Separation Of Oil Decomposing Bacteria And Study Their Function In Lipid Absorption Of The Host

The animal intestines harbored a vast community of microbes, which form a micro ecosystem in the host. With the development of biological technology, more and more research began to study the role of the intestinal microflora in the nutrition metabolism, immune development and other processes. Among them, the role of gut microbes in digestion and absorption of nutrients has received more and more attention, and recent results showed that intestinal microbes play important roles in host nutrient absorption and metabolism.The lack of fish oil, fish meal has limited the development of aquaculture, while improving the utilization efficiency of fat sources was one way to solve this problem. In recent years, researchers have carried out a lot of research to improve the utilization efficiency of the feeding diet, including selection of different sources of fat, adding feed additive. However, gut and the symbiotic bacteria which were regarded as important organs in lipid absorption, have not received enough concerns in aquaculture. The previous studies have shown that gut microbes increased the lipid droplet formation or size in intestinal epithelial in zebrafish. Our research showed different lipid sources had different absorption efficiency. But the exact role of intestinal microbe in lipid absorption remains unknown. In this study, six strains which could degrade fish oil or soybean oil were successfully screened from 286 strains. After sequencing analysis, four strains which could degrade soybean oil belong to the Citrobacter; one strain which could degrade fish oil belongs to the Citrobacter and the other onebelongs to the Aeromonas. One strain which could degrade soybean oil bacteria (SOB9) or fish oil bacteria (FOA4) were used for subsequent experiments.The fermentation products of soybean oil or fish oil by the bacteria were tested in vitro. The results showed that SOB9 can degrade soybean oil, producing palmitic acid, stearic acid, octadecatrienoic acid and arachidic acid,et al, and palmitic acid was the main product. FOA4 can degrade fish oil, producing palmitic acid, leinoleic acid and eicosenoic acid et al, while leinoleic acid was the main product.SOB9 was used to colonize germ-free zebrafish, and free fatty acid (LA) and egg yolk were used to feed germ-free zebrafish and SOB9 colonized zebrafish. Two hours later, zebrafish were collected for electron microscopy detection and the results showed that in SOB9 colonized group, the lipid droplet number and size are much more or larger than those from germ-free group, suggesting SOB9 help the accumulation of lipid droplets in intestinal epithelial.In order to further identify the role of intestinal bacteria in lipid metabolism, germ-free and conventional zebrafish fed with egg yolk or at starvated status were collected for transcriptome analysis. The results indicated that gene related to lipid metabolism changed greatly between in the germ-free zebrafish and conventional ones.In summary, this study isolated soybean oil degrading bacteria which helped lipid absorption in host, suggesting the important role of gut microbes in the metabolism of nutrients in host.