"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."
- Jonathan Swift

August 21, 2011

Caenorhabditis briggsae (KT0001)

Today's parasite is in the same genus as the famous and well-studied model lab nematode worm Caenorhabditis elegans. Caenorhabditis briggsae is a relative of C. elegans and is often used in comparative studies with its more famous counterpart because many of the tools developed for C. elegans can also be used on C. briggsae. While C. elegans is the darling lab worm due to its usefulness in studying genetics and developmental biology, until very recently, very little is known about its natural ecology.

Worms in the genus Caenorhabditis are often associated with invertebrates, hitching a ride on them as a way of traveling between food sources, or even opportunistically feeding on their ride if it happens to drop dead for whatever reason. In a paper published last year, a group of researchers reported on a strain of C. briggsae (KT0001) from South Africa displaying an ability not previously known for any Caenorhabditis species - it is capable of infecting and killing wax moth larvae. This strain of C. briggsae was found to be in a symbiosis with the pathogenic bacteria Serratia which presumably allows C. briggsae (KT0001) to become a parasitic killer.

Furthermore, when the researchers tested 10 wild strains of Caenorhabditis species which had not previously displayed any ability to infect insects - including a strain of C. elegans - and cultured them with Serratia, all but one strain gained the ability to infect, kill, and reproduce in insects, including the famous C. elegans. It seems that Serratia gives Caenorhabditis a license to kill - upon forming a partnership with the bacteria, these worms turn from mere passengers into deadly killers.

Abebe, E., Jumba, M., Bonner, K., Gray, V., Morris, K., Thomas, W.K. (2010) An entomopathogenic Caenorhabditis briggsae. Journal of Experimental Biology 213: 3223-3229.


  1. it would be even neater if the serratia turned them red

  2. That would be quite cool. Well apparently other species of entomopathogenic can turn their victim bright red to ward off peckish predators:
    But those worms kill their host with a different species of bacteria.

  3. Do the Caenorhaabditiae encyst their commensals or do the bacteria avoid digestion somehow

  4. It seems the bacteria are able to avoid digestion. Many pathogens have ways of avoiding digestion by their host and often the tools used by pathogens share commonality with those used by mutualists. Some mutualists might have evolve from pathogenic ancestors which have been "tamed" over the course of evolution by their hosts.

  5. I was very surprised about the statements in the paper. And I fully agree to the answer given by Rae and Sommer:

    J Exp Biol. 2011 Mar 15;214(Pt 6):1053; author reply 1053-4.
    Bugs don't make worms kill.
    Rae R, Sommer RJ.

  6. I was not able to obtain reprint copies of those correspondences - do you know where I might be able to get them?