"When times are good and there are plenty of nutrients in the water, the algae use photosynthesis to gain energy from sunlight, but when nutrients become sparse, they attack and become toxic," Driscoll said. "That's when they start swimming around looking for prey. They are a little bit like carnivorous plants in that way like a Venus fly trap."
The group observed that as soon as nutrients become scarce, the toxic population ceases to grow, but the cheaters keep multiplying.
Driscoll and his team think the cheating behavior could be an adaptation to the algae bloom life style.
"During a bloom you have killed off all the prey or a huge amount of it, so why produce toxins and go looking for something that isn't there? It might be better to just keep growing and not even try to bother to keep looking for prey because it's gone."
Driscoll said the research illustrates how little is known about the ecology of microbes.
"We're just starting to understand what the mechanisms are that maintain cooperation in microbes. The theory is heavily slanted toward multicellular organisms. Only recently have people started to think about microbes cooperating."
To better understand the genes and biochemical pathways that control how the algae make their toxins, the group in Hackett's lab is investigating which genes are active in the toxic compared to the non-toxic strains.
"We are finding a number of stress-related genes are regulated differently in the cheaters," Driscoll said. "A lot of the other genes have not been studied before, especially those most likely involved in toxin production."
"The problem is that nothing close to these algae has had its genome sequenced, so they're pretty mysterious. Many of the genes we have sequenced are novel, so understanding their function is a big part of the challenge."
Unraveling the molecular mechanisms behind all this chemical warfare, cheating
|Contact: Daniel Stolte |
University of Arizona