Study On The Inhibiting Mechanism Of Algae Stenotrophomonas Maltophilia JX14 By Bacterial Scrippsiella Trochoidea

Harmful algal blooms are an abnormal ecological phenomenon caused by the mass reproduction of plankton in water.In recent years,they are spreading to the whole world and threatening marine life and human health.Therefore,control has become an urgent problem to be solved.In addition,marine microbes play an important role in promoting the circulation of marine materials and maintaining the stability of ecosystems.Therefore,more and more researchers are trying to study the mechanism of algae inhibition by microorganisms.However,the research on algae-suppressing microorganisms is still in the early stage,and the discussion on the mechanism of algae inhibition based on molecular level is not deep enough.Therefore,this thesis adopts molecular means,taking the dominant red tide algae Scrippsiella trochoidea as the research object,from the screening of algae-suppressing algae strains,the analysis of algae inhibition mechanism and the verification of algae activity.Systematic research has mainly achieved the following results:(1)The first part of the thesis is the screening and identification results of high-efficiency algae-stable.180 strains of bacteria were isolated from the algae,and 8 strains of algae-inhibiting bacteria were obtained.Among them,the strain with high algae-inhibiting activity was JX14,which was identified as Stenotrophomonas maltophilia by 16 S rRNA gene sequence.(2)The second part of the thesis is the mechanism of algae inhibition by algae strain JX14.Under the action of strain JX14,the algae-inhibiting effect increased with the increase of bacterial density.The activity of reactive oxygen species(ROS)gradually increased at first,and then drop sharply.The chlorophyll content and biomass of algae decreased gradually,while the biomass of bacteria increased gradually.The algae consumption of inorganic nitrogen and phosphorus in nutrient solution was significantly reduced;the activity of elastase and cellobiase enzymatically secreted by strain JX14 was gradually increased,and the growth of algae cells was significantly inhibited.During the oxidative phosphorylation of algal cells,the(Nicotinamide adenine dinucleotide)dehydrogenase gene NADH,the coenzyme ? s ystem water molecule synthase gene,and the coenzyme ? s ystem cytochrome b gene Cytb are up-regulated,and the ADP synthase gene is down-regulated,resulting in The phototransfer phosphorylation electron transport process of algae cells is inhibited.During the algal cell protein export process,the signal peptide receptor protein gene FtsY is down-regulated,which can down-regulate the gene SEC61? which degrades the misfolded peptide chain,resulting in protein export-related physiological processes suppressed.(3)The third part of the thesis is the results of extraction of algae-killing compounds and the conclusion of activity verification.The strain JX14 does not compete with the host algae nutrition,but secretes extracellular high temperature resistant active substances and extracellular enzymes to inhibit algae.Algae-killing compounds JX-A? JX-B? JX-C? JX-D?JX-E? JX-F and JX-G are obtained,that the content of wich was 125 mg/L,264 mg/L,315 mg/L,704 mg/L,425 mg/L,392 mg/L,316 mg/L.JX-B,JX-C,JX-D are the same species of algae-killing compound JX-B3 continuously secreted by strain JX14 during co-culture of algae.The minimum algae-inhibiting concentration of JX-B3 for algae treatment for more than 2 h is 128.3 mg/L.