Blue bacteriophage
Image by NextGenRnD: https://nextgenrnd.com/insights/insight-no-1/

Bacteriophages (phages) are viruses that infect bacteria. Phage research led to ground-breaking discoveries illuminating how genetic information is stored, transferred, controlled (lysogeny), and protected (restriction and CRISPR/Cas systems). Restriction enzymes made genetic engineering possible, whereas phage display technology allowed the development of target-specific antibody medicines. Phages and technologies such as phage display have an enormous potential that has not yet been fully realized in medicine, diagnostics, and materials science/engineering.

In this insight, we would like to ask a very simple question — what is the color of the phage? This question sparked our attention when we came across several papers published from 1967 through 1970 mentioning the blue phage band. Since then, the mysterious blue band of phage had been spoken about in some publications but had never been demonstrated.

To see the blue phage band, researchers used a method called equilibrium sedimentation in density gradients introduced in 1957 and fully developed in 1963. In particular, a transparent tube is filled with 4–7 layers of cesium chloride (CsCl) solutions atop each other (typically, using Pasteur pipettes). The bottom layer has the highest density, whereas the top layer has the lowest density of CsCl. In this way, a discontinuous CsCl step density gradient is formed. Then, a sample containing phage is layered on top of this gradient, the tube is placed into a metal bucket, which is attached to a swinging-bucket rotor, which is spun for 1 hour in an ultracentrifuge at a speed of 40,000 revolutions per minute roughly corresponding to a relative centrifugal force of 200,000 g. As a result, the phage particles migrate toward the bottom of the tube and concentrate to form a band in the CsCl layer with a density equal to the (buoyant) density of the phage particles. Hence, the equilibrium sedimentation is achieved.

The photograph shows the result of such an equilibrium sedimentation experiment. Indeed, the phage particles are seen as a blue band. There are actually two blue bands. The lower, major one, contains at least 10¹³ infectious phage particles. The faint blue band seen above is not infectious as the capsids of the phages with this particular buoyant density are devoid of genetic material (they are empty). Finally, there is a thick pale white layer of cellular debris.

We have just demonstrated that the phage band is blue. This, however, begs two other questions related to the phage band: (1) why is it bright? and (2) why is it blue?…

Read the story in full here: https://nextgenrnd.com/insights/insight-no-1/
['Andrei Nikonov']
['Biotechnology', 'Short Story', 'Technology', 'Science', 'Virus']