Analysis Of The Microflora Community In The Intestine Of Pinctada Fucata Martensii

Intestinal microflora plays an important role in host nutrient absorption,immunity and development which has been a hotspot for researchers.Pearl oyster Pinctada fucata martensii is an important cultured species used to cultivate seawater pearls for its high economic values,but there are few reports about the intestinal microflora of it.In this study,research about structure of intestines microbes of the cultured P.f.martensii and water environment in the natural sea area was carried out.The structure of intestines microbes of P.f.martensii with microcapsules of different formulas were compared.The growth of the cultured P.f.martensii with artificial diet,physiological indicators and differences in the structure of the intestinal flora were showed.Finally,the intestinal flora of the P.f.martensii obtained in each phase of the experiment.The results of this study indicated that the structure of the intestinal flora of P.f.martensii hold highly plasticity and was greatly affected by the culture methods and nutrient conditions,but there was also relatively stable core flora.This study is the first research to show the structural composition of the intestinal microflora of P.f.martensii with multiple perspectives and accumulate basic data for the development of healthy breeding,disease prevention and control,microecological preparations and optimization of feed formulations.The main results were as follows:1.The samples(gut microflora(HP and DP)and seawater flora(HW and DW))were collected in Leizhou Houhong and Xuwen Dajinghai area.The results of 16 S rRNA-V4 region sequencing were as follows:(1)The dominant bacteria of HP and DP belong to Cyanobacteria,Tenericutes and Proteobacteria.The dominant genus are Synechococcus,Planctomyces and Mycoplasma.(2)The dominant bacteria of HW and DW belong to the Cyanobacteria,Proteobacteria and Bacteroidetes,and the dominant genus includes Synechococcus and Candidatus_Aquiluna.(3)The species richness and diversity of the flora in seawater were higher than that of the intestinal flora of P.f.martensii;the species richness and diversity of HP flora were higher than DP.2.The effects of formula feeds D5-3(ED1)and D5-5(ED2)on the growth rate,digestion,immunity,antioxidant capacity and intestinal flora of the 2nd-year-old shellfish were determined.The results showed that:(1)The difference of survival rate between ED1 and ED2 was not significant(P>0.05),but the absolute growth rate of shell length,shell width,shell height and total weight of ED1 was significantly higher than that of ED2(P<0.05).(2)The activities of amylase,protease,AKP,T-AOC,SOD,CAT and GPx in ED1 hepatopancreas were significantly higher than those in ED2 group(P<0.05),while MDA was significantly lower than ED1 group(P<0.05).The expressions of CAT,SOD,GPx,HSP70 and NF-κB in ED1 hepatopancreas were significantly higher than those in ED2 group(P<0.05),and the expression of HSP90 gene was not significantly different(P>0.05).(3)The species richness and diversity of ED1 gut microbiota were significantly higher than that of ED2.The dominant bacteria belonged to Proteobacteria,Firmicutes and Tenericutes,and the dominant genus could be identified as Mycoplasma,Lactococcus and Pseudomonas;ED2 intestinal flora has a single structure,thick-walled bacteria account for absolute advantage,the dominant genus is Bacillus,Lactococcus and Oceanobacillus.3.Comparison of growth rate,digestibility,immunity,antioxidant capacity and intestinal flora between chlorella powder(P0),formula feed D6-2(P2)and D6-5(P5)indoor cultured P.f.martensii and marine cultured P.f.martensii.The results showed that:(1)There was no significant difference in survival rate between the groups(P>0.05),but the absolute growth rate of shell length,shell width,shell height and total weight was significantly different(P<0.05),and the absolute growth rate of P2 was the largest.(2)The activities of amylase,protease,AKP,T-AOC,SOD,CAT and GPx in hepatopancreas were significantly different(P<0.05),and P2 had the highest immunity and antioxidant capacity.(3)The dominant phylum of group C are Cyanobacteria,Proteobacteria and Tenericutes,and the dominant genus is genus Synechococcus and Vibrio;The dominant gates of P0,P2 and P5 are all Proteobacteria,Tenericutes and Bacteroidetes.The main dominant genus is Mycoplasma.4.A joint analysis of the intestinal flora of 8 groups of P.f.martensii was carried out.The results show that:(1)At the level of the phylum,the common bacteria in the intestines of each group of P.f.martensii belong to 12 phylum.The top five bacteria in the HW,DW and C groups cultured in the sea area are composed of the Tenericutes,Cyanobacteria,Proteobacteria,Planctomycetes and Bacteroidetes.The cumulative relative abundance accounts for 89.16%-98.30% of the total bacteria.The top five bacteria in the relative abundance of P0,ED1,ED2,P2 and P5 in indoor culture accounted for 86.95%-99.92% of the total bacteria.However,the composition is different,only the Proteobacteria and the Tenericutes enter the top five.(2)At the genus level,there are 32 identifiable genus in the intestinal tract of 8 groups of P.f.martensii,and the cumulative relative abundance accounts for 9.57%-57.96% of the total bacteria.Among them,the genus of Mycoplasma genus,the genus Vibrio genus and the genus Planctomycetes have the largest relative abundance and a small coefficient of variation.