We did a lot of science communication in 2018. By we, I mean all the individuals who gave their time selflessly to write for this blog or record podcasts with me. Here is a summary of what we did last year.
All life forms on Earth harbor an array of genetic parasites, including viruses, plasmids, and transposons. Unfortunately, if cells could reduce their uptake of these elements, they would suffer as the entry of beneficial genes would be impaired (link to paper). In other words, genetic parasites are unavoidable.
Host behavior alteration by viruses is known to assist the development of another organism. An example is a parasitoid wasp that injects viruses along with eggs into a caterpillar. The viral genomes encode proteins that subvert the caterpillar immune response, allowing the wasp larva to develop. A similar strategy may enable safe development of a wasp byÂ a ladybeetle.
The parasitoid wasp D. coccinellae lays its eggs inside a ladybeetle. After 20 days of larval development, a prepupa emerges from the ladybeetle and fabricates a cocoon between the beetle’s legs. At the same time, the ladybeetle becomes paralyzed. It remains on top of the cocoon (pictured; image credit), protecting it until an adult wasp emerges. Remarkably, some ladybeetles then resumeÂ their normal lives!
Given what we know about how parasitoid viruses can alter the manipulation of their hosts, it was only logical to search for a virus that paralyzesÂ the ladybeetle. Sequencing of RNA from the heads of parasitized ladybeetles revealed the presence of an RNA virus which the authors call D. coccinellae paralysis virus, DcPV.Â The virus is a new member of a Iflaviruses, a family of picornavirus-like, (+) strand RNA viruses that infect insects. DcPV wasÂ found in wasps in Poland, Japan, and The Netherlands, confirming its cosmopolitain nature.
Viral particles were observed in cells lining theÂ wasp oviducts, but not in the lumen. Viral genomes were undetectable in wasp eggs, became more abundant during hatching, and ceased to replicate in adult wasps. The levels of virus in the ladybeetle abdomen and head increase with time to egress, suggesting that it was transmitted from the wasp larvae to the host. In ladybeetles where the wasp egg did not develop, viral replication does not occur.
DcPV appears to be neurotropic. Before larval egression, no changes were observed in the nervous system of the ladybeetle, but glial cells were full of virus particles. After egression, vaculoles developed in glial cells and neurons degenerated. This damage was less severe in beetles that survived and recovered from paralysis. An expansion of glial cells in these hosts might explain how normal brain functions were restored.
Insects respond to infection with an RNA-based antiviral response. Components of the RNA based immune system were down-regulated during larval development, possibly by viral proteins, allowing virus to invade the nervous system. Resumption of the antiviral reponse might enable recovery of the ladybeetle after emergenceÂ of the wasp.
It appears that DcPV is a wasp symbiont that manipulates the behavior of the ladybeetle host to ensure development of wasp offspring. This hypothesis can be tested by removing DcPV from infected wasps, or by adding DCpV to uninfected hosts, and determining the effect on larval development.
We now realize that animals are actually holobionts: an aggregate of eukaryotes, bacteria, and viruses. Therefore host-parasite interactions are really holobiont-holobiont interactions.
I started myÂ first podcast,Â This Week in Virology, in September 2008, together with Dickson Despommier, father of theÂ Vertical Farm. Although IÂ viewed the creation of a science podcast as an experiment, IÂ was surprised when people began to listen. Since then I haveÂ created fiveÂ other podcasts,Â scattered at different websites. Now you can find all of them atÂ MicrobeTV.
MicrobeTV is a podcast network for people who are interested in the life sciences. More specifically, the podcasts of MicrobeTV use conversations among scientistsÂ as teaching tools. Although I have been a research scientist my entire career, I have also had opportunities to teach graduate students, medical students, and undergraduate students. A long time ago I realized that I love to teach, and my podcasts are the outside-the-classroom expression of that sentiment.
My original idea behind TWiV was to teach virology to the broader public by recordingÂ conversations among scientists. The success of this approach led me to create This Week in Parasitism, This Week in Microbiology, Urban Agriculture, and This Week in Evolution, all of which can now be found at MicrobeTV.
You may ask why I do so many podcasts. The answer is simple – because I love talking about science and teaching others about this amazing field that makes our lives better. I could not do all these podcasts without my terrific co-hosts. I am also grateful to the American Society for Microbiology for their assistance and support for many years, especially Chris Condayan and Ray Ortega and the Communications Department.
MicrobeTV is the home for all of the podcasts that IÂ have producedÂ (and there are more to come!). But I’d also like to use MicrobeTV as a platform to showcase other science shows. The requirements are few: you should be passionate about your subject, you should have a great relationship with your audience, and your podcast audio mustÂ be excellent. If you are interested in joining MicrobeTV, send a note to firstname.lastname@example.org.
MicrobeTV – Science Shows by Scientists.
In the past five days we released three science shows on the TWi* network.
On This Week in Microbiology (TWiM) episode #51,Â Vincent, Michael, and Elio meet up with Hazel Barton to talk about cave microbiology.
On This Week in Parasitism (TWiP) episode #51,Â special guest Anthony A. James joins Vincent and Dickson to discuss how mosquitoes can be genetically modified to control infectious diseases.
On This Week in Virology (TWiV) episode #222, the complete TWiV team discusses the amazing finding that cyclic GMP-AMP synthase is a cytosolic innate immune DNA sensor.
Thanks for listening.
On episode #41 of the science show This Week in Parasitism, Vincent and Dickson review medically important arthropods.
You can find TWiP #41 at microbeworld.org/twip.