Bacterial diseases cause millions of deaths every year. Most of these bacteria were benign at some point in their evolutionary past, and we don’t always understand what turned them into disease-causing pathogens. In a new study, researchers have tracked down when this switch happened in one flesh-eating bacteria. They think the knowledge might help predict future epidemics. [more inside]
The Hidden Life Of the Cell (57:24) There is a battle playing out inside your body right now. It started billions of years ago and it is still being fought in every one of us every minute of every day. It is the story of a viral infection - the battle for the cell. This film reveals the exquisite machinery of the human cell system from within the inner world of the cell itself - from the frenetic membrane surface that acts as a security system for everything passing in and out of the cell, the dynamic highways that transport cargo across the cell and the remarkable turbines that power the whole cellular world to the amazing nucleus housing DNA and the construction of thousands of different proteins all with unique tasks. The virus intends to commandeer this system to one selfish end: to make more viruses. And they will stop at nothing to achieve their goal. Exploring the very latest ideas about the evolution of life on earth and the bio-chemical processes at the heart of every one of us, and revealing a world smaller than it is possible to comprehend, in a story large enough to fill the biggest imaginations.
You may be familiar with molecular movies from my two previous megaposts collecting them, but this extended documentary uses original animation that is collected into a coherent educational narrative and is just so fucking gorgeous. Enjoy.[more inside]
Does just what it says on the tin,
"So, naturalists observe, a flea has smaller fleas that on him prey; and these have smaller still to bite ’em; and so proceed ad infinitum." - Jonathan Swift
The Norovirus: A Study in Puked Perfection, "Each norovirus carries just nine protein-coding genes (you have about 20,000). Even with that skimpy genetic toolkit, noroviruses can break the locks on our cells, slip in, and hack our own DNA to make new noroviruses. The details of this invasion are sketchy, alas, because scientists haven’t figured out a good way to rear noroviruses in human cells in their labs. It’s not even clear exactly which type of cell they invade once they reach the gut. Regardless of the type, they clearly know how to exploit their hosts. Noroviruses come roaring out of the infected cells in vast numbers. And then they come roaring out of the body. Within a day of infection, noroviruses have rewired our digestive system so that stuff comes flying out from both ends." [more inside]
One of the many problems farmers of various kinds of legumes need to deal with is the pea aphid. They reproduce incredibly fast and live by sucking the sap out of the plants, an electron micrograph of one in action. However, while they are terrifying parasites of legumes, they have their own yet more horrific parasites, a parasitoid wasp. Here is a really nice close up picture of one doing its thing, a video of the act, and here is a brain meltingly horrific video of a dissection of the mummified aftermath 8 days later. Essentially, these wasps deposit their eggs in a pea aphid and the growing larva feeds on it, developing there for about a week, and then consuming the host from the inside out like a Xenomorph. When it’s done, the wasp larva dries the aphid’s cuticle into a papery brittle shell and an adult wasp emerges from the aphid mummy. Legume farmers love them, and you can even order their mummies online these days. However, farmers noticed that the wasps didn't work as effectively on all of the aphids, and so researchers went to work figuring out why. It turns out that all aphids have a primary bacterial endosymbiont living inside their cells, in addition to and just like a mitochondria, and that many have some combination of five other secondary endosymbionts. Interestingly, two of those other five, Hamiltonella defensa and Serratia symbiotica have been shown to confer varying levels of resistance to the parasitoid wasp, allowing the aphid to survive infection. However, it turns out that there is yet one more layer to this story, [more inside]
"Why do parasites harm their hosts? Conventional wisdom holds that because parasites depend on their hosts for survival and transmission, they should evolve to become benign, yet many parasites cause harm. Theory predicts that parasites could evolve virulence (i.e., parasite-induced reductions in host fitness) by balancing the transmission benefits of parasite replication with the costs of host death. This idea has led researchers to predict how human interventions—such as vaccines—may alter virulence evolution, yet empirical support is critically lacking." Two papers demonstrate empirical evidence for related models predicting the origin of virulence: [more inside]
Evolutionary biologist Paul Ewald, author of The evolution of infectious disease and an expert on the development of pathogen virulence (see this, this and this for a good intro), responds to this editorial in Scientific American and pours cold water on fears of pandemic influenza.