More and more patients develop bacterial infections immune against an increasing number of classes of antibiotics. Whilst the development of an antibiotic mostly takes several years and costs several millions, a bacterium sometimes needs very little time to develop a resistance thus declaring the antibiotic ineffective. So the development of new antibiotics is being worked on high speed.
Secret weapon against bacteria colonies
Scientists around Eshel Ben-Jacob at the Tel Aviv University introduce a promising approach in the battle against bacteria. They discovered that bacteria cannot only reproduce but – under certain circumstances – also become competitors and start killing each other (PNAS 2009; 106: 428-433; doi: 10.1073/pnas.0811816106). The mechanism serves the reproduction of the population and secures the survival of a certain number of bacteria after all. Cannibalism among bacteria can be observed during stress such as hunger, heat and damaging exposition to chemicals. If now the entire bacteria colony is exposed to the same chemical signals which build their bacteria to defend against competition, the fight for survival begins. The fact that bacteria hardly develop resistances against components they produce themselves is of advantage.
Unicellar organisms with social intelligence
Although it sounds a bit strange in the beginning cannibalism among bacteria under stress has to be understood as cooperative behaviour, says Ben-Jacob. As an answer to stressors, bacteria reduce their population similar to an organism suffering from constant hunger limiting the production of certain cells. Mind you, bacteria do not kill each other randomly. An additional interesting aspect is – so to say – that they seem to have a rudimentary form of social intelligence. The researchers found an elaborate and sensitive chemical dialogue between bacteria which supposedly guarantees that only a part of the cells is being killed.
The scientists observed this fact in two neighboring sibling colonies of the Paenibacillus dendritiformis, a special strain of social bacteria. Not only do the two colonies bar each other from growing into the area under the strain of lack of nutrition but also induce the death of each cell close to the boarder. The cell death stopped after the exchange of chemical messages between the two colonies has been interrupted. Both colonies withdrew simultaneously.
Beat with their own weapon
Kazuhiko Kurosawa and colleagues at the Massachusetts Institute of Technology already used the survival fight of bacteria strains to develop new antibiotics against Helicobacter pylori (Journal of the American Chemical Society 2008; 130: 1126-1127). They discovered that a lack of room of competing ground bacteria, one of them a strain of Rhodococcus fascians, stimulated them to produce substances killing the other bacteria colony. The two produced substances had been yet unknown and were named Rhodostreptomycin A and B. According to the scientists this discovery could very well become a starting point for the development of new antibiotics.
Ben-Jacob believes that bacteria know how to collect information from their environment, they communicate with each other, delegate chores and have a collective memory. The social intelligence transmitted via chemical language allows bacteria the transformation of their colonies into large brains. These process information, learn from experience to solve unknown problems and to handle new challenges. “If we want to stand the challenge of bacteria to us it first of all requires the realization that they are not simple creatures with a limited ability of performance”, says Ben-Jacob.