Remodeling and Alteration of the Gut Microbial Community in Suncus murinus Receiving Fecal Microbiota Transplantations from Mice with High-Fat Diet-Induced Obesity

Background: Obesity-associated gut microbiota can transmit metabolic traits in permissive recipients; however, microbial engraftment following fecal microbiota transplantation (FMT) is also constrained by the recipient’s intestinal environment. Suncus murinus (S. murinus) is an insectivorous and naturally obesity-resistant species with a distinctive gut ecology, making it a potential model for examining recipient filtering during cross-species FMT. Objectives: To determine whether cecal microbiota from high-fat diet (HFD)-fed mice induces persistent donor diet-specific microbial and host phenotypes in S. murinus relative to microbiota from normal chow diet (NCD)-fed donors. Methods: S. murinus recipients (n = 12) were randomly allocated to high-fat diet-recipient (HFD-r) and normal chow diet-recipient (NCD-r) groups (n = 6 per group). All recipients received the same normal trout diet throughout the study. The recipients were administered supernatants of donor cecal microbiota via oral gavage for three consecutive days. A 16S rRNA gene sequencing analysis was performed on fecal samples collected before antibiotic treatment and at weeks 4 and 8 post-FMT. Longitudinal microbial outcomes were analyzed using common baseline-constrained longitudinal models, restricted PERMANOVA, and false discovery rate correction. Results: Bacillota was the predominant phylum in both the HFD-r and NCD-r groups. The most consistent taxonomic response was a shared decrease in Campylobacterota and its major constituent genus Helicobacter after treatment, particularly at 4 weeks, whereas no robust phylum- or genus-level differences were detected between the HFD-r and NCD-r groups. Observed ASV richness and Faith’s phylogenetic diversity did not differ significantly among the groups. Principal coordinate analyses showed extensive overlap, and a restricted PERMANOVA detected no significant separation between the HFD-r and NCD-r groups. Histological examination revealed crown-like arrangements and heterogeneous adipocyte morphology, and variation in villus and crypt appearance in representative recipient sections. Conclusions: No significant differences in fecal microbial composition, body weight, or glucose tolerance were detected between the HFD-r and NCD-r groups. Recipient-associated ecological constraints remain a possible explanation requiring direct assessment of donor engraftment. Further work is needed to evaluate S. murinus as a model for investigating recipient-side constraints on microbiota colonization.