[
J Infect Dis,
2010]
BACKGROUND: The Liverpool epidemic strain (LES) of Pseudomonas aeruginosa is a particularly successful cystic fibrosis (CF) pathogen associated with transmissibility, increased patient morbidity, and, unusually, infection of the non-CF parents of a patient with CF. METHODS: Using assays for virulence-associated exoproducts, biofilm formation, Caenorhabditis elegans killing, and a murine model of acute respiratory infection, we compared the pathogenic behavior of representatives of 4 subtypes of the LES, including LES431, an isolate associated with the infection of a parent without CF. RESULTS: The quorum-sensing-defective lasR mutant LES400 produced less exoproduct and had less C. elegans killing activity than the other LES subtypes, which were represented by LES431, LESB58, and LESB65. LES431 was deficient in biofilm formation, compared with the other LES sub-types. The LES subtypes displayed a range of virulence in the mouse model, with LES431 being by far the most virulent. The genome-sequenced isolate LESB58, effective at establishing infections in a rat model of chronic infection, was the least virulent subtype in the murine acute infection model. CONCLUSIONS: LES isolates display widely variable pathogenic characteristics. LES431, associated with transmission to the non-CF parent of a CF patient, represents a "hypervirulent" subtype more adapted to acute infections than chronic infections.
Shimono K, Honda N, Hasegawa T, Takahashi M, Hashimoto N, Sudo Y, Hayashi S, Mizutani K, Miyauchi S, Yamamoto M, Takagi S, Yamashita K, Tsukamoto T, Murata T
[
J Biol Chem,
2016]
Thermophilic rhodopsin (TR) is a photoreceptor protein with an extremely high thermal stability and the first characterized light-driven electrogenic proton pump derived from the extreme thermophile Thermus thermophilus JL-18. In this study, we confirmed its high thermal stability compared with other microbial rhodopsins and also report the potential availability of TR for optogenetics as a light-induced neural silencer. The x-ray crystal structure of TR revealed that its overall structure is quite similar to that of xanthorhodopsin, including the presence of a putative binding site for a carotenoid antenna; but several distinct structural characteristics of TR, including a decreased surface charge and a larger number of hydrophobic residues and aromatic-aromatic interactions, were also clarified. Based on the crystal structure, the structural changes of TR upon thermal stimulation were investigated by molecular dynamics simulations. The simulations revealed the presence of a thermally induced structural substate in which an increase of hydrophobic interactions in the extracellular domain, the movement of extracellular domains, the formation of a hydrogen bond, and the tilting of transmembrane helices were observed. From the computational and mutational analysis, we propose that an extracellular LPGG motif between helices F and G plays an important role in the thermal stability, acting as a "thermal sensor." These findings will be valuable for understanding retinal proteins with regard to high protein stability and high optogenetic performance.