Analysis On The Community Structure Of Phycosphere Bacteria In The Filaments Of Porphyra Haitanensis And Gametophytes Of Saccharina Japonica

Both the Porphyra haitanensis filaments and the Saccharina japonica gametophytes are important germplasm resources.In the process of cultivation and preservation,the Porphyra haitanensis filaments and Saccharina japonica gametophytes are often contaminated by bacteria,so the studying of phycosphere microbial community structure will contribute to the understanding of pathogenic microorganisms.In this paper,the second-generation high-throughput sequencing technology was used to study the composition of the phycospherel bacteria community in the early seedling stage and the late seedling stage of shell filaments of the Porphyra haitanensis;the epiphytic bacteria of the free filaments of the Porphyra haitanensis and Saccharina japonica gametophytes and at different temperatures the composition of the free bacterial community structure in the culture medium;and the effect of adding antibiotics on the bacterial community of the Saccharina japonica ametophytes.The main findings are as follows:1.Phycosphere bacterial community structure of shell filaments of the Porphyra haitanensisIn the early seedling stage,25 phylum and 244 genus were found in the epiphytic bacteria community,and 19 phylum and 194 genus were found in the cultured water.In the late seedling stage,30 phylum and 250 genus were found in the epiphytic bacteria community,and 25 phylum and 176 genus were found in the cultured water.In these two different periods,the epiphytic bacteria community of shell filaments of the Porphyra haitanensis was dominated by Proteobacteria and Bacteroides,and the Proteobacteria was the first dominant bacteria.At the genus level,the structure of epiphytic bacteria in the two periods was different,in the early seedling stage,the first dominant genus of the filamentous epiphytic bacteria was Pelomonas.The first advantage in the late seedling stage is Ahrensia.Potential pathogenic genus such as Vibrio,Pseudoalteromonas,Pseudomonas,etc.were found in both periods,but the abundance of Pseudoalteromonas and Pseudomonas in early seedling stage was higher.Secondly,at the level of the Phylum,the bacteria in cultivated water are also dominated by the Proteobacteria and the Bacteroides.At the genus level,the bacterial community structure of the cultivated water was significantly different from that of the epiphytic bacteria of the of shell filaments of the Porphyra haitanensis.The diversity of the bacterial community in the cultured water was lower than that epiphytic bacteria of the shell filaments of the Porphyra haitanensis,but the abundance of Vibrio was larger.and the late seedling stage,the abundance of Vibrio in the cultivated water is higher than that in the early seedlin stage.2.Analysis of phycosphere bacteria community structure in free filaments of Porphyra haitanensisUnder the condition of culture at 20 °C,Proteobacteria and Bacteroidetes were the dominant bacteria in the free filamentous epiphytic community of P.haitanensis,and Proteobacteria was the first dominant bacterium.The ?-proteobacteria is the first dominant species.At the genus level,the dominant bacteria belong to Maritalea,Leisingera,Marinovum,and the first advantage belongs to Maritalea.Under the three different temperature conditions of 10 °C,20 °C and 30 °C,Proteobacteria and Bacteroides are the dominant bacteria,and ?-Proteobacteria is the first dominant fungus.At the genus level,the free bacterial communities in the culture medium under these three temperature conditions all took Marinovum as the first dominant genus,but the relative abundance was different in each group.Under these three temperature conditions,there were differences in the sub-dominant genus of free bacterial communities in culture medium,namely Maritalea,Winogradskyell,and Balneola.The experimental results showed that the free bacterial community structure in the free filamentous medium of P.haitanensis was different at lower temperature,higher temperature and suitable temperature,especially at the genus level.Under these three temperature conditions,the respective dominant genus different.3.Analysis of bacterial community structure of Saccharina japonica gametophytesIn the culture condition of 10 °C,Proteobacteria and Bacteroidetes were the dominant bacteria in the epiphytic bacteria community of Saccharina japonica,and the first dominant bacteria was Bacteroides.The Flavobacterium is the first dominant family.At the genus level,the first advantage belongs to Nonlabens,and the second advantage belongs to Maribacter.At 10 °C?15 °C?20 °C,in the free bacterial community of culture medium of the Saccharina japonica gametophytes,at the level of the phylum,both Proteobacteria and Bacteroidetes were dominant.At the level of the family,at 10 °C,TheFlavobacterium was the first dominant of the free bacterial community of the culture mediumat.while at 15 °C and 20 °C,the Vibrio family was the first dominant species.At the genus level,there are large differences in the advantages species under these three temperature conditions.At 10 °C?15 °C and 20 °C,the first advantages are Algibacter,Vibrio,and Marinobacte.at 15 °C,the abundance of the pathogenic bacteria Vibrio of the free bacterial community of culture medium in the Saccharina japonica gametophytes is largest.In the early stage of Saccharina japonica gametophytes cultivation,the composition of free bacterial community in the culture medium of Saccharina japonica gametophytes supplemented with antibiotics(penicillin + streptomycin)was significantly different from that of the control group.At the level of the phylum,the first dominant bacteria in the free bacterial community of the treatment group and the control group were all proteobacteria,but the relative abundance was different.In the treatment group,the relative abundance of the proteobacteria was 49.69%.In the control group,the relative abundance of the Proteobacteria was 93.01%.At the genus level,the most dominant genus of the free bacterial community of the culture medium of the treatment group was Kordia,followed by Klebsiella.The most dominant genus in the free bacterial community of the culture medium of the control group was Thiobacillus,followed by Colwellia.In the treatment group to which antibiotics were added,the genus of bacteria such as Colwellia,Thiobacillus,Vibrio,Pseudomonas,and Pseudomonas was relatively reduced.It is indicated that antibiotics inhibit the growth of potentially pathogenic bacteria such as Bacillus,Vibrio,Pseudoalteromonas,and Pseudomonas.