Marine Microalgae Symbiotic Bacterial Quorum Sensing Preliminary Research Activity And Algal Genes

The interaction of bacteria and alga is the research hotspot of marine biologicalcommunities interspecific relationship. It occupied an important position in themicroalgae elimination and community succession. Some research showed thatmicroalgicidal bacteria inhibited the growth of algae, even cracked algal cells to showthe dissolve algae effect. This kind of algicidal bacteria plays a very important role inbalancing the algae biomass. And proven the mechanism of action of algicidalbacteria is the key to research the interaction of bacteria and algal. Innovative putforward the microalgae symbiotic bacteria metabolic algal inhibition substances andPreliminary validation in this paper.Two hundred and six associated bacteria strains were isolated from marine algae.In order to characterize these strains, eleven bacteria with quorum sensing systemwere screened by biosensor method.11out of the206strains had quorum sensingsystem and they belong to three phylogenetic branches: α-Proteobacteria,γ-Proteobacteria and Gram bacteria. Acylhomoserine lactones (AHLs), as the quorumsensing signals, were detected in the extracts of active bacteria strains by gaschromatography-mass spectrometry (GC-MS). GC-MS analysis showed that all of the11screened strains contained C8-HSL, some also contained C6-HSL and C14-HSL.The algicidal activity study showed that9strains had inhibition effects in differentdegrees against four red tide microalgae including Prorocentrum donghaiense,Phaeocystis globosa, Thalassiosira sp. and Heterosigma akashiwo.Algal inhibiting compounds tracking filtering model was established bybioautography. Tetraselmis final concentration for105cell/mL was used as the targetalgal in this model. And cultivated6days in the light on solid medium. An algalinhibiting bacteria Rhodobacteraceae PD-2was taken as the research object andcultivated in large-scale. Its metabolic product was separated and purificated. An algalinhibiting compound was separated by TLC preparation based on the model ofscreening algal inhibiting compounds. LC-MS analysis showed that the molecularweight of the algal inhibiting compound was278.1643. Initially determined the molecular formula contained a benzene ring. HPLC analysis method according to thealgal inhibiting compound was established in this paper.And trace detected theMetabolic conditions of different growth period of PD-2. The production ofantibacterial substances of bacteria PD-2with density-dependence was confirmed,namely the production of antibacterial substances of bacteria PD-2was regulated byquorum sensing.The whole genome sequence of PD-2was sequenced by Illumina sequencingtechnology. Its whole genome sequence length was about4.915Mb. Encoding geneof PD-2sequencing data was predicted by Glimmer. And analysed the gene functionannotation by blasting the predicted sequence with COG, KEGG, GO, InterproScan,nr function database. The Acyl-homoserine lactone synthetase gene LuxI and LuxRgene fragments of quorum sensing transcriptional regulatory protein LuxR wasobtained from whole genome of bacteria PD-2, thus we preliminary demonstrated thatLuxI/LuxR quorum sensing regulatory system exist in bacteria PD-2from themolecule level.This work provided theoretical basis for microalgae-associated bacteriainhibiting activity of algal is regulated by quorum sensing. Provided a new way forred tide prevention and control.