I ran across this information the other day. It kind of shocked me- I guess I was not paying attention in my microbiology class. Actually, not- I checked my texts and found no mention in the index. You see, in 1954, Francois Jacob (Institut Pasteur, Paris) described a “pyocin”, a chemical exuded by a strain of microbes (Pseudomonas pyocyanea, now called Pseudomonas aeruginosa) that killed another species of P. aeruginosa. When examined under the electron microscope, these pyocins were found to resemble a rocket- the ones they show in cartoons- one thick tube with several fibers protruding out of its end. It turns out the thick tube also contains a thinner one, that gets expelled by the outer tube (via contraction) to inject itself into the cell wall of the target cell. Killing it.