Genesis of fecal floatation is causally linked to gut microbial colonization in mice

Abstract

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.

Effect of ageing on the physicochemical properties of human faeces in the context of onsite sanitation

“…The swelling observed in fresh faeces could be due to dissolved gasses which also cause ‘floaters’ ( Aalam et al. (2022) .…”

“…Floaters are caused by the metabolism of carbohydrates by gasogenic gut microbiota (e.g. Bacteroides ovatus ), producing gases such as H 2 and CO 2 , which are subsequently converted to CH 4 and H 2 S by hydrogenotrophic bacteria ( Aalam et al., 2022 ). Different types of faecal samples were received and mixed in the study, and it is assumed they included floaters.…”