Plant endophytic bacteria: a potential resource pool of electroactive microorganisms

Electroactive microorganisms play a significant role in microbial fuel cells (MFCs). These devices, which are based on a wide microbial diversity, can convert a large array of organic matter components into sustainable and renewable energy. At present, electricity-producing microorganisms are mostly isolated from sewage, anaerobic sediments and soil, however, the sources are very limited. For a more comprehensive understanding of the electron transfer mechanism of the electricity-producing microorganisms and the interaction with the environment, it is necessary to obtain a thorough understanding of their resource distribution and discover potential resources. In this study, plant tissues were selected to isolate endophytic bacteria, and the electrochemical activity potential of those bacteria was evaluated by high-throughput screening with a WO3 nanoprobe. Twenty-six strains of endophytic bacteria were isolated from plant tissues belonging to Angelica and Sweet Potato, of which 17 strains from 6 genera had electrochemical activity, including Bacillus sp., Pleomorphomonas sp., Rahnella sp., Shinella sp., Paenibacillus sp. and Staphylococcus sp.. Moreover, the electricity-producing microorganisms in the plant tissue are enriched. Microbial community analysis by high-throughput sequence indicated that Pseudomonas and Clostridioides are the dominant genera of MFC anode inoculated with angelica tissue.Staphylococcus and Lachnoclostridium 5 are the dominant genera in MFC anode inoculated with sweet potato tissue. And the most representative Gram-positive strain Staphylococcus succinus subsp. succinus H6 and plant tissue-inoculated MFC were further analyzed for electrochemical activity. After nearly 1500 h of voltage monitoring and cyclic voltammetry analysis, the results showed that a strain numbered H6 and plant tissue-inoculated MFC had a good electrogenerating activity. ImportanceSome biological characteristics of microorganisms are inextricably linked to their living environment. For plant endophytes, some of their biological characteristics have a profound impact on the host. The discovery of the production of electrobacteria in plants helps us to understand the interaction between microorganisms and plants more deeply. For example, there may be intercellular electron transfer between the internally producing bacteria and nitrogen-fixing bacteria to improve the efficiency of nitrogen fixation. In addition, there may be a connection between the weak electrical signal of the plant and the the endophytic electricity-producing microorganismsThe discovery of electricity-producing bacteria in plants also brings a more comprehensive understanding of the distribution of electricity-producing microbial resources and the mechanism of origin.