Small Things Considered

Where in the world is ERV-Fc? Tracing the spread of a virus over 30 million years, 28 species, and 5 continents.

by Zachary Williams | When doctors in the 1980s noticed that people were dying from severe immune deficiency, nobody had ever seen anything like it before; it was a completely novel and terrifying disease. Once we figured out it was caused by a virus, the natural question was, where did it come from? It turns out that HIV was the result of zoonosis: the transmission of a pathogen to humans from other animals Read more →

Parasites, Predators, and Piggyback Rides

by J. Jeffrey Morris | In the adorable kid's book My Lucky Day, a wily and disarmingly cute piglet tricks a fearsome fox into giving him a spaghetti dinner, a bath, and a massage. In the end, Mr. Pig slips away after Mr. Fox passes out from exhaustion. We later learn that, far from being an innocent... Read more →

Need protection? Hire a virus! – Part Deux

by Jamie Henzy | Readers of STC are likely aware that sequences from viruses infecting a host can sometimes wind up inserted into the host chromosomal DNA, even being passed on to offspring if the insertion occurs in an egg or sperm cell. This happens most frequently with retroviruses, which insert into host DNA as part of their replication strategy; consequently "endogenous" retrovirus (ERV) sequences comprise some 8% of the human genome (for perspective, compare this with ~2% of the genome that codes for proteins!) Read more →

Van Leeuwenhoek's freshwater microorganisms in 1674.Spirogyra or Anabaena ?

by Nanne Nanninga | As will be argued below the present definition of a prokaryote is highly unsatisfactory. To give an example: a prokaryote is "a cell or organism lacking a nucleus and other membrane-enclose organelles, usually having its DNA in a single circular molecule" (Brock, Biology of Microorganisms, 10th Ed.). This seems a summary of the original definition of Stanier & van Niel (1962), which I quote for the sake of completeness... Read more →

Active Lysogeny Regulatory Switches: Scars That Can Make Genes Whole

by Daniel P. Haeusser | Last year Small Things Considered was hurt by the loss of one of our regular contributors, Marvin Friedman, who had a strong passion and joy for microbiology and this blog. I found myself looking through some of his featured pieces in remembrance and was intrigued by one that discussed developmentally regulated prophage excision. Read more →

Need Protection? Hire a Virus!

by Jamie Henzy | Is there any denying that pregnancy is a form of parasitism? The developing organism originates at least in part from outside the host (in sexually reproducing creatures, at least), and mediates the rerouting of nutrient supplies at the host's expense. In the case of mammals (and many other classes), where the ... Read more →

Pictures Considered #33. Viral Abundance and Diversity.

by Elio | This picture should hang as a poster in every microbiological lab that is concerned with viruses (and which one isn't, one way or another?). It shows how diverse the viruses that affect hosts of the three domains of life actually are, both in replication strategy and morphology. I confess, ... Read more →

By the Numbers: Viral Burst Size

by Rob Phillips and Ron Milo | Viruses proliferate by infecting cells and hijacking their replication and protein synthesis machinery. After new viral proteins are synthesized and assembled, bursts of viruses are released from the infected (and usually soon to be dead) cells, starting the process all over again... Read more →

Phage Responses to the SOS Response

by Merry Youle | No matter where a bacterium lives, its DNA is sometimes damaged by UV radiation, reactive oxygen species (ROSs), toxins, or other nasty things. Faced with such assaults, as well as problems inherent in DNA replication, bacteria evolved sophisticated mechanisms to detect and repair DNA damage. One widely conserved system, the SOS response, was first... Read more →

An ongoing phage drama

by Jamie Henzy | Life is full of tough choices. Some of the more dramatic of them play out in the world of bacteria and the phages that infect them... Read more →