Light-Induced Patterning of Electroactive Bacterial Biofilms

Abstract

Electroactive bacterial biofilms can function as living biomaterials that merge the functionality of living cells with electronic components. However, the development of such advanced living electronics has been challenged by the inability to control the geometry of electroactive biofilms relative to solid-state electrodes. Here, we developed a lithographic strategy to pattern conductive biofilms of Shewanella oneidensis by controlling aggregation protein CdrAB expression with a blue light-induced genetic circuit. This controlled deposition enabled S. oneidensis biofilm patterning on transparent electrode surfaces, and electrochemical measurements allowed us to both demonstrate tunable conduction dependent on pattern size and quantify the intrinsic conductivity of the living biofilms. The intrinsic biofilm conductivity measurements enabled us to experimentally confirm predictions based on simulations of a recently proposed collision-exchange electron transport mechanism. Overall, we developed a facile technique for controlling electroactive biofilm formation on electrodes, with implications for both studying and harnessing bioelectronics.

Single molecule tracking of bacterial cell surface cytochromes reveals dynamics that impact long-distance electron transport

“…From the measured conduction currents (which did not account for flavin contributions) and using the full biofilm volume to define the conduction path (rather than only the cellular membrane surface), a biofilm conductivity (σ) of several nS/cm was estimated for S. oneidensis . Using the Nernst-Einstein relation ( SI Appendix , SI Materials and Methods ) to relate the apparent diffusion coefficient and conductivity ( 20 ), our calculated D ap of ∼1 µm 2 /s translates to σ ∼ 7 nS/cm, in remarkable agreement with the electrochemical gating measurements ( 59 ). These comparisons suggest that the simulated combination of electron hopping and cytochrome diffusion can explain many features of the observed redox conductivity of bacterial biofilms, at least in the case of S. oneidensis .…”

“…Taking an electron transport rate of 10 4 s −1 and a cytochrome concentration resulting from a representative fractional loading X = 0.5, this procedure results in D ap ∼1 µm 2 /s, which is on the lower end of D ap reported for electroactive bacterial biofilms ( 22 ). More recently, estimates of the redox conductivity of S. oneidensis have become available from electrochemical gating measurements of light patterned biofilms bridging interdigitated electrodes ( 59 ). From the measured conduction currents (which did not account for flavin contributions) and using the full biofilm volume to define the conduction path (rather than only the cellular membrane surface), a biofilm conductivity (σ) of several nS/cm was estimated for S. oneidensis .…”

Light-regulated gene expression in Bacteria: Fundamentals, advances, and perspectives

“…The above use cases compellingly illustrate how lightregulated gene expression can establish spatial patterns in bacterial communities. Beyond their utility in basic research, these approaches garner interest for the production of structured materials, as already hinted at in certain of the above examples (Zhao et al, 2022;Figure 5C). Several studies employed the CsgA protein which upon secretion forms so-called curli fibrils on the bacterial cell surface and mediates biofilm formation (Chen et al, 2014).…”

“…Beyond E. coli, the widely used CcaRS TCS (Tabor et al, 2011) enabled light-regulated gene expression in Synechocystis cyanobacteria (Abe et al, 2014;Miyake et al, 2014;Badary et al, 2015) and P. aeruginosa (Hueso- Gil et al, 2020). Likewise, the pDawn setup (Ohlendorf et al, 2012) underpinned applications in the probiotic E. coli Nissle 1917 strain (Magaraci et al, 2014;Alizadeh et al, 2020;Cui et al, 2021), P. aeruginosa (Pu et al, 2018), the marine bacterium Vibrio natriegens (Tschirhart et al, 2019;Wang et al, 2020), and Shewanella oneidensis (Zhao et al, 2022). Similarly, EL222 was used in Sinorhizobium meliloti (Pirhanov et al, 2021).…”

“…Precisely patterned biofilms not only benefit the study of the underlying biological processes, but also they are attractive for metabolic engineering, diagnostics, and material science. This idea is indeed borne out by a recent study that employed pDawn to photolithographically manufacture biofilms of Shewanella oneidensis (Zhao et al, 2022). These facultative anaerobic bacteria are of interest because of their capability of reducing metal ions and forming electrically conductive biofilms.…”