scholarly journals Enforced specialization fosters mutual cheating and not division of labour in the bacterium Pseudomonas aeruginosa

2021 ◽  
Author(s):  
Subham Mridha ◽  
Rolf Kuemmerli
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Natural Selection ◽  
Public Goods ◽  
Public Good ◽  
Experimental System ◽  
Division Of Labour ◽  
Iron Limitation ◽  
Mixing Ratios ◽  
Negative Frequency Dependent Selection ◽  
Complementary Goods

A common way for bacteria to cooperate is via the secretion of beneficial public goods (proteases, siderophores, biosurfactants) that can be shared among individuals in a group. Bacteria often simultaneously deploy multiple public goods with complementary functions. This raises the question whether natural selection could favour division of labour where subpopulations or species specialise in the production of a single public good, whilst sharing the complementary goods at the group level. Here we use an experimental system, where we genetically enforce specialization in the bacterium Pseudomonas aeruginosa with regard to the production of its two siderophores, pyochelin and pyoverdine, and explore the conditions under which specialization can lead to division of labour. When growing pyochelin and pyoverdine specialists at different mixing ratios in various iron limited environments, we found that specialists could only successfully complement each other in environments with moderate iron limitation and grow as good as the generalist wildtype but not better. Under more stringent iron limitation, the dynamics in specialist communities was characterized by mutual cheating and with higher proportions of pyochelin producers greatly compromising group productivity. Nonetheless, specialist communities remained stable through negative frequency-dependent selection. Our work shows that specialization in a bacterial community can be spurred by mutual cheating and does not necessarily result in beneficial division of labour. We propose that natural selection might favour fine-tuned regulatory mechanisms in generalists over division of labour because the former enables generalists to remain flexible and adequately adjust public good investments in fluctuating environments.

scholarly journals Quorum Sensing Protects Pseudomonas aeruginosa against Cheating by Other Species in a Laboratory Coculture Model

2015 ◽  
Vol 197 (19) ◽  
pp. 3154-3159 ◽  
Author(s):  
Nicole E. Smalley ◽  
Dingding An ◽  
Matthew R. Parsek ◽  
Josephine R. Chandler ◽  
Ajai A. Dandekar
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Public Goods ◽  
Public Good ◽  
Hydrogen Cyanide ◽  
Cooperative Behavior ◽  
Bacterial Species ◽  
Cell Communication ◽  
Content Type ◽  
Burkholderia Multivorans

ABSTRACTMany species of bacteria use a cell-cell communication system called quorum sensing (QS) to coordinate group activities. QS systems frequently regulate the production of exoproducts. Some of these products, such as proteases, are “public goods” that are shared among the population and vulnerable to cheating by nonproducing members of the population. Because the QS system of the opportunistic pathogenPseudomonas aeruginosaregulates several public goods, it can serve as a model for studying cooperation. Bacteria also commonly regulate antimicrobial production through QS. In this study, we focused on the hypothesis that QS-regulated antimicrobials may be important forP. aeruginosato protect against cheating by another bacterial species,Burkholderia multivorans.We assessed laboratory cocultures ofP. aeruginosaandB. multivoransand investigated the importance of threeP. aeruginosaQS-regulated antimicrobials, hydrogen cyanide, rhamnolipids, and phenazines, for competition. We found thatP. aeruginosadominates cocultures withB. multivoransand that the three antimicrobials together promoteP. aeruginosacompetitiveness, with hydrogen cyanide contributing the greatest effect. We show that these QS-regulated antimicrobials are also critical forP. aeruginosato preventB. multivoransfrom cheating under nutrient conditions where both species require aP. aeruginosaquorum-regulated protease for growth. Together our results highlight the importance of antimicrobials in protecting cooperating populations from exploitation by other species that can act as cheaters.IMPORTANCECooperative behaviors are threatened by social cheating, wherein individuals do not produce but nonetheless benefit from shared public goods. Bacteria have been shown to use several genetic mechanisms to restrain the emergence of cheaters from within the population, but public goods might also be used by other bacterial species in the vicinity. We demonstrate that a public good produced byPseudomonas aeruginosacan be used by another species,Burkholderia multivorans, to obtain carbon and energy. We also show thatP. aeruginosaantimicrobials that are coregulated with the public good prevent invasion by the cheating species. Our results demonstrate that cross-species cheating can occur and that coregulation of public goods with antimicrobials may stabilize cooperative behavior in mixed microbial communities.

scholarly journals Siderophores drive invasion dynamics in bacterial communities through their dual role as public good versus public bad

2021 ◽  
Author(s):  
Alexandre R. T. Figueiredo ◽  
Oezhan Oezkaya ◽  
Rolf Kuemmerli ◽  
Jos Kramer
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Ecosystem Services ◽  
Public Goods ◽  
Public Good ◽  
Bacterial Communities ◽  
Invasion Success ◽  
Invasion Dynamics ◽  
Public Bads ◽  
Invasion Assays

Microbial invasions can compromise ecosystem services and spur dysbiosis and disease in hosts. Nevertheless, the mechanisms determining invasion outcomes often remain unclear. Here, we examine the role of iron-scavenging siderophores in driving invasions of Pseudomonas aeruginosa into resident communities of environmental pseudomonads. Siderophores can be 'public goods' by delivering iron to individuals possessing matching receptors; but they can also be 'public bads' by withholding iron from competitors lacking these receptors. Accordingly, siderophores should either promote or impede invasion, depending on their dual effects on invader and resident growth. Using supernatant feeding and invasion assays, we show that invasion success indeed decreased when the invader was inhibited (public bad) rather than stimulated (public good) by the residents' siderophores. Conversely, invasion success often increased when the invader could use its siderophore to inhibit the residents. Our findings identify siderophores as a major driver of invasion dynamics in bacterial communities.

scholarly journals Adaptation to public goods cheats in Pseudomonas aeruginosa

2017 ◽  
Vol 284 (1859) ◽  
pp. 20171089 ◽  
Author(s):  
Siobhán O'Brien ◽  
Adela M. Luján ◽  
Steve Paterson ◽  
Michael A. Cant ◽  
Angus Buckling
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Public Goods ◽  
Public Good ◽  
High Frequency ◽  
Iron Acquisition ◽  
Siderophore Production ◽  
Fitness Costs ◽  
Negative Effects ◽  
Evolutionary Response ◽  
Selection For

Cooperation in nature is ubiquitous, but is susceptible to social cheats who pay little or no cost of cooperation yet reap the benefits. The effect such cheats have on reducing population productivity suggests that there is selection for cooperators to mitigate the adverse effects of cheats. While mechanisms have been elucidated for scenarios involving a direct association between producer and cooperative product, it is less clear how cooperators may suppress cheating in an anonymous public goods scenario, where cheats cannot be directly identified. Here, we investigate the real-time evolutionary response of cooperators to cheats when cooperation is mediated by a diffusible public good: the production of iron-scavenging siderophores by Pseudomonas aeruginosa . We find that siderophore producers evolved in the presence of a high frequency of non-producing cheats were fitter in the presence of cheats, at no obvious cost to population productivity. A novel morphotype independently evolved and reached higher frequencies in cheat-adapted versus control populations, exhibiting reduced siderophore production but increased production of pyocyanin—an extracellular toxin that can also increase the availability of soluble iron. This suggests that cooperators may have mitigated the negative effects of cheats by downregulating siderophore production and upregulating an alternative iron-acquisition public good. More generally, the study emphasizes that cooperating organisms can rapidly adapt to the presence of anonymous cheats without necessarily incurring fitness costs in the environment they evolve in.

On the Essence and Tipology of International Public Goods

2005 ◽  
pp. 131-141
Author(s):  
V. Mortikov
Keyword(s):  
Economic Policy ◽  
Social Construction ◽  
Public Goods ◽  
Public Good ◽  
Global Public Goods ◽  
Club Goods ◽  
Basic Properties ◽  
International Public Goods ◽  
Regional Public Goods ◽  
Joint Products

The basic properties of international public goods are analyzed in the paper. Special attention is paid to the typology of international public goods: pure and impure, excludable and nonexcludable, club goods, regional public goods, joint products. The author argues that social construction of international public good depends on many factors, for example, government economic policy. Aggregation technologies in the supply of global public goods are examined.

scholarly journals Bringing tax avoiders to light: moral framing and shaming in a public goods experiment

2021 ◽  
pp. 1-24
Author(s):  
Stefanos A. Tsikas
Keyword(s):  
Public Goods ◽  
Public Good ◽  
Social Dilemmas ◽  
Tax Avoidance ◽  
Social Contagion ◽  
Public Goods Game ◽  
Free Riders ◽  
Social Sanctions ◽  
Moral Framing ◽  
Public Goods Experiment

Abstract With a linear public goods game played in six different variants, this article studies two channels that might moderate social dilemmas and increase cooperation without using pecuniary incentives: moral framing and shaming. We find that cooperation is increased when noncontributing to a public good is framed as morally debatable and socially harmful tax avoidance, while the mere description of a tax context has no effect. However, without social sanctions in place, cooperation quickly deteriorates due to social contagion. We find ‘shaming’ free-riders by disclosing their misdemeanor to act as a strong social sanction, irrespective of the context in which it is applied. Moralizing tax avoidance significantly reinforces shaming, compared with a simple tax context.

Ethnic trust, minority status, and public goods in post-conflict societies

2021 ◽  
pp. 002234332098421
Author(s):  
Sam Whitt
Keyword(s):  
Public Goods ◽  
Public Good ◽  
Intergroup Contact ◽  
Minority Group ◽  
Civil Liberties ◽  
Minority Status ◽  
The Public ◽  
Attitudes And Behaviors ◽  
Post Conflict ◽  
History Of

This study considers how ethnic trust and minority status can impact the ability of ethnic groups to pursue cooperative public goods, focusing on groups with a history of conflict and lingering hostility. A public good experiment between ethnic Albanians and Serbs in postwar Kosovo reveals that subjects contribute far more to a mutually beneficial public good when they are part of an experimentally induced coethnic majority. However, when in the minority, subjects not only underinvest, but many actively divest entirely, privatizing the public good. Majority/minority status also has wide-ranging implications for how individuals relate to real-world public goods and the institutions of government that provide them. Compared to majority Albanians, survey data indicate how minority Serbs in Kosovo express greater safety and security concerns, feel more politically, socially, and economically excluded, are more dissatisfied with civil liberties and human rights protections, and are less likely to participate politically or pay taxes to support public goods. Conflict-related victimization and distrust of out-groups are strong predictors of these minority group attitudes and behaviors. This suggests a mechanism for how conflict amplifies out-group distrust, increasing parochial bias in public good commitments, especially among minorities who are wary of exploitation at the hands of an out-group majority. To restore trust, this study finds that institutional trust and intergroup contact are important to bridging ethnic divides that inhibit public good cooperation.

A Model of Inequality Aversion and Private Provision of Public Goods

2020 ◽  
Vol 20 (2) ◽  
Author(s):  
Hide-Fumi Yokoo
Keyword(s):  
Public Goods ◽  
Public Good ◽  
Theoretical Foundation ◽  
Inequality Aversion ◽  
Public Good Provision ◽  
Marginal Rate ◽  
Private Provision ◽  
Marginal Rate Of Substitution ◽  
Good Provision ◽  
Corner Solutions

AbstractI develop a model of inequality aversion and public goods that allows the marginal rate of substitution to be variable. As a theoretical foundation, utility function of the standard public goods model is nested in the Fehr-Schmidt model. An individual’s contribution function for a public good is derived by solving the problem of kinky preference and examining both interior and corner solutions. Results show that the derived contribution function is not monotonic with respect to the other individual’s provision. Thus, the model can be used to explain empirical evidence for the effect of social comparison on public-good provision.

scholarly journals Avoiding or restricting defectors in public goods games?

2015 ◽  
Vol 12 (103) ◽  
pp. 20141203 ◽  
Author(s):  
The Anh Han ◽  
Luís Moniz Pereira ◽  
Tom Lenaerts
Keyword(s):  
Experimental Data ◽  
Public Goods ◽  
Public Good ◽  
Common Good ◽  
Full Agreement ◽  
Group Interactions ◽  
The Common Good ◽  
Public Goods Games ◽  
The Common ◽  
Strategic Solution

When creating a public good, strategies or mechanisms are required to handle defectors. We first show mathematically and numerically that prior agreements with posterior compensations provide a strategic solution that leads to substantial levels of cooperation in the context of public goods games, results that are corroborated by available experimental data. Notwithstanding this success, one cannot, as with other approaches, fully exclude the presence of defectors, raising the question of how they can be dealt with to avoid the demise of the common good. We show that both avoiding creation of the common good, whenever full agreement is not reached, and limiting the benefit that disagreeing defectors can acquire, using costly restriction mechanisms, are relevant choices. Nonetheless, restriction mechanisms are found the more favourable, especially in larger group interactions. Given decreasing restriction costs, introducing restraining measures to cope with public goods free-riding issues is the ultimate advantageous solution for all participants, rather than avoiding its creation.

A Case for Private Provision but Collective Ownership of Public Goods

1998 ◽  
Vol 42 (1) ◽  
pp. 90-94 ◽  
Author(s):  
William D. Gerdes
Keyword(s):  
Public Goods ◽  
Public Good ◽  
Private Provision ◽  
The Public ◽  
Collective Ownership ◽  
Free Ride ◽  
Voluntary Exchange

One strategy for generating Pareto results in a public good model is to create an environment where traders internalize the public good externality. The model presented here accomplishes this by separating the provision and ownership of public goods. Such goods are privately provided but collectively owned. Under this arrangement, Lindahl prices are generated through the voluntary exchange activities of consumers. Persistent attempts to free ride are not consistent with maximizing behavior which leads to internalization.

scholarly journals A public goods model of outcomes from online knowledge sharing mediated by mental model processing

2019 ◽  
Vol 23 (1) ◽  
pp. 1-22 ◽  
Author(s):  
Ronald E. Rice ◽  
Marni Heinz ◽  
Ward van Zoonen
Keyword(s):  
Public Goods ◽  
Knowledge Sharing ◽  
Public Good ◽  
Mental Model ◽  
Structural Equation ◽  
Equation Modeling ◽  
Costs And Benefits ◽  
Learning Potential ◽  
Content Type ◽  
The Individual

Purpose This study aims to take a public goods approach to understand relationships between collecting and contributing knowledge to an online knowledge sharing portal (KSP), mental model processing and outcomes at the individual and collective levels. Design/methodology/approach This study reports on a survey (N = 602) among tax professionals, examining the perceived individual and collective benefits and costs associated with collecting and contributing knowledge. Hypotheses were tested using structural equation modeling. Findings Collecting and contributing knowledge led to considerable mental model processing of the knowledge. That in turn significantly influenced (primarily) individual and (some) collective costs and benefits. Results varied by the kinds of knowledge sharing. Whether directly from knowledge sharing, or mediated through mental modeling, the perceived costs and benefits may be internalized as an individual good rather than being interpreted at the collective level as a public good. Research limitations/implications The study is situated in the early stages of a wiki-type online KSP. A focus on the learning potential of the system could serve to draw in new users and contributors, heightening perceptions of the public goods dimension of a KSP. Practical implications A focus on the learning potential of the system could serve to draw in new users, and thus the number of subsequent contributors, heightening perceptions of the collective, public goods dimension of a KSP. Originality/value This study explores how knowledge sharing and mental model processing are directly and indirectly associated with individual and collective costs and benefits. As online knowledge sharing is both an individual and public good, costs and benefits must be considered from both perspectives.

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