Structural Characteristics In The Intestinal Microbial Community Of Antarctic Fish And Their Relationship With Environmental

The seawater temperature in the Antarctic Ocean is maintained below 0℃ all year round,with environmental characteristics such as stable low temperature,high dissolved oxygen,high nutrient salinity,and low chlorophyll a.Because of its extremely harsh ecological environment,fish living in the Antarctic Ocean have developed complex and unique environmental adaptations.Notothenioidei have the highest species richness and biomass in the Antarctic Ocean.At present,there are few reports on the intestinal microbial community composition and environmental adaptability analysis of Notothenioids.Based on the Illumina Mi Seq high-throughput sequencing platform and using the QIIME2 analysis process,we investigated the differences in intestinal microbial diversity and community structure of fish from the Antarctic Peninsula,Amundsen Sea,Cosmonaut Sea and Prydz Bay.1.Identification of Antarctic fish speciesIn this paper,DNA barcoding techniques were used to collect data from Antarctic Peninsula,Amundsen Sea,Cosmonauts Sea and Prydz Bay in different years for species identification.The results showed that 40 fish belonging to 4 orders,8 families,11 genera and 12 species were identified in the 37 th voyage,with the dominant species being Macrourus whitsoni;61 fish belonging to 2 orders,6 families,9 genera and 12 species were identified in the 38 th voyage,with the dominant species being Macrourus whitsoni,Prionodraco evansii and Trematomus scotti.2.Genus-based intestinal microbial diversity and functional predictions in Antarctic fish in different yearsThe intestinal contents of fishes of the Notothenioids were sequenced and analyzed using Illumina Mi Seq Platform,the results showed that in the 37 th voyage,a total of352 phyla,958 classes,2,778 orders,5,516 families,7,383 genera,3,655 species in the intestinal microorganisms of Notothenioids.in the 38 th voyage,a total of 680 phyla,1,359 classes,1,964 orders,2,724 families,2,753 genera,1,294 species were recorded from intestinal microorganisms of Antarctic fish.The sequencing data was reasonable.Burkholeria,Ralstonia and Pelomonas were the common dominant genera of intestinal microorganisms in the 37 th voyage,and these three genera were widely distributed in water environment.The results showed that the bacteria in the water environment had a great influence on the diversity and community structure of fish intestinal microorganisms.In addition,some Antarctic fish have a high abundance of Dorea,Prauserella,Lactobacillus,Moritella and other beneficial bacteria in the gut.Photobacterium,Mycoplasma and Acinetobacter were also highly abundant in the intestines of some Antarctic fish.Ophthalmolycus amberensis contains Psychromonas,a surface strain of algae,in high abundance.Macrococcus and Acinetobacter were dominant bacteria in the intestinal tract of Antarctic fish in the 38 th voyage,which were common opportunistic pathogens in the intestinal tract and could cause intestinal inflammation.Meanwhile,Psychrobacter,Blautia,Ruminococcus,Bifidobacterium and other bacteria with high abundance exist in the intestinal tracts of Antarctic fish.These bacteria are beneficial bacteria in the intestinal tracts of fish.All of them can improve the activity of antibacterial proteins,inhibit the growth of aquatic pathogens,and inhibit the occurrence of intestinal colitis.A high abundance of Synechococcus was found in the intestinal tract of the Trematomus scotti in Pryze Bay.According to functional prediction,the potential functions of intestinal microorganisms in different years were related to the synthesis and metabolism of carbohydrates,amino acids,fatty acids and vitamins.In addition,intestinal microorganisms of Antarctic fish in the 38 th voyage also had the function of metabolizing polyketones,which provided important reference value for the research and development of Marine secondary metabolites.3.Relationship between differences in intestinal microbial community structure of Antarctic fishes and water environmental factors in different yearsHistograms of relative abundance at the phylum level from different years showed that the relative abundance of intestinal microflora of Antarctic fish collected from the Antarctic Peninsula,Amundsen Sea and Cosmonauts Sea was significantly different.There was little difference in the relative abundance of microbes in the gut of Nototheniofishes collected from Prydz Bay.In addition,Histograms of relative abundance at the phylum level also showed that the relative abundance of dominant microbial flora in intestinal microflora of the same species of Antarctic fish living in different sea areas was significantly different in the 38 th voyage.The results of NMDS analysis and differences between groups analysis for different years showed that fish intestinal samples from Prydz Bay.were clustered separately.There were crossclustering among fish intestinal samples from the Antarctic Peninsula,Amundsen Sea and Cosmonauts Sea,indicating that the fish intestinal microbial community structure in Prydz Bay was significantly different from that in the other three sea areas(Antarctic Peninsula,Amundsen Sea and Cosmonauts Sea);There was no significant difference in intestinal microbial community structure between Antarctic Peninsula,Amundsen Sea and Cosmonauts Sea.In conjunction with marine environmental parameters,this result may be related to differences in seawater temperature in other areas of Prydz Bay.RDA redundancy analysis indicated that the main environmental factors influencing the abundance of gut microbes in Antarctic fish were surface and bottom seawater temperature,seawater depth in the 37 th voyage;It was mesopelagic chlorophyll a concentration and mesopelagic seawater salinity in the 38 th voyage.The intestinal microbial diversity and community structure of Antarctic fish in different years were analysed by high-throughput sequencing technology to compare the differences in the intestinal microbial characteristics of Antarctic fish between different years in the same sea.This will provide a theoretical basis for the study of the environmental adaptability of Antarctic fish.