The Genomics Of Bacillus LFB112 And Its Regulations On Meat Quality And Intestinal Microbiota In Broilers

In this study,the objective is to enhance the safety of meat and improve meat quality in broilers.We investigated the complete genome sequence of the probiotic strain Bacillus LFB112,the effects of substituting the antibiotic Chlortetracycline with the strain,the amount of optimum addition,and the regulations on meat quality and intestinal microbiota at the metagenomic level.Moreover,the relationship between intestinal bacterial changes and meat quality was studied to clarify the regula-tory mechanism of intestinal microbiota on meat quality.In trial 1,the Bacillus LFB112 genome was investigated to elucidate the genome basis of its broad-spectrum inhibition and probiotic traits.The genome sequence of LFB112 was available throughsecond-generation Hiseq2000 shotgun sequencing,splicing,and gap closure.The genome sequence was deposited into the NCBI(Accession no.CP006952).The genome size of the strain is 3942754bp,with 46.7%GCcontent without plasmids.LFB112 has a total of 3961 CDS,94tRNAs,and 10rRNAs.Genome analysis showed that LFB112 contains many gene clusters of secondary me-tabolite synthesis,confirming its excellent antibacterial properties.Secondly,abundant enzyme genes were discovered,benefiting absorption and utilization of nutrients.Comparative genomic analysis showed the bacterium belongs to the plant subspecies,and shares the closest kinship with the biocontrol strain CAU946,verifying the LFB112antibacterial activity.Furthermore,5 genomic islands were predicted.Compared to other strains within the species,the number of genomic islands is small,showing excellentevolutionary stability and security.In trial 2,The research was to investigate the effects of adding LFB112 to broiler diets on growth performance and meat quality.The results showed that Bacillus LFB112 added to broiler diets has enhanced ADG and improved meat quality such as meat color and fatty acids composition.On the other hand,carcass traits,chemical composition of the breast muscle,and shear force were not significant.In addition,this study also found that the low dosage of Bacillus LFB112(107 cfu/kg diet)can achieve the best effects on performance,slightly higher than that of the antibiotic group.Considering performance and meat quality results,the Bacillus groups obtained theoptimal effects.Bacillus LFB112 can act as an alternative to antibiotics to promote the growth of broilers and im-prove meat quality.In trial 3,the changes in the structure and abundance of broiler intestinal microbiota after being fed with LFB112 were studied toclarify the mechanism of action of probiotics.Thus Miseq sequenc-ing technology was used to sequence 16S rRNA V4-V5 regions of ileum and cecum flora in broilers among the Bacillus group,the antibiotic group,and the control group.The information on the com-position and abundance of microbiotawas obtained.The results showed that the bacterial diversity in the control group was not reduced,but the dominant bacteria,especially the probiotic bacteria,was not prominent and low in abundance.Secondly,the microbiota structure of the basal diet group was not stable with large amplitude of changes.The bacterial diversity of the Bacillus group did not in-crease;the structure stability of ileal microbiota and the abundance of the probiotic dominant bacte-ria were strengthened,improving growth performance and meat quality.Moreover,the multiple cor-relation analysis showed a significant positive correlation was found between fatty acids of breast meat and Lactobacillus agilis,showing the strain exerting significant influence on fatty acids com-position of breast meat.