Social evolution of toxic metal bioremediation in Pseudomonas aeruginosa

This is the final version. Available on open access from the Royal Society via the DOI in this recordThere is another ORE record for this publication: http://hdl.handle.net/10871/39858Bacteria are often iron-limited, and hence produce extracellular iron-scavenging siderophores. A crucial feature of siderophore production is that it can be an altruistic behaviour (individually costly but benefitting neighbouring cells), thus siderophore producers can be invaded by non-producing social ‘cheats’. Recent studies have shown that siderophores can also bind other heavy metals (such as Cu and Zn), but in this case siderophore chelation actually reduces metal uptake by bacteria. These complexes reduce heavy metal toxicity, hence siderophore production may contribute to toxic metal bioremediation. Here, we show that siderophore production in the context of bioremediation is also an altruistic trait and can be exploited by cheating phenotypes in the opportunistic pathogen Pseudomonas aeruginosa. Specifically, we show that in toxic copper concentrations (i) siderophore non-producers evolve de novo and reach high frequencies, and (ii) producing strains are fitter than isogenic non-producing strains in monoculture, and vice versa in co-culture. Moreover, we show that the evolutionary effect copper has on reducing siderophore production is greater than the reduction observed under iron-limited conditions. We discuss the relevance of these results to the evolution of siderophore production in natural communities and heavy metal bioremediation.AXANERCUniversity of Exete

No effect of intraspecific relatedness on public goods cooperation in a complex community

A.B. would like to acknowledge support from NERC (NE/P001130/1) and BBSRC (BB/K003240/1). S.O.B. was funded by a University of Exeter Ph.D studentship (2011–2015). A.G. is supported by a NERC Independent Research Fellowship (NE/K009524/1).Many organisms – notably microbes - are embedded within complex communities where cooperative behaviours in the form of excreted public goods can benefit other species. Under such circumstances, intraspecific interactions are likely to be less important in driving the evolution of cooperation. We first illustrate this idea with a simple theoretical model, showing that relatedness – the extent to which individuals with the same cooperative alleles interact with each other - has a reduced impact on the evolution of cooperation when public goods are shared between species. We test this empirically using strains of Pseudomonas aeruginosa that vary in their production of metal-chelating siderophores in copper contaminated compost (an interspecific public good). We show that non-siderophore producers grow poorly relative to producers under high relatedness, but this cost can be alleviated by the presence of the isogenic producer (low relatedness) and/or the compost microbial community. Hence, relatedness can become unimportant when public goods provide interspecific benefits.Publisher PDFPeer reviewe

Palliative care for Parkinson's disease: Patient and carer's perspectives explored through qualitative interview

Background: Palliative care is recommended for non-malignant illnesses, including Parkinson’s disease. However, past research with healthcare workers highlights unmet palliative needs in this population and referral rates to Specialist Palliative Care are low. Some healthcare workers perceive a ‘fear’ in their patients about introducing palliative care. However, less is known about the views of people with Parkinson’s disease and their carers about palliative care. Aim: (1) To explore the palliative care and related issues most affecting people with Parkinson’s disease and their families and (2) to examine perceptions about/understanding of palliative care. Design: This was a qualitative study; semi-structured interviews were conducted, transcribed and analysed using thematic analysis. Setting/participants: A total of 31 people participated, both people with Parkinson’s disease (n = 19) and carers (n = 12), across three Movement Disorder Clinics in the Republic of Ireland. Results: People with Parkinson’s disease and their carers were unfamiliar with the term palliative care. When informed of the role of palliative care, most felt that they would benefit from this input. People with Parkinson’s disease and carers experienced a high illness burden and wanted extra support. Crises requiring Specialist Palliative Care involvement may occur at diagnosis and later, with advancing illness. Participants wanted more information about palliative care and especially further supports to address their psychosocial needs. Conclusion: A holistic palliative care approach could address the complex physical and psychosocial symptoms experienced by people with Parkinson’s disease and their carers, and people with Parkinson’s disease and their carers are open to palliative care. Further research needs to explore how palliative care can be introduced into the routine care for people with Parkinson’s disease

The evolution of bacterial mutation rates under simultaneous selection by inter-specific and social parasitism.

This is a post-print of an article published in Proceedings of the Royal Society B. Please cite the published article. O’Brien S, Rodrigues AMM, Buckling A. 2013 The evolution of bacterial mutation rates under simultaneous selection by interspecific and social parasitism. Proc R Soc B 280: 20131913. http://dx.doi.org/10.1098/rspb.2013.1913Many bacterial populations harbour substantial numbers of hypermutable bacteria, in spite of hypermutation being associated with deleterious mutations. One reason for the persistence of hypermutators is the provision of novel mutations, enabling rapid adaptation to continually changing environments, for example coevolving virulent parasites. However, hypermutation also increases the rate at which intraspecific parasites (social cheats) are generated. Interspecific and intraspecific parasitism are therefore likely to impose conflicting selection pressure on mutation rate. Here, we combine theory and experiments to investigate how simultaneous selection from inter- and intraspecific parasitism affects the evolution of bacterial mutation rates in the plant-colonizing bacterium Pseudomonas fluorescens. Both our theoretical and experimental results suggest that phage presence increases and selection for public goods cooperation (the production of iron-scavenging siderophores) decreases selection for mutator bacteria. Moreover, phages imposed a much greater growth cost than social cheating, and when both selection pressures were imposed simultaneously, selection for cooperation did not affect mutation rate evolution. Given the ubiquity of infectious phages in the natural environment and clinical infections, our results suggest that phages are likely to be more important than social interactions in determining mutation rate evolution.University of ExeterAXAPDBD-IGCFC

mutation rates data

Data collected in the lab and analysed using R software. Malthusian parameters used to describe growth rates in competition experiments

Data from: The evolution of bacterial mutation rates under simultaneous selection by inter-specific and social parasitism

Many bacterial populations harbour substantial numbers of hypermutable bacteria, in spite of hypermutation being associated with deleterious mutations. One reason for the persistence of hypermutators is the provision of novel mutations, enabling rapid adaptation to continually changing environments, for example coevolving virulent parasites. However, hypermutation also increases the rate at which intraspecific parasites (social cheats) are generated. Interspecific and intraspecific parasitism are therefore likely to impose conflicting selection pressure on mutation rate. Here, we combine theory and experiments to investigate how simultaneous selection from inter- and intraspecific parasitism affects the evolution of bacterial mutation rates in the plant-colonizing bacterium Pseudomonas fluorescens. Both our theoretical and experimental results suggest that phage presence increases and selection for public goods cooperation (the production of iron-scavenging siderophores) decreases selection for mutator bacteria. Moreover, phages imposed a much greater growth cost than social cheating, and when both selection pressures were imposed simultaneously, selection for cooperation did not affect mutation rate evolution. Given the ubiquity of infectious phages in the natural environment and clinical infections, our results suggest that phages are likely to be more important than social interactions in determining mutation rate evolution

High virulence sub-populations in Pseudomonas aeruginosa long-term cystic fibrosis airway infections

BACKGROUND: Pseudomonas aeruginosa typically displays loss of virulence-associated secretions over the course of chronic cystic fibrosis infections. This has led to the suggestion that virulence is a costly attribute in chronic infections. However, previous reports suggest that overproducing (OP) virulent pathotypes can coexist with non-producing mutants in the CF lung for many years. The consequences of such within-patient phenotypic diversity for the success of this pathogen are not fully understood. Here, we provide in-depth quantification of within-host variation in the production of three virulence associated secretions in the Liverpool cystic fibrosis epidemic strain of P. aeruginosa, and investgate the effect of this phenotypic variation on virulence in acute infections of an insect host model. RESULTS: Within-patient variation was present for all three secretions (pyoverdine, pyocyanin and LasA protease). In two out of three patients sampled, OP isolates coexisted with under-producing mutants. In the third patient, all 39 isolates were under-producers of all three secretions relative to the transmissible ancestor LESB58. Finally, this phenotypic variation translated into variation in virulence in an insect host model. CONCLUSIONS: Within population variation in the production of P. aeruginosa virulence-associated secretions can lead to high virulence sub-populations persisting in patients with chronic CF infections

Evolution of Jigsaw - a national youth mental health service.

AIM There has been a global movement towards transformation of youth mental health services, but limited information on the core principles and characteristics of these new services is available. Jigsaw is one such service, established in Ireland in 2006, with the intent of creating change in Ireland's system of mental healthcare for 12-25 year olds. The aim of this paper is to describe the evolution of Jigsaw services, which are now firmly embedded in the Irish system of care for young people, and recognized internationally as an established service network. METHODS This paper describes provides an up-to-date description of the Jigsaw service model, key areas of evolution that have shaped this model, and identifies future directions in service development. RESULTS Key attributes of the Jigsaw service model including therapeutic service, scope of practice, youth mental health promotion, youth participation, and monitoring/evaluation are described in this paper. Information on key enablers (funding and governance/quality) and service providers is also included. CONCLUSIONS Information on the core principles and characteristics of youth mental health services is important. This paper addresses a gap in the literature by describing the Jigsaw service model, which continues to evolve so that it is responsive to the needs of young people

Immunomodulatory activity of 5 kDa permeate fractions of casein hydrolysates generated using a range of enzymes in Jurkat T cells and RAW264.7 macrophages

The in vitro bioactivity of 5 kDa ultrafiltration permeate fractions of casein hydrolysates produced using different enzymes were compared. Reverse phase ultra-performance liquid chromatography and gel permeation chromatography showed that the permeates had different physicochemical properties (molecular mass and degree of hydrolysis). The Flavourzyme® permeate had the highest activity in the 2,2’-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assay. Cellular antioxidant and immunomodulatory assays showed that none of the permeates exhibited in vitro antioxidant activity, while all permeates significantly (P < 0.05) decreased interleukin-6 (IL-6) production in ConA-stimulated Jurkat T cells at 0.50% (w/v) and LPS-stimulated RAW264.7 cells at 0.05 and 0.50% (w/v). Three permeates, obtained using Flavourzyme®, Flavorpro Whey and trypsin, also significantly (P < 0.05) decreased IL-1β production at 0.05% (w/v) in RAW264.7 cells. Western blot analysis showed that all permeates significantly decreased the expression of the NF-κB subunit, p65, in RAW264.7 cells indicating that anti-inflammatory activity may be associated with this pathway