Study On Transcriptome And Metabolome Of Escherichia Coli NCM3722 At Different Temperatures

In this study,high-throughput RNA sequencing and non-targeted metabolome were used to investigate the effects of different temperatures(28?,37?,42?)on the transcriptome and metabolome of Escherichia coli K-12 wild-type strain,NCM3722.By high throughput RNA sequencing,the expression changes of all genes in NCM3722 at different temperatures were obtained.By data analysis,657 differentially expressed genes were obtained.Among them,the number of differential genes of 28? versus 42? is 595,accounting for 90.56% of the total number of differential genes.The number of differential genes of 28? versus 37? is 236,and the number of differential genes of 37? and 42? is154.Then we analyze the trend of the variation of differential genes with increasing of temperature,which can be grouped into 8 trends,namely down-down(profile0),down-unchanged(profile1),down-up(profile2),unchanged-down(profile3),unchanged-up(profile4),up-down(profile5),up-unchanged(profile6)and up-up(profile7).Among them,profile0,profile1 and profile3 belong to the downward trend,and contain 175 genes.Profile4,profile6 and profile7 belong to the upward trend,and contain 445 genes.By the GO enrichment and pathway enrichment analysis of genes in ascending and descending trends,and by combining with operon analysis,we found that genes in the uptrend are mainly related to metabolism,transporter synthesis,enzyme synthesis and hormone synthesis.In the downward trend,the genes are mainly involved in maltose synthesis transporting proteins,biofilm protein synthesis and efflux of metal ion.The metabolites at 28?,37?,and 42? were qualitatively and quantitatively determined by non-targeted metabolomics analysis using gas chromatography-mass spectrometry.The number of metabolites quantified was 177 in the bacterial culture solution and 232 in the bacterial cells.The differential metabolites in the bacterial culture solution and the bacterial cells were screened separately,and the trends of the changes of metabolite content with the increasing of temperature were analyzed.It was found that a large amount of organic acids,alcohols,sugars and amino acids were contained in both of the rising trend andthe decreasing trend.In addition,the content of glycolysis-related metabolites increased at28?.In contrast,the content of intermediate metabolites in the TCA cycle increased at 37?and 42?.Finally,in order to study the mechanism of low temperature(28?)induced high expression of genes related to maltose metabolism and validate the transcriptome data,we respectively constructed the promoter-lacZ fusion strains of malE and malT.MalT encodes transcriptional activator of malE.We measured the ?-galactosidase activities of the two strains at 28?,37? and 42?.In consistent with the transcriptome data,the expression of malE was highly induced at low temperature but the expression of malT showed no changes.We predicted that at low temperature the ligand of MalT,maltotriose might accumulate and induce malEFG accordingly.