Too many of us are under the comforting illusion that we, humans, are the be-all-end-all of nature’s evolutionary process. We are the smartest, we build the biggest, we fly the highest and are the most creative of anything else out there. Among the numerous fields of study we seem to have mastered, cryptography (code making and breaking) appears no different. However, according to a new study by UC Davis researchers, bacteria and certain plants have left us embarrassingly outperformed.
“Like the German military scientists [in World War 2], single-celled bacteria communicate with each other using coded messages to coordinate attacks on their targets,” said Pamela Ronald, a professor of plant pathology at UC Davis and the lead researcher on the study.
Bacteria perform this cryptographic feat using a tiny protein called Ax21. Ax21 is made inside the bacteria and then released outside the cell. When other bacteria of the same kind perceive this secreted protein, they conglomerate into protective structures called biofilms.
“Biofilms render the bacteria resistant to dessication and antibiotic treatment,” Ronald said. “[Through] communication and communal living, bacteria increase their chances for survival and proliferation.”
But staying true to the World War 2 cryptographic plot, the plants targeted by these cooperative bacteria have figured out a way to intercept these coded messages, decipher them and turn them against their bacterial attackers.
“[Some] plants have developed a code-breaking system called the XA21 receptor that allows them to intercept the bacterial coded messages and trigger a strong immune response,” Ronald said.
The XA21 receptor can recognize distinguishing characteristics of invading bacteria and can also recognize the coded proteins that these bacteria use to communicate. This early interception of the bacterial messages gives the plant time to enact its immune response.
“Plants and bacteria are in an evolutionary arms-race,” said Richard Bostock, a professor of plant pathology at UC Davis. “The plant evolves to resist the bacteria, and the bacteria evolve to subvert the plant’s defenses.”
The two organisms have to continually evolve just to maintain the ecological status quo.
“Resistance to bacteria often comes naturally through evolution, but with most agricultural crops, resistance is achieved through selective breeding,” Bostock said.
Selective breeding has created an agricultural policy of using genetically identical clones for use in farming. Since all the plants are identical, it leaves the whole field open to mass infections.
By understanding how these bacteria communicate and attack, immunologists can begin to develop ways to fight back against many bacterial diseases for which there are no known treatments. A recent paper published by the Infectious Diseases Society of America claims that there is a quickly growing number of bacterial infections that are resistant to all current antibacterials.
Bacteria only start to form their tough biofilm shells once the population has reached a certain size. The population determines its size through a process called quorum sensing. The research underway to treat bacterial infections focuses on disrupting quorum sensing, which will render the bacteria unable to detect population size and therefore unable to form protective biofilms.
By stopping biofilm formation, we can dramatically reduce the infection rate of diseases like tuberculosis, staphylococcus and streptococcus, as well as prevent large-scale bacterial infections of important crops.
Breaking and learning these bacterial codes could give us another layer of protection against bacterial invaders.
HUDSON LOFCHIE can be reached at science@theaggie.org.
