Bacterial pathogenicity

The intracellular fate of Salmonella depends on the recruitment of kinesin Boucrot, E. et al. Science 308, 1174–1178 (2005)

Salmonella enterica serovar Typhimurium (S. typhimurium) replicates in host cells within a Salmonella-containing vacuole (SCV). S. typhimurium uses a type III secretion system (TTSS) encoded on a pathogenicity island to secrete effector proteins from the SCV into host cells. In a recent Science paper, Emmanuel Boucrot and colleagues report the results of their investigations into the specific role of one of these secreted effector proteins, SifA. Using a yeast two-hybrid screen, a host-cell SifA-binding protein named SKIP was identified. Analysis of the SifA–SKIP interaction in cultured cells showed that SKIP is recruited to the SCV in a SifA-dependent manner. Further work revealed that the recruitment of the molecular motor kinesin to SCVs requires a functional TTSS and is negatively regulated by SifA through SKIP.

Vaccines

Protection against P. aeruginosa with an adenovirus vector containing an OprF epitope in the capsid Worgall, S. et al. J. Clin. Invest. 115, 1281–1289 (2005)

Infections with Pseudomonas aeruginosa are particularly prevalent in cystic fibrosis patients and, as yet, no vaccine is available. In the latest issue of the Journal of Clinical Investigation, Worgall et al. report promising results in mice with a novel adenovirus-based anti-P. aeruginosa vaccine. The vaccine was constructed by incorporating immunogenic epitopes from the surface-exposed P. aeruginosa outer-membrane protein OprF into the capsid of replication-deficient adenovirus vectors. After assessing the humoral response, a candidate vaccine that contains OprF epitope 8 was taken forward and was shown to stimulate a detectable serum anti-OprF and anti-P. aeruginosa response and to induce protection against lethal pulmonary challenge with P. aeruginosa. Additionally, the anti-P. aeruginosa immune response could be boosted by repeated administration of the vaccine.

Fungal physiology

Leptosphaeria rhodopsin: bacteriorhodopsin-like proton pump from a eukaryote Waschuk, S. et al. Proc. Natl Acad.Sci USA 102, 6879–6883 (2005)

The retinal-containing membrane protein bacteriorhodopsin was first identified in Archaea more than 30 years ago. The hypothesis that this form of light-driven proton pumping was confined to the Archaea was disproved by some of the first environmental genomic surveys, which identified a similar light-driven proton pump, proteorhodopsin, in marine bacteria. Now, researchers have obtained direct experimental evidence that the rhodopsin present in the fungus Leptosphaeria maculans, the causative agent of blackleg in canola, a rapeseed cultivar, can act as a light-driven proton pump. Interestingly, Waschuk and colleagues comment that that the physiological function of the rhodopsin in L. maculans might not be bioenergetic, and that 'light-induced acidification of some cell compartments could be used to activate certain biochemical responses'.