Division of Experimental Pathology, Department of Laboratory Medicine and Pathology, Mayo Clinic, 200 First St SW, Rochester, MN, 55905, USA.
Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN, 55905, USA.
Sci Rep. 2022 Oct 27;12(1):18109. doi: 10.1038/s41598-022-22626-x.
The origin of fecal floatation phenomenon remains poorly understood. Following our serendipitous discovery of differences in buoyancy of feces from germ-free and conventional mice, we characterized microbial and physical properties of feces from germ-free and gut-colonized (conventional and conventionalized) mice. The gut-colonization associated differences were assessed in feces using DNA, bacterial-PCR, scanning electron microscopy, FACS, thermogravimetry and pycnometry. Based on the differences in buoyancy of feces, we developed levô in fimo test (LIFT) to distinguish sinking feces (sinkers) of germ-free mice from floating feces (floaters) of gut-colonized mice. By simultaneous tracking of microbiota densities and gut colonization kinetics in fecal transplanted mice, we provide first direct evidence of causal relationship between gut microbial colonization and fecal floatation. Rare discordance in LIFT and microbiota density indicated that enrichment of gasogenic gut colonizers may be necessary for fecal floatation. Finally, fecal metagenomics analysis of 'floaters' from conventional and syngeneic fecal transplanted mice identified colonization of > 10 gasogenic bacterial species including highly prevalent B. ovatus, an anaerobic commensal bacteria linked with flatulence and intestinal bowel diseases. The findings reported here will improve our understanding of food microbial biotransformation and gut microbial regulators of fecal floatation in human health and disease.
粪便漂浮现象的起源仍知之甚少。在偶然发现无菌和常规小鼠粪便浮力存在差异后，我们对无菌和肠道定植（常规和常规化）小鼠的粪便微生物和物理特性进行了表征。使用 DNA、细菌-PCR、扫描电子显微镜、流式细胞术、热重分析和比重瓶法在粪便中评估了与肠道定植相关的差异。基于粪便浮力的差异，我们开发了 levô in fimo test（LIFT）来区分无菌小鼠的下沉粪便（沉渣）和肠道定植小鼠的漂浮粪便（浮渣）。通过对粪便移植小鼠中微生物密度和肠道定植动力学的同步跟踪，我们提供了肠道微生物定植与粪便漂浮之间因果关系的直接证据。LIFT 和微生物密度之间罕见的不一致表明，产气肠道定植菌的富集可能是粪便漂浮的必要条件。最后，对常规和同基因粪便移植小鼠“浮渣”的粪便宏基因组学分析鉴定出 10 多种产气细菌的定植，包括高度流行的 B. ovatus，一种与胀气和肠道疾病相关的厌氧共生菌。这里报道的发现将提高我们对食物微生物生物转化和肠道微生物对人类健康和疾病中粪便漂浮的调节作用的理解。
