Does microbes have a social life?
Yes! Whether they are in the soil, in water, or in the human gut, microbes are rarely alone and typically share the environment with other microbes. The result is that microbes interact with each other, which may impact their growth and survival. Indeed, depending on the social interaction, microbes may grow better… but also die!
So, how may microbes help or harm each other? To answer this question, my thesis research focused on studying which of these two social interactions is most common: competition or cooperation?
What are competition and cooperation?
In biology, competition is an interaction between two or more organisms (or species) in which both need a resource that is in limited supply.
The one who acquires the limited resource most effectively will prevail.
Let’s make an example: lions, cheetahs and leopards are all competing to catch gazelles. However, competition may also occur within the same species: the slower gazelle will be eaten; the faster lion will easily have its breakfast. In other words: “It doesn’t matter whether you’re the lion or a gazelle – when competition comes up, you’d better be running”.
Instead, cooperation is where groups of organisms work together for common benefits. Cooperation can arise in many forms: Pollinators, like bees, pollinate flowers and in return receive food. The persistence of the first species over time depends on the second one, and vice versa.
Which type of interaction do we expect to prevail in nature then?
It took me some time before understanding that the problem was mainly linguistic. Indeed, if you check the dictionary, you will find that competition is the opposite of cooperation. But in reality, species interact via complex combinations of competition and cooperation, suggesting that social interactions cannot be reduced to a simple dichotomy. However, although many studies argue that competitive interactions dominate the ecosystems, many others are also fascinated by cooperation within and between species. One reason for this polarization is that it is still unclear when these social interactions arise and what make a species to help or harm another.
Do social interactions are intertwined?
To answer this question, I did not work with gazelles and lions. Instead, I focused my attention on a small microbial community.
My research suggests that social interactions are not just a question of “who competes” and “who cooperates”. Competition and cooperation are intertwined, and small environmental changes can lead to completely different dynamics.