[en] We have developed a new technology, the High Voltage Atmospheric Pressure Pulsed Plasma (HVAPPP), for bacteria killing. The aim of this paper is to present a simple device to generate plasma able to kill efficiently bacteria

[en] This study was conducted to evaluate the combined effect of gamma irradiation and different conditions (vacuum packaging, antioxidant and freezing) on the microbiological and sensory characteristics of freeze dried Manila clam porridge (MCP) for immuno-compromised patient food. McP can be sterilized at 1 kGy to 10 kGy. the initial counts of total aerobic bacteria and yeast molds in the non-irradiated MCP were 2.4±0.5 and 1.2±0.3 log CFU g"-'1, respectively, but gamma irradiation significantly decreased the total aerobic bacteria to below the detection limit (1 log CFU g"-"1) (5 kGy). Moreover, gamma irradiation effectively eliminated yeasts/molds at dose below than 1 kGy. However, gamma irradiation accelerated the increase of lipid oxidation and therefore, decreased the sensory characteristics of MCP as irradiation dose increased. to improve the sensory qualities of gamma irradiated MCP, combination treatment (vacuum packaging, 0.1% vitamin c) were applied. there was no significant difference in the overall acceptance scores between the combined-treatment sample (5.6 points) and the non-irradiated samples (6.0). the results indicate that combination treatment (vacuum packaging, 0.1% vitamin c) may help to maintain the quality of MCP. therefore, it considered that irradiation of MCP with combined treatment and this is an effective method for the consumption as a special purpose food such as for space travel or immuno-compromised patients

[en] We study the emergence of cell differentiation under the influence of tradeoffs between the different functions the cell needs to perform. In the model, the viability of a given colony, i.e. the chance to survive and then form propagules, is determined by the capability of its lower level units to perform different functions. Due to the existence of tradeoffs, it can be evolutionarily advantageous for the colony to evolve the division of labor whereby the cells can suppress their contributions to some of the activities through the activation of regulatory genes. Our simulation results show that cell differentiation is more likely as the number of tradeoffs increases, but the outcome also depends on their strength. We observe the existence of critical values for the minimum number of tradeoffs and their strength beyond that maximum cell differentiation can be attained. The occurrence of a maximum tradeoff strength beyond which the population is no longer viable imposes an upper level of constraint to the system. This maximum tradeoff strength decreases with the number of tradeoffs. Besides the statistical study of the model, as a concrete example, we apply the model to a simplified cyanobacteria system. In this line, variations of this model can be applied to a variety of systems when the underlying tradeoffs are known or can be estimated. (paper: biological modelling and information)

[en] Short communication

[en] Sharp chemoattractant (CA) gradient variations near food sources may give rise to dramatic behavioral changes of bacteria neighboring these sources. For instance, marine bacteria exhibiting run-reverse motility are known to form distinct bands around patches (large sources) of chemoattractant such as nutrient-soaked beads while run-and-tumble bacteria have been predicted to exhibit a ‘volcano effect’ (spherical shell-shaped density) around a small (point) source of food. Here we provide the first minimal model of banding for run-reverse bacteria and show that, while banding and the volcano effect may appear superficially similar, they are different physical effects manifested under different source emission rate (and thus effective source size). More specifically, while the volcano effect is known to arise around point sources from a bacterium’s temporal differentiation of signal (and corresponding finite integration time), this effect alone is insufficient to account for banding around larger patches as bacteria would otherwise cluster around the patch without forming bands at some fixed radial distance. In particular, our model demonstrates that banding emerges from the interplay of run-reverse motility and saturation of the bacterium’s chemoreceptors to CA molecules and our model furthermore predicts that run-reverse bacteria susceptible to banding behavior should also exhibit a volcano effect around sources with smaller emission rates. (paper)

[en] Poster presentation

[en] We study the formation of spot patterns seen in bacterial colonies when the bacteria are subjected to oxidative stress due to hazardous by-products of respiration. The cell density is coupled to a chemoattractant concentration as well as to nutrient and waste fields. The model combines the propagation of a front of motile bacterial radially outward from an initial site, a Turing instability of the uniformly dense state, and a reduction of motility for cells sufficiently far behind the front. The wide variety of patterns seen in the experiments is reproduced by the model by varying the details of the initiation of the chemoattractant emission as well as the transition to a nonmotile phase

No abstract available

[en] We investigate cellular response to extracellular signals by using information theory techniques motivated by recent experiments. We present results for the steady state of the following gene regulatory models found in both prokaryotic and eukaryotic cells: a linear transcription-translation model and a positive or negative auto-regulatory model. We calculate both the information capacity and the mutual information exactly for simple models and approximately for the full model. We find that (1) small changes in mutual information can lead to potentially important changes in cellular response and (2) there are diminishing returns in the fidelity of response as the mutual information increases. We calculate the information capacity using Gillespie simulations of a model for the TNF-α-NF-κ B network and find good agreement with the measured value for an experimental realization of this network. Our results provide a quantitative understanding of the differences in cellular response when comparing experimentally measured mutual information values of different gene regulatory models. Our calculations demonstrate that Gillespie simulations can be used to compute the mutual information of more complex gene regulatory models, providing a potentially useful tool in synthetic biology. (paper)

[en] This is a book of abstracts of oral communications and posters that were presented during the International Symposium on Biotechnology that was held in Sfax, Tunisia from May 4th to 8th, 2008. The following themes were covered : - Biotechnology for animal and human health and biopharmaceuticals; - Microbial and environmental biotechnology; - Agricultural, Food and marine biotechnology