Bacillus subtilis trapped in extracellular DNA in suspension
Source: Biotechnical Faculty of the University of Ljubljana

Publish Date: 04.12.2017

Category: Outstanding research achievements, Interdisciplinary research, Our contribution to sustainable development goals

Sustainable development goals: 15 Life on land (Indicators)

The fundamental discovery in the field of natural science about mechanical couplings between bacteria, previously considered non-existent, changes the way of looking at microorganisms, understanding bacterial co-operation and the impact of bacteria on the environment.

Authors : Simon Sretenović, Biljana Stojković, Iztok Dogša, Rok Kostanjšek, Igor Poberaj, David Stopar

A group of researchers from the Biotechnical Faculty of the University of Ljubljana, together with their associates from the Faculty of Medicine and the Faculty of Mathematics and Physics of the University of Ljubljana (Simon Sretenović, Biljana Stojković, Iztok Dogša, Rok Kostanjšek, Igor Poberaj in David Stopar), discovered mechanical couplings between bacteria that were previously considered by researchers to be non-existent, thereby rejecting the centuries-old dogma about unrelated planktonic bacterial cells. The fundamental discovery in the field of natural science changes the way of looking at microorganisms, understanding bacterial co-operation and the impact of bacteria on the environment.

The research findings point to physical connections between bacteria, but they cannot be detected using standard microscopic techniques. The researchers used an optical tweezer and were the first to observe that bacterial cells in the suspension connect to an invisible grid, following the motion of the optically trapped bacteria. By measuring viscous and elastic properties of the extracellular matrix the researchers discarded the idea that bacterial cells in the suspension are unrelated to one another and move only as a result of hydrodynamic interactions. The results show that bacteria in the suspension are capable of producing well-connected microbial structures over long distances (even more than 100 μm). Behind the visible bacterial structure, an invisible network of intercellular links is hidden, which represents the fundamental fabric of the ecosystem. Knowing that a completely new insight to the physiology of bacteria is possible is highly exciting and promising. As expected, the discovery will trigger an interest in examining the problems of resistance to antibiotics in dilute bacterial cultures, which will contribute to the development of new antimicrobial agents. The discovery will also help in understanding the production of marine microaggregates, which cause red tide.

Bacillus subtilis trapped in extracellular DNA in suspension (left); extracellular polymers physically connect individual cells to a grid (right) Source: Biotechnical Faculty of the University of Ljubljana