Microbial Symbiosis with Humans Flashcards
(36 cards)
1
Q
what is dysbiosis?
A
It is a disruption of the microbiome resulting in an imbalance in microbiota
2
Q
What do we know about diversity and dynamics of microbial populations in humans
A
- body caries about equal numbers of human cells as bacterial cells
-species r very diverse across individuals but phyla are pretty similar
Mostly firmicutes followed by bacteriodetes
Bacteriodetes rule stool
Firmicutes supreme in vagina
3
Q
Skin Microbiota
A
- difficult to colonize(salty, acidic, protective oils, dry)
- composition influenced by environmental factors, host factors (hygiene, puberty), each microenvironment like dry skin, moist skin and sebaceous skin
- mostly Gram +ve bacteria because they’re more resistant to salt and dryness
4
Q
S. epidermis
A
- skin commensal interactions with S.aureus
produces Abx that prohibits colonization and biofilm formation by S.aureus by producing endopeptidase, induces keratinocytes to produce antimicrobial peptides to kill S. aureus
5
Q
S.hominis
A
-skin commensal interactions
produces antibiotics synergies with human antimicrobial peptide to decrease S.aureus colonization
6
Q
Propionibacterium acnes
A
- causes acne, degrades skin oil, inflames sebaceous glands and causes acne
- skin commensal interactions
7
Q
Oral Cavities and Airways Microbiota
A
- complex heterogenous microbial habitat
- saliva contains antimicrobial enzymes
- high [nutrients] promote local growth
normally harms but can enter bloodstream producing bacteremia
8
Q
Bacteremia
A
bacteria in blood, big uh oh cause bacteria should be sterile
9
Q
Prebiotics
A
carbohydrates that are indigestible by human host but feed fermentative gut bacteria, promotes growth of “good” bacteria
10
Q
Probiotics
A
living microbes ingested to restore natural microbial balance, confer health benefit to the host
don’t know they work or if they really do
- commonly used genera: bifidobacterium, lactobacillus
- food supplements not medicine
- contraindicated for immunosuppressed patients
11
Q
Recommended clinical uses probiotics
A
- reduces the risk of Anxiety associated diarrhea
-increases remission rates in adults with ulcerative colitis
-reduces the incidence of necrotizing enterocolitis
12
Q
Bifidobacterium and Lactobacillus
A
- commonly found in yogurt and probiotic
- easily destroyed
- by acid pH of stomach
-enzymes and bile acids - obligate anaerobe: lil bitches when oxygen is around
13
Q
Probiotic Theory
A
- they may work by taking up space, limiting the ability of pathogens to colonize the gut, they don’t colonize though they work temporarily
14
Q
Oral and Nasal Cavities
A
- Have normal microbiota, infants mouth colonized with gram -ve(neisseria) and gram +ve(S, lactobacillus actinomyces),
- as teeth emerge other bacteria start growing, prevotella–> gums and teeth s.mutans –> enamel
15
Q
Lower Respiratory Tract
A
- first thought to be sterile but does harbour limited normal microbiota,
- ciliated mucus lining -> mucociliary escalator: sweeps foreign particles up and out of lung
lungs are really delicate so it can’t use strong immune responses, it kinda takes care of it’s self through mucus secretion and surfactants by epithelial cells
16
Q
upper respiratory tract
A
- microbes thrive, wet warm air
enter through breathing but are trapped in mucus and are expelled sneezing or swallowed then killed in stomach
17
Q
kidney and bladder microbiota
A
not a thing they are sterile but if environment changes big deal E.coli and P.mirabilis cause UTIs in biological women (super common infection, top 10 reasons ppl see doctors)
18
Q
STIs (sexually transmitted disease)
A
sometimes include UTIs (even though really UTIs are bladder infections)
important cause of patient morbidity
19
Q
Female genital tract microbiota
A
- weakly acidic with tons of glycogen
- tons of lactobacillus acidophilus which ferment glycogen and produce lactic acid
- lactic acid keeps it acidic
-L.acidophilus colonizes at puberty, when not of fertile/child bearing age pH is neutral - Yeast is opportunistic commensal it’s usually their handy dandy but when L. acidphilus is displaced cause the environment changed or smt Abx, douching, semen
20
Q
Male genital tract microbiota
A
- understudied
circumsion is the biggest influence on the composition of penis microbiome
foreskin covers glands allowing for anaerobic bacteria growth
also affected by sex and age
no known commensals yet
shared microbiota bwt sexual partners
21
Q
Traits of human GI tract and Microbiota
A
- mono gastric, omnivorous
- microbes in gut affect early development, health and predisposition to disease
- colonization of gut begins at birth
3 different environments storage small I and large I
response - responsible for digestion of food, absorption of nutrients and production of nutrients
22
Q
Trends down the GI system
A
- less and less oxygen
-pH increases and so does the # of cells
1-4h to transit from stomach to the large intestine
24h from mouth to anus
23
Q
GI microbiota diversity
A
3 major bacterial phyla: firmicutes, bacteroidetes, and proteobacteria
limited phyla diversity but high high species diversity
24
Q
Stomach and Small Intestine
A
acidity (pH abt 2) makes it hard to colonize
decreased acidity + hypochlorydia because cholera survives stomach passage and can establishes infection
25
Helicobacter pylori
can survive at pH 1 burrows into gastric mucosa can cause gastric ulcers, has been found in 50% of the world's population
26
Large Intestine
anoxic
1000 anaerobes:1 facultative organism
micro-organism carry metabolic runs that produce metabolites we need: vitamin production, mod of steroids, aa biosynthesis
tons of fermentation
27
Role of commensal bacteria in our gut
- development of innate and adpative immunity
- microbial barrier
- maintain epithelial integrity
- source of energy
- vitamin biosynthesis, transformation of bile salts, catabolism of complex plant sugars and mucins,
- metabolism of xenobiotics
28
How is an immune response to a gut infection triggered
1. there must be stimulation of innate cells: if barriers are broken, there's an imbalance or deregulation
2. the severity of pathology is a consequence of the host/pathogen relationship: for example the virulence of the microbiome influences response
29
Clostidium Difficile
commensal bacteria that causes an opportunistic infection
on the rise,
when Abx disrupt balance and kill commensal bacteria c. diff can over colonize and produce toxins
symptoms: diarrhea, fever, loss of appetite nausea, abdominal pain
30
When do humans gain their adult gut microbiota composition?
Adult-like gut microbiota comp is reached at 3 years of age, adult microbiome begins to develop before birth sourced from placenta, once out of embryonic membrane exposed to a lot more microbes from birth canal and outside
baby microbiomes more divers than that of adults
31
How does microbiome change with age and time
adult microbiota relatively stable 70% match over 5 years
bacteriodetes stay relatively stable
early experiences determine gut microbiomes
aging associated with decrease diversity (at home more diverse than in a home)
32
What is the hygiene hypothesis
our use of soaps, antibiotics and disinfectants has restricted our access to microbes so our microbiota appears less diverse, the narrowing of diversity could potentially contribute to inflammatory and auto immune disease
33
How does diet affect microbiota
breast-fed vs bottle -fed: breast fed babies have more commensal bacteria because breast milk has complex oligosaccharides that promote their colonization
at 4 months Brest-fed have more of taxa associated with probiotics, gut lining protection and immune system education (B. longum) bottle-fed have greater abundance of D.diff, citrobacter and enterobacter
High-fiber: can only be fermented by microbiota enzymes and causes the pH of colon to lower which selects bacteria that are able to survive acidic environment
High meat: lots of animal proteins can lead to production of harmful bacteria metabolites
34
Inflammatory diseases: Crohn's and uc
result of dysbiosis which can be due to abx or failure to develop tolerance
seems to have lower gut microbiome diversity
IBD may be transmissible through genome
35
How have mouse models helped with understand obesity
- it seems that mice that are genetically obese have more firmicutes and methanogens than lean mice
- normal mice are fatter than germ free mice after fecal transplant germ-free start gaining weight
- obese twin lean twin study: recipient mice with same diet which receive transplant from obese humans become obese
36
How are obesity and dysbiosis linked?
Microbes digest food we can't and produce SCFAs that our cells use, the amounts and rations of these SCFAs can influence obesity, so if there's dysbiosis and these ratios are modified it can lead to obesity
archaea tilt metabolic balance towards obesity so dysbiosis favouring them can lead to obesity
if gut microbes cause inflammation in situations of dysbioysis
- lipopolysaccharides or endotoxins produced by gram negative species can promote inflammations
- high fat diets can the promote the absorption of theses toxins across the intestinal epithelium
