Maurice Lectures Flashcards
Human eukaryotic cells exist with which 4 microorganisms? Which one isn’t present in all people?
bacteria
intestinal parasites (not all ppl)
viruses
archaebacteria
What is the microbiome referring to?
Bacterial genes
What does the microbiota refer to?
Bacterial cells
What is the opposite of pathogens?
Probiotics
What is another name for pathobionts?
Opportunistic pathogens
T or F: There are more bacterial cells and bacterial genes than there are human cells and genes in/on the human body
T - 3X more cells, 1000X more genes
What are the benefits of the human microbiome project?
- discover species associated with the human body
2. study what bacteria are doing on the body
What are 2 ways to perform sequencing on the microbiome?
- 16S sequencing
2. whole-genome sequencing
What is the 16S gene?
A marker for bacteria
How can you tell the difference between bacteria if they all contain the 16S gene?
Compare the variable regions
Which parts of the bacterial DNA does 16S sequencing involve?
Sequencing the 16S gene only, nowhere else
What does whole genome sequencing entail?
Sequencing ALL the bacterial genes
What are the 2 benefits of WGS?
- Determines which bacterial species are present
2. Determines what the bacterial species are capable of doing (by looking at the proteins being encoded)
What is the only result from 16S sequencing?
Identification of the bacterial species present
T or F: Microbial communities are diverse on the phyla, genera, and species level.
F - only diverse on the species level
What is a microbial signature?
The unique stains and species of bacteria present on each indvl
T or F: Each body part contains the same types of bacteria. Explain
F - each body part contains a dominant signature taxa. Each body part has different environmental conditions that can only support certain types of bacteria
Why are certain bacteria found in one part of body but not in another?
Each species requires different environmental conditions
Dominant bacteria on skin
Actinobacteria
Dominant bacteria in vagina
Lactobacillus
Dominant bacteria in gut
Bacteroidetes and Firmicutes
Dominant bacteria in mouth
Streptococcus
T or F: There is a core microbiota shared bw all healthy indvls.
F
T or F: There is a core microbiome shared bw all healthy indvls
T
Even though the microbiota composition is highly variable bw indvls, the ___ ___ ___ are similar
functional gene profiles
Why do babies born from c-section or vagina have different colonization patterns?
Exposed to different bacteria in the 2 methods. During vaginal birth, baby is exposed to bacteria in gut (ex. Lactobacillus). Babies born via c-section are mostly colonized with Actinobacteria
What causes changes in gut microbiota of a child?
Changes in diet: milk –> baby formula –> real food
T or F: Gut bacteria are replaced randomly as child grows and changes diet
F - There is chronological succession in how bacteria are replaced
Why might the gut microbiome change in seniors?
Weaker immune system, medications
Where is the most dense microbial community in body?
gut
T or F: There is more bacterial diversity in colon than in stomach. Explain
T - due to colon having a less extreme environment (not as acidic)
What types of molecules do Bacteroidetes degrade?
Complex glycans
3 characteristics of Bacteroidetes
- Gram neg
- Rod-shaped
- anaerobic
Which Gram stain will identify Firmicutes?
Crystal violet - gram +
3 characteristics of Firmicutes
- Gram +
- forms spores
- obligate anaerobes
T or F: anaerobic property of Bacteroidetes and Firmicutes are important for gut health
T
List 3 common genera in Firmicutes phylum
Clostridium, Lactococcus, Lactobacillus
Are C. difficile professional pathogens?
No, they are opportunistic pathogens.
Name an archaebacterial species found in the gut.
M. smithii
Why are fungi important in the skin microbiome?
They produce antimicrobials that prevent bacterial pathogens from invading
T or F: The vaginal microbiome is diverse. Explain
F - the bacteria have a specific function - to maintain acidic pH
Name an important function of lactic acid in vagina.
Prevents STDs (shown to inhibit C. trachomatis infections)
T or F: P. gingivalis can enter the bloodstream and cause sepsis
T
Which phylum does P. gingivalis belong to?
Bacteroidetes
Main bacterial species involved in cavities. They proliferate in response to what?
S. mutans - proliferate in response to high sugar diets
Which species produces prophyrin and therefore looks black when grown on blood agar?
P. gingivalis
T or F: P. gingivalis is a strict anaerobe
T
Which Gram stain will identify P. gingivalis?
Saffranin
List 5 functions of the human microbiome
- colonization resistance
- produce vitamins
- metabolize xenobiotics
- generate metabolites
- digest food (esp. dietary fibres)
Name a reason why different indvls may respond differently to the same drug
They have different git microbiota which may or may not activate or inactivate the drug, resulting in different effects
What 2 factors make up colonization resistance?
- number of microbiota
2. production of bacteriocins
Give an example of a bacterial metabolite
TMA (trimethylamine)
Which substrate is TMA derived from?
choline
Which gene cluster is responsible for turning choline into TMA?
choline utilization gene cluster (cut)
Where is TMA oxidized?
Liver
How is TMAO linked to cardiovascular disease in humans?
TMAO causes increased deposition of cholesterol in arteries
T or F: humans produce secondary bile acids
F - humans produce primary bile acids. Bacteria produce secondary bile acids
Where are most primary bile acids absorbed?
Small intestine
Which organ makes bile acids? What are they made from?
Liver; cholesterol
What is the main source of nutrients for gut bacteria?
Plant carbohydrates
Where do bacteria that break down plant carbohydrates reside?
Large intestine
What is the product of plant carb degradation?
Short chain fatty acids
100% of SCFA are used by ___ cells as ___
intestinal; energy source
List the 3 main SCFA that play a role in human health
butyrate, acetate, propionate
SCFA are found in high concentrations in the _____
large intestine
Butyrate inhibits or activates HDACs?
inhibits
What does butyrate do to DNA?
modulates how packed the DNA is by inhibiting removal of acetyl groups from histones (epigenetic modification)
T or F: butyrate causes increased histone acetylation
T
Does butyrate pack or unpack DNA?
pack, therefore prevents transcription
T or F: butyrate can regulate T cells
T, by regulating epithelial cell secretion of TGF-b
Which Clostridia classes produce butyrate?
Clostridia IV and XIVa
List 4 functions of butyrate
- inhibits HDAC –> DNA more acetylated –> DNA more packed
- regulates T cell
- Induces IL18 production
- Stimulates DCs + macrophages to produce IL10 and retinoic acid
What is the importance of a high-fibre diet?
Keeps balance of fibre-degrading and mucus-degrading bacteria; prevents mucus-degrading bacteria from taking over
T or F: during dysbiosis, an increase in bacterial diversity is observed
F - decrease
How do high levels of SCFA affect the blood brain barrier?
Ensures that the BBB is healthy and that tight junctions are tight
Diet with less complex carbs causes more or less permeable blood brain barrier?
More permeable
Which bacterium has been linked to colorectal cancer?
Fusobacterium nucleatus (Fn)
