Speaker: Clara Belzer
Department: Laboratory of Microbiology, Wageningen University, The Netherlands
Subject: Verrucomicrobia and the intestinal microbiome; the case of the Akkermansia muciniphila
Location: BioTechnology department TU Delft
Author: Mirte Golverdingen
To broaden my view of the studies done in the Applied Science building I visited a lunch lecture in the BioTechnology department. The microbiologist Clara Belzer from Wageningen University was the speaker and she spoke of the newly discovered Akkermansia muciniphila bacteria. Belzer and her group are interested in anaerobic micro-organisms that can degrade ligases and mucus in the gut. Verrucomicrobia is one of the phyla that lives in the gut, the bacteria Akkermansia muciniphila is one of the Verrucomicrobia and isolated by the group for a quest of new bacteria.
They discovered that the bacteria are very dominant along the mucus gut and an important player in human microbiota composition. The bacteria are a potential maker for healthy intestine and has an extraordinary mucus degrading capacity. The importance of the bacteria is shown in the fact that after a month after birth the bacteria can already be detected in the gut system. This is certainly not the case for all gut bacteria.
The human microbiota changes during life stages and perturbations, this is partly caused by the place of the bacteria on the body. However, over a life time the microbiota can also change due to physiological changes of the body by diet changes. Therefore, the change in microbiota can contribute to or starting diseases. Moreover, some microbiotia do not depend on food, they depend on mucus and mother milk.
Bacteria influence the host cell by a difference in glycal level. This has a microbial benefit; mucosal glycan foraging can solve the problem of the competition for glycans in the gut. For the host, the mucosal microbes can provide resistance against the colonization of pathogens. It directly inhibits the pathogens by production of antimicrobial compounds. Moreover, the depletion of nutrients modulates the immune response of the host.
In the gut, there are 5 major microbiological fila, some are mucus degraders and some are mucus binders. Mucus can be used as the source of growth because mucus glycans can be created by the bacteria. However, there are not only glucose molecules in these mucus glycans, there are also other more ‘awkward’ sugars which are hard to break down. These sugars need to be broken down by enzymes. The Akkermansia muciniphila is adapted to digest mucin, it contains a high number of genes that encodes for enzymes which can degrade mucin. None of all Verrucomicrobia have the same number of enzymes that are able to digest mucin as the A. muciniphila. So, the A. muciniphila is really adapted to the work of mucin digestion.
So, to find out if A. muciniphila is also present in other animals, Belzer et al. went to the zoo to find the bacteria in mucus of mammals and non-mammals (see figure 1). The A. muciniphila found in these animals differ as the animals have different digestive physiologies, diets and mucus structure. Still, the bacteria were not very different, which is very remarkable. The only difference between the animals A. muciniphila was found in the antibiotic resistance and CRISPR Cas system, as the animals differ in defending to bacteria and viruses in their environment.
So, why are the bacteria so similar? This could be due to a spontaneous infection very recently, so the bacteria were not able to evolve since. The bacteria could also have a very stable genome that does not evolve. Or the bacteria are not specific on the type of mucus. One genome, however, was different from the rest. The python strain of the A. muciniphila looks really different. Moreover, only a small number of all animals are tested on the A. muciniphila. Therefore, more different genomes could be discovered.
Belzer saw a similarity between organisms and the A. muciniphila system: As soon as the host was on a diet or starving, the A. muciniphila levels are going up. This is similar for all organisms and systems. This could indicate that A. muciniphila could be an obese related bacterium. Belzer moreover, showed that the A. muciniphila works as a growth support of beneficial microbes in the gut. Moreover, when the A. muciniphila levels rises in the gut, organisms were metabolic healthier.
It was very interesting to visit the BioTechonolgy department for this seminar. Some metabolic details were hard to follow for me; however, I was still able to follow her talk. I was surprised by the complex microbiota in the gut. The similarity of the A. muciniphila is very interesting and research for this bacteria in other animals can contribute to the understanding of this bacteria.
Figure 1: Akkermansia muciniphila is universally distributed in intestinal tracts all over the animal kingdom. (a) Phylogenetic tree indicating the position of A. muciniphila among selected full-length 16S rRNA clones from mammalian gut samples. Red colored samples derive from human sources. Thermotoga thermarum is used as an outgroup. The tree was generated using the neighbor joining method. Full details and high-resolution information are provided in Supplementary Figure S1. (b) Schematic representation of the tree in (a) with the five different clades their position and similarity to A. muciniphila. (c) Taxonomic tree of mammals generated using iTol webtool from tree of life project using all available sequences from NCBI (Letunic and Bork). Animal silhouettes indicate single species as a representative of that order. When an animal species from the mammalian orders was positive for Akkermansia-like sequences the animal logo belonging to that order is colored red, when it was negative the animal logo is colored gray. No Akkermansia sequences have been reported yet in any of the animals belonging to the mammalian orders depicted in black.
Adapted from: Belzer, C., & De Vos, W. M. (2012). Microbes inside—from diversity to function: the case of Akkermansia. The ISME journal, 6(8), 1449-1458.