dictyNews Electronic Edition Volume 41, number 6 March 27, 2015 Please submit abstracts of your papers as soon as they have been accepted for publication by using the form at http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit. Back issues of dictyNews, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. Follow dictyBase on twitter: http://twitter.com/dictybase ========= Abstracts ========= Concurrent co-evolution of intra-organismal cheaters and resisters Levin, Samuel; Brock, Debra; Queller, David; Strassmann, Joan Journal of Evolutionary Biology, in press The evolution of multicellularity is a major transition that is not yet fully understood. Specifically, we do not know if there are any mechanisms by which multicellularity can be maintained without a single cell bottleneck or other relatedness enhancing mechanisms. Under low relatedness, cheaters can evolve that benefit from the altruistic behaviour of others without themselves sacrificing. If these are obligate cheaters, incapable of co-operating, their spread can lead to the demise of multicellularity. One possibility, however, is that co-operators can evolve resistance to cheaters. We tested this idea in a facultatively multicellular social amoeba, Dictyostelium discoideum. This amoeba usually exists as a single cell but, when stressed, thousands of cells aggregate to form a multicellular organism in which some of the cells sacrifice for the good of others. We used lineages that had undergone experimental evolution at very low relatedness, during which time obligate cheaters evolved. Unlike earlier experiments, which found resistance to cheaters that were prevented from evolving, we competed cheaters and non-cheaters that evolved together, and cheaters with their ancestors. We found that non-cheaters can evolve resistance to cheating before cheating sweeps through the population and multicellularity is lost. Our results provide insight into cheater- resister co-evolutionary dynamics, in turn providing experimental evidence for the maintenance of at least a simple form of multicellularity by means other than high relatedness. Submitted by Samuel Levin [samuel.r.levin@gmail.com] ---------------------------------------------------------------------- Lipid Droplet Dynamics at Early Stages of Mycobacterium marinum Infection in Dictyostelium Caroline Barisch1, Peggy Paschke2, Monica Hagedorn3, Markus Maniak2 and Thierry Soldati1* 1Department of Biochemistry, Science II, University of Geneva, 30 quai Ernest-Ansermet, 1211 Geneva-4, Switzerland 2Department of Cell Biology, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany 3Section Parasitology, Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-Stra§e 74, 20359 Hamburg, Germany Cellular Microbiology, in press Lipid droplets exist in virtually every cell type, ranging from mammals to plants, but also to eukaryotic and prokaryotic unicellular organisms such as Dictyostelium and bacteria. They serve amongst other roles as energy reservoir that cells consume in times of starvation. Mycobacteria and some other intracellular pathogens hijack these organelles as a nutrient source and to build up their own lipid inclusions. The mechanisms by which host lipid droplets are captured by the pathogenic bacteria is extremely poorly understood. Using the powerful Dictyostelium discoideum / Mycobacterium marinum infection model we observed that, immediately after their uptake, lipid droplets translocate to the vicinity of the vacuole containing live but not dead mycobacteria. Induction of lipid droplets in Dictyostelium prior to infection resulted in a vast accumulation of neutral lipids and sterols inside the bacterium-containing compartment. Subsequently, under these conditions, mycobacteria accumulated much larger lipid inclusions. Strikingly, the Dictyostelium homologue of perilipin and the murine perilipin 2 surrounded bacteria that had escaped to the cytosol of Dictyostelium or microglial BV-2 cells, respectively. Moreover, bacterial growth was inhibited in Dictyostelium plnA knockout cells. In summary, our results provide evidence that mycobacteria actively manipulate the lipid metabolism of the host from very early infection stages. Submitted by Thierry Soldati [thierry.soldati@unige.ch] ---------------------------------------------------------------------- Live Imaging of Mycobacterium marinum Infection in Dictyostelium discoideum Caroline Barisch, Ana T. L—pez-JimŽnez, and Thierry Soldati Department of Biochemistry, Science II, University of Geneva, 30 quai Ernest-Ansermet, 1211 Geneva-4, Switzerland Methods Mol Biol. 2015;1285:369-85. The pdf file of the chapter is available upon request The Dictyostelium discoideumÐMycobacterium marinum hostÐpathogen system is a recently established and powerful model system for mycobacterial infection. In this chapter, two simple protocols for live imaging of Dictyostelium discoideum infection are described. The first method is used to monitor the dynamics of recruitment of GFP-tagged Dictyostelium discoideum proteins at single time-points corresponding to the main stages of the infection (1.5Ð72 h post infection). The second method focuses at the early stages of the establishment of an infection (0Ð3 h post infection). In addition, several procedures to improve the imaging of the bacterium-containing compartment are described. Basic bacterial parameters such as bacterial growth and the recruitment of host proteins to the bacterium-containing compartment can be easily and precisely quantified using macros for ImageJ. These methods can be adapted to monitoring mycobacteria infection in other systems using mammalian cells. Submitted by Thierry Soldati [thierry.soldati@unige.ch] ============================================================== [End dictyNews, volume 41, number 6]