Cell envelope constituents of Pseudomonas putida contributing to growth and survival in low-water-content habitats

The ability of bacteria to respond to the ever changing environmental conditions they encounter requires the utilization of a broad range of colonization and survival strategies. One of the most important and probably least understood factors determining bacterial activity in terrestrial habitats is water availability. The goal of this dissertation research was to identify traits that contribute to maintaining a functional cell envelope when cells are dehydrated, which will help us to assess the scope of physiological changes necessary for growth in low-water-content habitats. The primary objective was to identify genes that are specifically regulated by dehydration (matric stress), and not by a thermodynamically-equivalent solute (osmotic) stress. We used transposon mutagenesis combined with a screen to identify genes in the soil and rhizosphere colonizing Pseudomonas putida strain mt-2. Although some of the w&barbelow;ater d&barbelow;eprivation-c&barbelow;ontrolled (wdc) genes were regulated by growth phase, temperature, or toluene exposure, most were specifically induced by matric stress, indicating that bacteria respond differently to a matric stress than to a solute stress. The knowledge of the function of these matric stress-regulated wdc genes allowed us to develop a model of tolerance mechanisms necessary for growth and survival in water-limited environments. Moreover, we found that most wdc loci contributed to survival in low-water-content habitats. One of the identified wdc genes encodes a putative periplasmic lysophospholipase, indicating that dehydration stress disrupts membrane integrity. We determined that lysophospholipids (LPL) accumulated in the wild type when grown under matric stress conditions, but not when grown in the absence of stress or under solute stress conditions. In contrast, the putative lysophospholipase-deficient mutant accumulated LPL even in the absence of a matric stress, indicating that this periplasmic lysophospholipase removes LPL. Exogenously supplied LPL was toxic to P. putida and the mutant was more sensitive than the wild type to LPL. Finally, we observed that biofilm cells are more desiccation-tolerant than planktonic cells and that matric stress is more stressful to cells than solute stress

Heterarchical control systems for production cells - a case study

Most control systems of flexible production cells have a hierarchical structure. They become very complicated and difficult to maintain and modify when the underlying production cells grow in size and complexity. Moreover, they are characterized by a relatively high sensitivity to failures. As opposed to that, heterarchical control systems are flexible, modular, easy to modify, and to some extent fault tolerant. In this paper, a heterarchical control system of a flexible production cell is formally specified in the CSP-based language chi . This language is well suited for the description of autonomous components cooperating with each other by exchanging informatio

Development and Validation of Functional Model of a Cruise Control System

Modern automobiles can be considered as a collection of many subsystems working with each other to realize safe transportation of the occupants. Innovative technologies that make transportation easier are increasingly incorporated into the automobile in the form of functionalities. These new functionalities in turn increase the complexity of the system framework present and traceability is lost or becomes very tricky in the process. This hugely impacts the development phase of an automobile, in which, the safety and reliability of the automobile design should be ensured. Hence, there is a need to ensure operational safety of the vehicles while adding new functionalities to the vehicle. To address this issue, functional models of such systems are created and analysed. The main purpose of developing a functional model is to improve the traceability and reusability of a system which reduces development time and cost. Operational safety of the system is ensured by analysing the system with respect to random and systematic failures and including safety mechanism to prevent such failures. This paper discusses the development and validation of a functional model of a conventional cruise control system in a passenger vehicle based on the ISO 26262 Road Vehicles - Functional Safety standard. A methodology for creating functional architectures and an architecture of a cruise control system developed using the methodology are presented.Comment: In Proceedings FESCA 2016, arXiv:1603.0837

Model-based testing with chi and TorX : a case study of the ASML laser subsystem

Within the TANGRAM project, a case study on model-based testing of the ASML laser subsystem has been performed. The approach used in the case study is based on the proposed model-based testing framework, instantiated with state-of-the-art tooling from the TANGRAM project partners: chi as specification language and TorX as test tool. A chi specification model of the laser state behavior and communication interface has been developed. After verification and validation, the model has been used for automatic model-based testing with TorX. Using this approach, discrepancies between the implementation and specification of the laser subsystem have been found