Growth Characteristics Of An Oligotrophic Bacterium Bacillus Subtilis G1 And Genes Expression And Regulation Of Glucose Metabolism

Oligotrophic Bacteria are widely possessed in barren environments.Currently,there are few reports on glucose utilization,glucose metabolism and regulation mechanism of Oligotrophic Bacteria.This research based on a oligotrophic bacterium Bacillus subtilis G1(G1 strain for short)which was isolated from desert biological crust to study the bacteria growth,characteristics of glucose and energy metabolism,expression and regulation of key enzyme genes in glucose metabolism pathway under different glucose concentrations.It is expected to provide new basic research data for elucidating the nutritional characteristics of Oligotrophic Bacteria.The main research results are as follows:(1)Compared with the control Bacillus subtilis 168 strain(168 strain for short),G1 strain showed low glucose consumption rate,low growth rate,less acid production,long growth cycle and high final biomass at the same initial glucose concentration,and the extracellular polysaccharide yield of G1 strain was lower than that of 168 strain under the same initial glucose concentration.(2)Among the 11 key genes of glycolysis,tricarxylic acid cycle and energy metabolism pathway in G1 strain and 168 strain,the corresponding enzymes of zwf,citA,sdhB and atpG genes were significantly different in primary structure,with the similarity of 5.32%,7.32%,6.75%and 5.61%,respectively,but the 11 enzymes were highly similar in their secondary and tertiary structures.(3)The expression levels of genes related to glucose metabolism were different between G1 strain and 168 strain during the growth process.The overall trend was that the gene expression levels reached the highest in the middle logarithmic phase and decreased in the stable phase.However,compared with 168 strain,the expression levels of key genes in G1 strain changed little at different culture stages,and were significantly lower than that of 168 strain.(4)The sequences of-10 and-35 regions of promoter PpfkA,PsdhB,Pzwf were the same between strain G1 and 168 with the same distance of 17 bp.Within 7 bp upstream of-10 region,the conserved sequences and loci of the two strains were very different.Therefore,the difference in promoter strength between the two strains may be caused by the difference of 7 bp base in the upstream of-10 region.(5)The promoter intensity of key enzyme gene of glucose metabolism in G1 strain was lower than that of corresponding promoter in 168 strain,and the promoter intensity of G1 strain was significantly lower than that of 168 strain in logarithmic growth period.In different culture periods,the promoter intensity also changed,but the change range of promoter intensity of G1 strain was much lower than that of 168 strain.