Spring Conference 2011 - Society for General Microbiology

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Please note: Abstracts are published as received from the authors and are not subject to editing. 15 Spring Meeting 11–14 April 2011 Harrogate – www.sgmharrogate2011.org.uk SESSION AbSTrACTS ↑Contents HA03 Cont. i review a series of models and data highlighting the importance of population structure in determining microbial social behaviours and consequent virulence, and highlight the peculiar role and importance of microbial mobile elements (plasmids, phages) in generating this structure. Finally, i discuss the possible therapeutic implications of understanding the social dynamics of microbial pathogens. Public goods, private shares JAN-ulriCH KrEFT1 , Stefan Schuster2 , Anja Schroeter2 1 2 Centre for Systems Biology, School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT; Dept of Bioinformatics, School of Biology & Pharmaceutics, Ernst-Abbe-Platz 2, Friedrich Schiller University of Jena, D-07743 Jena, Germany (Email: j.kreft@bham.ac.uk; stefan.schu@uni-jena.de; an.schroeter@uni-jena.de) Extracellular effectors such as exoenzymes, siderophores, antibiotics, and autoinducers are public goods since they benefit not only producing but also non-producing cells, which are called cheaters as they do not pay the production costs. Cheaters outcompete the producers if the benefits are shared equally. This can be avoided in a spatially structured environment where neighbours are next of kin and receive more of the benefit. A simpler mechanism consists in partially ‘privatizing’ the ‘public’ good. For example, invertase produced by yeast remains bound to the cell wall, thereby generating glucose and fructose closer to the cell’s own transporters than any neighbours’. To some extent, the public good is made less public, and the behaviour less cooperative, but the point is that privileged access can act as an evolutionary refuge from cheaters, allowing the evolution of a mechanism for public good production from which cooperation can readily and repeatedly evolve. Similar arguments hold for autoinducer sensing. We show that partially privatized public good production is evolutionarily stable over a wide range of conditions in a model with minimal assumptions, essentially Monod kinetics. While this model is generic, it can explain the experimental observations of Greig & Travisano (2004). Ecological drivers of the evolution of public-goods cooperation in bacteria MiCHAEl BrOCKHurST1 , Michelle Habets1 , Angus Buckling2 , Andy Gardner2 1 2 Institute of Integrative Biology, University of Liverpool, Liverpool; Dept of Zoology, University of Oxford, Oxford The role of ecological processes in the evolution of social traits is increasingly recognized. We have explored, using general theoretical models and experiments with bacteria, the effects of common ecological variables (e.g., disturbance frequency and resource supply) on the evolution of cooperative biofilm formation. Our results demonstrate that cooperation tends to peak at intermediate frequencies of disturbance but that the peak shifts toward progressively higher frequencies of disturbance as resource supply increases. This arises due to increased growth rates at higher levels of resource supply, which allows cooperators to more rapidly exceed the density threshold above which cooperation is beneficial following catastrophic disturbance. These findings demonstrate the importance of ecological processes in the evolution of public-goods cooperation and suggest that cooperation can be favored by selection across a wide range of ecological conditions. Using bacterial lobster traps and scanning electrochemical microscopy to probe polymicrobial interactions Marvin Whiteley The University of Texas at Austin, Section of Molecular Genetics & Microbiology Prokaryotes are social organisms capable of coordinated group behaviors (referred to as quorum sensing, QS); however, how these behaviors proceed in the small populations commonly observed in nature (e.g., thousands of cells) are unknown. Here, i will discuss the use of two novel approaches for probing bacterial social interactions in small populations. The first approach utilizes multi-photon lithography to create picoliter-sized porous cavities capable of capturing a single bacterium and tracking growth and behavior of the resultant microcolony in real time. These bacterial ‘lobster traps’ allow for examination of behaviors in small, defined bacterial populations similar in size to those observed in nature. The second approach involves the use of scanning electrochemical microscopy (SECM) to monitor group behaviors in a bacterial biofilm through quantification of QS-controlled products. SECM has the unique ability to set the exact distance from an ultramicroelctrode sensing tip to a biological substrate through a feedback approach curve, and thus is able to measure the local concentration over a defined region (μm scale) of a biofilm. using these technologies we provide insight not only into the number of bacteria, but also the concentration of small molecules required to elicit social responses. s o c i e t y f o r g e n e r a l Microbiology
Please note: Abstracts are published as received from the authors and are not subject to editing. 16 Spring Meeting 11–14 April 2011 Harrogate – www.sgmharrogate2011.org.uk SESSION AbSTrACTS HA04 Vaccines ↑Contents Exploiting host recognition of fungi for vaccine development Stuart M. levitz University of Massachusetts Medical School, Worcester, USA Glucan particles (GPs) are purified Saccharomyces cerevisiae cell walls treated so they are primarily β1,3-d-glucans and free of mannans and proteins. We have loaded GPs with the model antigen ovalbumin (OVA) and tested GP-OVA as a receptor-targeted vaccine delivery system. immune responses in C57Bl/6 mice following immunization with GP-OVA were compared with OVA absorbed onto the adjuvant alum (Alum/OVA). While both GP-OVA and Alum-OVA formulations induced high igG titres, only GP-OVA stimulated antigenspecific CD4+ T cell lymphoproliferative and EliSPOT responses. Moreover, the T-cell responses induced by GP-OVA were Th1-biased (determined by iFN-γ EliSPOT) and Th17-biased (determined by il-17a EliSPOT). responses were long-lasting and robust even if with just two immunizations and with low doses of antigen. Encapsulation of antigen in the GPs was essential for optimal immunogenicity. Although GPs are phagocytosed by dectin-1 in vitro, in vivo immune responses were preserved in dectin-1 knockout mice, likely because of complement opsonization. Thus, the GP-based vaccine platform combines adjuvanticity and antigen delivery to induce strong humoral and Th1- and Th17-biased CD4 + T-cell responses. Studies examining protection against pathogens are ongoing. Fungal cell wall vaccines John Edwards Div of Infectious Diseases, Harbor/UCLA Medical Center, 1124 W Carson St, RB2, 2nd Fl, Torrance, CA 90502, USA During efforts to identify adhesins for Candida to human cells, we discovered that both Als1 and Als3 encoded cell wall proteins which were strong adhesins for human umbilical cord endothelial cells. To determine whether these adhesins could function as vaccines for prevention of hematogenously disseminated candidiasis (HDC) we produced recombinant proteins from the N-terminus of Als1p (r-Als1pN) and Als3p (r-Als3pN) in Saccharomyces and tested them in the mouse model for HDC. Considerable protection occurred in a lethal challenge for multiple strains and species of Candida. Focusing on r-Als3pN, both an adhesin and invasin for Candida, we found protection for oral/pharyngeal and vulvovaginal candidiasis also in the murine model. Structural, three dimensional homology studies showed Als3pN to have high levels of homology to staphylococcal surface proteins. The r-Als3p was also protective in the murine staphylococcal challenge model. The mechanism of action of the r-Asl3pN for both organisms is proposed to be through the Th1/Th17 pathway. This vaccine is currently in Phase 1 clinical development. Another Candida vaccine candidate in Phase 1 clinical development is based on the SAP2 antigen presented by a virosome delivery technology. A third Candida vaccine candidate based on diphtheria toxoid conjugated to cell surface beta-glucan is highly effective in murine models and is in late-stage preclinical development. Extensive investigation is in preclinical development stages for coccidioidomycosis, histoplasmosis, and blastomycosis also. Protecting against plague Diane Williamson Dstl Porton Down, Salisbury SP4 0JD Plague, caused by the bacterium Yersinia pestis, is an ancient disease, which still exists in the world today and which emerges with lethal effect from time-to-time. in endemic areas, the bacterium is maintained in enzootic reservoirs and is vectored by fleas. Man is an accidental host who may become infected by a flea that has fed on an infected animal. Existing killed whole cell vaccine fomulations afford protection against the flea-vectored bubonic form of the disease. Since pioneering work in the 1950s and 1960s into the pathogenicity of this bacterium, significant advances have been made in protecting people more comprehensively against this disease and particularly the most feared, pneumonic plague. This presentation will review the most recent advances in developing new and efficacious vaccines and describe how our understanding of this serious pathogen has advanced with modern technology to achieve a recombinant sub-unit vaccine currently in clinical development. HA04 ↑Contents s o c i e t y f o r g e n e r a l Microbiology
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Spring Conference 2011 - Society for General Microbiology

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