Reproductive Tract Microbial Transitions from Late Gestation to Early Postpartum Using 16S rRNA Metagenetic Profiling...

Area of Science:

• Reproductive biology
• Microbial ecology
• Mammalian reproduction

Background:

• Reproductive tract microbial communities are vital for mammalian health and reproductive success.
• Postpartum uterine inflammation can arise from bacterial contamination following parturition, particularly in first-time mothers.
• Limited research exists on the spatio-temporal microbial shifts in the reproductive tracts of primigravid females.

Purpose of the Study:

• To characterize and compare vaginal microbial communities in late gestation with vaginal and uterine communities in early postpartum in first-pregnancy heifers.
• To identify distinct microbial profiles and transitions within the bovine reproductive tract during the critical period of first pregnancy and parturition.

Main Methods:

• 16S rRNA V4 region metagenetic sequencing was performed on vaginal samples from 33 first-pregnancy heifers at late gestation (day 258 ± 4) and on vaginal and uterine samples at early postpartum (day 7 ± 2).
• Bioinformatic analysis utilized Mothur MiSeq SOP for processing sequence data.
• Statistical analyses included assessing microbial community composition, richness, diversity, and employing unsupervised clustering (probabilistic Dirichlet Multinomial Mixtures) and differential abundance analysis (LEfSe).

Main Results:

• Reproductive tract bacterial communities comprised 1255 genus-level OTUs across 30 phyla, dominated by Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes, and Fusobacteria.
• Significant microbial compositional shifts were observed between prepartum vagina (Vag-pre), postpartum vagina (Vag-post), and postpartum uterus (Utr-post).
• The Utr-post group showed lower Proteobacteria and higher Bacteroidetes, Fusobacteria, and Tenericutes compared to Vag-pre, with Vag-post exhibiting intermediate profiles. Utr-post also had reduced bacterial richness and diversity.

Conclusions:

• The bovine reproductive tract harbors a dynamic microbial landscape that undergoes significant temporal and spatial transitions during the first pregnancy and parturition.
• Distinct microbial signatures characterize the prepartum vagina and postpartum uterus, with the postpartum vagina showing a transitional microbial profile.
• These findings underscore the complexity of the reproductive tract microbiome and offer insights for future research in bovine reproductive health and microbial ecology.