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Can Simpson's paradox explain co-operation in Pseudomonas aeruginosa biofilms?

Can Simpson's paradox explain co-operation in Pseudomonas aeruginosa biofilms?
Can Simpson's paradox explain co-operation in Pseudomonas aeruginosa biofilms?
Co-operative behaviours, such as the production of public goods, are commonly displayed by bacteria in biofilms and can enhance their ability to survive in environmental or clinical settings. Non-co-operative cheats commonly arise and should, theoretically, disrupt co-operative behaviour. Its stability therefore requires explanation, but no mechanisms to suppress cheating within biofilms have yet been demonstrated experimentally. Theoretically, repeated aggregation into groups, interleaved with dispersal and remixing, can increase co-operation via a ‘Simpson's paradox’. That is, an increase in the global proportion of co-operators despite a decrease in within-group proportions, via differential growth of groups. We investigate the hypothesis that microcolony formation and dispersal produces a Simpson's paradox that explains bacterial co-operation in biofilms. Using the production of siderophores in Pseudomonas aeruginosa as our model system for co-operation, we use well-documented co-operator and siderophore-deficient cheat strains to measure the frequency of co-operating and cheating individuals, in-situ within-microcolony structures. We detected significant within-type negative density-dependant effects that vary over microcolony development. However, we find no evidence of Simpson's paradox. Instead, we see clear within-microcolony spatial structure (cheats occupying the interior portions of microcolonies) that may violate the assumption required for Simpson's paradox that group members share equally in the public good.
biofilm development, simpson's paradox, co-pperation, siderophore production, pseudomonas aeruginosa
0928-8244
226-235
Penn, Alexandra S.
d848e4c6-c29f-4594-8815-1971e8a27b19
Conibear, Tim C.R.
4aa05e19-b488-479c-99c7-7077c4b2a47d
Watson, Richard A.
ce199dfc-d5d4-4edf-bd7b-f9e224c96c75
Kraaijeveld, Alex R.
4af1791a-15cf-48b9-9fd8-b3a7fb450409
Webb, Jeremy S.
ec0a5c4e-86cc-4ae9-b390-7298f5d65f8d
Penn, Alexandra S.
d848e4c6-c29f-4594-8815-1971e8a27b19
Conibear, Tim C.R.
4aa05e19-b488-479c-99c7-7077c4b2a47d
Watson, Richard A.
ce199dfc-d5d4-4edf-bd7b-f9e224c96c75
Kraaijeveld, Alex R.
4af1791a-15cf-48b9-9fd8-b3a7fb450409
Webb, Jeremy S.
ec0a5c4e-86cc-4ae9-b390-7298f5d65f8d

Penn, Alexandra S., Conibear, Tim C.R., Watson, Richard A., Kraaijeveld, Alex R. and Webb, Jeremy S. (2012) Can Simpson's paradox explain co-operation in Pseudomonas aeruginosa biofilms? [in special issue: Biofilms II] FEMS Immunology & Medical Microbiology, 65 (2), 226-235. (doi:10.1111/j.1574-695X.2012.00970.x).

Record type: Article

Abstract

Co-operative behaviours, such as the production of public goods, are commonly displayed by bacteria in biofilms and can enhance their ability to survive in environmental or clinical settings. Non-co-operative cheats commonly arise and should, theoretically, disrupt co-operative behaviour. Its stability therefore requires explanation, but no mechanisms to suppress cheating within biofilms have yet been demonstrated experimentally. Theoretically, repeated aggregation into groups, interleaved with dispersal and remixing, can increase co-operation via a ‘Simpson's paradox’. That is, an increase in the global proportion of co-operators despite a decrease in within-group proportions, via differential growth of groups. We investigate the hypothesis that microcolony formation and dispersal produces a Simpson's paradox that explains bacterial co-operation in biofilms. Using the production of siderophores in Pseudomonas aeruginosa as our model system for co-operation, we use well-documented co-operator and siderophore-deficient cheat strains to measure the frequency of co-operating and cheating individuals, in-situ within-microcolony structures. We detected significant within-type negative density-dependant effects that vary over microcolony development. However, we find no evidence of Simpson's paradox. Instead, we see clear within-microcolony spatial structure (cheats occupying the interior portions of microcolonies) that may violate the assumption required for Simpson's paradox that group members share equally in the public good.

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More information

e-pub ahead of print date: 23 April 2012
Published date: July 2012
Keywords: biofilm development, simpson's paradox, co-pperation, siderophore production, pseudomonas aeruginosa
Organisations: Agents, Interactions & Complexity, Centre for Biological Sciences

Identifiers

Local EPrints ID: 273199
URI: http://eprints.soton.ac.uk/id/eprint/273199
ISSN: 0928-8244
PURE UUID: 67930def-8f13-460d-a09f-0acd7559ea55
ORCID for Richard A. Watson: ORCID iD orcid.org/0000-0002-2521-8255
ORCID for Alex R. Kraaijeveld: ORCID iD orcid.org/0000-0002-8543-2640
ORCID for Jeremy S. Webb: ORCID iD orcid.org/0000-0003-2068-8589

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Date deposited: 07 Feb 2012 10:49
Last modified: 15 Mar 2024 03:26

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Contributors

Author: Alexandra S. Penn
Author: Tim C.R. Conibear
Author: Richard A. Watson ORCID iD
Author: Jeremy S. Webb ORCID iD

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