Beijing time on September 3, according tomedia reports, cluster bacteria will die when the “scream”, to remind the surrounding bacteria dangerous approach. Of course, these screams of death are indible. Instead, they are chemical alerts, signals sent by bacteria on the verge of death, called “death signaling.” By “death signaling” this behavior, bacteria can alert their neighbors in the cluster to the presence of a deadly threat, thereby saving most of the bacteria in the cluster (i.e., moving bacterial groups).
When faced with threats such as antibiotics, the chemical death screams of bacteria can give surviving bacteria plenty of time to get mutations that deliver antibiotic resistance, scientists write in a new study.
Many kinds of bacteria swim at high speed under the action of the slender tail structure “whiplash”. Sometimes, bacteria like E. coli have billions of bacteria in their clusters that move on a fixed surface in a group- and coordinated manner.
“Bacterial clusters are metabolically active and thrive,” the researchers wrote. For this reason, scientists suspect that clusters may also have their own evolutionary mechanisms for antibiotic resistance. However, this mechanism may be different from the evolutionary mechanism of drug resistance in individual cells.
Previously, researchers have noted that about 25 percent of cluster bacteria die when they encounter antibiotics. Dead bacteria seem to be protecting the surviving bacteria in some way. After some of the cluster mates die, the surviving cells appear to actively stay away from antibiotics. But at the time, researchers didn’t know exactly what motivates bacteria to behave in this way.
In the new study, scientists looked at what happens when E. coli clusters encounter antibiotics to reveal how dead cells save the remaining clusters.
Billions of E. coli move in groups on solid surfaces.
Signals from dead cells.
The researchers found that E. coli, which dies in the cluster, releases a death signal: a protein that can be combined with the outer membrane of living cells in the cluster.
With these dying chemical “screams,” dead bacteria can activate the mechanisms in the membranes of living cells and “start excreting antibiotics,” said study co-author Rashika Halsey, a professor of biological sciences. Studies have shown that this suggests that the “screaming” compound can send out “emergency” signals to alert live bacteria to the dangers.
The gene cascades opened by death signals not only protect surviving clusters from antibiotics, but also strengthen resistance to compounds that kill their comrades. What’s more, scientists realize that subgroups of clustered bacteria are also genetically mutated; some are more susceptible to antibiotics than others. Different clusters of bacteria may work together to create different sub-groups as an evolutionary survival strategy – if new antibiotics kill the weak members of the cluster, their sacrifice will protect the remaining members.
“Dead cells are helping the whole cluster survive,” Halsey said.
The results show that exposure to low doses of antibiotics actually helps bacteria clusters gain antibiotic resistance in dense bacterial clusters. This is very instructive in studying how to fight bacterial infections.