Another example of the complexity and interconnectedness of life; a marine microbe initiates metamorphosis and settlement of the larva of a marine invertebrate.
The little larva is floating along in the ocean looking for a place to settle and start a family. How does it decide when and where to do this? It’s thought that cues from marine biofilms consisting of various bacteria are involved. In this case, the larva floating along in the ocean is that of the tubeworm Hydroides elegans, and the bacterium associated with the biofilm is Pseudoalteromonas luteoviolacea. So how does the interaction between organisms go down? Well, some folks at Cal Tech and their colleagues may have discovered a piece of the puzzle.
Previously the scientists had figured out that if P. luteoviolacea were not part of the biofilm then the larva would not go through its metamorphosis. So they started examining the bacterium. They started looking through the genome and found a set of genes, that when deleted, resulted in no response from the larva. Interesting! How does a gene in a bacterium dictate the actions of an invertebrate larva swimming in the ocean?!
After many more hours of science they figured out that the genes were a blue print for a needle-like structure, termed MAC (Metamorphosis Associated Contractile structure). Once the microbe produces the MAC’s, it goes through self-lysis (still not known why they do this), and release the MAC’s into the environment. The floating MAC’s then interact with the larva and initiate settlement and metamorphosis. Though this process is beneficial for the larva to grow and mature, it is unclear what the benefit is for the bacterium, or biofilm. Furthermore, mac-like genes have been found in other microbes, hinting this pathway may also be important for other marine invertebrates. Further studies from the group at Cal Tech should reveal some fascinating findings!
As in all scientific endeavors, one answer produces two more questions, here are few that the scientist are trying answer next:
1) What is the interaction between the MAC and the larva?
2) Is the interaction beneficial for the microbe?
3) Do the MAC transport some peptide/molecule to the larva?
4) …Or maybe the bacterium just shoots the larva with its cupid arrow and they come to love each other in a very special way!