Effects Of Different Culture Methods On Growth And Metabolic Mechanism Of Euglena Gracilis

The microalgae,with a wide variety of nutrients,has high application value,and has become a hot research topic.In this paper,Euglena gracilis was used as the experimental object.This paper studied the changes of physiological,biochemical and metabolites of E.gracilis under four cultivation modes(autotrophic,mixotrophy,heterotrophic and photoinduced)from physiological,biochemical and molecular level.The aim of this study is to provide a scientific basis for elucidating the response of E.gracilis to different culture methods,and to provide theoretical support for its development and application.The results are as follows:1.Ecotoxicological method was used to study the sensitivity of E.gracilis to four kinds of antibiotics.The results are as follows: from strong to weak,the susceptibility to four antibiotics of E.gracilis is as follows: Geneticin G418>Terramycin>Chloramphenicol>Penicillin.According to the changes of cell density and chlorophyll-a content under the action of four antibiotics,penicillin can be used as an alternative antibiotic for the establishment of aseptic strain of E.gracilis.2.The changes of intracellular products of E.gracilis under four cultivation methods were studied by means of experimental ecological method.The results are as follows: the contents of chlorophyll-a from high to low are: mixotrophy >photoinduced>autotrophic>hetetrophic;Chl-b are: heterotrophic>photoinduced>mixotrophy>autotrophic;Carotenoids are:mixotrophy>photoinduced>autotrophic>heterotrophic;Fatty acid are: photoinduced>heterotrophic>mixotrophy>autotrophic;saturated fatty acid(SFA): heterotrophic>photoinduced>autotrophic>mixotrophy;monounsaturated fatty acid(MUFA): photoinduced>Heterotrophic>mixotrophy>autotrophic;polyunsaturated fatty acid(PUFA): photoinduced>mixotrophy>autotrophic>heterotrophic;amino acid: photoinduced> mixotrophy>heterotrophic>autotrophic.3.The ultrastructure of E.gracilis under four cultures was observed by transmission electron microscopy.The results are as follows: the order of pigment body content from high to low is autotrophic>mixotrophy>photoinduced>heterotrophic.During heterotrophic process,the pigment body degenerated and the lamellar structure disappeared.The pigment body and inner lamellar structure recovered after photoinduction.The order of starch content from highto low is: heterotrophic>photoinduced>autotrophic>mixotrophy.4.A total of 120,086 Unigenes genes were obtained by molecular biological method from the transcriptome sequencing of E.gracilis,with an average length of 636 bp.There are differences in gene expression patterns among four cultures.There were 1969 DEGs between autotrophic group and mixotrophy group,among which,886 genes were up-regulated and1083 genes were down-regulated.There were 5061 DEGs between heterotrophic group and mixotrophy group,among which,2466 genes were up-regulated and 2595 genes were down-regulated.There were 2872 DEGs between heterotrophic group and photoinduced group,among which,1541 genes were up-regulated and 1331 genes were down-regulated.5.The results of KEGG Pathway Annotation of differential genes by Molecular Biology are: the differentially expressed genes are significantly enriched in the photosynthesis pathway.A total of 60 genes were enriched in the photosynthesis pathway,among which 3genes were differentially expressed between autotrophic and mixotrophy groups,and 21 DEGs were differentially expressed between heterotrophic and mixotrophy groups,and 18 DEGs were differentially expressed between heterotrophic and photoinduced groups.