Membrane permeabilization underlies the enhancement of extracellular bioactivity in Shewanella oneidensis by a membrane-spanning conjugated oligoelectrolyte

Abstract

A stilbene-based membrane spanning conjugated oligoelectrolyte 4,4'-bis(4'-N,N-bis(6"-(N,N,N-trimethyl ammonium) hexyl) amino)-styryl) stilbene tetraiodide (DSSN+) has been reported to be able to interact with bacterial cells and enhance their bioelectricity generation in bioelectrochemical devices, although the mechanism remains elusive. The goal of this study was to elucidate the impacts of DSSN+ on extracellular bioactivity and the underlying mechanism. Specifically, extracellular ferrihydrite reduction by Shewanella oneidensis was used to evaluate the influence of cell-DSSN+ interaction. Our results show that DSSN+ enhanced ferrihydrite reduction by S. oneidensis in a growth-dependent manner. The incorporation of DSSN+ into S. oneidensis cell membrane increased the extracellular concentration of redox shuttles, i.e., flavins, and extracellular enzyme activities without significantly decreasing cell viability. The findings suggested that membrane permeabilization is the dominant mechanism for the enhancement of extracellular bioactivity in S. oneidensis by DSSN+. We further demonstrated that the interaction between DSSN+ and S. oneidensis cells enhanced biofilm formation and stability without compromising the overall biofilm activity. Taken together, our results suggest that membrane spanning conjugated oligoelectrolytes, of which DSSN+ is one of many possible molecular structures, may be applied to enhance extracellular bioactivity in bacteria toward more efficient biofilm-based biocatalysis.

Effect of Modified Phospholipid Bilayers on the Electrochemical Activity of a Membrane-Spanning Conjugated Oligoelectrolyte

“…Also, a 1 μM concentration corresponds to a value near the lower end of the range of functional concentrations examined in the literature. [8][9][10][11] Negative charge was introduced to the supported bilayers by adding cholic acid at different concentrations to the membrane during casting, as shown in Figure 4. Cholic acid is a moderately hydrophilic molecule that is negatively charged near neutral pH and which incorporates near the hydrophilic headgroups of phospholipid membranes promoting side chain disorder.…”

Membrane permeabilization by conjugated oligoelectrolytes accelerates whole-cell catalysis

“…The resulting ltrates were probed for extracellular ALP activity by monitoring conversion of non-uorescent 4-methylumbelliferyl phosphate (MUP) to uorescent 4-methylumbelliferone (4-MU). 30,34,35 The uorescence intensity linearly increased over 60 min for ltrates from both unstained, untreated (UT) and DSSN+ treated cells (selected examples are shown in Fig. 2).…”

“…10,15,21,22 Despite its utility, the origin of DSSN+ improvement in bioelectrochemical devices remains under debate. 9,10,17,21,[23][24][25][26][27][28][29][30] Model membrane studies have shown that COEs increase ion conductance across the membrane. 13 To add to mechanistic complexity, recent results suggest that COEs may interact with other components in the cell envelope, such as lipopolysaccharides and cholic acid.…”

Adjustable bidirectional extracellular electron transfer between Comamonas testosteroni biofilms and electrode via distinct electron mediators

“…Samples collected from chambers with biofilm A and C were filtered through 0.20 μm filters (Pall Corporation, Singapore) before acetate quantification using HPLC (Shimadzu, Singapore) as described in previous work [19,20].…”