Copper homeostasis in Salmonella is atypical and copper-CueP is a major periplasmic metal complex.

Salmonella enterica sv. typhimurium (S. enterica sv. Typhimurium) has two metal-transporting P(1)-type ATPases whose actions largely overlap with respect to growth in elevated copper. Mutants lacking both ATPases over-accumulate copper relative to wild-type or either single mutant. Such duplication of ATPases is unusual in bacterial copper tolerance. Both ATPases are under the control of MerR family metal-responsive transcriptional activators. Analyses of periplasmic copper complexes identified copper-CueP as one of the predominant metal pools. Expression of cueP was recently shown to be controlled by the same metal-responsive activator as one of the P(1)-type ATPase genes (copA), and copper-CueP is a further atypical feature of copper homeostasis in S. enterica sv. Typhimurium. Elevated copper is detected by a reporter construct driven by the promoter of copA in wild-type S. enterica sv. Typhimurium during infection of macrophages. Double mutants missing both ATPases also show reduced survival inside cultured macrophages. It is hypothesized that elevated copper within macrophages may have selected for specialized copper-resistance systems in pathogenic microorganism such as S. enterica sv. Typhimurium.

Simulation in user-centred design: Helping designers to empathise with atypical users

Time and budget constraints frequently prevent designers from consulting with end-users while assessing the ease of use of the products they create. This has resulted in solutions that are difficult to use by a wide range of users, especially the growing older adult population and people with different types of impairments. To help designers with this problem, capability-loss simulators have been developed with the aim of temporarily representing users who are otherwise difficult to access. This paper questions the reliability of existing tools in providing designers with meaningful information about the users' capabilities. Consequently, a new capability-loss simulation toolkit is presented, followed by its empirical evaluation. The new toolkit proved to be significantly helpful for a group of designers identifying real usability problems with everyday devices. © 2012 Copyright Taylor and Francis Group, LLC.