Some of the best moments in my job as a Weizmann science writer are the times when a scientist I’m interviewing slips in a finding that shifts my understanding of how the world works. Not long ago, for instance, I was speaking with a researcher about his work on phytoplankton. Now, the fact that phytoplankton release about half of all the free oxygen on the planet should be an eye-opener to anyone, and a reminder of the importance of ocean health. (But that wasn’t the surprise.)
Dr. Assaf Vardi researches the chemicals that phytoplankton produce to communicate. Of course, all sorts of bacteria have been shown to communicate, some of them in quite sophisticated ways, so the fact that phytoplankton send each other chemical signals shouldn’t be too big a surprise. It does, however, put a new spin on the social life of phytoplankton (the word means “plant drifters”), especially when you contemplate the fact that their messaging system can affect the whole aquatic food chain. Phytoplankton are the very bottom of the chain, on the one hand, so their numbers count, but they can also multiply out of control, choking off waterways or forming toxic “red tides,” on the other. (In fact, Vardi thinks that the toxins produced by red tides may be a kind of “infochemical.”)
Here’s the bit made me raise my eyebrows: In both phytoplankton and the viruses that infect them, Vardi found genes for apoptosis – cell suicide. Why is this surprising? Apoptosis is a basic mechanism – though quite a complex one – known from multi-celled organisms, in which badly damaged cells kill themselves for the greater good of the whole. Why would single-celled organisms need a suicide option? Vardi has yet to figure out exactly what’s going on in the phytoplankton, but it does imply that those mindless little drifters are evolved to the point where some of them will take a hit for their buddies. I don’t know about you, but that one certainly gives me pause.