Bacteria form alliances

Even among bacteria, there are selfless benefactor. They help whole groups of microbes that resist the attack of an antibiotic.

As bacteria are supporting each other, discovered by U.S. researchers in the study of a colony of Escherichia coli bacteria, which they finally kicked daily increasing amounts of an antibiotic. Surprisingly, only a few bacteria actually develop a resistance to the drug, the scientists observed. Nevertheless, the colony grew steadily more resistant to the drug. The trick: The resistant individuals produced a messenger, who helped their fellows, to activate various defense mechanisms against the lethal substance. Accordingly, the emergence of resistant bacterial colonies completely different than previously thought, write Henry Lee from the Howard Hughes Medical Institute in Boston and his colleagues in the journal Nature.


Until now, scientists the development of resistance in bacterial colonies as follows: An antibiotic attacks the microbes and blocks such as their ability to reproduce. Eventually, however, change one or more of the bacteria, their genetic material so that they are able to make the drug harmless. This can reproduce these bacteria, the antibiotic during their fellows still doing so. The result: Over time, dominate the offspring of the resistant bacteria, the colony and eventually displace the microbes that have no resistance - a fully resistant group was created.

Selfless behavior at the expense of their own fitness
The observations of Lee and his colleagues could correct the performance. The scientists had faced bacteria in the laboratory with the antibiotic norfloxacin and observed the survival and reproductive ability of the microbes. Two things they fell on this: First, was the dose tolerated the individual bacteria, extremely varied - some were killed even at low concentrations of the drug, others survived problems even higher. On the other hand was the antibiotic quantity that was used to kill the bacteria in the group, significantly greater than that which killed isolated nuclei.

Further tests, the researchers also the cause of these effects. Apparently in a single bacterial colony only develop a genuine resistance to an antibiotic. How generous benefactor these germs to help but then their counterparts, with the active ingredient to be done: Although the detriment of their own fitness is, they produce a neurotransmitter called indole and enter it into the environment. He throws in two defense mechanisms in the colony comrades: a molecular pump with which the antibiotic can be transported from the cell, and a general defense system against stress. In this way, the colony as a whole more resistant to attacks than their individual members. Especially in view of the steadily growing number of resistant germs, which is tackled with any antibiotic more, was the discovery of interest, write the researchers is to show that the blocking of the Indolwirkung possibly the penetration can increase antimicrobial drugs - and that bacteria are much Communities are more complex than previously thought.