Isolation And Identification Of Commensal Bacteria Of Euglena Gracilis And The Research Of Algal-bacterial Co-cultures

In this study,Euglena gracilis was used as an experimental object to isolate and identify cultivatable interstitial bacteria of Euglena gracilis.The isolated bacteria were then co-cultured with Euglena gracilis,and by measuring the growth indicators of Euglena gracilis(cell density and chlorophyll a content),the strains that promoted the growth of Euglena gracilis were screened,and the dominant strains were identified.The optimal initial inoculation concentration was further explored through the study of the metabolites of Co-culture of algae and bacteria system and the pure algae culture system to explore the mechanism of co-cultivation of algae and bacteria to promote the growth of Euglena gracilis1.Isolate the algae bacteria of Euglena gracilis by using the dilution coating plate method,and then purify the bacteria with the method of streaking the plate.After that,the bacteria were identified by 16 S r DNA molecules and the physiological,biochemical indicators and morphological characteristics of bacteria.Finally,5 algae bacteria strains isolated from Euglena gracilis which can be cultivated were ?-proteobacteria:E1-Paraburkholderia fungorum(MG₅76012),?-proteobacteria:E3-Methylobacterium radiotolerans(NR₀36824),?-proteobacteria:E5-Sphingomonas dokdonensis(NR₀43612),?-proteobacteria: E6-Ralstonia insidiosa(AF₄88779)and Actinomycetes :ET2-Leifsonia soli(MH₄97612).2.Co-culture the five isolated strains with Euglena gracilis,and evaluate the effects of the five Euglena gracilis on the growth of Euglena gracilis by measuring the growth indicators of Euglena gracilis.The results show that E5,E3 and E1 strains have significant effects on the growth of Euglena gracilis.E5 has the most significant effect on promoting the growth of Euglena gracilis.The two strains of E6 and ET2 have no significant effect on Euglena gracilis.Effect.The five different initial inoculation concentrations of E5 strains 104?105?106 ?107and 108 cfu/m Lall promoted the growth of Euglena gracilis.The promotion effect of Euglena gracilis in the concentration range of 105-107 cfu / m L increased with increasing concentration.Increase,the best promotion concentration is 107 cfu / m L.3.Based on the analysis of metabolites of E5(Sphingomonas dokdonensis)strains of Euglena gracilis co-culture system and pure algae culture system,we explored the mechanism of E5 bacteria-algae co-culture to promote the growth of Euglena gracilis.The metabolite detection results were a total of 82 differential metabolites detected in positive and negative ion modes,mainly amino acid,fatty acid,phosphate,nucleotide and other metabolites.Among them,51 different metabolites were detected in positive ion mode.Compared with the control group,arginine,asparagine,deoxyadenosine,and adenine,fatty acids and other metabolites were significantly up-regulated.Glutamate and histidine Metabolites such as amino acids,alanine,and choline were significantly down-regulated.A total of 46 differential metabolites were detected in the negative ion mode.Among them,asparagine,aspartic acid,and fatty acids such as myristic acid and palmitoleic acid were significantly up-regulated.Glutamate,alanine,tryptophan,and casein Amino acids such as amino acids,phosphoric acid,and succinic acid are significantly down-regulated.