ViroBlogy

See on Scoop.it – Virology and Bioinformatics from Virology.ca

“The flagellotropic phage 7-7-1 infects motile cells of Agrobacterium sp H13-3 by attaching to and traveling along the rotating flagellar filament to the secondary receptor at the base, where it injects its DNA into the host cell.”

This is an interesting paper, because it describes a phage infecting Agrobacterium – and touches on a subject that has intrigued me for years, which is: How does a phage which attaches to a flagellum, get its genome inside the cell?  This throws some mud onto a previous model, which suggested a passive mode of transport like a well-oiled nut moving towards the head of a bolt, as in this case that would result in transport the other way.  Expectr more on this topic!

Image sourced from the paper

See on www.virologyj.com

See on Scoop.it – Virology News

“Apicomplexans are an important group of pathogens that include the causative agents of malaria, toxoplasmosis, and cryptosporidiosis. These single-celled eukaryotic parasites evolved from photosynthetic algae. A remnant chloroplast, called the apicoplast, is a telltale hold-over from this more benign past in the ocean. 1The apicoplast is essential for parasite growth and development and therefore a potential target for drug therapy. The fact that humans and animals lack chloroplasts suggests that using approaches to target the apicoplast may provide parasite specificity. What are the critical functions of the apicoplast that should be targeted? In addition to the obvious medical relevance this question has broader biological implications. Why do organisms maintain an ancient symbiotic relationship when the initial rationale for this relationship has fallen by the evolutionary wayside? A new study by Yeh and DeRisi provides important clues. Their work demonstrates that antibiotic-induced loss of the apicoplast in cultured malaria parasites can be chemically rescued by providing isopentenyl-pyrophosphate (IPP) in the medium. IPP is generated by the apicoplast resident isoprenoid biosynthesis pathway and is apparently the one apicoplast metabolite that the parasite cannot live without in the red blood cell. This finding could be of great importance for the development of drugs and vaccines. The ability to produce and maintain parasite lines that lack the apicoplast also offers exciting experimental possibilities for the future.”

Great review – and malaria is important enough to be considered an honorary virus (B-), so it is appropriate to cover it here.  The review also illustrates yet another aspect of the fascinating evolutionary propensity for eukaryotic algae, themsleves the result of endosymbiosis between a photosynthetic prokaryote and a eukaryote, for themselves becoming endosymbionts.

See on www.plosbiology.org

See on Scoop.it – Virology News

“Imaging protein assemblies at molecular resolution without affecting biological function is a long-standing goal. The diffraction-limited resolution of conventional light microscopy (∼200–300 nm) has been overcome by recent superresolution (SR) methods including techniques based on accurate localization of molecules exhibiting stochastic fluorescence; however, SR methods still suffer important restrictions inherent to the protein labeling strategies. Antibody labels are encumbered by variable specificity, limited commercial availability and affinity, and are mostly restricted to fixed cells. Fluorescent protein fusions, though compatible with live cell imaging, substantially increase protein size and can interfere with their biological activity. We demonstrate SR imaging of proteins tagged with small tetracysteine motifs and the fluorescein arsenical helix binder (FlAsH-PALM). We applied FlAsH-PALM to image the integrase enzyme (IN) of HIV in fixed and living cells under experimental conditions that fully preserved HIV infectivity. The obtained resolution (∼30 nm) allowed us to characterize the distribution of IN within virions and intracellular complexes and to distinguish different HIV structural populations based on their morphology. We could thus discriminate ∼100 nm long mature conical cores from immature Gag shells and observe that in infected cells cytoplasmic (but not nuclear) IN complexes display a morphology similar to the conical capsid. Together with the presence of capsid proteins, our data suggest that cytoplasmic IN is largely present in intact capsids and that these can be found deep within the cytoplasm. FlAsH-PALM opens the door to in vivo SR studies of microbial complexes within host cells and may help achieve truly molecular resolution.”

Beautiful pictures, a great technique – and one which may allow ~1 nm resolution imaging inside cells in the near future.  Oh, and incidentally showed that HIV capsids persist all the way to the nuclear membrane.

See on www.pnas.org