“sign-mediated interspecies interactions between two bacterial strains”
This is a living and wet computer thats basis is bacterial quorum sensing. This type bacterial cell-to-cell communication enables bacterial cells to coordinate their behaviour, imbuing them, like ants and bees, with a form of social intelligence. Moreover, quorum sensing allows these sophisticated life forms to work together in teams, to overcome obstacles to great for the few, to hunt prey as microscopic wolf packs, and to build biofilms and other complicated structures.
The BacterioEncephalon comprises two living bacterial components, a signal emitter, the bacterium Erwinia carotovora that produces the autoinducer C6-Homoserine Lactone (C6-HSL), and Chromobacterium violaceum CV026, the signal detector. In wild type strains of C. violaceum, the production of their characteristic purple pigment, violacein, is controlled by a quorum sensing. In the system here, the protein LuxI produces the quorum sensing signal C6-HSL, and then a second protein, LuxR, detects this and then coordinates changes in gene expression so that the production of the purple coloured violacein only occurs at high concentrations of C6-HSL, and thus at high bacterial cell densities. The signal detector in the BacterioEncephalon is CV026, which in a sense is a bacterial mute, in that it is a luxI mutant that cannot produce its own C6-HSL. Because of this, in pure culture, it grows as a white colony (and not a purple colony like wild type strains) because it doesn’t generate any C6-HSL for the LuxR component to detect. However, in CV026 the quorum sensing signal detecting mechanism remains intact so that if CV206 is grown in proximity to a C6-HSL producing species of bacterium (such as E. carotovora here) it is capable of detecting and responding to this by producing violacein.
In the BacterioEncephalon E. carotovora and CV026 have both been inoculated into swim agar which has a reduced agar content and thus is semi-solid. This provides them with a freedom beyond normal bacteriological media, allowing the two species of bacteria to swarm, move and interact with each other. Where the two species meet in the agar, and interact, the media turns purple because of the production of C6-HSL byE. carotovora and then its subsequent detection and response to this by CV026.
The BacterioEncephalon After Overnight Incubation. The movement of the two bacterial species is evident but there is limited interaction and thus limited production of the purple pigmented (below).
The BacterioEncephalon After Three Days Incubation. The production of the purple pigment is now extensive and reveals the manifold interactions and computations of billions of living bacteria cells (below)
Just wish I could understand what the bacteria are trying to tell me!