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This paper explains the biophysical principles which, according to us, govern the Proteus mirabilis swarm phenomenon. Then, this explanation is translated into a mathematical model, essentially based on partial differential equations. This model is then implemented using numerical methods of the finite volume type in order to make simulations. The(More)
Following the analysis of the biochemical and functional properties of the P. mirabilis extra cellular matrix performed in the first part of this study, the viscoelasticity of an actively growing colony was investigated in relation to water activity. The results demonstrate that the P. mirabilis colony exhibits a marked viscoelastic character likely due to(More)
We mapped the space-time distribution of stationary and swarmer cells within a growing Proteus mirabilis colony by infrared (IR) microspectroscopy. Colony mapping was performed at different positions between the inoculum and the periphery with a discrete microscope-mounted IR sensor, while continuous monitoring at a fixed location over time used an optical(More)
Infrared fingerprints of molecules in biology contain much information on cells metabolism allowing one to distinguish between healthy and altered tissues. Here, to collect infrared signatures, we used evanescent wave spectroscopy based on an original infrared transmitting tapered glass fiber. A strict control of the fiber diameter in the tapered sensing(More)
Fiber evanescent wave spectroscopy (FEWS) explores the mid-infrared domain, providing information on functional chemical groups represented in the sample. Our goal is to evaluate whether spectral fingerprints obtained by FEWS might orientate clinical diagnosis. Serum samples from normal volunteers and from four groups of patients with metabolic(More)
The dynamics of bacterial colonies is complex in nature because it correlates the behavior of numerous individual cells in space and time and is characterized by emergent properties such as virulence or antibiotics resistance. Because there is no clear-cut evidence that periodic swarming of P. mirabilis colonies is ruled by chemical triggers responsible for(More)
Exopolysaccharides (EPS) were extracted from a sponge, Celtodoryx girardae recently discovered in the Golfe du Morbihan in 2000. Sponge samples were collected monthly from November 2007 to May 2008. SEC analysis of EPS samples showed that they exhibit a unique molecular weight of approximately 800 kDa. However, infrared analysis revealed that structural(More)
In most of oviparous animals, vitellogenins (VTG) are the major egg yolk precursors. They are produced in the liver under the control of estrogens. In rainbow trout (Oncorhynchus mykiss), the vtg genes cluster contains an unusually large number of almost identical gene copies. In order to identify the regulatory elements in their promoters, we used a(More)
It is getting increasingly evident that physical properties such as elastoviscoplastic properties of living materials are quite important for the process of tissue development, including regulation of genetic pathways. Measuring such properties in vivo is a complicated and challenging task. In this paper, we present an instrument, a scanning air puff(More)