Transmissible spongiform encephalopathies (TSEs) are rare, but always fatal, neurodegenerative disorders of humans and other mammals. They are characterized by long incubation periods, spongiform changes in the brain associated with loss of neurons, and the absence of host responses. TSEs are caused by infectious proteins called prions. Insight into how prions cause TSEs comes from the observation that …
A study of sexual transmission of Zika virus among mice (link to paper) demonstrates beautifully that viral nucleic acid detected by polymerase chain reaction (PCR) is not the same as infectious virus. Male mice were infected with Zika virus and then mated with female mice. Efficient sexual transmission of the virus from males to females was observed. This …
Bacteriophages are the most abundant biological entities on Earth. There are 1031 of them on the planet, and they infect 1023 to 1025 bacteria every second. That’s a lot of lysis, and it leads to the release of huge quantities of DNA that can be taken up by other organisms, leading to new traits. It …
Bacteria do not develop transmissible spongiform encephalopathies, but they have been found to produce prions – proteins that can adopt alternative conformations with different functions. Prion diseases, a frequent topic on this blog, are caused by misfolding of a normal cellular prion protein (illustrated; image copyright ASM Press). Prion proteins are found in other organisms, where the alternative conformation …
You might recall learning in high school biology that bacteriophage infection of a host can lead to either replication and cell lysis, or integration of the viral genome into the host (illustrated). The latter event, called lysogeny, spares the host from virus induced killing. For some phages, the decision between lysis and lysogeny appears to be communicated …
A unique feature of eukaryotic cells, which distinguishes them from bacteria, is the presence of a membrane-bound nucleus that contains the chromosomal DNA (illustrated; image credit). Surprisingly, a nucleus-like structure that forms during viral infection of bacteria is the site of viral DNA replication (link to paper). During infection of Pseudomonas bacteria with the phage 2O1phi2-1, a …
