5,840 research outputs found
Role of mutation in pseudomonas aeruginosa biofilm development.
No full textThe survival of bacteria in nature is greatly enhanced by their ability to grow within surface-associated communities called biofilms. Commonly, biofilms generate proliferations of bacterial cells, called microcolonies, which are highly recalcitrant, 3-dimensional foci of bacterial growth. Microcolony growth is initiated by only a subpopulation of bacteria within biofilms, but processes responsible for this differentiation remain poorly understood. Under conditions of crowding and intense competition between bacteria within biofilms, microevolutionary processes such as mutation selection may be important for growth; however their influence on microcolony-based biofilm growth and architecture have not previously been explored. To study mutation in-situ within biofilms, we transformed Pseudomonas aeruginosa cells with a green fluorescent protein gene containing a +1 frameshift mutation. Transformed P. aeruginosa cells were non-fluorescent until a mutation causing reversion to the wildtype sequence occurs. Fluorescence-inducing mutations were observed in microcolony structures, but not in other biofilm cells, or in planktonic cultures of P. aeruginosa cells. Thus microcolonies may represent important foci for mutation and evolution within biofilms. We calculated that microcolony-specific increases in mutation frequency were at least 100-fold compared with planktonically grown cultures. We also observed that mutator phenotypes can enhance microcolony-based growth of P. aeruginosa cells. For P. aeruginosa strains defective in DNA fidelity and error repair, we found that microcolony initiation and growth was enhanced with increased mutation frequency of the organism. We suggest that microcolony-based growth can involve mutation and subsequent selection of mutants better adapted to grow on surfaces within crowded-cell environments. This model for biofilm growth is analogous to mutation selection that occurs during neoplastic progression and tumor development, and may help to explain why structural and genetic heterogeneity are characteristic features of bacterial biofilm populations
Do dolphins benefit from nonlinear mathematics when processing their sonar returns?
No full textAn interview with author Tim Leighton about the paper
Opportunities for linking young surveyors across professional surveying member organisations and FIG
No full textCo-operation and Group structure in Bacterial Biofilms
No full textA key problem in understanding major transitions in evolution is the evolution of cooperation: how are mutants that exploit the benefits of cooperation without paying the costs (cheats) suppressed within populations? Biofilms, which display properties of both single cell and multicellular organisms, provide an excellent model system to address this question. Biofilms exhibit grouped population structure – they exist primarily as dense aggregates of cells called microcolonies. We aim to test the hypothesis that cell-grouping displayed by microcolonies in bacterial biofilms provides a mechanism to suppress cheats within the biofilm population. We are using the co-operative trait of siderophore production (an extracellular iron-chelating molecule) within Pseudomonas aeruginosa biofilms to investigate cooperation in biofilms. Under iron-limited conditions, production of siderophores enhanced wild type growth, but microcolonies containing GFP-tagged, pyoverdin-mutant ‘cheats’ developed poorly. In iron-rich conditions, cheats are favoured as siderophore production is costly. With mixed strain biofilms, cheats are dependant on the wild type for successful growth. We suggest that, if cheats reduce colony size, thus self-limiting their global population, microcolony-based group structures may be an important (potentially evolved) mechanism to suppress cheats in bacterial populations
Tim Di Muzio on 'Sabotage'
No full textIn a series of essays published in 2013 and 2014 on capitaspower.com, political economist Tim Di Muzio explored the concept of ‘sabotage’ as it applies to capitalist power. I recently rediscovered these essays and was so impressed by them that I have reposted them here as a single piece.
About the author: Tim Di Muzio is a researcher at the University of Wollongong. He is the author of numerous books, including Debt as power, Carbon capitalism, and The 1% and the Rest of us
1996-1997 Tim Gautreaux
No full textTim Gautreaux is the author of three novels and two earlier short story collections. His work has appeared in The New Yorker, The Best American Short Stories, The Atlantic, Harper’s, and GQ. After teaching for thirty years at Southeastern Louisiana University, he now lives, with his wife, in Chattanooga, Tennessee. (Photo credit: Randy Bergeron)https://egrove.olemiss.edu/grisham_res/1023/thumbnail.jp
Can Simpson's paradox explain co-operation in Pseudomonas aeruginosa biofilms?
No full textCo-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
First person - Tim Petzold
No full textFirst Person is a series of interviews with the first authors of a selection of papers published in Biology Open, helping researchers promote themselves alongside their papers. Tim Petzold is first author on ‘ Connexin 41.8 governs timely haematopoietic stem and progenitor cell specification’, published in BiO. Tim conducted the research described in this article while a PhD student in Julien Bertrand's lab at the Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, Switzerland. He is now a postdoc in the lab of Holger Gerhardt at the Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany, investigating developmental biology – previously his focus was on how blood stem cells develop and now it has shifted to how the vascular system develops
Tim Seibles, 40th Annual ODU Literary Festival
No full textTim Seibles is the author of several poetry collections including Hurdy-Gurdy, Hammerlock, Buffalo Head Solos, and Fast Animal, which was a finalist for the 2012 National Book Award. In 2013 he received both the Pen Oakland Josephine Miles Award for poetry and an honorary Doctorate of Humane Letters from Misericordia University for his literary accomplishments. His latest collection, One Turn Around the Sun, has just been released. Tim is the current Poet Laureate of Virginia and is a Professor of English at Old Dominion University where he teaches literature as well as classes in the MFA in writing program
Tim Seibles, 39th Annual ODU Literary Festival
No full textTim Seibles is the author of several poetry collections including Hurdy-Gurdy, Hammerlock, Buffalo Head Solos, and Fast Animal, which was a finalist for the 2012 National Book Award. In 2013 he received both the Pen Oakland Josephine Miles Award for poetry and an honorary Doctorate of Humane Letters from Misericordia University for his literary accomplishments. His latest collection, One Turn Around the Sun, has just been released. Tim is the current Poet Laureate of Virginia and is a Professor of English at Old Dominion University where he teaches literature as well as classes in the MFA in writing program
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