A 2023 porcine study expanded Part 1’s coverage to include stomach and small intestine microbiota:
“Identification of individual intestinal microbes affecting phenotypes and diseases depends on statistical analyses between these two main variables. Because the phenotypes or diseases are typically well-defined, success of statistical analyses on these studies depend on precise elucidation of gut microbiome composition.
This work with genetically homogenous sibling pigs grown in a cohoused condition to minimize experimental errors showed that composition of the gut microbiome constantly changed in response to local environmental changes of the GI tract. Pigs are omnivorous and have the most similar digestive mechanisms to humans.
The stomach and small intestine microbiomes – which are rich in nutrients – were very different from the large intestine and feces microbiomes in terms of both composition and diversity. Firmicutes, Proteobacteria, Actinobacteria, Cyanobacteria, and Fusobacteria phyla were relatively more dominant in the stomach and small intestine than the large intestine and feces. Bacteroidetes was more heavily dominated in the large intestine and feces.
Sampling locations within the GI tract were determined based on their anatomical feature: stomach, duodenum (small intestine_1), jejunum (small intestine_2 ~ small intestine_5), ileum (small intestine_6), cecum (large intestine_1), colon (large intestine_2 ~ large intestine_6), and rectum (large intestine_7).
The gut microbiome between locations within an individual was significantly different, while individual differences at the same locations of the GI tract were not as significant. Fecal microbiome was more closely related to the gut microbiome in large intestine than stomach or small intestine.
Intestinal bacteria in terms of both species number and their prevalence were dramatically increased as intestinal matter transited from the stomach to the large intestine. Cooccurrence network analysis showed the gradual adaptation of intestinal microbiota from stomach to large intestine:
- At the same time, the highly dense and diverse bacteria in the large intestine were closely related to each other.
- Fecal microbiome did not represent any microbiome at the 14 locations.
This work demonstrated that the fecal microbiome does not represent the overall composition of the gut microbiome. Despite significant roles of gut microbiome in various phenotypes and diseases of its host, causative microbes for such characteristics identified by one research fail to be reproduced in others.
Since fecal microbiome is a result of the gut microbiome rather than the representative microbiome of the GI tract of the host, there is a limitation in identifying causative intestinal microbes related to these phenotypes and diseases by studying fecal microbiome. It seems urgent to develop new methods for gut microbiome analysis.”
https://www.hindawi.com/journals/cmi/2023/6868417/ “Fecal Microbiome Does Not Represent Whole Gut Microbiome”
This study showed that pig stomach and small intestine microbiota had few associations with fecal microbiota samples. Part 1 showed that only 6% of large intestine microbiota genes producing a secondary metabolite were found in human fecal samples.
What’s the point of poop microbiota studies when those microbiota don’t fairly represent ANY preceding gut microbiota, either overall or in actionable stages?
I don’t endorse this study’s Conclusions section suggestions of “endoscopic methods” because it ignores iatrogenic injuries and deaths. I’ll continue to give my trillion+ microbiota partners what they need, and expect reciprocity.