Although biofilm-based bioprocesses have been increasingly used in various applications, the long-term robust and efficient biofilm performance remains one of the main bottlenecks. In this study, we demonstrated that biofilm cohesiveness and performance of Shewanella oneidensis can be enhanced through disrupting putrescine biosynthesis. Through random transposon mutagenesis library screening, one hyperadherent mutant strain, CP2-1-S1, exhibiting an enhanced capability in biofilm formation, was obtained. Comparative analysis of the performance of biofilms formed by S. oneidensis MR-1 wild type (WT) and CP2-1-S1 in removing dichromate (Cr ₂ O ₇ ²⁻ ), i.e., Cr(VI), from the aqueous phase showed that, compared with the WT biofilms, CP2-1-S1 biofilms displayed a substantially lower rate of cell detachment upon exposure to Cr(VI), suggesting a higher cohesiveness of the mutant biofilms. In addition, the amount of Cr(III) immobilized by CP2-1-S1 biofilms was much larger, indicating an enhanced performance in Cr(VI) bioremediation. We further showed that speF , a putrescine biosynthesis gene, was disrupted in CP2-1-S1 and that the biofilm phenotypes could be restored by both genetic and chemical complementations. Our results also demonstrated an important role of putrescine in mediating matrix disassembly in S. oneidensis biofilms.

Efficiently transporting extracellular electrons from microbial biofilms to the electrodes is challenging and critical in achieving high‐performance microbial fuel cells (MFCs). In this work, we develop a simple and effective method to fabricate hybrid electroactive biofilms by inserting bacteria into graphene–carbon‐nanotube (G–CNT) networks (namely, G–CNT‐biofilm) as an anode for MFCs. This novel architecture greatly enhances direct extracellular electron transfer between Shewanella oneidensis and the electrode, due to strong adhesion of the hybrid conducting biofilm onto the anode surface, as well as the large surface area of graphene and the high conductivity of CNTs. A current density of 120 μA cm⁻² and a maximum power density of 97.9 μW cm⁻² are obtained in the MFC with the hybrid biofilm anode, which is significantly higher than those of a naturally growing biofilm anode (20 μA cm⁻² and 6.5 μW cm⁻²).