Anti-infectives

Ecological theory suggests that antimicrobial cycling will not reduce antimicrobial resistance in hospitals Bergstrom, C. T. et al. Proc. Natl Acad. Sci. USA (August 12 2004) doi:10.1073/pnas.0402298101

Going to hospital should solve medical problems, but the spectre of hospital-acquired infections by antibiotic-resistant bacteria is an increasing concern. Bergstrom et al. have developed a mathematical model to test whether a common tactic of healthcare practioners to reduce resistance — cycling of antibiotics — will be effective. Simulations showed that, theoretically, cycling won't reduce the evolution or spread of antibiotic resistance. A different strategy — treating patients with one of several concurrently used antibiotics — was predicted to be successful in preventing resistance. The authors propose that the latter regime provides a more heterogeneous mixture relative to bacterial populations than cycling, thereby reducing instances of resistance.

Virus structure

Three dimensional rearrangement of proteins in the tail of bacteriophage T4 on infection of its host. Leiman, P. G. et al. Cell 118, 419–429 (2004)

Studying phage built the foundations of molecular biology and there is considerable genetic and biochemical information available for these viruses. Leiman et al. have produced a 17-Å three-dimensional reconstruction of the chemically contracted tail of T4 phage using cryo-EM. Analysis of this structure, together with previously solved structures of the hexagonal baseplate, tail and head proteins allowed the structural rearrangements that occur during tail contraction to be visualized for the first time. The baseplate changes from a hexagonal to a star shape, which causes the sheath surrounding the tail tube to contract. After the tail tube protrudes from the baseplate, it pierces the outer and inner cell membranes before viral DNA injection. Biologists can now 'see' the structural transitions that the tail undergoes after surface attachment owing to two excellent movies that accompany this paper.

Bacterial physiology

Complex formation of Vipp1 depends on its α-helical PspA-like domain Aseeva, E. et al. J. Biol. Chem. 279, 35535–35541 (2004)

Assembling a thylakoid membrane in cyanobacteria and chloroplasts requires Vipp1. Cyanobacteria have a second vipp1 allele (pspA) that is conserved in some bacteria and is induced by a range of stresses. How these important proteins function isn't yet clear, but PspA seems to assist in secretion of proteins across the bacterial membrane. Using negative-staining EM and biochemical tools, Aseeva et al. show that Vipp1, in common with PspA, forms a huge complex — 400 Å × 140 Å — that is composed of ring assemblies of Vipp1 dimers. These proteins might have more similar functions than previously suspected.