I was surprised this past week when after writing the “unicellular” blog to find a paper titled “social interactions in a unicellular world. “ Fascinating. The authors seem to struggle in a way with the concept, because it appears that many “social” interactions among microbes appear to be beneficial and not necessarily competitive. They even mentioned that Darwin struggled with the concept that living creatures can benefit another creature, without receiving a benefit in return.
One example they used was the cooperation among “unicellular” DIctyostelium discoideum an amoeba which assembles multicellular structures via cooperation. The structure they form is a fruiting body which culminates in a spore forming tip. So in the soil this microbe can be very happy living as a disorganized mob, but when it comes time to start a colony somewhere in the beyond, they get organized and form a fruiting body. The authors note that when they get together to organize a multicellular fruiting body, 20% of the cells lyse (kill themselves) to form a cellulosaic structure ( I like that word cellulosaic for some reason). The cellulosaic structure is apparently a dead stalk which supports the fruiting body. So how do we explain this apparent act of selfless behavior in this slime mold? Can slime molds really exhibit selfless behavior? Do we really care? I find it fascinating that biologists are interested in this. It appears to me that the ideas which embody evolution drive them to see these ideas of selfless or selfish behavior in living organism. Why are biologists interested in these concepts?
The authors also discuss the discovery of genes which are thought to be responsible for co-operation; these genes are called "greenbeard genes." They mention the discovery of the greenbeard gene Flo-1 in yeast which codes for a protein which makes yeast work together.
1 Find out more about DIctyostelium discoideum. What role does it play in nature?
2 What advantages are there to living as an organism which can experience both a closely nit multicellular stage and a loosely nit unicellular-like stage? i.e. what could organisms accomplish living in this way?
3 Why are biologists interested in the concepts of selfless behavior or selfish behavior as demonstrated at the cellular level?
4 How does the Flo-1 gene promote yeast communities?