There are certain bacteria that carry social behaviors, and one such species is Myxococcus xanthus. This soil dwelling bacterium has the ability to organize into multi-cellular, three-dimensional groupings made up of thousands of bacteria that actually work together to hunt for food.
According to Dr. Oleg Igoshin, an assistant professor of bioengineering at Rice University: “For the first 100 years of microbiology, researchers were trying to find model organisms to study bacteria, and most were selected because they had some medical or industrial significance influence, such as E. coli, and because they grow very well in the standard test tube. But when you base your choice on their behavior in a test tube, and not on social behavior or spatial structure, you lose some interesting species to study”. Igoshin goes on further to say, “The story is quite different for Myxococcus xanthus. They are a very social bacteria that form really cool structures, and rely on each other for survival.”
This predatory bacterium is of interest to biologists because of its self-made spatial formations and its ability to kill effectively and digest a wide range of microbes. Igoshin and colleagues are using both data-driven modeling and simulations to understand how M. xanthus behaves when there is sufficient food around and when there is not. They are trying to understand how these bacteria achieve their multi-cellular behaviors.
Igoshin notes, “The most primitive form of life is single-cell life. The next step up would be going from single cells to multicellular organisms. These bacteria are somewhat in the middle.” These microbes allow scientists to address questions about how individual cells can break their symmetry to organize into many-celled structures. This may teach scientists about the evolution of multi-cellularity.
It is known that when food is plentiful, M. xanthus moves in coordinated swarms (ripples) that often contain thousands of cells. They secrete enzymes to kill their prey, digest them outside and then take in the resulting nutrients. This bacterium has the ability to make antibiotics that kill other species as well. Igoshin notes, “Single cells can’t produce enough of these antibiotics or enzymes to effectively kill their prey, which is why they hunt together as a group.” However, when little food is available, these bacterium take on another shape forming spores called fruiting bodies. These fruiting bodies can survive for a long time until conditions become hospitable again. At that time they rejuvenate.
Understanding M. xanthus may help researchers design new antibiotics and possibly develop new pest-resistant seeds. By deciphering this basic biology of multi-cellular organization, this may lead to understanding complex manifestations such as embryonic development.
Igoshin notes, “I use reverse engineering approaches to look at these microscopic structures and try to figure out what these individual cells should do in order to produce this type of behavior. I put in parameters such as size, velocity, flexibility, speed—some we can measure, some we can guess—and see whether the computer simulations will produce structures similar to those observed.”