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Microbial co-culture simulates the natural ecosystem through the combination of artificial microbes. This approach has been widely applied in the study of activating silent genes to reveal novel secondary metabolites. However, there are still challenges in determining the biosynthetic pathways. In this study, the effects of microbial co-culture on the morphology of the microbes were verified by the morphological observation. Subsequently, through the strategy combining substrate feeding, stable isotope labeling, and gene expression analysis, the biosynthetic pathways of five benzoic acid derivatives N1-N4 and N7 were demonstrated: the secondary metabolite 10-deoxygerfelin of A. sydowii acted as an inducer to induce B. subtilis to produce benzoic acid, which was further converted into 3-OH-benzoic acid by A. sydowii. Subsequently, A. sydowii used 3-OH-benzoic acid as the substrate to synthesize the new compound N2, and then N1, N3, N4, and N7 were biosynthesized upon the upregulation of hydrolase, hydroxylase, and acyltransferase during co-culture. The plate zone analysis suggested that the biosynthesis of the newly induced compounds N1-N4 was mainly attributed to A. sydowii, and both A. sydowii and B. subtilis were indispensable for the biosynthesis of N7. This study provides an important basis for a better understanding of the interactions among microorganisms, providing new ideas for studying the biosynthetic pathways of the newly induced secondary metabolites in co-culture.

Interspecific interaction mediated crosstalk was regarded as an important feature among the microorganisms under natural conditions and also the key mechanism for the biosynthesis of newly induced compounds in the co-culture. However, there is still a lack of direct experimental evidence for this mechanism. In this study, the interaction between A. sydowii and B. subtilis in the co-culture was firstly verified by the morphological observation. Subsequently, through the strategy combining substrate feeding, stable isotope labeling and gene expression analysis, the crosstalk in the co-culture for the production of five benzoic acid derivatives (N1-N4 and N7) were demonstrated: the secondary metabolites 10-deoxygerfelin of A. sydowii acted as an inducer to induce B. subtilis to produce benzoic acid, which was further converted into 3-OH-benzoic acid by A. sydowii. Subsequently, A. sydowii used 3-OH-benzoic acid as the substrate to synthesize the new compound N2, and then N1, N3, N4 and N7 were biosynthesized upon the up-regulation of hydrolase, hydroxylase, and acyltransferase during co-culture. The plate zone analysis suggested that the biosynthesis of the newly induced compounds N1-N4 was mainly attributed to A. sydowii, and both A. sydowii and B. subtilis were indispensable for the biosynthesis of N7. The current study provides an important basis for a better understanding of the metabolites transfer and the biosynthetic pathways of the newly induced compounds in the co-culture, providing a new insight into the interaction-mediated crosstalk among microorganisms.

For the pulse wave signal acquired by the pulse analyzer, it’s necessary to remove the large number of noise signal by noise reduction processing. For signal noising processing using wavelet transform method in the time domain and frequency domain and the signals can characterize the ability of local information, and it is self-adaptive. Determine the main wave peak and trough points based on extreme value method and pulse wave periodicity, using the threshold method to determine the dicrotic wave starting point and dicrotic wave peaks, we also use the MATLAB programming to implement the algorithm.

In the traditional precision machining, it is easy to introduce positioning error because of the separation of the machining and the measurement. In order to solve this problem, an online measurement technique for aspheric grinding has been put forward. It measured the workpiece with sensor which was fixed to the high-precision machine tool. It processed data with the algorithm of Two-dimensional weighted average filtering and curve fitting based on Gauss-Newton and Levenberg-Marquardt least-square method. The experimental results indicated that the fitting residual error was less than 3×10-6 mm. In the grinding process, the measurement error was of the order of the magnitude of 10-3 mm. It can be concluded that the technique measures the surface exactly, and improves the machining accuracy effectively by providing accurate data for compensation.