The Microbiota Is Not an Organ: Introducing the Muco-Microbiotic Layer as a Novel Morphofunctional Structure

Abstract

In this paper, we want to refute the notion that the microbiota should be considered an organ, given that an organ comprises tissue of similar or different embryological origin, while the microbiota is a pool of different microbial species originating individually from single replications and not from a common ancestral cellular element. Hence, we would like to propose a new morphological interpretation of its nature, based on the comprehensive context in which these microbes live: a muco-microbiotic layer of hollow organs, such as the airways and the bowel. The above concept should represent not only a new terminological annotation but also a more accurate portrayal of the physiology and pathophysiology of these organs. Indeed, a better understanding of the biological nature of this part of the human body can help scientists develop more specific experimental protocols, potentially leading to the establishment of better therapeutic strategies.

Dysbiosis by Eradication of Helicobacter pylori Infection Associated with Follicular Gastropathy and Pangastropathy

“…This structure is the product of the union of the mucus layer and microorganisms. Although in most routine histologic evaluations the muco-microbiotic layer is unfortunately not visible due to the processing of the sample, the detection of microbial morphologies in H. pylori-negative subjects, as observed in our study, can elucidate a possible key role of these bacteria in the gastrointestinal physiology and pathophysiology [42].…”

From Dysbiosis to Neurodegenerative Diseases through Different Communication Pathways: An Overview

“…The term microbiome was first coined by combining the terms "micro" and "biome" to identify a specific microbial population in a clearly defined environment that is characterized by distinctive physicochemical properties. Although many scientists today refer to the human microbiome as our "last organ" (meaning the most recently discovered one) [9], we disagree with this opinion because, as previously stated, it would be better considered as a part of the innermost layer of the intestine, the muco-microbiotic (MuMi) layer, i.e., the layer made not only by the microbiota but also by a mucous matrix and by nanovesicles (which are very important for cell cross-talk) that are secreted by both human and microbiotic cellular elements [4,5,10].…”

Nanovesicular Mediation of the Gut–Brain Axis by Probiotics: Insights into Irritable Bowel Syndrome

“…It participates in digestion as part of the intestinal barrier, where it contributes to the prevention of pathogenic colonization, promotes mucus production and regeneration of intestinal epithelium cells, and participates in the synthesis of neuroactive substances [11]. Furthermore, the bowel mucosa establishes multiple connections with other anatomical districts through nanovesicular trafficking [9]. Consequently, alterations in the composition of the gut microbiota led to a condition known as dysbiosis, resulting in damage to the epithelial barrier and impaired nutrient absorption.…”

“…Among the myriad of claimed advantages, probiotics are renowned for their role in stabilizing the gut microbiota, mitigating gastrointestinal disorders, such as irritable bowel syndrome (IBS), and modulating the host immune system [5][6][7][8]. The muco-microbiotic (MuMi) layer of the intestine houses the microbiota along with all the soluble factors that allow communication between the microbial elements and the epithelial cells of the intestinal mucosa [9,10]. These microorganisms have co-evolved with the host to perform numerous beneficial functions, ranging from simple food fermentation to extensive effects on immune system development, stress responses, and behavior [11][12][13].…”