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Mechanobiology of Disease
Thursday Speaker Abstracts
30
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.