Effect Of Carbon Source On Secondary Metabolic Regulation Of Serratia Marcescens By Flow Cytometry

Serratia marcescens(S. marcescens) is a Gram-negative bacteria, which widely exists in environment. It is reported as an opportunistic pathogen of coelenterates, insects,nematodes, plants, and mammals including humans. The nature red pigment prodigiosin(PG) is a kind secondary metabolite of S. marcescens, it has been certified possessing multiple biological activities. It is noticeable because the mechanism of cancer cell apoptosis resulted from PG is quite different from the current clinical anti-cancer drugs.It is promising to be new anti-cancer drugs. Research on the cell cycle is mainly in the eukaryotic cell currently, however, this article innovatively applied flow cytometry to study the pattern of growth and metabolism of prokaryotic cells in S. marcescens. The present work may provide a theoretical basis for the clinical study of infections caused by this Gram-negative bacteria and improving PG production, and but also is an important reference for studying prokaryotic cell cycle.In order to find out the regulation of carbon source on secondary metabolic in S.marcescens, first the cyclic adenosine monophosphate(cAMP) was added in the medium,sucrose as the carbon source, to study the influence of cAMP on carbon metabolism in bacteria. Then we use different carbon sources such as beef extract, sucrose, glycerol and glucose to compare the synthesis of the secondary metabolites PG. The main work was as follows: 1. As the intracellular cAMP level elevated, carbon source utilization was more efficiency, and cells division,DNA replication accelerated, and the morphology of the cells changed, and at last the biosynthesis of PG was blocked. Those results show that cAMP plays an important role in the carbon metabolism. 2. Fermentation with different carbon sources, the dry cell weight was compared: beef extract >sucrose> glycerol>glucose, and PG level was compared: sucrose> glucose> glycerol >beef extract.Combined with flow cytometry analysis, we obtained the following results: using different carbon sources, it causes a series of changes in the metabolic pathway, cell division and growth speed, replication rate of genes, morphological structure, and PG production. To sum up, we know that carbon sources enormously influenced thesecondary metabolites PG biosynthesis in S. marcescens. Of the four carbons, beef extract, sucrose, glycerol and glucose, sucrose is more suitable. 3 The results also confirmed that cell division and growth, gene duplication and the genome distribution,secondary metabolic states are normally coordinated with nutrient substances.We investigated the fermentation process of S. marcescens in five liters fermenter,including the effects of carbon, phosphate, media formulations, dissolved oxygen and feed supplement on PG production. The preliminary results are as flollows: to maintain more than 30% dissolved oxygen, and limit phosphate; initial media formulations: 0.25%sucrose, 1.5% peptone, 0.5% NaCl, 0.25% anhydrous magnesium chloride, 0.5%Tween-80; feeding supplements after 60 hours and its formulations: 0.5% sucrose and 0.5 % Tween-80.