dictyNews Electronic Edition Volume 31, number 1 July 4, 2008 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu or 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. ========= Abstracts ========= 3’-phosphoinositides regulate the coordination of speed and accuracy  during chemotaxis Gruver, J. S., J. P. Wikswo, and C. Y. Chung 1Department of Pharmacology, Vanderbilt University Medical Center 2Departments of Physics and Astronomy, Biomedical Engineering, and  Molecular Physiology and Biophysics, Vanderbilt University, Nashville TN 37232 Biophysical J., in press The PI3K/PTEN pathway, as the regulator of 3'-phosphoinositide (3'-PI)  dynamics, has emerged as a key regulator of chemoattractant gradient sensing  during chemotaxis in Dictyostelium and other cell types. Previous results  have shown 3'-PIs to be important for regulating basal cell motility and sensing  the direction and strength of the chemoattractant gradient. We examined  the chemotaxis of wild-type cells and cells lacking PTEN or PI3K1 and 2 using  analytical methods that allow us to quantitatively discern differences  between the genotypes ability to sense and efficiently respond to changes in  gradient steepness during chemotaxis. We find that cells are capable of  increasing their chemotactic accuracy and speed as they approach a micropipette  in a manner that is dependent on the increasing strength of the concentration  gradient and 3’-PI signaling. Further, our data shows that 3'-PI signaling  affects a cell's ability to coordinate speed and direction in order to increase  chemotactic efficiency. Using a new measurement of chemotactic efficiency  that reveals the degree of coordination between speed and accuracy, we find  that cells also have the capacity to increase their chemotactic efficiency as they  approach the micropipette. Like directional accuracy and speed, the increase in  chemotactic efficiency of cells with increased gradient strength is sensitive to  3'-PI dysregulation. Our evidence suggests that receptor-driven 3'-PI signaling  regulates the ability of the cell to capitalize on stronger directional inputs as  well as minimize the effects of inaccurate turns in order to increase  chemotactic efficiency. Submitted by: Chang Chung [chang.chung@vanderbilt.edu] -------------------------------------------------------------------------------- Functional analysis of spontaneous cell movement under different physiological conditions Hiroaki Takagi 1,2,3, Masayuki J. Sato 1,3, Toshio Yanagida 1, Masahiro Ueda 1,3 1. Laboratories for Nanobiology, Graduate School of Frontier Biosciences,     Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan. 2. Department of Physics, School of Medicine, Nara Medical University,  Nara, 634-8521, Japan. 3. JST, CREST, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan. PLoS ONE, in press Cells can show not only spontaneous movement but also tactic responses to environmental signals. Since the former can be regarded as the basis to realize the latter, playing essential roles in various cellular functions, it is important to investigate spontaneous movement quantitatively at different physiological conditions in relation to a cell's physiological functions. For that purpose, we observed a series of spontaneous movements by Dictyostelium cells at different developmental periods by using a single cell tracking system. Using statistical analysis of these traced data, we found that cells showed complex dynamics with anomalous diffusion and that their velocity distribution had power-law tails in all conditions. Furthermore, as development proceeded, average velocity and persistency of the movement increased and as too did the exponential behavior in the velocity distribution. Based on these results, we succeeded in applying a generalized Langevin model to the experimental data. With this model, we discuss the relation of spontaneous cell movement to cellular physiological function and its relevance to behavioral strategies for cell survival. Submitted by: Hiroaki Takagi [takagi@naramed-u.ac.jp] -------------------------------------------------------------------------------- Dictyostelium transcriptional responses to Pseudomonas aeruginosa: common and specific effects from PAO1 and PA14 strains Sergio Carilla-Latorre1*, Javier Calvo-Garrido1*, Gareth Bloomfield2, Jason Skelton3, Robert R. Kay2, Alasdair Ivens3, Jose L. Martinez4 and Ricardo Escalante1 1 Instituto de Investigaciones Biomedicas Alberto Sols. Universidad Autonoma de Madrid-Consejo Superior de Investigaciones Cientificas. Madrid. Spain. 2 MRC Laboratory of Molecular Biology, Cambridge. UK. 3 Wellcome Trust Sanger Institute, Hinxton. UK. 4 Centro Nacional de Biotecnología. CSIC. Madrid and CIBERESP Spain. BMC-Microbiology, in press Background Pseudomonas aeruginosa is one of the most relevant human opportunistic bacterial pathogens. Two strains (PAO1 and PA14) have been mainly used as models for studying virulence of P. aeruginosa. The strain PA14 is more virulent than PAO1 in a wide range of hosts including insects, nematodes and plants. Whereas some of the differences might be attributable to concerted action of determinants encoded in pathogenicity islands present in the genome of PA14, a global analysis of the differential host responses to these P. aeruginosa strains has not been addressed. Little is known about the host response to infection with P. aeruginosa and whether or not the global host transcription is being affected as a defense mechanism or altered in the benefit of the pathogen. Since the social amoeba Dictyostelium discoideum is a suitable host to study virulence of P. aeruginosa and other pathogens, we used available genomic tools in this model system to study the transcriptional host response to P. aeruginosa infection. Results We have compared the virulence of the P. aeruginosa PAO1 and PA14 using D.  discoideum and studied the transcriptional response of the amoeba upon infection. Our results showed that PA14 is more virulent in Dictyostelium than PA01using different plating assays. For studying the differential response of the host to infection by these model strains, D. discoideum cells were exposed to either P. aeruginosa PAO1 or P. aeruginosa PA14 (mixed with an excess of the non-pathogenic bacterium Klebsiella aerogenes as food supply) and after 4 hours, cellular RNA extracted. A three-way comparison was made using whole-genome D. discoideum microarrays between RNA samples from cells treated with the two different strains and control cells exposed only to K. aerogenes. The transcriptomic analyses have shown the existence of common and specific responses to infection. The expression of 364 genes changed in a similar way upon infection with one or another strain, whereas 169 genes were differentially regulated depending on whether the infecting strain was either P. aeruginosa PAO1 or PA14. Effects on metabolism, signalling, stress response and cell cycle can be inferred from the genes affected. Conclusions Our results show that pathogenic Pseudomonas strains invoke both a common transcriptional response from Dictyostelium and a strain specific one, indicating that the infective process of bacterial pathogens can be strain-specific and is more complex than previously thought. Submitted by: Ricardo Escalante [rescalante@iib.uam.es] ============================================================== [End dictyNews, volume 31, number 1]