Cooperation among various species of bacteria as well as gene transfer have been known to occur, but a new study has shown that when both cooperative genes and “cheater” genes are transferred among bacteria, cooperation is favored. This study has provided yet another example of the importance of cooperation in living organisms. The fact that this example was shown in bacteria, which are the vestiges of the earliest forms of life on Earth, hints at the importance of cooperation in evolution.
Competition is known to be a driving force in evolution in some situations, however, cooperation can also be a driving force toward evolutionary advances. Cases of cooperation have been described as mutualistic symbiosis in an evolutionary setting. Mutualistic symbiosis is thought to have contributed to major transitions in the evolution of life. The complexity of ecosystems can be attributed to the development of many symbiotic relationships that create inter-relatedness among many plants and animals.
On the level of cells, many bacterial species have social relationships with each other and some produce “public good” molecules that help neighboring cells. The genes that are related to these behaviors are called cooperative genes. On the other hand, some bacteria are invaders to the system and are “cheaters” that only take the molecules for their own use and do not produce anything for others. The genes that are related to these cheating behaviors are called cheater genes.
In the recently reported study, the researchers used an experimental set up with cells and also developed a simulation study to analyze genetic information exchange and selection of cooperative traits. In the simulations and experiments, the public good secretion of molecules and gene transfers were controlled. Their analyses showed that gene transfer favored cooperation in the simulations and experiments. Selection for cooperation increased the assortment among cooperative gene alleles.
The study was carried out by researchers at the Université Paris Descartes in France and at the University of Edinburgh in the United Kingdom. Ariel B. Lindner and Francois Taddei were the lead scientists on the study and the study report was published in the journal Proceedings of the National Academy of Sciences. The authors of the study report suggested that their study has relevance to human health. Bacterial cooperation in producing “public good” molecules can change their environment and this can increase virulence or antibiotic resistance. Virulence is the degree to which an infectious agent can cause disease and the degree of severity it produces. Antibiotic resistance is the ability of bacteria to resist being destroyed by an antibiotic.
The study of the importance of cooperation in an evolutionary setting is an emerging field in biology. It has roots in the early days of the ecology movement and also has emerged from studies of cell behaviors in petri dishes. Competition in natural selection is no longer seen as the only force that drives evolution forward. Harmonious relationships among species and balance that promotes equilibrium are part of the equation as well. Showing that the transfer of cooperative genes among bacteria means success, and results in a state of cooperation in the bacterial colony, is another observation that supports the benefit of cooperative behavior.
Opinion By Margaret Lutze