Intestinal Microbiota In Large Yellow Croaker(Larimichthys Crocea) And The Relationship To Host Economic Traits

The large yellow croaker(Larimichthys crocea)is mainly distributed in coastal regions of East Asia,it is the most important carnivorous mariculture fish and has the largest marine cage culture production in China.In recent years,with the rapid development of large yellow croaker marine aquaculture,a series of problems regarding the degradation of biological characters emerged,such as slow growth,sexual precocity,frequent disease outbreak and poor taste,all of these have led to severe economic loss for aquaculture farmers.The intestinal microflora is sometimes referred to as a host “forgotten organ”,and these microorganisms contribute to digestion,nutrition,growth,pathogens resistance and immune system modulation of host.Many studies have reported the intestinal microbiota of fishes,very few studies reported intestinal microbiota of large yellow croaker and the relationship to host ecomomic traits was not clear.Previous studies were mainly based on traditional culture technique and 16 S rDNA gene based methods.Some research on intestinal microbiota of different morphology and gender host are help to know the relationship between differences and intestinal microbiota,which is really significant for germplasm improvement,probiotic research and the promotion of cultured industry healthy development of large yellow croaker.In this study,PCR-DGGE and Illumina Miseq sequencing technology were used to investigate the bacterial communities in the intestines of large yellow croaker and the relationship between it and corresponding economic traits.The results were as follows:1.PCR-DGGE and Illumina sequencing of large yellow croaker with different weights and sexes(1)Bacteriodidetes,Firmicutes and Tenericutes were detected in the intestine of large yellow croaker with different weights and sexes using both PCR-DGGE and Illumina approach.What’s more,Actinobacteria,Planctomycetes and Nitrospirae were also detected by Illumina sequencing.(2)The intestinal microbiota of large yellow croaker was corelation to host weights and sexes.At phylum level,Proteobacteria was permanent symbiotic dominant bacteria of large yellow croaker,Planctomycetes and Nitrospirae were found only in large & male fish.At genus level,the intestinal microbiota of large,medium and small fish were great different,and thatbetween female and male with the same weight were also different.Intestinal microbiota of large& female group were great different from others,and that of medium & male group were also different from others,while,that between female and male of small fish were not much difference.The PCR-DGGE results indicated that Enhydrobacter sp.and Sphingomonas and Uncultured bacterium clone were predominant in large fish,while,Uncultured bacterium in small fish and Mycoplasma,Acinetobacter sp.and some Uncultured bacterium clone in medium fish.The intestinal microbiota is different in large yellow croaker with different sexes,Pseudomons aeruginosa strain and Uncultured bacteriumwere most abundant in large & female and small & male fish,Myroides odoratimimus strain and Myroides sp.were most abundant in small & female and large & male fish.Those were different from the results of Illumina that Stenotrophomonas and Cupriavidus were predominant in large & female fish,and Comamonadaceae_unclassified was predominant in large & male and both of small fish.2.PCR-DGGE and Illumina sequencing of healthy and diseased large yellow croaker(1)Healthy and diseased large yellow croaker was dominanted by Proteobacteria,Fusobacteria and Firmicutes,Bacteriodidetes were induced obviously.What’s more,Planctomycetes and Tenericutes were also detected by Illumina approach.DGGE results also indicated that Uncultured bacterium,Cetobacterium sp.,Lactococcus lactis clone were predominant in both groups.(2)The results of both approaches indicated that bacterial diversity of healthy group is higher than diseased group,but not significantly different.The results from the DGGE reveled that some potential probiotics such as Lactococcus and Cetobacterium were rich in healthy group,which were rare in diseased group,on the contrary,some potential pathogen such as Achromobacter xylosoxidans and Ralstonia sp.were only detected in diseased group.However,some conditional pathogen such as Photobacterium and Vibrio were found in healthy group.While,the Illumina results reveled that Vibrio was the most dominanted in healthy group,and induced obviously in diseased group.On the contrary,Limnobacter was predominant in diseased group,and induced obviously in heathy group.Moreover,Enterobibrio、Vibrio and Moraxella were the most significantly different bacteria between two groups.