Biophysical Society Thematic Meeting | Singapore

Mechanobiology of Disease

Thursday Speaker Abstracts

Interplay between Morphology and Metabolism in Pseudomonas Aeruginosa Biofilms Lars Dietrich . Columbia University, New York, NY, USA. The relationship between structure and function is a fundamental theme in biology. For communities of cells, overall structure influences access to resources and therefore the metabolisms that can support survival for individuals within. On the other hand, resident cells can control the overall community structure and thereby modulate resource availability. We study the roles of endogenous electron shuttling compounds in the biofilm physiology of Pseudomonas aeruginosa, a bacterial pathogen. These compounds, called phenazines, can act as electron acceptors for P. aeruginosa metabolism when oxygen is not available. While wild-type colony biofilms are relatively smooth, phenazine-null mutant biofilms are wrinkled. Initiation of wrinkling coincides with a maximally reduced intracellular redox state, suggesting that wrinkling is a mechanism for coping with electron acceptor limitation. Mutational analyses and in situ expression profiling have revealed roles for PAS-domain and other redox-sensing regulatory proteins, as well as genes involved in motility and matrix production, in colony morphogenesis. To characterize endogenous electron acceptor production, we have developed a chip that serves as a growth support for biofilms and allows electrochemical detection and spatiotemporal resolution of phenazine production in situ. We are further developing this chip for detection of various redox-active metabolites. Through these diverse approaches, we are developing a broad picture of the mechanisms and metabolites that exert an integrated influence over redox homeostasis and thereby biofilm morphogenesis in P. aeruginosa. The Physical Basis of Coordinated Tissue Spreading in Zebrafish Gastrulation Carl-Philipp Heisenberg , Hitoshi Morita. Institute of Science and Technology Austria, Klosterneuburg, Austria. Embryo morphogenesis relies on highly coordinated movements of different tissues. Yet, remarkably little is known about how tissues coordinate their movements to shape the embryo. In zebrafish embryogenesis, coordinated tissue movements become first apparent during ‘doming’ when the blastoderm begins to spread over the yolk sac, a process involving coordinated epithelial surface cell layer expansion and mesenchymal deep cell intercalations. Here, we find that active surface cell expansion represents the key process coordinating tissue movements during doming. By using a combination of theory and experiments, we show that epithelial surface cells not only trigger blastoderm expansion by reducing tissue surface tension, but also drive blastoderm thinning by inducing tissue contraction through radial deep cell intercalations. Thus, coordinated tissue expansion and thinning during doming relies on surface cells simultaneously controlling tissue surface tension and radial tissue contraction.

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