␣,␣-Trehalose is a disaccharide accumulated by many microorganisms, including rhizobia, and a common role for trehalose is protection of membrane and protein structure during periods of stress, such as desiccation. Cultured Bradyrhizobium japonicum and B. elkanii were found to have three enzymes for trehalose synthesis: trehalose synthase (TS), maltooligosyltrehalose synthase (MOTS), and trehalose-6-phosphate synthetase. The activity level of the latter enzyme was much higher than those of the other two in cultured bacteria, but the reverse was true in bacteroids from nodules. Although TS was the dominant enzyme in bacteroids, the source of maltose, the substrate for TS, is not clear; i.e., the maltose concentration in nodules was very low and no maltose was formed by bacteroid protein preparations from maltooligosaccharides. Because bacteroid protein preparations contained high trehalase activity, it was imperative to inhibit this enzyme in studies of TS and MOTS in bacteroids. Validamycin A, a commonly used trehalase inhibitor, was found to also inhibit TS and MOTS, and other trehalase inhibitors, such as trehazolin, must be used in studies of these enzymes in nodules. The results of a survey of five other species of rhizobia indicated that most species sampled had only one major mechanism for trehalose synthesis. The presence of three totally independent mechanisms for the synthesis of trehalose by Bradyrhizobium species suggests that this disaccharide is important in the function of this organism both in the free-living state and in symbiosis.Trehalose is a nonreducing disaccharide with an unusual ␣,␣-1,1 linkage between the two glucose molecules. Trehalose is commonly found in fungi, Saccharomyces cerevisiae, some bacteria, and insects, and it serves a variety of roles in these organisms. In many organisms it serves to protect membranes and proteins under a variety of stress conditions such as desiccation, cold, and heat (5).The biosynthesis of trehalose is remarkable in that three completely independent mechanisms for synthesis have been reported. The first involves the formation of trehalose-6-phosphate from UDP-glucose and glucose-6-phosphate. This enzyme, trehalose-6-phosphate synthetase (TPS), has been extensively studied in a wide range of organisms, and only a few examples of early publications are provided here (2, 4, 11, 21); more-recent references to TPS are available in the recent review by Elbein et al. (5). The product of TPS (trehalose-6-phosphate) is subsequently dephosphorylated to form trehalose. TPS functions with various nucleotide phosphate derivatives of glucose, and polyanions such as heparin are strong activators of TPS with some NDP-glucose substrates (11,20). The presence of TPS has previously been reported in studies of Bradyrhizobium japonicum and B. elkanii, the organisms of interest here, although the levels of activity were low (22).The second mechanism involves conversion of maltooligosaccharides to maltooligosyl trehalose by intramolecular transglucosylation of the terminal g...

A multi-agent system based on behaviour for controlling the navigation task of a mobile robot in office-like environments is presented. The set of agents is structured into a three-layer hybrid architecture. A high level of abstraction plan is created using a topological map of the environment in the Deliberative layer. It is composed by the sequence of rooms and corridors to traverse and doors to cross in order to reach a desired room. The Execution and Monitoring layer translates the plan into a sequence of available skills in order to achieve the desired goal and monitors the execution of the plan. In the Control layer there is a set of agents that implements fuzzy and visual behaviours that run concurrently to guide the robot. Fuzzy behavior manages the vagueness and uncertainty of the range sensor information allowing to navigate safely in the environment. Visual behavior locates a required door to cross and fixate it, indicating the appropriate direction to reach it. Artificial landmarks are placed beside the doors to show its position. The system has been implemented in a Nomad 200 mobile robot and has been validated in numerous experiments in a real office-like environment.

This paper presents a novel approach for continuous gesture recognition using depth range sensors. Our approach can be seen as an extension of Motion Templates [1] using multiple layers that register the three-dimensional nature of the human gestures. Our Multi-Layered templates are created using depth silhouettes, the extension of binary silhouettes when depth information is available. Both the original Motion Templates and our extension have been tested using several classification approaches in order to determine the best one. These approaches include the use of Hu-moments (originally employed in [1]), PCA and Support Vector Machines. Finally, we propose a methodology for creating a continuous gesture recogniser using motion templates. The methodology is applied both to our representation approach and to the original proposal. In order to validate our proposal, several stereo-video sequences have been recorded showing eight people performing a total of ten different gestures that are prone to be confused when monocular vision is used. The conducted experiments show that our proposal performs a 20% better than the original method. This work has been partially supported by the Spanish MEC project TIN2006-05565 and Andalusian Regional Government project TIC1670.