Abstract
SummaryThe ability to directly modify native and established biofilms has enormous potential in understanding microbial ecology and application of biofilm in 'real‐world' systems. However, efficient genetic transformation of established biofilms at any scale remains challenging. In this study, we applied an ultrasound‐mediated DNA delivery (UDD) technique to introduce plasmid to established non‐competent biofilms in situ. Two different plasmids containing genes coding for superfolder green fluorescent protein (sfGFP) and the flavin synthesis pathway were introduced into established bacterial biofilms in microfluidic flow (transformation efficiency of 3.9 ± 0.3 × 10‐7 cells in biofilm) and microbial fuel cells (MFCs), respectively, both employing UDD. Gene expression and functional effects of genetically modified bacterial biofilms were observed, where some cells in UDD‐treated Pseudomonas putida UWC1 biofilms expressed sfGFP in flow cells and UDD‐treated Shewanella oneidensis MR‐1 biofilms generated significantly (P < 0.05) greater (61%) bioelectricity production (21.9 ± 1.2 µA cm−2) in MFC than a wild‐type control group (~ 13.6 ± 1.6 µA cm−2). The effects of UDD were amplified in subsequent growth under selection pressure due to antibiotic resistance and metabolism enhancement. UDD‐induced gene transfer on biofilms grown in both microbial flow cells and MFC systems was successfully demonstrated, with working volumes of 0.16 cm3 and 300 cm3, respectively, demonstrating a significant scale‐up in operating volume. This is the first study to report on a potentially scalable direct genetic engineering method for established non‐competent biofilms, which can be exploited in enhancing their capability towards environmental, industrial and medical applications.
Highlights
Microbial biofilms are one of the most widely distributed and successful modes of life on Earth, where they drive vital biogeochemical cycling processes of most elements in water, soil, sediments and subsurface environments (Stoodley et al, 2002)
A ultrasound-mediated DNA delivery (UDD) system consisting of samples submerged in a commercial ultrasonic water bath was set up to examine the effectiveness of ultrasound to transfer plasmids to biofilms of Pseudomonas putida UWC1 and Shewanella oneidensis MR-1 (Fig. 1A and B)
Before UDD, the P. putida UWC1 biofilm was established in microfluidic flow cells (Fig. 1A) and the S. oneidensis MR-1 biofilm was established on an electrode surface (Fig. 1B)
Summary
Microbial biofilms are one of the most widely distributed and successful modes of life on Earth, where they drive vital biogeochemical cycling processes of most elements in water, soil, sediments and subsurface environments (Stoodley et al, 2002). Biofilms can be useful and have long been exploited in bioengineered applications including the degradation of wastewater and solids applied to the filtration of potable water (Halan et al, 2012; Meckenstock et al, 2015). A key feature of most biofilms is that they are composed of diverse communities, enabling them to perform functions that are difficult or impossible for individual species to achieve (Stewart and Franklin, 2008; Elias and Banin, 2012). Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology
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