Topic 1-2 Flashcards
What is the microbiota?
The mixture of organisms regularly found at any anatomical site
How do bacteria benefit from hosts?
1) has a supply of nutrients
2) Lives in a stable environment
3) Has a mode of transport
How do hosts benefit from microbiota?
1) Microbial antagonism (plugs up sites so harmful pathogens don’t have place to colonize)
2) Nutritional synergism (we share metabolic products, some of which we cannot make (ex. vitamin K))
3) Stimulate immune system (induce humoral response that “trains” the system against related pathogens, thus preventing invasion by other harmful bacteria) (critical for normal immune system development)
What types of organisms are found in the microbiota?
Bacteria, eukaryoitc fungi, methanogenic archea
How are microbiota adapted to not cause an immune response?
Unknown for sure; but suggested that microbiota detoxify their LPS to render then less sensitive to the immune system
How can microbiota be harmful?
1) if they end up somewhere where they are not usually supposed to be (eg. E. coli in urinary tract) (pathogenic potential if introduced into other body sites or if host status changes; ex. immunocompromised)
2) Produce intestinal gas - produce gaseous by-products
How is the host-microbiota interaction important?
1) Microbiota can affect the brain through the gut-brain axis
2) the balance of microbiota can contribute or prevent colorectal cancer
3) Can influence obesity, diabetes
What are source of microbiota in humans?
1) from birth (birth canal)
2) exposure to other humans and pets
3) ingestion of food, fluids
4) inhalation of air-borne microorganisms
*2-4 is basically from environment
What factors/changes in the host’s internal environment affect microbiota composition?
1) Diet - diet encourages some bacteria to colonize/proliferate
2) Infection - leads to temporary increase in pathogen number
3) Oral antibiotic therapy - cause decrease in microbiota; normally returns to normal after therapy
Overall though, relatively constant otherwise
What are three explanations why bacteria are located at specific anatomical sites?
1) Some bacteria exhibit a tissue preference (ex. growth factor expression, or straight up unihospitable)
2) Attachment to host receptors, which are expressed only in specific reagions)
3) Construction of biofilms in a particular location promoting the proliferation of another member of the microbiota within the film
Why are microbiota usually associated with sweat glands?
1) it’s warm
2) Has high moisture content (bacteria live close to sweat glands for moisture)
3) secretions contain microbial nutrients
Why are most skin microorganisms transient?
Unable to multiply; usually die from low moisture content, low pH, and are out competed by permanent resident microbiota
Factors affecting microbiota of the skin?
Weather - may change temperature/moisture content of skin
Age - young children tend to have more varied microbiota (ex. playing in dirt mb)
Personal hygiene
Diet
Where do microbiota colonize in the oral cavity?
Food particles, epithelial debris (NOT saliva; saliva contains antibacterial substances)
Bacterial populations changes from what processes?
Development of the teeh
What is plaque?
A form of biofilm created by acidic glycoproteins from saliva
What causes dental caries? (cavities)
Damage is caused by acid-producing bacteria in plaque (produces lactic acid)
What are periodontal diseases?
Diseases affecting the supporting structures AROUND the TEETH, such as the gingiva (gums), cementum (attachment point for teeth), periodontal membrane (resists stress from chewing), and the alveolar bone (bone in which there is teeth go into; teeth sockets)
Where are the majority of the human microbiota ?located?
Gastrointestinal tract (GI tract)
What type of bacteria are the majority in the intestinal microbiota?
Anaerobes (due to anaerobic environment)
How do babies get their microbiota?
Diet - intestinal tract initially sterile
How does the character of microbiota change along the length of the gastrointestinal tract?
It increases as you go down - duodenum is sparse, ileum contains a moderately mixed mount, and the large intestine contains a large amount (“anaerobic fermentation chamber”)
*difference in bacterial composition between individuals & different stretches of GI tract
What areas of the respiratory tract are usually/mostly sterile?
Sinuses, lower respiratory tract (trachea, lungs)
Where are most bacteria in the respiratory tract located?
Upper respiratory tract (nasopharynx)
How do bacteria enter the respiratory tract?
Breathing
How are bacteria expelled from the respiratory tract?
Nasal secretion (ex. mucus)
Is the urinary tract sterile?
Yes, as it is flushed with urine every few hours
Is the vagina and urethra sterile?
No to the vagina
No to the first bit of the urethra
What do bacteria in the vagina do?
Since they occupy the space there, they help prevent infection by other bacteria (Lactobacillus lower the pH, which inhibits growth by other bacteria)
What does “gnotobiotic” mean?
Literally, “known life”
Figuratively and usually when used in speech or writing, “germ free”
What are characteristics of gnotobiotic animals?
-abnormal anatomical and physiological features
- underdeveloped lymphatic tissue & poorly developed immune systems
thin intestinal wall - low antibody titer (amount of antibodies)
- higher susceptibility to pathogens
- reduced susceptibility to certain diseases that are dependent o microbe activity (ex. cavities/caries)
What is the difference between internal tissue and surface tissue?
Internal tissues - normally free of microorganisms
Surface tissues - in constant contact w/ the environment; readily colonized by some bacteria
What is the normal flora?
Population of microorganisms that colonize the body WITHOUT causing disease
What is difference between mutualism and commensalism
Mutualism: both organisms benefit
Commensalism: One organisms has a benefit with no cost to other (but no gain either; ex. microbe benefits and doesn’t cause disease)
How long does it take for microbiota to establish on newborn children?
2-3 days
What are some characteristics of skin?
Impregnable Dry low pH high salt concentration Anti-microbial peptides Fatty acids
Are microbiota required to live?
No, but are required to live WELL
