Lecture 38: Gut microbiome III Flashcards
Aside from bacteria, name 3 other types of organisms present in the gut microbiome.
Fungi, viral microbiota (bacteriophages), and helminths
The collection of fungi in the gut microbiome is called […]
Mycobiome
The collection of helminths in the gut microbiome is called […]
Macrobiota
The collection of viral microbiota in the gut microbiome is called […]
Virome
What are probiotics?
Live microorganisms which when administered in adequate amounts confer a health benefit to the host.
Name 4 current issues with probiotics.
- Inadequate studies(uncertain health benefits, concerns about data quality)
- Limited mechanistic understanding of effects of current probiotics
- Effectiveness of probiotic to altering a disease state is not currently provided.
- There is the possibility of transferrable microbial properties (i.e. antibiotic resistance genes) to the gut microbiota.
What is the effect of probiotics said to be after disease?
It is claimed that taking probiotics when sick can help the gut microbiota return to normal after a perturbation.
Describe the setup and goal of the Suez et al. 2018 study.
They treated both humans and mice with antibiotics ciprofloxacin and metronidazole, then put them on bi-daily probiotics administration. The goal was to test whether probiotics do in fact help the gut microbiome recover after antibiotic perturbation.
Describe the results of the Suez et al. 2018 study in mice.
It was found that mice without antibiotic exposure were not colonized by probiotics. For those that did receive antibiotics, probiotic colonization was mild in mucosal layers.
Describe the results of the Suez et al. 2018 study in humans.
In humans, probiotic colonization was site and person-specific. Antibiotics significantly enhanced probiotic colonization in musosal layers. Overall, probiotics delay gut microbiome reconstitution and its metabolism, which is unexpected.
How do probiotics compare to FMT in terms of mucosal microbial diversity and metabolism?
FMT restores mucosal microbial diversity and metablism very effectively as compared to probiotics.
What are the 3 major helminths in the gut?
Nematodes, cestodes, and trematodes.
How much of the world’s population is affected by helminth infection?
25%
What is the typical effect of helminths on the body?
It induces Th2 response, which is a chronic immune response, allowing for decade-long infections. There is also the possibility of protection from malaria, but this is uncertain.
What is the hygiene hypothesis?
It is the hypothesis that excessive hygiene in the developed world, which causes lack of exposure to helminths, might be the cause of the high prevalence of autoimmune disorders in these regions
Name 2 roles of helminths in the gut.
They can alleviate bleeding in inflammatory bowel disease and can decrease the number of Bacteroides species involved in intestinal inflammation.
How can gut helminths affect the airways?
Their interactions with the gut bacteria can alleviate asthma symptoms, as their metabolites can behave as neurotransmitters and affect the tissue.
What is worm therapy? How effective is it?
It is when chronically ill individuals purcahse helminths to put into their guts to attempt to alleviate their disease symptoms. However, there is very little known about the details and effects of this method.
What are bacteriophages? Where are they found?
They are viruses that infect bacteria that are obligatory parasites without inherent metabolism. They exist everywhere that bacteria are present.
How prevalent are bacteriophages in microbial communities?
There is typically a bacteriophage:bacteria ratio of 10:1. The exception is the gut, which has a lower, 1:1 ratio (can range between 0.1:1 and 3:1).
What are the two most prevalent phage types in the gut?
CrAssphages (most prevalent) and Lak phages.
What is known about phage diversity? Why?
There are various types, including DNA and RNA as well as with capsids or envelopes. However, most phages remain unknown because there is no common genetic marker (such as 16S rDNA) and the databases are limited.
What are the two major bacteriophage replication cycles?
The lytic cycle and the lysogenic cycle.
Describe the lytic cycle of bacteriophages.
They infect the cell and inject their DNA/RNA into it, which becomes plasmids. The bacteriophage genome replicates, which produces more phages in the cell. The cell lyses and the bacteriophages break free to infect another cell.
