| Lactobacillus rhamnosus is one of the common commercialized probiotics.At present,the research on its physiological properties and functions is relatively mature.With the development of genome sequencing,the genomes of L.rhamnosus have been more availabe.Till now 162 L.rhamnosus genomes have been published in NCBI database.Based on the studies of correlation between genome and physiological and biochemical properties,the adhesion,carbohydrate utilization and antibiotic resistance of L.rhamnosus are analyzed.However,the existing research is limited to foreign strains and the relevant data of L.rhamnosus in China is rare.In this paper,L.rhamnosus isolated from Chinese subjects were studied in the genomic and physiological and biochemical properties,which will provide theoretical basis for the breeding and development of L.rhamnosus suitable for Chinese subjects.The main results are as follows:(1)By comparative genomics approach,70 L.rhamnosus strains were isolated from different Chinese subjects,and were genomic sequenced.The results showed that the predicted genome size of L.rhamnosus was 2.77 Mb~3.10 Mb,and the number of ORFs was 2676~3024.The number of tRNA genes was 30~61,and the GC content was 46.60%~47.49%.The pan-genome size is 8395,and it is currently in an open state.The results are similar to those of L.rhamnosus abroad.Phylogenetic tree constructed by homologous genes and ANI values indicated that there was no significant relationship between strain clustering and host region and age as well as ethnicity.In addition,19 strains contained spaCBA gene and 2 strains contained spaBA gene.(2)The carbohydrate utilization ability of L.rhamnosus was analyzed by genome and physiological and biochemical properties correlation.The results showed that 70 L.rhamnosus and foreign strain LGG genomes contain 27 GH family genes including ?-trehalase and fucosidase,and their distribution reflects individual differences among the strains.Carbohydrate utilization experiments showed that 70 L.rhamnosus can utilize glucose,D-ribose,galactose,D-trehalose,L-fucose,sucrose and D-mannitol.Most strains can utilize D-cellobiose,D-Sorbitol,lactose and maltose.A few strains can utilize XOS,L-arabinose,raffinose,FOS and xylose.Combining with genome analysis,the results showed that the carbohydrate utilization of the strain was related to GH family genes,PTS system and gene clusters.(3)Antibiotic resistance of L.rhamnosus was studied by genome and physiological and biochemical properties correlation analysis.The results demonstrated that 70 L.rhamnosus and LGG genomes contain vancomycin,tetracycline,fluoroquinolone antibiotics and other related resistance genes,transporter proteins and efflux pump types ranging from 55 to 60.The number of resistance genes ranged from 113 to 137 in the genomic.Antibiotic resistance test showed that 70 strains were completely resistant to vancomycin and susceptible to streptomycin.Combining with genome analysis,the results showed that the resistance of strains was related to antibiotic resistance genes,efflux pumps and corresponding proteins.(4)The performance of 70 L.rhamnosus against specific environment was studied by simulating gastric juice and intestinal juice in vitro.The results showed that the survival rate of 70 strains in simulated gastric juice was more than 31.50%,and the tolerance of 8 strains to intestinal juice was less than 0.01%.The tolerance of L.rhamnosus in Chinese intestine was not as good as that of LGG.Combining with genome analysis,the results showed that the acid tolerant is related to genes such as dapA,clpP and amino acid metabolizing enzymes.While bile salt-tolerant ability was effected by the taurine ABC transporter and bile salt transport system. |
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