Transient electric birefringence of the bacteriophages T3 and T7

The Effect of Zero-Valent Iron Nanoparticles (nZVI) on Bacteriophages

Bacteriophages are viruses that attack and usually kill bacteria. Their appearance in the industrial facilities using bacteria to produce active compounds (e.g., drugs, food, cosmetics, etc.) causes considerable financial losses. Instances of bacteriophage resistance towards disinfectants and decontamination procedures (such as thermal inactivation and photocatalysis) have been reported. There is a pressing need to explore new ways of phage inactivation that are environmentally neutral, inexpensive, and more efficient. Here, we study the effect of zero-valent iron nanoparticles (nZVI) on four different bacteriophages (T4, T7, MS2, M13). The reduction of plaque-forming units (PFU) per mL varies from greater than 7log to around 0.5log depending on bacteriophages (M13 and T7, respectively). A comparison of the importance of oxidation of nZVI versus the release of Fe2+/Fe3+ ions is shown. The mechanism of action is proposed in connection to redox reactions, adsorption of virions on nZVI, and the effect of released iron ions. The nZVI constitutes a critical addition to available antiphagents (i.e., anti-bacteriophage agents).

Viral information

Viruses are major drivers of global biogeochemistry and the etiological agents of many diseases. They are also the winners in the game of life: there are more viruses on the planet than cellular organisms and they encode most of the genetic diversity on the planet. In fact, it is reasonable to view life as a viral incubator. Nevertheless, most ecological and evolutionary theories were developed, and continue to be developed, without considering the virosphere. This means these theories need to be to reinterpreted in light of viral knowledge or we need to develop new theory from the viral point-of-view. Here we briefly introduce our viral planet and then address a major outstanding question in biology: why is most of life viral? A key insight is that during an infection cycle the original virus is completely broken down and only the associated information is passed on to the next generation. This is different for cellular organisms, which must pass on some physical part of themselves from generation to generation. Based on this premise, it is proposed that the thermodynamic consequences of physical information (e.g., Landauer's principle) are observed in natural viral populations. This link between physical and genetic information is then used to develop the Viral Information Hypothesis, which states that genetic information replicates itself to the detriment of system energy efficiency (i.e., is viral in nature). Finally, we show how viral information can be tested, and illustrate how this novel view can explain existing ecological and evolutionary theories from more fundamental principles.

Fluorescence polarization study of tertiary structure of DNA within bacteriophage lambda

The fluorescence polarization of acridine orange-stained, oriented lambda phages was measured. The parameters of DNA packing within the phage head cos2 theta and cos4 theta were calculated (theta, angle between the direction of a small segment of DNA and the phage axis). It is shown that simple models of lambda phage DNA tertiary structure are not consistent with calculated values. A new model is proposed.

Structure of bacteriophage T7. Small-angle X-ray and neutron scattering study

Small-angle x-ray and neutron scattering techniques were applied to bacteriophage T7 solutions at different scattering densities. Scattering curves determined under a variety of experimental conditions were used to derive a set of parameters characterizing the shape, size, and weight of the whole phage particle and of its DNA and protein components. The T7 head has an icosahedral shape with an edge of 37.7 +/- 0.5 nm, a volume of (12.0 +/- 1.0) x 10(4) nm3, and a small tail amounting to 6--7% of the head volume. The intraphage DNA region is most probably a hollow sphere. The best fit to the data was obtained with a model in which the hollow sphere filled with a protein core with a diameter of 24 nm. The average degree of swelling (i.e., the ratio of the hydrated to the dry volume) of the particle is 2.3; the degree of swelling of the DNA component is higher, 3.2, and that of the protein part is lower, 1.2.

Structure of DNA within three isometric bacteriophages

This paper describes a model for the structure of DNA contained in three morphologically similar bacteriophages--T7, P22 and phiCd-1--based on the transient electric dichroism of intact phage. The reduced dichroism of each of the phages at perfect orientation is within the range +0.12 to +0.19. Assuming that the phage orientation axis is that which passes from the apex through the tail, the measured dichroism suggests that DNA is wrapped in closely packed, co-axial solenoids with the axis of the solenoids tipped 43.5 degrees +/- 2.5 degrees from the orientation axis of the phage. All three phages show a large permanent dipole moment, with respective values of 5600, 200,000 and 500,000 Debye for T7, phiCd-1 and P22. The radius of the equivalent sphere for the three phages calculated from the rotational relaxation time for the rise of dichroism is in agreement with birefringence and electron microscope observations. The circular dichroism spectra of all three bacteriophages indicate that the local DNA helicity is similar in each case.