| The giant panda(Ailuropoda melanoleuca)is a unique species with more than 99% of its diet composed of bamboo.Giant pandas consume about 12.5 kg bamboo per day and spent almost 14 h on foraging.But the giant panda still retains the simple digestive tract typical of a member of the order Carnivora,resulting insufficient fermentation of food.Compared to other food sources bamboo has low nutrition levels.Under these circumstances,to meet the nutritional needs of the body,the gut microbiota of giant pandas may have evolved and adapted to play a vital role in the digestion of bamboo,aiding in the effective absorption and transformation of nutrients.At present,the provisioning of bamboo to captive pandas is restricted by conditions such as transportation and preservation,so that there will feed a single part of bamboo to captive giant panda for a long time.However,the nutrient content were significant differences in different parts of bamboo,shoot was rich in crude protein,culm contained more crude fiber.And the apparent digestibility also different when captive giant panda fed in different bamboo parts,which resulted in significant difference in the nutrient components used by gut microbes,the composition and function of gut microbes would also change.Previous research showed that continuous feeding a single part of bamboo could have adverse effects on captive giant pandas,but the change of gut microbiome’s composition and function under different feeding conditions is still unknown.This study was conducted to investigate the composition of gut microbes of captive giant panda fed under three different exclusive bamboo diets based on part(shoot,leaf and culm)by using 16 s rRNA gene sequencing techniques.We then compared these results with wild giant pandas and other mammals.The function of gut microbes was annotated by using metagenome sequencing techniques,to explore the effects of composition and function of gut microbiota in giant pandas with feeding different bamboo parts,and to probe into the effects of nutrients on gut microbes.The total serum bile acid of captive giant pandas was determined by enzyme circulation method,to verify the functional relationship between gut microbiome and energy needs of host.We look forward to providing a theoretical basis for selection of feeding different bamboo parts.Three experiments were carried out:Exp.1 Effects of different Bamboo parts on gut microbiota composition of captive Giant PandaTo study the effect of continuous feeding single bamboo part on gut microbiota composition of giant panda,the feces of captive giant pandas were collected.There were three groups divided by feeding three bamboo parts(shoot,leaf,culm)to captive giant pandas,9 samples were collected in one group.Maintained single bamboo part feeding to panda for more than 20 days before sample collection.The 16 S rRNA gene sequencing technique was used for investigating composition of gut microbes.The results showed that the composition of gut microbiota in the CULM group was significantly different from the other two groups,and the CULM group was closer with wild giant panda and four omnivores.Exp.2 Effects of different Bamboo parts on gut microbiota function of captive Giant PandaTo explore the effect of gut microbial composition change caused by dietary changes(shoot,culm,leaf)on captive giant panda,we carried out metagenome sequencing with nine samples(three per group).Maintained single bamboo part feeding for more than 20 days before sample collection.The results showed that the gut microbiota composition of giant panda at species level changed significantly in three feeding period,then the function of gut microbiota changed obviously.The CULM group microbiota had more genes annotated in cellulase and hemicellulose,and the microbiota was enriched in α-amylase and maltogenic amylase families(GH13 and CBM48)that can bind and degrade starch.The CULM group had higher abundance of enzymes in fatty acid biosynthesis(ko00061),bile acid biosynthesis(ko00120,ko00121)and 8 essential amino acids biosynthesis(arginine,ko00220;lysine,ko00300;phenylalanine,tyrosine and tryptophan biosynthesis,ko00400;valine,leucine and isoleucine biosynthesis,ko00290).The LEAF group had higher enzymes abundance in the TCA cycle(ko00020)which could provide more energy.LEAF group also had higher abundance in pathogens of enterotoxigenic E.coli(ETEC)infection(H00280): hemolysin E(K11139),the pathogens could increase the risk of intestinal tract disease.However,there were two enzymes detected from the detoxification mechanism enriched in the LEAF group,included cyanate lyases(EC 4.2.1.104)which related with cyanide detoxification and lysozyme(EC 3.2.1.17)which related with antibacterial,anti-inflammatory and anti-viral functions.In the pentose phosphate pathway(ko00030),the SHOOT group had higher abundance with sum of all involved enzymes and key enzyme(glucose 6 phosphate 1 dehydrogenase,K00036).Moreover,the energy provided by gut microbiota act seemingly as a supplement to remedy the caloric deficiency of the body during different periods of the exclusive bamboo part diet,the supposition still needs further study.Exp.3 Effects of different Bamboo parts on serum total bile acid of captive Giant PandaThe CULM group had higher abundance of enzymes in bile acid biosynthesis,bile acids play a key role in the metabolism of fat.We measured the bile acids in giant panda serum to explore the relationship between the content of bile acid in the host and the biosynthesis ability of gut microbiota,and to further explore the functional relationship between gut microbiota and host energy in captive giant panda.There were three experimental groups according to fed captive giant panda with three bamboo parts(shoot,culm,leaf),and we proceeded blood collection and separation of blood from panda.Maintained single bamboo part feeding for more than 20 days before sample collection.Finally,9 giant panda blood samples were collected from bamboo shoot group,6 from bamboo leaf group and 4 from bamboo culm group.The detection results of the serum TBA in giant panda were concurred our supposition,the TBA content of bamboo culm group was the lowest,and the gut microbiota of CULM group had a strong ability of bile acid biosynthesis,the result provided a new basis for gut microbiota to bring beneficial effects on the energy balance of the host.Herein,the data showed that gut microbiota could help the host adapt to dietary change.It was found that the gut microbiota of fed exclusively culm group had significantly different from shoot and leaf group,and the gut microbiota of culm group was similar to four omnivores.Additionally,the CULM group showed stronger digestive capabilities for cellulose,hemicellulose and starch.Furthermore,there was also a stronger biosynthesis of amino acids to satisfy the compensatory TCA cycle of the host in the culm group.In contrast,lignin utilization of gut microbes was stronger in the leaf group,but fed a leaf diet alone for a long period could increase the abundance of virulence factors that cause intestinal disease,however,there were detoxification mechanisms during this period to deal with the adverse effects.In conclusion,gut microbiota can help giant pandas adapt to feeding on different bamboo parts. |
PDF Full Text Request