Responses Of Two Species Of Marine Bait Microalgae To The Interference Of Associated Heterotrophic Bacteria And Environmental Factors

Marine resource is an important natural resource.In marine ecosystems,as an important primary productivity,marine microalgae especially bait microalgae has a close relationship with Symbiosis of heterotrophic bacteria including beneficial symbiosis and mutual antagonism.Symbiotic system of algae and bacteria can regulate the population structure and quantity of the microalgae and bacteria,inhibit the growth of harmful bacteria and show advantages compared with using microalgae alone.In recent years,with the living environment of the marine bait microalgae becoming more and more serious for the matters of environment and other issues and the increasing of the demand for high quality aquatic products,the systematic study to the protection of marine bait microalgae and the symbiotic system of algae and bacteria is imperative.In this study,we choose two kinds of high-quality marine bait microalgae-Pyramimonas sp.and Platymonas subcordiformisas the research material.The ecological methods is systematically used to study the response to the coercion of the two kinds of marine bait microalgae to the heterotrophic bacteria and the influence of environmental factors to them.The purpose is to explore the rule between marine microalgae and associated heterotrophic bacteria and define the best environmental conditions of the interaction.Also,the study is aimed at providing scientific theoretical basis to restore and maintain the reasonable structure of the marine ecosystem and improve the ecological environment of aquaculture water.The main results of the study are as follows:1.Identify the associated heterotrophic bacteria W-TJ01 preserved in laboratory by phenotypic observation,Gram stain method and 16 S r DNA and it was found that the similarity of the W-TJ01 and Bacillus cereus(KT462576.1)is 100% and belongs to the genus Bacillus.Choose 2216 E as the medium and produce at 30?,160r/min with continuing for 48 hours and make sampling every 2 hours in the first 6 hours and every 3 hours in the following hours.Determine the relationship of the optical density(OD)and the p H to time variation.The growth characteristics of the associated heterotrophic bacteria W-TJ01 is supposed to be mastered: bacteria W-TJ01 enters the logarithmic growth phase at 2h,enters the stable period after 18 h and lasts so long,the p H shows drop at first and keeps increasing during logarithmic growth phase.The study provides convenience to the following research to explore the relationship of marine bait microalgae and associated heterotrophic bacteria W-TJ01 and avoids determining the density of the complex operation each time.The 2216 E plate coated colony counting method is used to determine the linear relationship between the bacterial population density and the density of the optical density-y=26.12x-5.893,r2=0.917.2.(1)According to the experimental results of physiological response to the coercion given by Pyramimonas sp.to seven kinds of concentrations of associated heterotrophic bacteria such as 101,103,105,106,5×106,107,108cfu/m L: when the concentration is lower than 5×106cfu/m L and 107cfu/m L,with the concentration increasing,the content of chlorophyll a in Pyramimonas sp.keeps increasing;when the concentration is over 107cfu/m L,with the concentration of the associated heterotrophic bacteria increasing,the content of chlorophyll a in Pyramimonas sp.shows declining compared with control group and the concentration where the associated heterotrophic bacteria W-T01 promotes the content of chlorophyll a in Pyramimonas sp.most is 5×106cfu/m L.The response to coercion of SOD activity of Pyramimonas sp.and content of GSH to associated heterotrophic bacteria in different concentration shows similar regularity to content of chlorophyll a.The treatment group of 5×106cfu/m L brings best effect to SOD activity of Pyramimonas sp.and content of GSH.When the concentration of the associated heterotrophic bacteria is 5×106cfu/m L,the content of MDA in Pyramimonas sp.is reduced and ensuring the healthy grows of cells.(2)The result predictions of influence for the nine different treatments to the content of chlorophyll a in Pyramimonas sp.: The mode of action of associated heterotrophic bacteria to Pyramimonas sp.is cell direct action and combined action of intracellular product and high-temperature macromolecular extracellular product.(3)The result indication of influence for the three environmental factors such as temperature,light period and salinity to associated heterotrophic bacteria acting on Pyramimonas sp.: The suitable temperature of associated heterotrophic bacteria acting on Pyramimonas sp.is 20-30? and the best temperature is 25?.The light period of 12:12h shows best effect to associated heterotrophic bacteria acting on Pyramimonas sp.and the suitable salinity range is 20-30.With the increasing of salinity,the content of chlorophyll a in Pyramimonas sp.keeps decreasing and the most suitable salinity is 25.3.(1)According to the experimental results of physiological response to the coercion given by Platymonas subcordiformis to seven kinds of concentrations of associated heterotrophic bacteria such as 101,103,105,106,5×106,107,108cfu/m L: when the concentration is lower than 5×106cfu/m L,with the concentration increasing,the content of chlorophyll a in Platymonas subcordiformiskeeps increasing;when the concentration is close to 107cfu/m L,with the concentration of the associated heterotrophic bacteria increasing,the content of chlorophyll a in Platymonas subcordiformisshows heavy declining compared with control group and the concentration where the associated heterotrophic bacteria promotes the content of chlorophyll a in Platymonas subcordiformismost is 106cfu/m L.The response to coercion of SOD activity of Platymonas subcordiformisand content of GSH to associated heterotrophic bacteria in different concentration shows similar regularity to content of chlorophyll a.The treatment group of 106cfu/m L brings best effect to SOD activity of Platymonas subcordiformisand content of GSH.When the concentration of the associated heterotrophic bacteria is 106cfu/m L,the content of MDA in Platymonas subcordiformis is reduced and ensuring the healthy grows of cells.(2)The result predictions of influence for the nine different treatments to the content of chlorophyll a in Platymonas subcordiformis: The mode of action of associated heterotrophic bacteria to Platymonas subcordiformisis cell direct action and combined action of intracellular product and high-temperature micromolecular extracellular product.(3)The result indication of influence for the three environmental factors such as temperature,light period and salinity to associated heterotrophic bacteria acting on Platymonas subcordiformis: when the temperature is 30?,the content of chlorophyll a in Platymonas subcordiformisis in the highest level but the data in control group is in high level at the same time.On balance,the temperature range of associated heterotrophic bacteria acting on Platymonas subcordiformistakes up a large place from 20? to 30? and the most suitable temperature is about 25?.The light period of 12:12h shows best effect to associated heterotrophic bacteria acting on Platymonas subcordiformis.The suitable salinity range is 25-35.With the increasing of salinity,the content of chlorophyll a in Platymonas subcordiformiskeeps increasing and the most suitable salinity is 35.