Establishment And Molecular Ecology Studies Of Human Breast Milk Microbiota-associated Mouse Model

Human breast milk is recognized as an important source of commensal bacteria for the infant gut,but previous studies identified a limited number of milk bacterial species that colonize the infant gut,including bacteria from Bifidobacterium,Staphylococcus,Lactobacillus,and Escherichia/Shigella.Here,normal chow-fed germ-free mice were orally inoculated with the breast milk collected from a 38-year-old human mother two days after vaginal delivery.According to 16 S rRNA gene-based denaturant gradient gel electrophoresis and Illumina sequencing,bacteria at > 1% abundance in the milk inoculum were only Streptococcus(56.0%)and Staphylococcus(37.4%),but in the feces of recipient mice were Streptococcus(80.3 ± 2.3%),Corynebacterium(10.0 ± 2.6 %),Staphylococcus(7.6 ± 1.6%)and Propionibacterium(2.1 ± 0.5%)that were previously shown as dominant bacterial genera in the meconium of C-section-delivered human babies;the abundance of anaerobic gut-associated bacteria,Faecalibacterium,Prevotella,Roseburia,Ruminococcus and Bacteroides,was 0.01%-1% in the milk inoculum and 0.003%-0.01% in mouse feces;the abundance of Bifidobacterium spp.was below the detection limit of Illumina sequencing in the milk but at 0.003%-0.01% in mouse feces.The human breast milk microbiota-associated mouse model may be used to identify additional breast milk bacteria that potentially colonize the infant gut.13 strains from Staphyloccus and 4 strains from Streptococcus were obtained from breast milk and breast milk microbiota-associated mice by microbiological cultivation.An animal model was needed to evaluate the influences of these breast milk bacteria on host health.With an isolated E.coli(Escherichia coli)strain D80,which was at dominant abundance in the gut of an obese child,we studied the feasibility of using the Caenorhabditis elegans(C.elegans)model to evaluate the influence of bacteria on host health.D80 significantly shortened the average lifespan of C.elegans,and wild-type C.elegans showed aversive behavior to D80.Besides,the treatment of sulfamethoxazole(SMX),which is a drug that inhibits the bacterial folate synthesis,to E.coli D80 did not normalize the lifespan of C.elegans.These results suggest that the E.coli D80 that is associated with child obesity is harmful to the health of C.elegans host health,and its mechanism to shorten the life span of C.elegans may not depend on folate metabolism pathways.C.elegans can be used as a model to screen the influences of breast milk bacteria on host health in future studies.