Characterization and mechanism of the effects of Mg–Fe layered double hydroxide nanoparticles on a marine bacterium: new insights from genomic and transcriptional analyses

Background Layered double hydroxides (LDHs) have received widespread attention for their potential applications in catalysis, polymer nanocomposites, pharmaceuticals, and sensors. Here, the mechanism underlying the physiological effects of Mg–Fe layered double hydroxide nanoparticles on the marine bacterial species Arthrobacter oxidans KQ11 was investigated. Results Increased yields of marine dextranase (Aodex) were obtained by exposing A. oxidans KQ11 to Mg–Fe layered double hydroxide nanoparticles (Mg–Fe-LDH NPs). Furthermore, the potential effects of Mg–Fe-LDH NPs on bacterial growth and Aodex production were preliminarily investigated. A. oxidans KQ11 growth was not affected by exposure to the Mg–Fe-LDH NPs. In contrast, a U-shaped trend of Aodex production was observed after exposure to NPs at a concentration of 10 μg/L–100 mg/L, which was due to competition between Mg–Fe-LDH NP adsorption on Aodex and the promotion of Aodex expression by the NPs. The mechanism underling the effects of Mg–Fe-LDH NPs on A. oxidans KQ11 was investigated using a combination of physiological characterization, genomics, and transcriptomics. Exposure to 100 mg/L of Mg–Fe-LDH NPs led to NP adsorption onto Aodex, increased expression of Aodex , and generation of a new Shine-Dalgarno sequence (GGGAG) and sRNAs that both influenced the expression of Aodex . Moreover, the expressions of transcripts related to ferric iron metabolic functions were significantly influenced by treatment. Conclusions These results provide valuable information for further investigation of the A. oxidans KQ11 response to Mg–Fe-LDH NPs and will aid in achieving improved marine dextranase production, and even improve such activities in other marine microorganisms.