The potential utility of black soldier fly larvae (BSFL) to convert animal waste into harvested protein or lipid sources for feeding animal or producing biodiesel provides a new strategy for agricultural waste management. In this study, the taxonomic structure and potential metabolic and nutrient functions of the intestinal bacterial communities of BSFL were investigated in chicken and swine manure conversion systems. Proteobacteria, Firmicutes and Bacteroidetes were the dominant phyla in the BSFL gut in both the swine and chicken manure systems. After the larvae were fed manure, the proportion of Proteobacteria in their gut significantly decreased, while that of Bacteroidetes remarkably increased. Compared with the original intestinal bacterial community, approximately 90 and 109 new genera were observed in the BSFL gut during chicken and swine manure conversion, and at least half of the initial intestinal genera found remained in the gut during manure conversion. This result may be due to the presence of specialized crypts or paunches that promote microbial persistence and bacteria-host interactions. Ten core genera were found in all 21 samples, and the top three phyla among all of the communities in terms of relative abundance were Proteobacteria, Firmicutes and Bacteroidetes. The nutrient elements (OM, TN, TP, TK and CF) of manure may partly affect the succession of gut bacterial communities with one another, while TN and CF are strongly positively correlated with the relative abundance of Providencia. Some bacterial taxa with the reported ability to synthesize amino acids, Rhizobiales, Burkholderia, Bacteroidales, etc., were also observed in the BSFL gut. Functional analysis based on genes showed that intestinal microbes potentially contribute to the nutrition of BSFL and the high-level amino acid metabolism may partly explain the biological mechanisms of protein accumulation in the BSFL body. These results are helpful in understanding the biological mechanisms of high-efficiency nutrient conversion in BSFL associated with intestinal microbes.

Strand displacement reactions are important bricks for the construction of various DNA nanodevices, among which the toehold-mediated strand displacement reaction is the most prevalently adopted. However, only a limited number of tools could be used to finely regulate the toehold reaction, thus restricting DNA nanodevices from being more multifunctional and powerful. Herein, we developed a regulation tool, Clip, and achieved multiple regulatory functions, including subtle adjustment of the reaction rates, allosteric strand displacement, selective activation, and resetting of the reaction. Taking advantages of the multiple functions, we constructed Clip-toehold-based DNA walking machines. They showed behaviors of controllable walking, concatenation, and programmable pathways. Furthermore, we built Clip-toehold-based AND and OR logic gates and integrated those logic gates to construct multilayer circuits, which could be reset and reused to process different input signals. We believe that the proposed Clip tool has expanded the functionality of DNA strand displacement-based nanodevices to a much more complex and diverse level and anticipate that the tool will be widely adopted in DNA nanotechnology.

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