Lecture 12 - Human-Microbe Interactions Flashcards
How many microbes does each human body host?
40 trillion
What does the following terminology mean
-Microbiota, Microbiome, ‘‘Normal Microflora’’
Microbiota = microflora
-all microbial species
Microbiome
-all microbial species+their function
'’Normal’’ Microflora
-microbes in a healthy human body
Where do normal microflora live and not live?
LIVE
- Skin, respiratory tract, digestive tract, urogenital tract
- all exposed to environment
DON’T LIVE
- Internal organs
- Blood, lymph, nervous system
- Not exposed to environment
Why do normal microflora live in areas exposed to the environment? What kinds of habitat conditions factor into their choice of environment?
Diifferent body areas make for different microenvironments
Habitat conditions
- Oxygen levels
- Acidity, pH
- Available Nutrients
What kinds of effects can normal microflora have?
Benign (most)
- no positive/negative effects
- occupy human microhabitats
Beneficial (some)
- positive effects
- metabolism and defense
Pathogenic (few)
- negative effects
- cause infectious disease
How are normal microflora established?
Humans are born without exposure to microbes
-uterus is sterile environment so born without microflora
Colonization of microbes
- horizontally transmitted from environment
- enters body and grows
What is a pathogen?
live on/in hosts and cause disease
what is pathogenicity?
ability of pathogen to cause disease
what are opportunistic pathogens?
cause disease in the absence of normal host resistance
what are the surface areas of the normal microflora environments?
Skin
-medium surface area
Oral Cavity
-small surface area
Gastrointestinal tract
-very large surface area
Mucosal tissue
-large surface area
What kinds of microenvironments does the skin have?
Multiple with different chemical and physical conditions resulting in different populations of bacteria
Sebaceous
- upper chest
- oily areas
Moist Skin
- armpits
- high moisture
Dry Skin
- forearms
- low moisture
What factors affect the skin microflora?
Host Factors
- Age: higher variability and more pathogens in young vs adult
- Personal hygeine: more microbes
Environmental Factors
-Weather: affect skin temp and moisture
What disrupts the normal skin microflora?
Acne
-pore blockage by bacteria
Body Odor
-gases released by microbial metabolism
Disease
-resident microbes prevent pathogen colonization
Mosquitoes
-type of skin microbiome correlates with mosquitoes
What are the characteristics of the oral cavity?
Heterogeneous Habitat
Antimicrobial chemicals present in oral cavity
-saliva has lysozyme
Nutrient sources
-food particles and cell debris near teeth/gums
High diversity of microbes
Primarily anaerobic metabolism
-facultive and obligate anaerobes
Colonize tooth surfaces
-form bacterial layers, biofilms, called dental plaques
How are dental plaques and tooth decay related?
Dental plaques that form on teeth undergo anaerobic metabolism and produce lactic acid decaying the teeth
High sugar intake results in tooth decay because fermentation of sugars produce the lactic acid
How do you prevent dental caries?
restrict sucrose
-sucrose allows bacteria to produce substance to adhere to teeth
brush teeth
enhance enamel w/ flouride
What are the characteristics of the gastrointestinal tract?
Heterogeneous Habitat
- stomach
- small/large intestines
Antimicrobial conditions
-low pH
Lots of Nutrients Sources
-variety of food intake
What is the relationship between pH and oxygen level in the gastrointestinal tract?
Inversely correlated
- low pH = High oxygen level
- high pH = low oxygen level
What are the characteristics of the stomach, small intestine and large instestine?
Stomach
- highly acidic, pH=2
- only acidophiles survive
Small intestine
- fairly acidic, pH=4.5
- similar to stomach but more microbes as pH increases
Large intestine
- neutral pH = 7
- strictly anoxic, no oxygen
- largest number of microbes
- fermentation vessel
What are the functions of gastrointestinal microbes?
Vitamin Synthesis
Steroid metabolism
Produce gas
What is microflora turnover?
10 trillion bacteria removed each day
-fecal matter is 1/3
Remaining populations double 1-2x per day
How is a large intestine similar to a chemostat?
Open system
Log phase growth
What does disrupting the normal intestinal microflora result in?
Diarrhea
-side effect of oral antibiotics
Alteration of digestive function
-impaired vitamin synthesis
Pathogen colonization
-no competition from normal microbes
How do we restore normal intestinal microflora?
Probiotics
Fecal Microbiota Transplant
