E4. Gut mibrobiology Flashcards
what is a commensal microorganism?
microorganism that derives food/other benefits from another organism without hurting or helping it
what is a symbiont microorganism?
microorganism that lives together in harmony with another organism, providing a benefit to one/both organisms
What is a pathobiont microorganism?
microorganism that can cause disease in certain conditions (opportunistic pathogens), but not typically if healthy
microbiomes have a range of functions including?
-Protecting the body by establishing themselves as normal residents
-Aiding in digestion and the maturation/development of our immune system
Common sites of the human microbiome include?
-Nose, ears, conjunctiva
-Skin, lungs, breast milk
-Genitourinary tract
-Gastrointestinal (GI) tract:
i.e. oral cavity (mouth), oesophagus, stomach and small/large intestines (gut)
Where do our microbiomes come from in the first place?
-Prior to birth babies are in a sterile environment (uterus), unless in utero infection passed from mother via placenta
-Within 12 hours of delivery, new-born babies are colonised by many species of bacteria, as well as fungi and protozoa
-Our first dose of microbes typically comes from our mother. Others acquired from people/things they touch (family, nurses, environment)
-During birth, the foetal membrane breaks and exposes the unborn baby to the environment
-Vaginal delivery:
Babies covered in microbes as they pass through the birth canal (including bacteria that help babies digest their first meal) such as Lactobacillus species
-Caesarean:
Babies colonised mainly by skin microbes of different species (Staphylococci and Streptococci)
Describe breast fed babies
-Acquire a wide spectrum of gut bacteria includingStaphylococci, Streptococci, Corynebacteria,lactic acid bacteria,Propionibacteria, andBifidobacteria
-Some species help metabolise sugars into acids that protect the baby from certain intestinal infections
Describe formula fed babies
-Acquire mainly mix of Lactobacilli, Staphylococci, enteric Streptococci and coliforms
-Some formula milk is fortified with probiotics (microbes) and prebiotics
what happens to microbes weeks from birth?
-Within weeks the types of microbes living in different parts of the body start to specialise
-Different environments better suited for certain species
-Further exposure to surroundings and other people = species start to compete for space and resources
-Beginning solids = changes in populations of microbes colonising the baby
-Different microbes grow best on different types of food and require different nutrients
How do microbes change from 6 months to 3 years old?
-Species of microbes continually increase in number
-Despite commonalities, microbial populations vary a lot, even among families
-Individual differences and genetics play a part
From 6 months to 3 years, the microbe continues due to what several factors?
-Factors include nutrition, infection, medications and environment
-Microbiome variation is highest during childhood
-Parents, family and relatives still influence our microbiome
-Sharing of environments and other lifestyle factors
-Influence of the mother is lessened over time and young children’s microbiomes come to resemble both parents
Describe our changing microbiome in adulthood
-By the time we become adults, we will have approx. 1000 species of microbes in our guts = our normal gut microbiome
-The adult microbiome is now more stable, but is affected by a range of factors
Describe biological factors changing our microbiome during adulthood
-Age: variation decreases following adulthood and after age 65, the number of microbial species decreases more rapidly
-Hormones: changes during puberty, pregnancy and menopause
-Genetics: biological sex and individual genetic variation
Describe environmental/external factors changing our microbiome during adulthood
Diet, drug therapy, climate and occupation
Describe the microbiome in the mouth
-The mouth is populated with a diverse range of commensal microbes that contribute to our health
-600+ different species
-Aerobic Streptococcus species are common
-Saliva contains 5 x 109 bacteria cells per mL
-Many microhabitats within the mouth
-Cheek epithelium (S. sanguis, S. salivarius, S. mitis)
-Tongue, floor of mouth, tooth enamel (S. mutans, S. sanguis)
Describe plaque
-Soft biofilm on teeth containing saliva, food particles and diverse community of bacteria
-Bacteria ferment sugars to lactic acid, causing damage to enamel
-Fermentation combined with bacterial proteolytic enzymes = tooth decay
Describe tartar
Hard yellow to brown matrix of biofilm that is difficult to remove
Plaque and tartar build up can lead to?
Gingivitis = gum inflammation
Periodontitis = gum disease
Periodontitis results in?
-Periodontitis results in chronic inflammation of gums, can cause gums to bleed
-Bacteria in oral cavity may enter bloodstream
-Increases risk of cardiovascular disease and stroke
-CVD examples = pericarditis and endocarditis
-Streptococci can activate platelets in the blood, making them clump together and form blood clots
-Studies suggest oral cavity dysbiosis is also associated with liver disease, GI disease and dementia
good hygiene for the oral cavity?
-Regularly remove plaque:
Toothbrush, fluoride toothpaste, interdental brushes, floss
-Visit dentist regularly for check-ups and hygienist:
Check oral health and for gum disease
Professional teeth cleaning by dental hygienist to remove tartar
-Antiseptic and/or plaque inhibiting mouthwashes:
Chlorohexidine, CHX (e.g. Corsodyl)
Cetylpyridinium chloride, CPD (e.g. OralB)
What healthy lifestyle habits should one practice for oral cavity microbiome?
-Avoiding food/drinks that accelerate tooth decay (high sugar content)
-Avoiding smoking
-Smoking alters the oral cavity microbiome
-Resulting in more anaerobic species and fewer aerobic species
-Increases risk of periodontitis
changes in pH along GI tract?
Oral cavity = pH 7
Stomach = pH 2
Small intestine = pH 7
Large intestine = pH 8
-Anaerobicity increases as you move though GI tract
where is the main site of the human microbiome?
the large intestine
-Exposed to the environment from foods we consume
-More than 30% of fecal volume is bacteria: Anaerobic bacteria including Bacteroides, Bifidobacterium, Clostridium, Lactobacillus
-Many species ferment waste to generate vitamins: B12, Vitamin K, pyridoxine, riboflavin, thiamine
-Bacterial digestive enzymes can break down sugars/aid steroid metabolism
-Certain nutrients aid growth
Benefits of the gut microbiome?
-Digestion of plant carbohydrates into short chain fatty acids (SCFA)
-Synthesis of a range of essential vitamins
-Metabolism of drugs and toxins
-Competition with pathogens and suppress their growth
-Programming of the immune system
synthesis of what range of essential vitamins in the gut microbiome?
-Biotin (B7) = coenzyme for carboxylase enzymes
-Pantothenic acid (B5) = required for CoA synthesis
-Folic acid (B9) = involved in production of nucleotides
-Precursor for vitamin K = involved in blood clotting
