A recent study reported the existence of a diverse microbiota in 5-to-7-month-old calf fetuses, suggesting that colonization of the bovine gut with so-called “pioneer” microbiota may begin during mid-gestation. In the present study, we investigated 1) the presence of microbiota in bovine fetuses at early gestation (12 weeks), and 2) whether the fetal microbiota is influenced by the maternal rate of gain or dietary supplementation with vitamins and minerals (VTM) during early gestation. Amniotic and allantoic fluids, and intestinal and placental (cotyledon) tissue samples obtained from fetuses (n = 33) on day 83 of gestation were processed for the assessment of fetal microbiota using 16S rRNA gene sequencing. The sequencing results revealed that a diverse and complex microbial community was present in each of these fetal compartments evaluated. Allantoic and amniotic fluids, and fetal intestinal and placenta microbiota each had distinctly different (0.047 ≥ R2 ≥ 0.019, P ≤ 0.031) microbial community structures. Allantoic fluid had a greater (P < 0.05) microbial richness (number of OTUs) (Mean 122) compared to amniotic fluid (84), intestine (63) and placenta (66). Microbial diversity (Shannon index) was similar for the intestinal and placental samples, and both were less diverse compared with fetal fluid microbiota (P < 0.05). Thirty-nine different archaeal and bacterial phyla were detected across all fetal samples, with Proteobacteria (55%), Firmicutes (16.2%), Acidobacteriota (13.6%) and Bacteroidota (5%) predominating. Among the 20 most relatively abundant bacterial genera, Acidovorax, Acinetobacter, Brucella, Corynebacterium, Enterococcus, Exiguobacterium and Stenotrophomonas differed by fetal sample type (P < 0.05). A total of 55 taxa were shared among the four different microbial communities. qPCR of bacteria in the intestine and placenta samples as well as scanning electron microscopy imaging of fetal fluids provided additional evidence for the presence of a microbiota in these samples. Minor effects of maternal rate of gain and VTM supplementation, and their interactions on microbial richness and composition were detected. Overall, the results of this study indicate that colonization with pioneer microbiota may occur during early gestation in bovine fetuses, and that that the maternal nutritional regime during gestation may influence the early fetal microbiota.

中文翻译：

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与暴露于不同子宫内营养的 12 周大牛胎儿相关的微生物群特征

最近的一项研究报告了 5 至 7 个月大的小牛胎儿中存在多种微生物群，这表明所谓的“先锋”微生物群可能在妊娠中期开始在牛肠道中定植。在本研究中，我们调查了 1) 妊娠早期 (12 周) 牛胎儿中微生物群的存在，以及 2) 胎儿微生物群是否受母体增重率或膳食补充维生素和矿物质 (VTM) 的影响早孕。使用 16S rRNA 基因测序处理从妊娠第 83 天（n = 33）胎儿（n = 33）获得的羊水和尿囊液以及肠道和胎盘（子叶）组织样本，用于评估胎儿微生物群。测序结果显示，在评估的每个胎儿区室中都存在多样化且复杂的微生物群落。尿囊液和羊水以及胎儿肠道和胎盘微生物群各自具有明显不同的微生物群落结构（0.047 ≥ R2 ≥ 0.019，P ≤ 0.031）。与羊水 (84)、肠 (63) 和胎盘 (66) 相比，尿囊液的微生物丰富度（OTU 数）（平均 122）更高（P < 0.05）。肠道和胎盘样本的微生物多样性（香农指数）相似，与胎儿体液微生物群相比，两者的多样性都较低。P < 0.05)。在所有的胎儿样品检测三十九个不同古细菌和细菌门，与变形菌（55％），厚壁菌门小号（16.2％），Acidobacteriota（13.6％）和Bacteroidota（5％）为主的。在20个最丰富的细菌属中，嗜酸菌属、不动杆菌属、布鲁氏菌属、棒状杆菌属、肠球菌属、微小杆菌属和狭养单胞菌属因胎儿样本类型而异（P< 0.05)。四种不同的微生物群落共有 55 个分类群。肠道和胎盘样本中细菌的 qPCR 以及胎儿体液的扫描电子显微镜成像为这些样本中存在微生物群提供了额外的证据。检测到母体增重率和 VTM 补充的轻微影响，以及它们对微生物丰富度和组成的相互作用。总体而言，这项研究的结果表明，先驱微生物群可能在牛胎儿的早期妊娠期间定植，并且妊娠期间母体的营养状况可能会影响早期胎儿微生物群。