World Premiere — Cell Wars: Alien Viral Invasion Destroyed By Bacterial Enzyme

Look at the photos above and below.

What do you see?

They're vidcaps from a six-second long film of the first ever real-time capture of a bacterial enzyme destroying invading viral DNA before it could infect the host.

Watch the movie here.

Here's Alan Cane's story from today's Financial Times describing the work.
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Enzyme action captured on film

In one of the most remarkable biological sequences ever captured on film, scientists have managed to photograph in real time an enzyme in a bacterium under threat of attack by a virus helping to ward off the enemy by cutting through its genetic material.

The film, recorded in Japan using a device called a fast-scan atomic force microscope, lasts several seconds and clearly shows the enzyme - one of a group of proteins capable of cutting through strands of genetic material - threading through a loop in the virus's DNA in order to break it before it could infect the bacterium. Robert Henderson, leader of the Cambridge University researchers, said it was the first time the process had been seen in real time: "To be able to see these nano-mechanisms as they are really happening is incredibly exciting," he said.

The team used one of only three fast-scan atomic force microscopes so far built to picture these tiny objects. The microscope measures the force between the objects and a finely pointed probe: the analogy is the needle of a record player tracing the grooves in a record. The research is expected to contribute to our understanding of the way damaged DNA is repaired in nature. The film can be viewed at http://www.bbsrc.ac.uk/media/pressreleases/video_enzyme_unravelling_dna.html
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Here is a link to the abstract of the Henderson group's paper, published on July 23, 2007; the abstract follows.
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Fast-scan atomic force microscopy reveals that the type III restriction enzyme EcoP15I is capable of DNA translocation and looping

Many DNA-modifying enzymes act in a manner that requires communication between two noncontiguous DNA sites. These sites can be brought into contact either by a diffusion-mediated chance interaction between enzymes bound at the two sites, or by active translocation of the intervening DNA by a site-bound enzyme. EcoP15I, a type III restriction enzyme, needs to interact with two recognition sites separated by up to 3,500 bp before it can cleave DNA. Here, we have studied the behavior of EcoP15I, using a novel fast-scan atomic force microscope, which uses a miniaturized cantilever and scan stage to reduce the mechanical response time of the cantilever and to prevent the onset of resonant motion at high scan speeds. With this instrument, we were able to achieve scan rates of up to 10 frames per s under fluid. The improved time resolution allowed us to image EcoP15I in real time at scan rates of 1–3 frames per s. EcoP15I translocated DNA in an ATP-dependent manner, at a rate of 79 ± 33 bp/s. The accumulation of supercoiling, as a consequence of movement of EcoP15I along the DNA, could also be observed. EcoP15I bound to its recognition site was also seen to make nonspecific contacts with other DNA sites, thus forming DNA loops and reducing the distance between the two recognition sites. On the basis of our results, we conclude that EcoP15I uses two distinct mechanisms to communicate between two recognition sites: diffusive DNA loop formation and ATPase-driven translocation of the intervening DNA contour.