology and Organizational Effectiveness: Re-evaluation of the Radical Transformations 1980-2010

Organizacija ◽  
2010 ◽  
Vol 43 (6) ◽  
pp. 233-237 ◽  
Author(s):  
Markku Sääksjärvi
Keyword(s):  
Information Technology ◽  
Organizational Structure ◽  
Organizational Effectiveness ◽  
Business Success ◽  
Complex Interplay ◽  
It Productivity Paradox ◽  
Evaluation Models ◽  
Ecosystem Level ◽  
The Individual ◽  
Virtual Ecosystem

Information Technology and Organizational Effectiveness: Re-evaluation of the Radical Transformations 1980-2010The idea of this paper is to review and summarize the complex interplay between information technology (IT) and organization in stages that impacted radically both the organizational structure and the evolution of effectiveness and economic performance. We could identify five major stages where the underlying technology, the typical organizational structure, and the criteria of performance or business success changed, increasing the complexity of evaluation models proposed. It seemed that the effectiveness impacts of IT escalated from the individual to the team level, from the organizational to the virtual ecosystem level, and from the corporate to the national or global level. Therefore, the IT productivity paradox could not be refuted until 2003.

scholarly journals Power, competition, and the nature of history

Paleobiology ◽  
2019 ◽  
Vol 45 (4) ◽  
pp. 517-530 ◽  
Author(s):  
Geerat J. Vermeij
Keyword(s):  
High Frequency ◽  
Evolutionary History ◽  
Metabolic Evolution ◽  
Competition And Cooperation ◽  
The Past ◽  
Directional Change ◽  
History Of ◽  
Repeated Evolution ◽  
Ecosystem Level

AbstractHistorians have debated whether pathways and events from the past to the present are influenced largely by contingency, the dependence of outcomes on particular prior conditions, or whether there is long-term emergent directional change. Previous arguments for predictability in evolutionary history relied on the high frequency of convergence, but the repeated evolution of widely favored adaptations need not imply long-term directionality. Using evidence from the fossil record and arguments concerning the metabolic evolution of organisms, I show here that power (total energy taken up and expended per unit time) has increased stepwise over time at ecosystem-level and global scales thanks to the ratchet-like, cumulative effects of competition and cooperation and to the disproportionate influence of powerful top competitors and opportunistic species on emergent ecosystem properties and processes. The history of life therefore exhibits emergent directionality at large ecosystem-wide scales toward greater power.

scholarly journals Percolation–like scaling exponents for minimal paths and trees in the stochastic mean field model

2005 ◽  
Vol 461 (2055) ◽  
pp. 825-838 ◽  
Author(s):  
David J. Aldous
Keyword(s):  
Minimum Spanning Tree ◽  
Optimization Problems ◽  
Travelling Salesman Problem ◽  
Mean Field ◽  
Independent Random Variables ◽  
Cavity Method ◽  
Scaling Exponent ◽  
Scaling Exponents ◽  
Mean Field Model ◽  
The Mean

In the mean field (or random link) model there are n points and inter-point distances are independent random variables. For 0 < ℓ < ∞ and in the n → ∞ limit, let δ ( ℓ ) = 1/ n times the maximum number of steps in a path whose average step-length is ≤ ℓ . The function δ ( ℓ ) is analogous to the percolation function in percolation theory: there is a critical value ℓ * = e −1 at which δ (·) becomes non-zero, and (presumably) a scaling exponent β in the sense δ ( ℓ ) ≈ ( ℓ − ℓ * ) β . Recently developed probabilistic methodology (in some sense a rephrasing of the cavity method developed in the 1980s by Mézard and Parisi) provides a simple, albeit non-rigorous, way of writing down such functions in terms of solutions of fixed-point equations for probability distributions. Solving numerically gives convincing evidence that β = 3. A parallel study with trees and connected edge-sets in place of paths gives scaling exponent 2, while the analogue for classical percolation has scaling exponent 1. The new exponents coincide with those recently found in a different context (comparing optimal and near-optimal solutions of the mean-field travelling salesman problem (TSP) and the minimum spanning tree (MST) problem), and reinforce the suggestion that scaling exponents determine universality classes for optimization problems on random points.

scholarly journals Molecular signatures of resource competition: clonal interference drives the emergence of ecotypes

2020 ◽  
Author(s):  
Massimo Amicone ◽  
Isabel Gordo
Keyword(s):  
Evolutionary Dynamics ◽  
Resource Competition ◽  
Ecological Model ◽  
De Novo ◽  
Clonal Interference ◽  
Microbial Ecosystems ◽  
Difficult Challenge ◽  
Asexual Populations ◽  
Analytical Approaches ◽  
Different Levels

AbstractMicrobial ecosystems harbor an astonishing diversity that can persist for long times. To understand how such diversity is generated and maintained, ecological and evolutionary processes need to be integrated at similar timescales, but this remains a difficult challenge. Here, we extend an ecological model of resource competition to allow for evolution via de novo mutation, focusing on large and rapidly adapting asexual populations. Through numerical and analytical approaches, we characterize adaptation and diversity at different levels and show how clonal interference – the interaction between simultaneously emerging lineages – shapes the eco-evolutionary dynamics. We find that large mutational inputs can foster diversification under sympatry, increasing the probability that phenotypically and genetically distinct clusters arise and stably coexist, constituting an initial form of community. Our findings have implications beyond microbial populations, providing novel insights about the interplay between ecology and evolution in clonal populations.

scholarly journals Costless metabolic secretions as drivers of interspecies interactions in microbial ecosystems

2018 ◽  
Author(s):  
Alan R. Pacheco ◽  
Mauricio Moel ◽  
Daniel Segrè
Keyword(s):  
Microbial Interactions ◽  
Fitness Cost ◽  
Microbial Consortia ◽  
Interspecies Interactions ◽  
Large Space ◽  
Microbial Ecosystems ◽  
Scale Models ◽  
Genome Scale ◽  
Synthetic Microbial Consortia ◽  
Metabolic Exchange

ABSTRACTMetabolic exchange can mediate beneficial interactions among microbes, helping explain diversity in microbial communities. These interactions are often assumed to involve a fitness cost, prompting questions on how cooperative phenotypes can be stable and withstand the emergence of cheaters. Here we use genome-scale models of metabolism to investigate whether a radically different scenario, the pervasive release of “costless” metabolites (i.e. those that cause no fitness cost to the producing organism), can serve as a prominent mechanism for inter-microbial interactions. By carrying out over 1 million pairwise growth simulations for 14 microbial species in a combinatorial assortment of environmental conditions, we find that there is indeed a large space of metabolites that can be secreted at no cost, which can generate ample cross-feeding opportunities. In addition to providing an atlas of putative costless interdependencies, our modeling also demonstrates that oxygen availability significantly enhances mutualistic interactions by providing more opportunities for metabolic exchange through costless metabolites, resulting in an over-representation of specific ecological network motifs. In addition to helping explain natural diversity, we show how the exchange of costless metabolites can facilitate the engineering of stable synthetic microbial consortia.

scholarly journals Metabolically cohesive microbial consortia and ecosystem functioning

2020 ◽  
Vol 375 (1798) ◽  
pp. 20190245 ◽  
Author(s):  
Alberto Pascual-García ◽  
Sebastian Bonhoeffer ◽  
Thomas Bell
Keyword(s):  
Ecosystem Functioning ◽  
Microbial Consortia ◽  
Recent Theory ◽  
Microbial Community Ecology ◽  
In The Wild ◽  
Ecosystem Level ◽  
Metabolic Interactions ◽  
Evolutionary Consequences ◽  
Competition For Resources ◽  
Theory And Experiments

Recent theory and experiments have reported a reproducible tendency for the coexistence of microbial species under controlled environmental conditions. This observation has been explained in the context of competition for resources and metabolic complementarity given that, in microbial communities (MCs), many excreted by-products of metabolism may also be resources. MCs therefore play a key role in promoting their own stability and in shaping the niches of the constituent taxa. We suggest that an intermediate level of organization between the species and the community level may be pervasive, where tightly knit metabolic interactions create discrete consortia that are stably maintained. We call these units Metabolically Cohesive Consortia (MeCoCos) and we discuss the environmental context in which we expect their formation, and the ecological and evolutionary consequences of their existence. We argue that the ability to identify MeCoCos would open new avenues to link the species-, community- and ecosystem-level properties, with consequences for our understanding of microbial ecology and evolution, and an improved ability to predict ecosystem functioning in the wild. This article is part of the theme issue ‘Conceptual challenges in microbial community ecology’.

Competing through Co-operation in Nonhuman Primates: Developmental Aspects of Matrilineal Dominance

1996 ◽  
Vol 19 (1) ◽  
pp. 7-23 ◽  
Author(s):  
Bernard Chapais
Keyword(s):  
Social Life ◽  
Nonhuman Primates ◽  
Japanese Macaques ◽  
Species Competition ◽  
Complex Interplay ◽  
Captive Group ◽  
The Social ◽  
Lower Ranking ◽  
Rank Relations ◽  
Competition For Resources

This paper's major aim is to illustrate how competition and co-operation are causally interrelated in the social life of nonhuman primates. In many species, competition for resources and mates commonly leads to xenophobic alliances and to the formation of intra-group dominance orders in which coalitions and alliances play a major role. In this sense, competition fosters co-operation. After briefly reviewing the nature of alliances in primates, this paper focuses on matrilineal dominance systems, which characterise many species of the Cercopithecidae family (macaques, baboons, etc.). In these societies, females socially inherit their mother's rank above lower-ranking matrilines with the result that kin rank next to each other. This paper summarises 10 years of experimental research on the composition and dynamics of alliances in a captive group of Japanese macaques (Macacafuscata). The main experimental paradigm consisted in manipulating the composition of the group, thereby dismantling existing alliances and inducing the formation of new alliances and new rank orders. Results reveal the existence of a complex interplay of kin and nonkin alliances responsible for the acquisition of rank and, later, for the maintenance of rank relations within and between kin groups. Opportunistic, selfishly motivated interventions in conflicts, performed by juveniles sharing the same targets (common targeting principle), appear to account for the initial formation of alliances in these dominance systems and, possibly, in various other situations as well. Such relatively simple processes may have paved the way for ontogenetically and phylogenetically more sophisticated forms of co-operation, such as reciprocity involving delayed benefits to the donors.

scholarly journals Microbial metabolically cohesive consortia and ecosystem functioning

2019 ◽  
Author(s):  
Alberto Pascual-García ◽  
Sebastian Bonhoeffer ◽  
Thomas Bell
Keyword(s):  
Microbial Communities ◽  
Ecosystem Functioning ◽  
Recent Theory ◽  
In The Wild ◽  
Ecosystem Level ◽  
Metabolic Interactions ◽  
Evolutionary Consequences ◽  
By Products ◽  
Competition For Resources ◽  
Theory And Experiments

AbstractRecent theory and experiments have reported a reproducible tendency for the coexistence of microbial species under controlled environmental conditions. This observation has been explained in the context of competition for resources and metabolic complementarity given that, in microbial communities, many excreted by-products of metabolism may also be resources. Microbial communities therefore play a key role in promoting their own stability and in shaping the niches of the constituent taxa. We suggest that an intermediate level of organisation between the species and the community level may be pervasive, where tightly-knit metabolic interactions create discrete consortia that are stably maintained. We call these units Metabolically Cohesive Consortia (MeCoCos) and we discuss the environmental context in which we expect their formation, and the ecological and evolutionary consequences of their existence. We argue that the ability to identify MeCoCos would open new avenues to link the species-, community-, and ecosystem-level properties, with consequences for our understanding of microbial ecology and evolution, and an improved ability to predict ecosystem functioning in the wild.

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