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

Abstract

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. Electronic supplementary material The online version of this article (10.1186/s13068-019-1528-2) contains supplementary material, which is available to authorized users.

Molecular Mechanisms of Nanomaterial-Bacterial Interactions Revealed by Omics—The Role of Nanomaterial Effect Level

“…Although a mutation analysis of the GOQD-exposed B. cereus was not conducted ( Mu et al, 2019 ), ENM-induced genetic mutations in bacteria have been reported. For example, the changed transcript sequence was one of the underlying mechanisms of the stimulatory effect of Mg–Fe layered double hydroxide (Mg–Fe LDH) in the marine bacterium Arthrobacter oxidans which increased its exodextranase yields upon ENM exposure ( Ren et al, 2019b ). Namely, transcriptomics revealed that exposure to Mg–Fe LDH led to formation of a new Shine-Dalgarno sequence (ribosomal binding site in bacterial messenger RNA) that influenced the expression of dextranase.…”

“…Fe-S clusters have been reported to be sensitive to ROS and metal ions such as copper, silver, cadmium and zinc ( Xu and Imlay, 2012 ; Vernis et al, 2017 ), which explains the dysregulation of these proteins in several studies with Ag NPs ( McQuillan and Shaw, 2014 ; Gambino et al, 2015 ) and a study involving CdTe QDs ( Aunins et al, 2019 ). Also, Mg-Fe LDHs at stimulatory concentrations were reported to downregulate the Fe-S cluster assembly ( Ren et al, 2019b ). The primary role of Fe-S clusters is electron transfer, but also transcriptional and translational regulation via sensing the changes in cellular redox conditions ( Kiley and Beinert, 2003 ).…”

“…Second, risk assessment of ENM exposures to environmental and beneficial bacteria may be of interest ( Holden et al, 2013 , 2014b ). Lastly, as an emerging trend, ENMs can stimulate beneficial bacterial functions ( Mu et al, 2019 ; Peng et al, 2019 ; Ren et al, 2019b ; Yan et al, 2019 ). Successful accomplishment of these aims requires detailed knowledge of the underlying mechanisms of ENM-bacterial interactions.…”

Isolation and Characterization of Cellulolytic Marine Bacteria for Litopenaeus Vannamei Aquaculture Using Sugarcane Bagasse as Carbon Source

“…In addition, the oceans, which covers more than three quarters of the Earth's surface, is an open ecosystem. It has been estimated that at least 50%, and potentially more than 90%, of all marine species are undescribed [33][34][35][36]. Marine microorganisms have been recognized as potential sources of novel enzymes with better biocatalytic properties than their terrestrial counterparts.…”

“…Marine microorganisms have been recognized as potential sources of novel enzymes with better biocatalytic properties than their terrestrial counterparts. These properties, such as salt tolerance, hyperthermostability, barophilicity, alkali-resistance, and low optimum temperatures, are necessary for e cient bioprocesses exploitation [33][34][35][36]. Hainan is a big maritime province in China and rich in marine resources, but the knowledge of cellulolytic microbes isolated from this area is limited.…”