| Red tide,also known as harmful algae blooms(HABs),is a global phenomenon of marine disasters.Red tide occurrence will have numerous impact on the marine environment and human health.Marine bacteria that closely related to the outbreak of red tide,are diverse,abundant and different functions,and have become a hot research sought in recent years.The growth of Phaeocystis globosa is closely related to the phyosphere bacteria,in the algae environment is often accompanied by fixed group of microorganisms.Therefore,the phyosphere bacteria will be significantly affected by the use of algicidal reagent.However,the response of microbioal communities in the process of algae suppression was rarely studied.In this paper,we first constructed a stable simulating system of 20 L P.globosa to determine the simulated culture conditions of the species.Then the responding bacterial communities in a 10 m3 volume simulated P.globosa bloom,which was treated with prodigisin,were investigated.We quantified the total numbers of bacteria by DAPI staining method,and observed the number of bacteria in the pridigiosin treated group was very high.The bacterial communities were further characterized by amplicon-based analysis of 16S rRNA V4 region genes through Illumina sequencing.Finally,in order to solve the problem of the prodigisin algicidal affectd,and obvious pigment residual substance when the harmful algae blooms break out,in this study,an algicidal Mameliella strain Bac4 was isolated and purified from the algae solution.The effects of the prodigisin on the growth of this strain and the adjuvant effect of the strain when treating algae with prodigism was also studied.(1)The culture was carried out under the condition of light intensity of 2000-3000 Lux,illumination period 12h/12h,temperature 20? salinity 30‰,pH 8,air volume 9 L/min.After protozoan contamination,100 mL of algae solution was treated with 5 ?L of 8%NaClO(final concentration of 0.004 ?g/?L)for 4 h,and the corresponding amount of sodium thiosulfate was used to dissolve chlorine,which could effectively inhibit the growth of protozoa.(2)In the early hours of algal cell culture,most of the bacteria in phyosphere were Sulfitobacter,Sulfurimonas,Hydrogenovibrio,Thiomicrospira and other species related to electron transport.The total number of bacteria increased at 24 h post treatment,when the number of algal cells maintained itsprevious level.At genus taxonomic level,three genera(Alteromonas,Pseudoalteromonas and Pseudomonas),frequently reported with algicidal activity,were significantly enriched in the treated group both in 24 h and 48 h samples,and the highest abundance appeared at 24 h post treatment.Another three genera(Neptuniibacter,Oceanospirillum and Pseudospirillum)were also enriched in the 24 h and 48 h samples,the highest abundance appeared at 48 h time point,and these bacteria were putatively thought to play an important role in organic matter degradation.Vibrio is very special,and it has high abundance only at 24 h processing time piont.Our results also indicated that after 24 h treatment the abundance of Rhodobacteraceae significantly increased.Moreover,an algicidal strain Bac4 newly isolated from the P.globosa culture was identified to belong to this family as well.(3)The strain Bac4 was identified 99.93%similarity with Mameliella alba DSM 26384T.Its growth rate was significantly influenced by prodigiosin.Bac4 could improve the algicidal effect of prodigisin and significantly reduce the amount of solid residue after algicidal effect. |
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