Background. Inferior quality of biological material compromises data, slows discovery, and wastes research funds. The gut microbiome plays a critical role in human health and disease, yet little attention has been given to optimizing collection and processing methods of human stool. Methods. We collected the entire bowel movement from 2 healthy volunteers: one to examine stool sample heterogeneity and one to test stool sample handling parameters. Sequencing and bi-oinformatic analyses were used to examine the microbiome composition. Results. The microbiome profile varied depending on where the subsample was obtained from the stool. The exterior cortex of the stool was rich in specific phyla and deficient in others while the interior core of the stool revealed opposite microbiome profiles. Sample processing also re-sulted in varying microbiome profiles. Homogenization and stabilization at 4°C gave superior microbial diversity profiles compared to the fresh or frozen subsamples of the same stool sample. Bacterial proliferation continued in the fresh subsample when processed at ambient temperature. Bacteroidetes proliferated and Firmicutes diminished during the 30-minute processing of fresh sample. The frozen sample had good overall diversity but Proteobacteria diminished likely be-cause of the freeze/thaw. Conclusions. The microbiome profile is specific to the section of the stool being sampled. Stool sample collection, homogenization, and stabilization at 4°C for 24 hours provides a “neat”, high-quality sample of sufficient quantity that can be banked into aliquots with nearly identical microbial diversity profiles. This collection pipeline is essential to accelerate our understanding of the gut microbiome in health and disease.

Dietzia natronolimnaea C79793-74 has emerged as a potential probiotic strain with implications for managing Crohn's disease. This study evaluates the safety profile of D. natronolimnaea C79793-74 as a probiotic sup-plement. Genotypic characterization involved a 16S rRNA gene and genomic sequencing and genome an-notation. The safety assessment included interrogation of the assembled genome for antibiotic resistance genes and virulence factors, utilizing the CARD and VFDB databases. Notably, the analysis revealed an ab-sence of antibiotic resistance or virulence factors in Dietzia natronolimnaea C79793-74. The safety and tol-erability of D. natronolimnaea C79793-74 were further investigated in an 8-week double-blind, place-bo-controlled clinical trial involving healthy adult participants. A daily dose of 5 x 109 CFU of the probiotic strain was administered. This clinical trial represents the first assessment of the safety of D. natronolimnaea C79793-74 in human subjects. Results demonstrated that participants in both the Dietzia and Placebo groups maintained clinical and hematologic markers within the normal range throughout the study. More-over, the probiotic strain was well-tolerated, with nearly all participants experiencing no severe or medium adverse events. Collectively, the comprehensive data obtained in this study support the inference that Dietzia natronolimnaea C79793-74 is safe and well-tolerated as a nutritional supplement for human con-sumption