This week in PLOS Biology

In PLOS Biology this week you can read about life without microbes, host-parasite coevolution, the temporal precision of distinguishing odours and how viruses package their genomes.

Life in a World without Microbes

According to Louis Pasteur, “Life would not long remain possible in the absence of microbes.” Or would it? In a new Perspective, Jack Gilbert and Josh Neufeld explore the challenges of a microbe-free existence. In doing so they hope to promote discussion about the value of microbial services supporting life on this planet. They explore the human gut microbiome, the scenario of a world without Bacteria and Archaea, and conclude with the implications of a world without all microbes, including microbial eukaryotes and viruses.

Parasitism Drives the Evolution of Complexity

It is obvious to any observer that evolution often proceeds towards increasing complexity. But when and why is greater complexity favoured? One hypothesis is that antagonistic coevolution between hosts and parasites drives this process by promoting evolutionary ‘arms races.’ As it would be incredibly difficult to examine this kind of evolution using conventional experiments, instead Luis Zaman, Charles Ofria & colleagues used the digital evolution of self-replicating computer programs in a scenario where hosts and parasites compete for processing power; their results show that coevolution promotes complexity and evolvability. Note that PLOS Biology featured a paper using a related digital evolution approach back in May

Smellyvision – Mice Perceive Odours with a Resolution of 13 Milliseconds

Different odours evoke different spatial patterns of activity in the odour-processing regions of the brain. For example, the timing of neuronal activity in a brain region called the olfactory bulb, relative to when an animal sniffs, conveys important information about odours. In a study published this week in PLOS Biology, Michelle Rebello, Justus Verhagen and collaborators provide evidence that the mammalian olfactory system is capable of very high rates of transmission of transient information. Using an innovative optogenetics approach, they found that mice can precisely discriminate virtual “odour movies” associated with patterns of neuronal activity that differed by as little as 13 ms. Read more in the synopsis.

Viral DNA-Packing Machine in the Corner

Chuan Hong, Wah Chiu & colleagues have used cryo-electronmicroscopy and modelling to tease apart how PRD1, a dsDNA membrane-containing virus, packages its genome. They characterise a unique vertex of this icosahedral virus, identifying the structure and function of a complex of proteins that forms a DNA-packaging motor and a transmembrane conduit which together serve to fill the viral particle with its genome. Check out the following stunning movies:

Movie S1: http://youtu.be/6daQvMfUnAw

Movie S2: http://youtu.be/g554Q0kCYzI

Movie S3: http://youtu.be/WhzvuL9lgTw