In my undergraduate-oriented research laboratory here at the University of Puget Sound, I work with students on several microbiology-related projects. I have long had an interest in predatory microbes, including the wonderful and wily Bdellovibrio.
Bdellovibrio has an interesting life cycle. Free swimming "attack phase" cells swim very quickly (up to 50 cell lengths per second) in search of prey. When an "attack phase" cell contacts the "correct" prey (pretty much any Gram negative bacterium), it quickly enters the periplasm. Swiftly, the predator modifies the outer membrane of the prey so that subsequent Bdellovibrio attacks do not occur readily. It also begins to degrade prey cell macromolecules swiftly and quite efficiently. The invading Bdellovibrio (nestled within the prey cell periplasm) causes the prey to "round up" into a structure called a bdelloplast. After several hours, the depleted prey organism bursts, releasing a number of progeny Bdellovibrio cells. And the Circle of Predatory Life™ begins anew.
It sounds like a super-bacteriophage, but in fact Bdellovibrio in attack phase has an extremely high metabolic rate as it chase prey. So until we find some kind of girus with innate metabolism, this remains a good rule of thumb to exclude that "super virus" thinking.
Some researchers are beginning to think of Bdellovibrio as a "living antibiotic," and have begun investigations in chickens and other systems to see if the predator could be used to reduce pathogenic bacteria during infections.
It's a challenging system with which to work, especially with undergraduates. I have long loved working with "undomesticated microbes" but they do seem refractory to cool and simple molecular techniques. I take it a little personally. But Bdellovibrio is fascinating. And my wife Jennifer Quinn, who is not only a brilliant mathematician but quite a creative artist, made the following "stop motion" video for me, using her iPad, an app called "Stop Motion," iTunes, iMovie, Play-Doh, and a whole lot of creativity:
I hope you enjoy her video as much as I did. And keep in mind that microbial predation is quite widespread in nature. Which brings us back to Jonathan Swift:
So, naturalists observe, a flea
Has smaller fleas that on him prey;
And these have smaller still to bite 'em;
And so proceed ad infinitum.
(from: Poetry, a Rhapsody)It's true that Swift was referring to editors in this very long poem, not predatory bacteria. But Bdellovibrio is still a fascinating, fascinating system. And predators and prey continue to do their coevolutionary dance, even among the tiniest of creatures!