How many microbes does each human body host?
What does the following terminology mean
-Microbiota, Microbiome, ''Normal Microflora''
Microbiota = microflora
-all microbial species
-all microbial species+their function
-microbes in a healthy human body
Where do normal microflora live and not live?
-Skin, respiratory tract, digestive tract, urogenital tract
-all exposed to environment
-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
What kinds of effects can normal microflora have?
-no positive/negative effects
-occupy human microhabitats
-metabolism and defense
-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?
-medium surface area
-small surface area
-very large surface area
-large surface area
What kinds of microenvironments does the skin have?
Multiple with different chemical and physical conditions resulting in different populations of bacteria
What factors affect the skin microflora?
-Age: higher variability and more pathogens in young vs adult
-Personal hygeine: more microbes
-Weather: affect skin temp and moisture
What disrupts the normal skin microflora?
-pore blockage by bacteria
-gases released by microbial metabolism
-resident microbes prevent pathogen colonization
-type of skin microbiome correlates with mosquitoes
What are the characteristics of the oral cavity?
Antimicrobial chemicals present in oral cavity
-saliva has lysozyme
-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?
-sucrose allows bacteria to produce substance to adhere to teeth
enhance enamel w/ flouride
What are the characteristics of the gastrointestinal tract?
Lots of Nutrients Sources
-variety of food intake
What is the relationship between pH and oxygen level in the gastrointestinal tract?
-low pH = High oxygen level
-high pH = low oxygen level
What are the characteristics of the stomach, small intestine and large instestine?
-highly acidic, pH=2
-only acidophiles survive
-fairly acidic, pH=4.5
-similar to stomach but more microbes as pH increases
-neutral pH = 7
-strictly anoxic, no oxygen
-largest number of microbes
What are the functions of gastrointestinal microbes?
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?
Log phase growth
What does disrupting the normal intestinal microflora result in?
-side effect of oral antibiotics
Alteration of digestive function
-impaired vitamin synthesis
-no competition from normal microbes
How do we restore normal intestinal microflora?
Fecal Microbiota Transplant
What are the characteristics of mucosal tissues?
-upper vs lower respiratory
-entrapment, removal, low pH in vagina
Low Diversity of Microbes
Is the upper or lower respiratory tracts exposed to airborne microbes?
Upper yes but lower no b/c removal by ciliated epithelia cells
Is the urogenital tract exposed to environmental microbes?
-lactic acid bacteria that maintain low pH environment
What is virulence and what is pathogenesis?
-measure of pathogenicity
-process by which microbes cause disease
How do we measure virulence?
-amount of pathogen that kills 50% of hosts
-low LD50 = high virulence
-high LD50 = low virulence
What is attenuation?
Decrease or loss of virulence
-used in vaccines
In nature attenuation is selected for
-pathogenic to mutualism