Effects Of Ammonia Nitrogen Stress On Immune System And Intestinal Microbiotaof Carassius Auratus

Intensive aquaculture production,high density and excessive use of protein feed,resulting in ammonia content increased.And this could cause water pollution,destroy the ecological environment and cause huge economic losses.Ammonia nitrogen can cause the damage of intestinal mucosa system,and affect the immune system of fish.We used the hydrostatic flow test to determine the LC50 of ammonia nitrogen for crucian carp and its safe concentration.The effects of ammonia stress on the immune system of crucian carp were studied by subacute toxicity test.The effect of different concentrations of ammonia concentration on the structure of intestinal flora in crucian carp was analyzed by high throughput sequencing technology.Main results obtained as follows:1.The LC50 of ammonia-nitrogen for crucian carp at 96 hours was 1.538 mg·L^-1,and the safe concentration was 0.1538 mg·L^-1.2.In group B,the expression of immune-related genes and antioxidant enzyme-related genes weresignificantly up-regulation at 15 d compared with control.In group C,the expression of immune-related genes and antioxidant enzyme-related genes weresignificantly down-regulation at 15 d and 30 d compared with control.After 15 days of no ammonia treatment,immune-related genes and antioxidant enzyme-related gene expression can be restored to the control level.3.Through 16 S rDNA microbial diversity analysis,we found that 1)Ammonia nitrogen stress had no significant effect on the abundance of intestinal microflora.2)Ammonia nitrogen stress had significant effect on the composition of intestinal microflora,the proportion of Bacteroides and Pleurotus increased first and then decreased with the increase of ammonia concentration at the genus level.3)In the high concentration group,the relative content of Flavobacterium was increased with the exposure time of ammonia nitrogen,and the relative content increased by nearly 25% compared with the control at 30 days.Increased pathogen content may be associated with a significant reduction in immune gene.In summary,ammonia nitrogen stress had a certain impact on the crucian carp immune system and intestinal flora structure.High concentration of ammonia nitrogen stress inhibited the expression of immune and antioxidant enzymes related genes,and the contents of Flavobacterium was increased in the intestine of crucian carp.