| The gut microbiota plays an important role in growth and development,metabolism,immune system maturation and disease resistance in young ruminants.Consequently,maintaining the gut microbial balance is crucial for the healthy development of ruminants.Yak is a rare breed of cattle of the Tibetan Plateau,which plays an important role in the rural revitalization and economic development of Tibetan regions.However,calving yaks with immature gastrointestinal development are more susceptible to gut microbial imbalance due to extreme environments,nutrient shortages,and weaning stress,which could cause gastrointestinal or other diseases,seriously restricting the development of the yak industry.Supplementation with probiotic preparations in vitro is considered to be an effective way to regulate the host gut microbiota and metabolism,and promote growth performance.However,to date,studies regarding the yak-derived Bacillus subtilis remains scarce.Therefore,our aim was to isolate yak-derived B.subtilis and explore its potential probiotic properties by in vitro experiments and whole genome technology.Meanwhile,mice experiments and calving yaks experiments were used to reveal the relieving effect of B.subtilis supplementation on oxidative stress and the effects on gut microbiota,metabolism,growth performance and antioxidant capacity of calving yaks.The main research contents are as follows:1 Isolation and identification of yak-derived B.subtilis and evaluation of its probiotic characteristicsThis study aimed to isolate B.subtilis with potential probiotic properties from intestinal contents and feces of healthy yaks.For this purpose,a total of 65 Bacillus strains were isolated,of which 30 were identified as B.subtilis and named BS1-BS30.To screen B.subtilis that could serve as potential probiotic candidate strains,we conducted a series of in vitro tests to verify its acid and bile tolerance,antibiotic susceptibility,hemolytic activity,antibacterial activity,hydrophobic property,autoagglutination,cell adhesion.Results indicated that 6 strains of B.subtilis(BS2,BS3,BS6,BS7,BS18 and BS22)had excellent probiotic properties.Moreover,results of in vitro antioxidant test showed that BS3 had the highest hydroxyl radical scavenging and DPPH scavenging ability of 55.70%% and 48.3%.2 Complete genome analysis of B.subtilis derived from yaksProbiotics have attracted increasing attention due to their multiple health benefits to the host.Yaks inhabiting the Tibetan plateau exhibit excellent disease resistance and tolerance,which may be associated with their inner probiotics.Currently,research on probiotics mainly focuses on their positive effects on the host,but information regarding their genome remains scarce.To reveal the potential functional genes of B.subtilis isolated from yaks,we sequenced its whole genome.Results indicated that the genomic length of B.subtilis(BS3)was 866,044,638 bp,with 4,429 coding genes.The genome of this bacteria is composed of one chromosome and one plasmid with lengths of 4,214,774 bp and 54,527 bp,respectively.Moreover,B.subtilis contains 86 t RNAs,27 r RNAs(916S＿r RNA,9 23S＿r RNA and 9 5S＿r RNA)and 114 other nc RNA.KEGG annotation indicated that most genes in B.subtilis were associated with carbon metabolism and biosynthesis of amino acids.GO annotation demonstrated that most genes in B.subtilis were related to nucleic acid binding transcription factor activity,transporter activity,antioxidant activity and biological adhesion.Egg NOG showed uncovered that most genes in B.subtilis were related to energy production and conversion,amino acid transport and metabolism,carbohydrate transport and metabolism.CAZy annotation indicated that glycoside hydrolases(33.65%),glycosyl transferases(22.11%),polysaccharide lyases(3.84%),carbohydrate esterases(14.42%),auxiliary activities(3.36%)and carbohydrate-binding modules(22.59%)were found.In conclusion,this study first investigated the genome and genetic properties of B.subtilis derived from yaks,which contributed to understanding the potential prebiotic mechanism of probiotics from the genetic perspective.3 B.subtilis attenuates D-galactose-induced oxidative damage by modulating gut microbiota and metabolismOxidative stress is considered as a crucial driver of aging and multiple degenerative diseases,seriously threatening host health.Probiotics have been demonstrate to participate in the active regulation of antioxidant system,intestinal microbiota and metabolism,but studies regarding the antioxidant mechanisms of yak-derived B.subtilis remain scarce.Here,we aimed to investigate the ameliorative effects of B.subtilis isolated from yaks on oxidative stress induced by D-galactose and its underlying molecular mechanisms.Results indicated that B.subtilis administration dramatically ameliorated pathological consequences caused by oxidative stress such as decreased organic index,antioxidase imbalance,abnormal transaminase,hepatic and intestinal injury.Moreover,B.subtilis could also maintain intestinal mucosal barrier and attenuate hepatic oxidative stress through modulating the expression of tight junction proteins and activating Nrf-2 signaling pathway.Integrated microbiome-metabolomics indicated that B.subtilis administration could reshape the composition of intestinal microbiota and metabolism and reverse the decline of microbial index and metabolic disorders induced by oxidative stress.In summary,these findings demonstrated that the positive regulation effect of B.subtilis on gut microbiota and intestinal mucosal barrier may be one of its underlying mechanisms to alleviate oxidative stress.Additionally,this study also indicated that B.subtilis isolated from yaks may serve as a promising candidate to ameliorate oxidative damage.4 Effects of B.subtilis supplementation on growth performance,gut microbiota and metabolism in calving yaksYaks,mainly distributed in the Qinghai-Tibet Plateau,suffers from high morbidity rate and slow growth performance due to extreme conditions and nutritional deficiency.The B.subtilis has been widely acknowledged due to its positive effects in growth performance,gut microbiota,metabolism and host health,but studies regarding the effect of B.subtilis on yaks remains scarce.Therefore,this study aims to investigate the effects of B.subtilis derived from yak intestine on growth performance,serum biochemistry,antioxidant indices,gut microbiota and intestinal metabolism of calving yaks.Results indicated that B.subtilis supplementation dramatically increased the growth performance and antioxidant capacity of calving yaks.Moreover,B.subtilis supplementation also resulted in a significant increase in the alpha diversity index of the gut microbiota,accompanied by significant alterations in taxonomic compositions.Bacterial taxonomic analysis demonstrated that some genera of putatively beneficial bacteria(Bacillus,Ruminococcaceae＿UCG-004,Ruminiclostridium＿9,Lachnospiraceae＿UCG-010,Alistipes,Butyricimonas,etc.)were significantly increased,whereas several potential intestinal pathogens(Terrisporobacter,Tyzzerella,Streptococcus,Acinetobacter,Gallibacterium,Slackia,etc.)were noticeably decreased.Metabolomics analysis showed that 797 differential metabolites were totally identified,involved in 10 metabolic pathways including vitamin digestion and absorption and tyrosine metabolism.In summary,this study indicated that B.subtilis supplementation not only increased growth performance and antioxidant ability of calving yaks but also altered gut microbial composition and diversity as well as intestinal metabolism.Additionally,this study also indicated that the altered intestinal microbiota and metabolism may be one of the key pathways for B.subtilis to exert its probiotic effects. |
PDF Full Text Request