Editors' ChoiceMicrobiology

Exciting times for biofilms

Sci. Signal.  10 Nov 2015:
Vol. 8, Issue 402, pp. ec328
DOI: 10.1126/scisignal.aad8158

Different regions of Bacillus subtilis biofilms undergo periodic cycles of proliferation. Cells at the periphery of a biofilm consume a lot of glutamate as they proliferate, thus starving cells in the interior of the biofilm of glutamate. Without glutamate, the interior cells produce less ammonium ions. Without the ammonium ions from the interior cells, the peripheral cells stop dividing and consuming glutamate. As glutamate becomes available to the interior cells, these cells resume proliferating and producing ammonium ions, which releases the peripheral cells from growth arrest, and the cycle begins anew. Membrane potential controls the uptake of glutamine and the retention of ammonium ions. Using a microfluidic device and a voltage-sensitive fluorescent dye, Prindle et al. demonstrated that oscillations in membrane potential across B. subtilis biofilms correlated with metabolic oscillations. Voltage clamp experiments showed that these changes in membrane potential correlated with potassium ion (K+) efflux from cells within the biofilm and depended on the presence of the K+ channel YugO, a protein required for biofilm formation. Removing glutamate from the growth medium caused wild-type, but not yugO mutant, cells to release K+. YugO was also required for propagation of the K+ wave across biofilms. Mathematical modeling revealed that such K+ waves could drive the membrane potential oscillations characterized by the microfluidics experiments. These findings demonstrate that bacteria can generate electrical signals that propagate across a biofilm and suggest that electrical signals may coordinate metabolism across the biofilm. Beagle and Lockless note that electrical signaling could also control other bacterial social behaviors or perhaps even mediate communication between bacterial communities and their eukaryotic hosts.

A. Prindle, J. Liu, M. Asally, S. Ly, J. Garcia-Ojalvo, G. M. Süel, Ion channels enable electrical communication in bacterial communities. Nature 527, 59–63 (2015). [PubMed]

S. D. Beagle, S. W. Lockless, Electrical signalling goes bacterial. Nature 527, 44–45 (2015). [PubMed]

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