Longitudinal and Comparative Analysis of Gut Microbiota of Tunisian Newborns According to Delivery Mode.

Microbiota colonization is a dynamic process that impacts the health status during an individual's lifetime. The composition of the gut microbiota of newborns is conditioned by multiple factors, including the delivery mode (DM). Nonetheless, the DM's influence remains uncertain and is still the subject of debate. In this context, the medical indication and the emergency of a cesarean delivery might have led to confounding conclusions regarding the composition and diversity of the neonatal microbiome. Herein, we used high-resolution shotgun sequencing to decipher the composition and dynamics of the gut microbiota composition of Tunisian newborns. Stool samples were collected from 5 elective cesarean section (ECS) and 5 vaginally delivered (VD) newborns at the following time points: Day 0, Day 15, and Day 30. The ECS and VD newborns showed the same level of bacterial richness and diversity. In addition, our data pointed to a shift in microbiota community composition during the first 2 weeks, regardless of the DM. Both ECS and VD showed a profile dominated by Proteobacteria, Actinobacteria, and Firmicutes. However, ECS showed an underrepresentation of Bacteroides and an enrichment of opportunistic pathogenic species of the ESKAPE group, starting from the second week. Besides revealing the intestinal microbiota of Tunisian newborns, this study provides novel insights into the microbiota perturbations caused by ECS.

Solution structure of a truncated anti-MUC1 DNA aptamer determined by mesoscale modeling and NMR.

Mucin 1 is a well-established target for the early diagnosis of epithelial cancers. The nucleotides of the S1.3/S2.2 DNA aptamer involved in binding to variable number tandem repeat mucin 1 peptides have been identified using footprinting experiments. The majority of these binding nucleotides are located in the 25-nucleotide variable region of the total aptamer. Imino proton and 2D NMR spectra of truncated and total aptamers in supercooled water reveal common hydrogen-bonding networks and point to a similar secondary structure for this 25-mer sequence alone or embedded within the total aptamer. NMR titration experiments confirm that the TTT triloop structure is the primary binding site and show that the initial structure of the truncated aptamers is conserved upon interaction with variable number tandem repeat peptides. The thermal dependence of the NMR chemical shift data shows that the base-paired nucleotides melt cooperatively at 47 ± 4°C. The structure of the 25-mer oligonucleotide was determined using a new combined mesoscale molecular modeling, molecular dynamics and NMR spectroscopy investigation. It contains three Watson-Crick pairs, three consecutive mispairs and four Watson-Crick pairs capped by a TTT triloop motif. The 3D model structures (PDB 2L5K) and biopolymer chain elasticity molecular models are consistent with both NMR and long unconstrained molecular dynamics (10 ns) in explicit water, respectively. Database Structural data are available in the Protein Data Bank and BioMagResBank databases under the accession numbers 2L5K and 17129, respectively.