A Preliminary Exploration Of The Relationship Between Nannochloropsis Maritime And Marine Bacteria

Algae are the undisputed primary producers in the aquatic ecosystem and contribute approximately half of the global net primary productivity.It's gradually building up a complex and intimate interaction between eukaryotic algae and prokaryotic bacteria after a long natural evolution.Algae and bacteria can affect each other's physiological and metabolic processes in a variety of ways.The co-evolution of algae and bacteria reforms the ecosystem in many aspects.Besides,these widespread interactions are of ecological and biogeochemical significance.N.maritimebelongs to Chlorophyta which is simple in structure and rich in nature pigments.N.maritime is a kind of emerging economic algae which has a strong ability to accumulate biolipid.In order to understand the composition of microbial community,16 S rDNA gene sequences were employed to analyze members of the community by using the high-throughput sequencing technology.The results demonstrated that there was a large quantity of bacteria within the phycosphere.Totally,127 unique OTUs and 46016 aligned sequences were identified.Based on the analysis of different OTUs,the composition of microbial community were photosynthetic organisms(64.4%),Alphaproteobacteria(16.5%),Flavobacteria(13.1%),and others(5.9%).In addition,the analysis results of species dominance index were: Cyanobacteria(64.4%),Bacteroidetes(13.25%),Firmicutes(0.21%),and Actinobacteria(0.05%)respectively.Some symbiosis systems were built up between microalgae and marine bacteria,which were N.maritime mixed with Roseobacter sp.,Marinobacter sp.,and Stappia indica respectively.The influences of Roseobacter sp.and Marinobacter sp.on the growth of N.maritime were hardly observed.However,in the combination of N.maritime and S.indica,some significant promoting effects were observed on the growth of algae.Thus,S.indica seems to act as an algae growth-promoting bacteria.Moreover,in the aspect of microalgae's photosynthetic parameters,there were a visible difference between the experimental group and control group.The results above suggests that S.indica might play an important role in the microalgae-bacteria symbiotic system.