Volume 6 Issue 3, March 2008

The influence of the microbiome on human development, physiology, immunity and nutrition is almost entirely unknown. A new National Institutes of Health initiative aims to address this deficit.

CRISPR systems, which are composed of direct repeats that are separated by similarly sized non-repetitive spacers, confer resistance to phages in many bacteria and most archaea. This new antiviral tactic is thought to involve an RNA-interference-like mechanism, and is reviewed in this Progress article.

Leah Cowen reviews the mechanisms that potentiate the evolution of fungal drug resistance, with an emphasis on the central role of the molecular chaperone heat shock protein 90 (Hsp90) in altering the relationship between genotype and phenotype in an environmentally contingent manner, which thereby 'sculpts' the course of evolution.

Stewart and Franklin discuss the processes that generate chemical gradients in biofilms, the genetic and physiological responses of the bacteria as they adapt to these gradients and the techniques that can be used to visualize and measure microscale physiological heterogeneities of bacteria in biofilms.

Knipe and Cliffe review the mechanisms that underlie the switch from a lytic to a latent infection in the widespread pathogen herpes simplex virus (HSV). They propose a new model in which an epigenetic switch determines whether a lytic or a latent infection occurs and discuss viral functions that might regulate chromatin assembly on the HSV genome and effect this epigenetic switch.

Bacteria can precisely adjust their membrane lipid compositions to control the biophysical properties of their membranes, which allows them to thrive in various physical environments. Here, Charles Rock and Yong-Mei Zhang review the biochemical processes that are responsible for bacterial membrane lipid homeostasis.

The insertion of proteins into the bacterial cytoplasmic membrane is a complex and dynamic process. Sophisticated translocases are responsible for decoding the topogenic sequences within membrane proteins that direct membrane protein insertion and orientation. Here, Xie and Dalbey highlight what is known about the role of the Sec and YidC translocases in the folding and insertion of bacterial membrane proteins.

The archaeal domain comprises two phyla, the Euryarchaeota and the Crenarchaeota. Phylogenetic and genomic analyses now show that mesophilic crenarchaeota should not be considered as crenarchaeota. Based on this, the authors advocate the creation of a third archaeal phylum, which they propose to name Thaumarchaeota (from the Greek 'thaumas', meaning wonder).