Earlier electron microscope studies of isolated Listeria comet tails identified different populations of actin filaments oriented both oblique and parallel to the comet axis (Sechi et al., 1997). But the intact tails were too thick to resolve details of the structure close to the bacterium. However, where tails became splayed on the electron microscope support film individual filaments could be resolved. Re-analysis of these images revealed branch junctions like those seen in comet tails of baculovirus.
Negatively-stained comet tail of isolated protrusion induced by Listeria in a PtK2 cell. One region of the tail was splayed out on the support film
Enlarged region of Listeria comet tail showing branch junctions encircled.