Chemotaxis system

Phytochrome is found not only in higher plants but also in algae, where it controls the movement of chloroplasts,611 and also in cyanobacteria.623 54 Cyano-bacterial phytochromes contain histidine kinase domains, which may function in a two-component system with a response regulator similar to protein CheY of the chemotaxis system in E. coli (Fig. 19-5).624/625 Some nonphotosynthetic bacteria also use bacteriophytochromes for light sensing. In some cases biliverdin (Fig. 24-24) is the chromophore.6253... 

Match the major components of the chemotaxis system of E. coli in the left column with the appropriate descriptions from the right column. 

Table 1 summarizes the advantages and disadvantages of established chemotaxis assays, including microfluidic methods. In the following sections, we discuss methods for developing two new types of microfluidic chemotaxis systems (1) a pPlug model... 

This book reviews some of the best-characterized chemotaxis systems, from bacteria to human eells. In so doing, the book demonstrates how basic chemotaxis is to life, how widespread it is, and how versatile its physiologieal funetions are. The book attempts to present the state of the art of a number of representative molecular mechanisms of chemotaxis, to indicate unanswered questions surrounding each mechanism, and to suggest future direetions for researeh. In some systems, the implications for health eonditions are diseussed. Thus, in the next chapter (Chapter 2), Joseph Lengeler surveys the systems and ph enomena in which chemotaxis appears to have a role. Some issues... 

This publication is aimed to serve as both a textbook for beginners and a reference book for professionals. For easier reading, each chapter that reviews a certain chemotaxis system follows a standard scheme it starts with a description of the motility mechanism specific to the system (motility is a prerequisite for chemotaxis) and ends with a description of how this motility is modulated by chemotaxis. 

The chemotaxis receptors for PTS carbohydrates are enzymes II [10]— membrane proteins that transport certain hexoses, hexosamines, polyhy-dric alcohols, and disaccharides [582, 602]. The mechanism of transport involves activation of enzyme II by phosphorylation, carried out by two cytoplasmic protein kinases enzyme I and histidine-containing protein (HPr) [582], Unlike the case of the periplasmic binding proteins, the PTS primary receptor—enzyme II—does not interact directly with an MCP As will be discussed in Section 8.2.7, it is enzyme I which links the occupancy of enzyme II with the chemotaxis system. 

CheZ is a unique protein that, of the known bacterial chemotaxis systems and two-component regulatory systems, exists only in chemo-tactic enteric bacteria such as E. coli and Salmonella [494] as well as in P. aeruginosa [339, 709]. Its role is to enhance CheY P dephosphorylation [293]. (The term phosphatase is used in this chapter to describe, in the broader sense, the activity of CheZ. It does not connote the mechanism of CheZ action.) CheZ does so with a high specificity, as evident from its failure to dephosphorylate CheB [293], even though the N-terminal portion of the latter is homologous to CheY as a whole [696]. Initially it was assumed, on the basis of second-site suppression analysis in which mutations in cheZ were phenotypically suppressed by... 

Loake, G.J., Ashby, A.M. and Shaw, G.H. (1988). Attracdon of Agrobacterium tumefaciens C58G towards sugars involves a highly sensitive chemotaxis system. J. Gen. Microbiol. 134,1427-1432. 

M. mnthus development. The key to bacterial coordinated behavior resides in the ability of a cell to receive, interpret, and respond to these signals. Relaying the information may require direct contact between the donor and the recipient cells or it may be carried out from a distance, i.e., by means of diffusible molecules, which are detected through their interaction with specific receptors. As discussed in Chapter 3, bacterial chemotaxis is the most completely understood of the bacterial sensory transduction systems. While the role of chemotaxis in intercellular communication is still not clear, in some cases, mutants deleted for chemotaxis genes fail to carry out one or another of the processes mentioned above. Components of the chemotaxis system seem to play a role in swarming motility, pattern formation, and myxobacterial development. In fact, it appears that certain chemotaxis functions have been recruited by certain species to mediate intercellular communication. In this chapter, we review some examples, and provide evidence as well as hypotheses concerning a role for proteins and systems involved in chemotaxis in multicellular behavior. 

Chemotaxis Systems in Bacterial Swarming 3.1. Swarming motility... 

Burkart, M., Toguchi, A. and Harshey, R.M. (1998). The chemotaxis system, but not chemotaxis, is essential for swarming motflity in Escherichia coli. Proc. Natl. Acad. Sci. U.S.A. 95, 2568-2573. 

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